The giant Upper Yangtze Pb-Zn metallogenic province,also known as the Sichuan-Yunnan-Guizhou(SYG)Pb-Zn province hosting>500 carbonate-hosted epigenetic Pb-Zn deposits that contain>20 Mt Pb+Zn base metal reserves...The giant Upper Yangtze Pb-Zn metallogenic province,also known as the Sichuan-Yunnan-Guizhou(SYG)Pb-Zn province hosting>500 carbonate-hosted epigenetic Pb-Zn deposits that contain>20 Mt Pb+Zn base metal reserves.The giant Maoping Pb-Zn deposit is the second largest deposit in this province and owns>5 Mt Pb+Zn metal reserves with ore grades of 12 wt.%-30 wt.%Pb+Zn.Such large tonnages and high grades make it among the top 100 similar mineral deposits in the world.The ore bodies are predominantly located within the strata of the Upper Devonian(Zaige Formation)and Lower(Baizuo Formation)-Upper(Weining Formation)Carboniferous.The principal ore minerals consist of galena(Gn),sphalerite(Sp),and pyrite(Py),while the primary gangue minerals include dolomite(Dol),calcite(Cal),and quartz(Qtz).Three mineralization stages of carbonate minerals have been identified:(1)pre-sulfide stage 1,(2)syn-sulfide stage 2,and(3)post-sulfide stage 3.Trace elements and C-O-Sr isotopes of three stages’carbonate minerals,together with S-Pb isotopes of sulfides,revealing that the metamorphic basement rocks played the role of the metal source during the early stage of Pb-Zn mineralization,whereas the metal contribution of the sedimentary wall rocks found to be more prominent during the late stage of Pb-Zn mineralization.In addition,the dissolution of marine carbonate rocks and CO_(2)degassing may have also played an important role in the formation of the Maoping deposit.Furthermore,syn-sulfide stage 2 calcite has a U-Pb age of 214±20 Ma obtained by LA-ICPMS in-situ analyses,suggesting that the hydrothermal mineralization occurred during the Triassic.Our study proposes a new coupled metallogenic model of fluid-structure-lithology assemblage and provides new insights about the formation and evolution of the Maoping deposit with significant implication for understanding and exploration of similar Pb-Zn deposits worldwide.展开更多
A total of 393 potholes(368 fluvial and 25 marine potholes)were studied at seven different sites in both the fluvial and marine environments.Diverse bedrock properties and large-scale delivery of tools and grinders re...A total of 393 potholes(368 fluvial and 25 marine potholes)were studied at seven different sites in both the fluvial and marine environments.Diverse bedrock properties and large-scale delivery of tools and grinders regulate the dynamic growth,truncation,and amalgamation of potholes.Therefore,the principal objectives of the study are(i)to examine the relationship between the growth of potholes and substrate lithological with structural characteristics(applying geospatial and Schmidt hammer for rock strength analysis)and(ii)to measure the morphology,and size of tools and grinders,processes of truncation and amalgamation in hydro-geomorphic environment using various indices and field techniques.The result showed that large potholes are stretched in the direction of lineament axes and roughly parallel to the river flow direction.Here,the steady growth of pothole depth-diameter is controlled by active bedrock structures,tools,or grinders,and monsoonal high-velocity bank full discharge.Consequently,the deepening and widening of potholes are relatively slow at Bindu,Deuli,and marine beach Neil Island due to fewer structures and little supply of tools or grinders.In small stretches,(Damodar,Subarnarekha,and Rarhu)canyons and gorge-like features(bedrock incision)are formed at Rajrappa,Bhakuyadi,and Guridih sites due to cyclic truncation and amalgamation.Truncation and amalgamation processes restrict the vertical depth threshold value of potholes within 3m,particularly at Rajrappa,Bhakuyadi,and Guridih sites.Scientific study of the pothole's dynamic growth is greatly necessary for the different environmental engineering and river hydraulic projects like excavation,dredging,and dam or barrage construction.Successively,it is essential to compute the cost of rock excavation or dredging,primarily for the mechanical strength of the bedrock river channel and its stability.展开更多
Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area.The South China Sea(SCS)is a typical marginal sea ...Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area.The South China Sea(SCS)is a typical marginal sea that includes Paleo SCS and New SCS tectonic cycles.The latter includes continental marginal rifting,intercontinental oceanic expansion and oceanic shrinking,which controlled the evolution of basins,and the generation,migration and accumulation of hydrocarbons in the deepwater basins on the continental margin of the northern SCS.In the Paleogene,the basins rifted along the margin of the continent and were filled mainly with sediments in marine-continental transitional environments.In the Neogene–Quaternary,due to thermal subsidence,neritic-abyssal facies sediments from the passive continental margin of the SCS mainly filled the basins.The source rocks include mainly Oligocene coal-bearing deltaic and marine mudstones,which were heated by multiple events with high geothermal temperature and terrestrial heat flow,resulting in the generation of gas and oil.The faults,diapirs and sandstones controlled the migration of hydrocarbons that accumulated principally in a large canyon channel,a continental deepwater fan,and a shelf-margin delta.展开更多
Jiama,with more than 11 Mt of copper metal,is the largest porphyry-skarn copper system in the Gangdese metallogenic belt,Xizang,China,creating ideal conditions for deciphering the origin of porphyry ores in a collisio...Jiama,with more than 11 Mt of copper metal,is the largest porphyry-skarn copper system in the Gangdese metallogenic belt,Xizang,China,creating ideal conditions for deciphering the origin of porphyry ores in a collision setting.Despite massive studies of the geology,chronology,petrogenesis,and ore-related fluids and their sources in Jiama,there is a lack of systematic summaries and reviews of this system.In contrast to traditional porphyry copper systems in a subduction setting,recent studies and exploration suggest that the Jiama deposit includes porphyry-type Mo-Cu,skarn-type Cu polymetallic,vein-type Au and manto orebodies.This paper reviews the latest studies on the geology,chronology,petrogenesis,fluid inclusions,and isotopic geochemistry(hydrogen,oxygen,sulfur,and lead)of the Jiama deposit.Accordingly,a multi-center complex mineralization model was constructed,indicating that multi-phase intrusions from the same magma reservoir can form multiple hydrothermal centers.These centers are mutually independent and form various orebodies or are superimposed on each other and form thick,high-grade orebodies.Finally,a new comprehensive exploration model was established for the Jiama porphyry copper system.Both models established in this study help to refine the theories on continental-collision metallogeny and porphyry copper systems.展开更多
The Mirge-Naqshineh gold district is situated at northwest of Iran with a NW-trending brittle- ductile shear zone. It is hosted by Precambrian meta-sedimentary and meta-volcanic units traversed by mineralized quartz v...The Mirge-Naqshineh gold district is situated at northwest of Iran with a NW-trending brittle- ductile shear zone. It is hosted by Precambrian meta-sedimentary and meta-volcanic units traversed by mineralized quartz veins. In terms of cross-cutting relationships and sulfide content three types of quartz veins are identified in the region. Among those, parallel to bedding quartz vein （type I） is the main host for gold mineralization. Gold is found in three different forms： 1） submicrometer-size inclusions of gold in arsenian pyrite, 2） as electrum and 3） in the crystal lattice of sulfides （pyrite, galena and chalcopyrite）. Six types of pyrite （Pyl-Py6） were identified in this ore reserve. Py3 coexists with arsenopyrite and contains the greatest As-Au concentrations. There is a negative correlation between the As and S contents in Py2 and Py3, implying the substitution of sulfur by arsenic. Pyrites and mineralized quartz veins were formed via metamorphic-hydrothermal fluid and reflect the gold-transportation as Au（HS）2 under reducing and acidic conditions. The gold precipitation mainly controlled by crystallization of arsenian pyrite during fluid/rock interactions and variation offO2. The volcanic host rock has played an important role in gold concentration, as Py3 in this rock contains inclusion of gold particles, but gold is within the lattice of pyrite in phyllite or other units.展开更多
The new recently demonstrated reserves of oil and gas in the Ordos basin are found at the top of petroliferous basins in China. Gas pools discovered in recent years in the Permian system have become the main natural g...The new recently demonstrated reserves of oil and gas in the Ordos basin are found at the top of petroliferous basins in China. Gas pools discovered in recent years in the Permian system have become the main natural gas resource in the basin. Therefore, synthetic research on fluid inclusions should be done in order to ascertain the pool-forming stage, the maturity of organic matters and the properties of Paleo-fluids. The main types of fluid inclusions in the Permian system in the basin include brine inclusions, carbon dioxide inclusions and organic inclusions. Homogenization temperatures （HT） of brine inclusions can be divided into four intervals： 66-83 ℃, 86-108 ℃, 112-138 ℃ and 142-153℃. The fluid inclusions in the interval of 112-138 ℃ are much more than that of other intervals, indicating that the second stage of hydrocarbon migration associated with the third temperature interval is the most important stage of gas pool formations. The fluid inclusion has extensive applications in the study of gas geology, not only in ascertaining the formation stage of gas pools, but also in estimating the maturity of organic matter and restoring Paleo-fluids. The result of testing the HT of brine inclusions shows that there are two stages of gas pool formations in the Permian system occurring ＋150 Ma and ±100 Ma. The maturity of organic matter is moderate to high, a conclusion based on the color of fluid inclusions （radiated by fluorescence）. The high salinity of Paleo-fluids of the NaCI-H2O and CaCl2-H2O systems shows good preservation conditions of the Paleo-fluids. Two stages of reservoir filling, high maturity of organic matter and good preservation conditions are factors favorable for the formation and preservation of large-scale gas pools in the Permian system in the Ordos basin.展开更多
The Tongyu copper deposit,located in the western part of the North Qinling Orogen,China,is one of several volcanic-hosted massive sulphide(VHMS)deposits with industrial value and is also a typical example of mineraliz...The Tongyu copper deposit,located in the western part of the North Qinling Orogen,China,is one of several volcanic-hosted massive sulphide(VHMS)deposits with industrial value and is also a typical example of mineralization related to the subduction and metallogenesis during the Caledonian orogeny.We conducted systematic lead-sulphur isotope geochemical analyses of the Tongyu deposit to understand the possible ore-forming material sources and tectonic settings.Twenty-six sulphide samples yielded clusteredδ^34SCDT values of 1.13‰-3.36‰,average 2.22‰,and show a tower-type distribution,implying that the sulphur of the Tongyu copper deposit mainly originated from a mantle source.The Pb isotope compositions of sulphides(^206Pb/^204Pb=17.59225-18.56354,average 18.32020;^207Pb/^204Pb=15.51770-15.69381,average 15.66217;^208Pb/^204Pb=37.99969-39.06953,average 38.52722)are close to the values of the volcanic host rocks(^206Pb/^204PbPb=18.10678-18.26293,average 18.21158;^207Pb/^204PbPb=15.63196-15.68188,average 15.65345;^208Pb/^204PbPb=38.43676-38.56360,average 38.49171),thus consistent with the Pb in ores and volcanic host rocks having been derived from a common source that was island-arc Pb related to oceanic crust subduction.The northward subduction of the Palaeo-Qinling oceanic crust triggered dehydration of the slab,which generated a large amount of high-oxygen-fugacity aqueous hydrothermal fluid.The fluid rose into the mantle wedge,activated and extracted metallogenic material and promoted partial melting of the mantle wedge.The magma and ore-forming fluid welled up and precipitated,finally forming the Tongyu VHMS copper deposit.展开更多
The Bayan Obo supergiant carbonatite-related rare-earth-element-niobium-iron(REE-Nb-Fe) endogenetic deposit(thereafter as the Bayan Obo deposit), located at 150 km north of Baotou City in the Inner Mongolia Autonomous...The Bayan Obo supergiant carbonatite-related rare-earth-element-niobium-iron(REE-Nb-Fe) endogenetic deposit(thereafter as the Bayan Obo deposit), located at 150 km north of Baotou City in the Inner Mongolia Autonomous Region, is the largest rare-earth element(REE) resource in the world. Tectonically,this deposit is situated on the northern margin of the North China Craton and adjacent to the Xing’anMongolian orogenic belt to the south. The main strata within the mining area include the Neoarchean Se’ertengshan Group and the Mesoproterozoic Bayan Obo Group. Generally, the rare earth, niobium, and iron mineralization within the deposit are intrinsically related to the dolomite carbonatites and the extensive alteration of the country rocks caused by the carbonatite magma intrusion. The alteration of country rocks can be categorized into three types: contact metasomatism(anti-skarn and skarn alteration), fenitization,and hornfelsic alternation. As indicated by previous studies and summarized in this review, the multielement mineralization at Bayan Obo is closely associated with the metasomatic replacement of siliceous country rocks by carbonatite magmatic-hydrothermal fluids. The metasomatic process is comparable to the conventional skarnification that formed due to the intrusion of intermediate-acid magmatic rocks into limestone strata. However, the migration pattern of Si O2, Ca O, and Mg O in this novel metasomatic process is opposite to the skarn alteration. Accordingly, this review delineates, for the first time, an antiskarn metallogenic model for the Bayan Obo deposit, revealing the enigmatic relationship between the carbonatite magmatic-hydrothermal processes and the related iron and rare earth mineralization.Moreover, this study also contributes to a better understanding of the REE-Nd-Fe metallogenetic processes and the related fluorite mineralization at the Bayan Obo deposit.展开更多
North Carnarvon Basin is a gas province with minor oily sweet spots in deepwater area with water depth more than 500 m,which is one of the hot spots of global petroleum exploration for its series of giant hydrocarbon ...North Carnarvon Basin is a gas province with minor oily sweet spots in deepwater area with water depth more than 500 m,which is one of the hot spots of global petroleum exploration for its series of giant hydrocarbon discoveries in recent years.However,the degree of oil and gas exploration in deepwater area is still low,and the conditions for oil and gas accumulation are not clear.Based on the current exploration situation and latest database of fields,applying multidisciplinary analysis of hydrocarbon geology,hydrocarbon accumulation elements and its exploration direction of North Carnarvon Basin in deepwater area are analyzed.The results show that there are three sets of main source rocks in deepwater area of North Carnarvon Basin,which are Triassic marine shale in Locker Formation and delta coal-bearing mudstone with thin carbonaceous mudstone in Mungaroo Formation,Lower–Middle Jurassic paralic carbargilite and coal measure strata in Athol Formation and Murat Formation,Cretaceous delta mudstone in Barrow Group and marine shale in Muderong Formation.Most source rock samples show gas-prone capability.The coarse sandstone of delta facies in Middle–Upper Triassic Mungaroo Formation is the most important reservoir in deepwater area,Lower Cretaceous Barrow Group deep-water gravity flow or underwater fan turbidite sandstone is the secondly main reservoir.Lower Cretaceous marine shale in Muderong Formation is most important regional caprock.Triassic mudstone in Mungaroo Formation is an important interlayer caprock in deepwater area.There are two main reservoir accumulation assemblages in deepwater area,one is Triassic structural-unconformity plane reservoir accumulation assemblage of Locker Formation to Mungaroo Formation,and the other is Lower–Middle Jurassic Athol Formation and Murat Formation–Lower Cretaceous stratigraphic lithology-structural reservoir accumulation assemblage of Barrow Group to Muderong Formation.There are three main control factors of hydrocarbon Accumulation:One is coupling of source and seal control hydrocarbon distribution area,the second is multi-stage large wave dominated deltas dominate accumulation zone,the third is direction of hydrocarbon migration and accumulation in hydrocarbon-rich generation depression was controlled by overpressure.The south of Exmouth platform in deepwater area is adjacent to hydrocarbon rich depression zone,reservoir assemblage is characterized by“near source rocks,excellent reservoir facies,high position and excellent caprocks”,which is the main battlefield of deepwater oil and gas exploration in North Carnarvon Basin at present.There are a lot of fault block traps in the northern structural belt of Exmouth platform,and the favorable sedimentary facies belt at the far end of delta plain in Mungaroo Formation is widely distributed,which is the next favorable exploration zone.The Lower Cretaceous,which is located at the concave edge uplift adjacent to the investigator depression and the Exmouth platform,also has a certain exploration prospect in northwest of deepwater area.展开更多
The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits ass...The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits associated with granitic intrusion. The deposit consists of ore bodies in altered granite or along the contact zone between granite and Proterozoic meta-sedimentary rocks. The Cu-bearing intrusion is sub-alkaline I-type granite. It has a zircon U-Pb age of ~776 Ma, and has subduction-related geochemical signatures. Geochemical analysis reveals that the intrusion may be formed by melting of mafic lower crust in a subduction regime. Three stages of alteration and mineralization are identified in the Suoi Thau deposit, i.e., potassic alteration; silicification and Cu mineralization; and phyllic alteration. Two-phase aqueous fluid inclusions in quartz from silicification stage show wide ranges of homogenization temperatures （140-383℃） and salinities （4.18wt%- 19.13wt%）. The high temperature and high salinity natures of some inclusions are consistent with a magmatic derivation of the fluids, which is also supported by the H-O-S isotopes. Fluids in quartz have JD values of-41.9‰ to -68.8%. The fluids in isotopic equilibrium with quartz have j180 values ranging from 7.9‰ to 9.2%. These values are just plotted in the compositional field of magmatie- hydrothermal fluids in the ~Dwater versus jlSOwater diagram. Sulfide minerals have relatively uniform j34S values from 1.84%o to 3.57%0, which is supportive of a magmatic derivation of sulfur. The fluid inclusions with relatively low temperatures and salinities most probably represent variably cooled magmatic-hydrothermal fluids. The magmatic derivation of fluids and the close spatial relationship between Cu ore bodies and intrusion suggest that the Cu mineralization most likely had a genetic association with granite. The Suoi Thau deposit, together with other deposits in the region, may define a Neoproterozoic subduction-related ore-forming belt.展开更多
Iran is a country that benefits from nice nature, diverse continent, areas full of unique geological phenomena. Thus, it is necessary to study these attractions for better recognition of them. In this regard, Hormoz I...Iran is a country that benefits from nice nature, diverse continent, areas full of unique geological phenomena. Thus, it is necessary to study these attractions for better recognition of them. In this regard, Hormoz Island with valuable geoheritage, biodiversity, cultural, historical and political diversity is very important. The accumulation of these attractions and its being located in Persian Gulf strategic area made it of considerable significance in national and international communities. Hormoz Island is a spherical salt dome which is located in Hormoz strait. This Island is composed of evaporites, igneous rocks and sedimentary rocks, and sediments mainly belong to Mishan and Aghajari formations and salt, gypsum and, to a lesser extent, limestone evaporites. In sedimentary formations of Hormoz, Aouthigenic minerals such as Pyrite, Dolomite, quartz, Anhydrite, gypsum and halite are frequently seen. Mineralization of volcanic leads to formation of high temperature minerals, such as oligiste, pyroxene, amphibole and low temperature and hydrothermal minerals such as Pyrite, quartz... in the tracks of igneous rocks. This unique geodiversity in rocks and mineral which made various colors in Hormoz Island made it a mineraogical reservoir. Beside considerable mineralogical attractions, there are other potentials like ochre mine, coral reefs, rock seashore, sea caves, salt caves, plant cover and wild life which have added to various tourism capabilities of this Island and made it a unique place in the world. This paper studies Hormoz Island in terms of geological features and geotourism potentials.展开更多
The Liziyuan gold deposit,situated on the south side of the Shangdan suture zone,West Qinling Orogen,occurs in metamorphic volcanic rocks(greenschist facies)of the early Paleozoic Liziyuan Group and in Indosinian Tian...The Liziyuan gold deposit,situated on the south side of the Shangdan suture zone,West Qinling Orogen,occurs in metamorphic volcanic rocks(greenschist facies)of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite.Orebodies in the Liziyuan gold field are controlled by the ductile-brittle shear zone,and by thrusting nappe faults related to the Indosinian orogeny.In detail,this paper analyzed the geological characteristics of the Liziyuan gold field,and the Pb isotopes of the Lziyuan host rocks,granitoids(Tianzishan monzogranite and Jiancaowan syenite porphyry),sulfides,and auriferous quartz veins by multiple-collector inductively coupled plasma mass spectrometry(MC-ICPMS).In addition,previous data on the sulfur,hydrogen,and oxygen isotopes were employed to discuss the possible sources of the ore-forming fluids and materials,and to further understand the tectonic setting of the Liziyuan gold deposit.The sulfides and their host rocks(Lziyuan Group),Tianzishan monzogranite and Jiancaowan syenite porphyry,and auriferous quartz veins have similar Pb isotopic compositions.Zartman’s plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves.In the△β-△γdiagram,which genetically classifies the lead isotopes,most of the data fall within the range of the subduction-zone lead mixed with upper crust and mantle.This indicates that a complex source of the ore lead formed in the orogenic environment.Theδ34S values of the sulfides range from 3.90 to 8.50‰(average6.80‰),with a pronounced mode at 5.00‰-8.00‰.These values are consistent with that of orogenic gold deposits worldwide,indicating that the sulfur sourced mainly from reduced metamorphic fluids.The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the oreforming fluids,with possible mixing of minor magmatic fluids,but the late stage was dominated by meteoric water.The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide.展开更多
Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, e...Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, erosion by ephemeral streams shortly after the eruption disrupted the lateral continuity of the 270 to 300 cm-thick pumice deposit. Co-evolution of the surface- and ground-water systems in a low-relief, low-slope landscape allowed diffuse groundwater discharge from the banks of the evolving stream system. Accumulation of organic material from groundwater dependent ecosystems at these sites of discharge allowed peat deposits to form on gently sloping erosion surfaces cut into the pumice deposit. Following early stream incision, fine-grained, silt-rich deposits accumulated in valleys and contributed permeability barriers to the lateral migration of water in the pumice aquifer. Fens discharge from the pumice aquifer through gently sloping surfaces patterned after the slope of the erosion surface cut into the pumice deposit and overlain by approximately 1 m of peat on the sloping surface and alluvium or iron-cemented pumice overlain by alluvium at the toe of the slope. The predominant source of groundwater is snowmelt which infiltrates the pumice deposit during the freshet. However, shallow groundwater flow also takes place along permeable pathways in bedrock units. Locally, low volume discharge takes place along faults. The snowmelt-dependent hydrologic system that supports the fens of the Walker Rim study area occurs at elevations primarily above 1585 m.展开更多
1 Introduction The Weibei Uplift is located in the southwest of the North China Plate,where is the stable block(the Ordos Block)in the north and the active belt(the QinlingOrogenic Belt)in the south(Ren et al,2014,201...1 Introduction The Weibei Uplift is located in the southwest of the North China Plate,where is the stable block(the Ordos Block)in the north and the active belt(the QinlingOrogenic Belt)in the south(Ren et al,2014,2015).And the belt is separated from the Weihe basin.The Weibei uplift has a uniform crystalline basement with the North展开更多
Extensive thickly folded sedimentary sequences are exposed onshore of the Rio del Rey Basin contrary to previous reports of their rarity. Shales predominate, frequently intercalated by marlstones, sandstones...Extensive thickly folded sedimentary sequences are exposed onshore of the Rio del Rey Basin contrary to previous reports of their rarity. Shales predominate, frequently intercalated by marlstones, sandstones, mudstones, limestones and marls and have been intruded in places by volcanic rocks of the Cameroon Volcanic Line (CVL). An integration of lithostratigraphic, paleontologic, granulometric and petrographic data generated from field and laboratory studies, permitted the identification of eleven (11) lithofacies which were subsequently grouped into three facies associations to facilitate the reconstruction of the paleo-depositional environment. Graphic logs constructed from the different outcrops studied revealed general coarsening upward sequences. Mega body fossils recovered from these sediments include severely altered, ferruginized fish and turtle-like heads, bivalve shells and moulds. Two bivalve taxa were identified: Exogyra ponderosa (Roemer) and members of theVenericardiinae sub-family. Textural and mineralogical details were obtained from granulometric and thin sections (microscopy). Interpretation of these data inferred an open relatively deeper marine, probably middle neritic to near shore transitional intertidal environments into which these sediments previously dated as Lower to Upper Cretaceous were deposited. Elements of a possible petroleum system: source and reservoir rocks, migratory pathways and trapping conditions, have been pointed out and thought to exist in space and time.展开更多
This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered...This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered by the weak regulations, pollution, increasing user population and industrialization coupled with the present limited knowledge of the true geological condition prevailing within the groundwater domain of the Niger Delta are the considerations that compelled this review study. The hydraulic properties of the region’s aquifers are discussed. The Niger Delta is characterized by a complex multilayered aquifer system hosted in the Benin Formation with the main body of fresh water, with increasing occurrence of intercalating clay units towards the coast. Lithological analysis indicates the prevalence of unconsolidated sand and sandy gravels in the aquiferous horizons, presenting them as pervious and prolific aquifers. Reported hydrochemical data gathered from wells drilled suggest that the quality of groundwater in the Niger Delta is considered generally very good and compares favorably with WHO standards for drinking water. However, relatively high iron/manganese and chloride values are localized in time and space. In the coastal areas however, seawater intrusion has been identified as one of the major influences on hydrochemistry of groundwater in the shallow unconfined aquifers. Regional groundwater flow direction is from north to south. Changes in groundwater flow directions which occur at some places generally serve localized discharge areas. The resultant flow path eventually joins and feeds the major regional north-south flow direction. The increasing pressure on groundwater, the need for urgent attention and the absence of strong institutions and regulations have made the management of groundwater resources in the region a difficult task. Therefore, future ground water resources development in the Niger Delta requires adequate observational data, investments in infrastructure and an integrated management approach to ensure optimal basin-wide benefits.展开更多
The NW-SE trending Santanghu basin is located in Xinjiang,NW China,between Tianshan Mountains and Altai Mountains.The tectonic evolution history of north Xinjiang has long been debated,especially the question when did...The NW-SE trending Santanghu basin is located in Xinjiang,NW China,between Tianshan Mountains and Altai Mountains.The tectonic evolution history of north Xinjiang has long been debated,especially the question when did that area began its intraplate rift evolution stage.This abstract discusses the features and possible origin of the hydrothermal exhalative dolostone of Lucaogou Formation in Santanghu basin,aiming to provide relevant information about this question.The target dolostone are characterized by extreme thin lamina of 0.3cm–1 cm thick.Dolomite,ankerite,potassium feldspar and analcite are dominant composition.Most dolomite is poor crystallized and is in anhedral or subhedral shapes.Ankerite is generally porphyritic,few is in irregular shapes.It has to be noted that the porphyritic ankerite commonly develop zonal textures characterized by rings with various Fe O content.Potassium feldspar and analcite（<50%）are commonly observed in dolostones.Thin sections show some analcite is tetragonal trisoctahedron with harbour–like corrosion rims.Besides,few fragments of carbonatite rocks are observed in Lucaogou Formation and they perform intermittent or scattered distribution in rock layers.Previous work done by our study team showsδ13C PDB values are 4.8‰;1.4‰,6.93‰on average.Theδ18 O PDB values are between-5‰;21.1‰,-10.94‰on average.Paleosalinity calculated byδ13C andδ18 O is between 128.35 and 136.81,134.42 on average.Sr content of dolostones in study area reaches to164×10-6;37×10-6（379.1×10-6 on average）,most dolostone in target area are between 0.70457;.706194, average at 0.705360.Considering either accompanying residual tuff or residual leucite is found via electron probe,this indicates the analcite may derive form analcime phonolite.Furthermore,fragments of carbonatite rocks proves mantle-derived magmatism exist.The rapid variation ofδ18 O indicates multiple interactions of hydrothermal fluids with lake water during Lucaogou sedimentary period.87Sr/86Sr values are much lower than that of crustal silica rocks while are more close to mantle derived rocks,which indicates diagenetic hydrothermal fluid is mantle-origin.It has been reported that dolostone does not intergrow with iron-rich dolostone in study area.According to the latest X diffraction results of cores,iron-rich dolostone distributes rather locally.Given that ankerite commonly develop zonal textures characterized by various Fe O content,we confirm it is due to multiple hydrothermal fluids activities in different hydrothermal vents.There should be abundant hydrothermal vents during Lucaogou period.Deep faults and its relevant fractures built plenty paths for mantle-origin hydrothermal fluids to run up.Different vents owned various fluid properties,so did relevant sedimentation products.Hence we inclined to believe Santanghu basin was at intraplate rift evolution stage,under regional extension condition in late Carboniferous.During early-mid Permian the basin was a starved,deep lacustrine intracontinental rift basin.Accordingly,in northern Xinjiang,ocean basin may close in late Carboniferous and started continental sedimentary development in early Permian.展开更多
The discovery of patches of a coal deposit and other associated sedimentary and volcanic rocks in Tabenken North West Cameroon has raised the question of the geology and palaeoenvironment of that area. This Region, wh...The discovery of patches of a coal deposit and other associated sedimentary and volcanic rocks in Tabenken North West Cameroon has raised the question of the geology and palaeoenvironment of that area. This Region, which is predominantly characterized by a granitoid basement of Precambrian age is in most parts overlain by Cenozoic basalts, hawaite, mugearite, trachyte and rhyolites. Volcanic outpours modified the geomorphology of the area into a series of hills and valleys. We investigated the geological setting in view of reconstituting the palaeodepositional environment of the Tabenken Coal Seam. Field studies show that the coal occurs in form of inclusions within sandstones, high grade coal bed, massive beds exposed by landslides and in alkali rhyolites. The results of Ultimate analyses of the coal indicate bituminous coal with 58% Carbon, sulfur content as low as 0.12% and ash content of 17%. The occurrence of a well stratified dark volcanic ash bed in the area is interpreted to be an interactive product of the explosive volcanic activity and weathering. Field examination of the area suggests that it was a micro-continental sedimentary palaeo-basin which was later infilled with Cenozoic volcanic outpours which probably modified the chemistry of the coal to meta-anthracites. The actual ages of the coal as well as the associated sedimentary units have not been established, meanwhile, the volcanism started some 31 ma ago.展开更多
The Yinyan porphyry tin deposit is a blind deposit associated with a small granite porphyry stock.The petrology and geochemistry of the Yinyan granite porphyry suggest that it is genetically of the transfor-mation typ...The Yinyan porphyry tin deposit is a blind deposit associated with a small granite porphyry stock.The petrology and geochemistry of the Yinyan granite porphyry suggest that it is genetically of the transfor-mation type,emplaced at the late stage of fractional crystallization within a high-level magma chamber.Ore-forming fluids are derived predominantly from the granitic magma and they interact with the wall rocks intensely when finding their way upwards through the granite porphyry.From the lower part of the porphyry upwards the following alteration zones can be distinguished(a)slightly altered granite porphyry (with weak potash feldspathization),(b)protolithionite-quartz greisenization zone,(c)to-paz-quartz greisenization zone,(d)senicite-quartz sericitization zone,and （e）silicification zone (quartz core at the surface).Tin mineralization is related to greisenization,especially to topaz-quartz greisenization.Rock and ore-forming temperatures and oxygen fugacities are estimated,respectively.There are significant differences in many aspects between the Yinyan porphyry tin deposit and volcan-ic-subvolcanic porphyry tin deposits.展开更多
基金supported by the National Natural Science Foundation of China(41872095,U1812402 and 42172082)the Research Startup Project(YJRC4201804)of Yunnan University to J.-X.Zhou.
文摘The giant Upper Yangtze Pb-Zn metallogenic province,also known as the Sichuan-Yunnan-Guizhou(SYG)Pb-Zn province hosting>500 carbonate-hosted epigenetic Pb-Zn deposits that contain>20 Mt Pb+Zn base metal reserves.The giant Maoping Pb-Zn deposit is the second largest deposit in this province and owns>5 Mt Pb+Zn metal reserves with ore grades of 12 wt.%-30 wt.%Pb+Zn.Such large tonnages and high grades make it among the top 100 similar mineral deposits in the world.The ore bodies are predominantly located within the strata of the Upper Devonian(Zaige Formation)and Lower(Baizuo Formation)-Upper(Weining Formation)Carboniferous.The principal ore minerals consist of galena(Gn),sphalerite(Sp),and pyrite(Py),while the primary gangue minerals include dolomite(Dol),calcite(Cal),and quartz(Qtz).Three mineralization stages of carbonate minerals have been identified:(1)pre-sulfide stage 1,(2)syn-sulfide stage 2,and(3)post-sulfide stage 3.Trace elements and C-O-Sr isotopes of three stages’carbonate minerals,together with S-Pb isotopes of sulfides,revealing that the metamorphic basement rocks played the role of the metal source during the early stage of Pb-Zn mineralization,whereas the metal contribution of the sedimentary wall rocks found to be more prominent during the late stage of Pb-Zn mineralization.In addition,the dissolution of marine carbonate rocks and CO_(2)degassing may have also played an important role in the formation of the Maoping deposit.Furthermore,syn-sulfide stage 2 calcite has a U-Pb age of 214±20 Ma obtained by LA-ICPMS in-situ analyses,suggesting that the hydrothermal mineralization occurred during the Triassic.Our study proposes a new coupled metallogenic model of fluid-structure-lithology assemblage and provides new insights about the formation and evolution of the Maoping deposit with significant implication for understanding and exploration of similar Pb-Zn deposits worldwide.
文摘A total of 393 potholes(368 fluvial and 25 marine potholes)were studied at seven different sites in both the fluvial and marine environments.Diverse bedrock properties and large-scale delivery of tools and grinders regulate the dynamic growth,truncation,and amalgamation of potholes.Therefore,the principal objectives of the study are(i)to examine the relationship between the growth of potholes and substrate lithological with structural characteristics(applying geospatial and Schmidt hammer for rock strength analysis)and(ii)to measure the morphology,and size of tools and grinders,processes of truncation and amalgamation in hydro-geomorphic environment using various indices and field techniques.The result showed that large potholes are stretched in the direction of lineament axes and roughly parallel to the river flow direction.Here,the steady growth of pothole depth-diameter is controlled by active bedrock structures,tools,or grinders,and monsoonal high-velocity bank full discharge.Consequently,the deepening and widening of potholes are relatively slow at Bindu,Deuli,and marine beach Neil Island due to fewer structures and little supply of tools or grinders.In small stretches,(Damodar,Subarnarekha,and Rarhu)canyons and gorge-like features(bedrock incision)are formed at Rajrappa,Bhakuyadi,and Guridih sites due to cyclic truncation and amalgamation.Truncation and amalgamation processes restrict the vertical depth threshold value of potholes within 3m,particularly at Rajrappa,Bhakuyadi,and Guridih sites.Scientific study of the pothole's dynamic growth is greatly necessary for the different environmental engineering and river hydraulic projects like excavation,dredging,and dam or barrage construction.Successively,it is essential to compute the cost of rock excavation or dredging,primarily for the mechanical strength of the bedrock river channel and its stability.
基金supported by the National Science and Technology Major Project(Grant nos.2016ZX05026,2016ZX05026–007–007)the National Natural Science Foundation of China(Grant nos.91528303,41502127)+1 种基金the Opening Foundation of State Key Laboratory of Continental Dynamics,Northwest University,the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2017JM4013)the Scientific Team Foundation of Department of Geology,Northwest University,Xi’an。
文摘Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area.The South China Sea(SCS)is a typical marginal sea that includes Paleo SCS and New SCS tectonic cycles.The latter includes continental marginal rifting,intercontinental oceanic expansion and oceanic shrinking,which controlled the evolution of basins,and the generation,migration and accumulation of hydrocarbons in the deepwater basins on the continental margin of the northern SCS.In the Paleogene,the basins rifted along the margin of the continent and were filled mainly with sediments in marine-continental transitional environments.In the Neogene–Quaternary,due to thermal subsidence,neritic-abyssal facies sediments from the passive continental margin of the SCS mainly filled the basins.The source rocks include mainly Oligocene coal-bearing deltaic and marine mudstones,which were heated by multiple events with high geothermal temperature and terrestrial heat flow,resulting in the generation of gas and oil.The faults,diapirs and sandstones controlled the migration of hydrocarbons that accumulated principally in a large canyon channel,a continental deepwater fan,and a shelf-margin delta.
基金supported by the National Key Research and Development Program of China(2022YFC2905001)the National Natural Science Foundation of China(42272093,42230813)+1 种基金China Scholarship Council projectthe Geological Survey project(DD20230054)
文摘Jiama,with more than 11 Mt of copper metal,is the largest porphyry-skarn copper system in the Gangdese metallogenic belt,Xizang,China,creating ideal conditions for deciphering the origin of porphyry ores in a collision setting.Despite massive studies of the geology,chronology,petrogenesis,and ore-related fluids and their sources in Jiama,there is a lack of systematic summaries and reviews of this system.In contrast to traditional porphyry copper systems in a subduction setting,recent studies and exploration suggest that the Jiama deposit includes porphyry-type Mo-Cu,skarn-type Cu polymetallic,vein-type Au and manto orebodies.This paper reviews the latest studies on the geology,chronology,petrogenesis,fluid inclusions,and isotopic geochemistry(hydrogen,oxygen,sulfur,and lead)of the Jiama deposit.Accordingly,a multi-center complex mineralization model was constructed,indicating that multi-phase intrusions from the same magma reservoir can form multiple hydrothermal centers.These centers are mutually independent and form various orebodies or are superimposed on each other and form thick,high-grade orebodies.Finally,a new comprehensive exploration model was established for the Jiama porphyry copper system.Both models established in this study help to refine the theories on continental-collision metallogeny and porphyry copper systems.
基金supported by Urmia UniversityIMIDRO(Iranian Mines and Mining Industries Development and Renovation Organization)
文摘The Mirge-Naqshineh gold district is situated at northwest of Iran with a NW-trending brittle- ductile shear zone. It is hosted by Precambrian meta-sedimentary and meta-volcanic units traversed by mineralized quartz veins. In terms of cross-cutting relationships and sulfide content three types of quartz veins are identified in the region. Among those, parallel to bedding quartz vein （type I） is the main host for gold mineralization. Gold is found in three different forms： 1） submicrometer-size inclusions of gold in arsenian pyrite, 2） as electrum and 3） in the crystal lattice of sulfides （pyrite, galena and chalcopyrite）. Six types of pyrite （Pyl-Py6） were identified in this ore reserve. Py3 coexists with arsenopyrite and contains the greatest As-Au concentrations. There is a negative correlation between the As and S contents in Py2 and Py3, implying the substitution of sulfur by arsenic. Pyrites and mineralized quartz veins were formed via metamorphic-hydrothermal fluid and reflect the gold-transportation as Au（HS）2 under reducing and acidic conditions. The gold precipitation mainly controlled by crystallization of arsenian pyrite during fluid/rock interactions and variation offO2. The volcanic host rock has played an important role in gold concentration, as Py3 in this rock contains inclusion of gold particles, but gold is within the lattice of pyrite in phyllite or other units.
基金Project 2003CB214603 supported by the Development Plan of the State Key Fundamental Research, China
文摘The new recently demonstrated reserves of oil and gas in the Ordos basin are found at the top of petroliferous basins in China. Gas pools discovered in recent years in the Permian system have become the main natural gas resource in the basin. Therefore, synthetic research on fluid inclusions should be done in order to ascertain the pool-forming stage, the maturity of organic matters and the properties of Paleo-fluids. The main types of fluid inclusions in the Permian system in the basin include brine inclusions, carbon dioxide inclusions and organic inclusions. Homogenization temperatures （HT） of brine inclusions can be divided into four intervals： 66-83 ℃, 86-108 ℃, 112-138 ℃ and 142-153℃. The fluid inclusions in the interval of 112-138 ℃ are much more than that of other intervals, indicating that the second stage of hydrocarbon migration associated with the third temperature interval is the most important stage of gas pool formations. The fluid inclusion has extensive applications in the study of gas geology, not only in ascertaining the formation stage of gas pools, but also in estimating the maturity of organic matter and restoring Paleo-fluids. The result of testing the HT of brine inclusions shows that there are two stages of gas pool formations in the Permian system occurring ＋150 Ma and ±100 Ma. The maturity of organic matter is moderate to high, a conclusion based on the color of fluid inclusions （radiated by fluorescence）. The high salinity of Paleo-fluids of the NaCI-H2O and CaCl2-H2O systems shows good preservation conditions of the Paleo-fluids. Two stages of reservoir filling, high maturity of organic matter and good preservation conditions are factors favorable for the formation and preservation of large-scale gas pools in the Permian system in the Ordos basin.
基金jointly supported by National Natural Science Foundation of China(Grant Nos.41421002,41272092,and 41030423)MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest University,China
文摘The Tongyu copper deposit,located in the western part of the North Qinling Orogen,China,is one of several volcanic-hosted massive sulphide(VHMS)deposits with industrial value and is also a typical example of mineralization related to the subduction and metallogenesis during the Caledonian orogeny.We conducted systematic lead-sulphur isotope geochemical analyses of the Tongyu deposit to understand the possible ore-forming material sources and tectonic settings.Twenty-six sulphide samples yielded clusteredδ^34SCDT values of 1.13‰-3.36‰,average 2.22‰,and show a tower-type distribution,implying that the sulphur of the Tongyu copper deposit mainly originated from a mantle source.The Pb isotope compositions of sulphides(^206Pb/^204Pb=17.59225-18.56354,average 18.32020;^207Pb/^204Pb=15.51770-15.69381,average 15.66217;^208Pb/^204Pb=37.99969-39.06953,average 38.52722)are close to the values of the volcanic host rocks(^206Pb/^204PbPb=18.10678-18.26293,average 18.21158;^207Pb/^204PbPb=15.63196-15.68188,average 15.65345;^208Pb/^204PbPb=38.43676-38.56360,average 38.49171),thus consistent with the Pb in ores and volcanic host rocks having been derived from a common source that was island-arc Pb related to oceanic crust subduction.The northward subduction of the Palaeo-Qinling oceanic crust triggered dehydration of the slab,which generated a large amount of high-oxygen-fugacity aqueous hydrothermal fluid.The fluid rose into the mantle wedge,activated and extracted metallogenic material and promoted partial melting of the mantle wedge.The magma and ore-forming fluid welled up and precipitated,finally forming the Tongyu VHMS copper deposit.
基金jointly funded by the National Key Research and Development Program of China (2022YFC2905301)the National Natural Science Foundation of China (42072114)+1 种基金geological survey projects (DD20230366, DD202211695)the scientific research projects supported by the Baotou Steel (Group) Co., Ltd. (HE2224, HE2228, and HE2313)。
文摘The Bayan Obo supergiant carbonatite-related rare-earth-element-niobium-iron(REE-Nb-Fe) endogenetic deposit(thereafter as the Bayan Obo deposit), located at 150 km north of Baotou City in the Inner Mongolia Autonomous Region, is the largest rare-earth element(REE) resource in the world. Tectonically,this deposit is situated on the northern margin of the North China Craton and adjacent to the Xing’anMongolian orogenic belt to the south. The main strata within the mining area include the Neoarchean Se’ertengshan Group and the Mesoproterozoic Bayan Obo Group. Generally, the rare earth, niobium, and iron mineralization within the deposit are intrinsically related to the dolomite carbonatites and the extensive alteration of the country rocks caused by the carbonatite magma intrusion. The alteration of country rocks can be categorized into three types: contact metasomatism(anti-skarn and skarn alteration), fenitization,and hornfelsic alternation. As indicated by previous studies and summarized in this review, the multielement mineralization at Bayan Obo is closely associated with the metasomatic replacement of siliceous country rocks by carbonatite magmatic-hydrothermal fluids. The metasomatic process is comparable to the conventional skarnification that formed due to the intrusion of intermediate-acid magmatic rocks into limestone strata. However, the migration pattern of Si O2, Ca O, and Mg O in this novel metasomatic process is opposite to the skarn alteration. Accordingly, this review delineates, for the first time, an antiskarn metallogenic model for the Bayan Obo deposit, revealing the enigmatic relationship between the carbonatite magmatic-hydrothermal processes and the related iron and rare earth mineralization.Moreover, this study also contributes to a better understanding of the REE-Nd-Fe metallogenetic processes and the related fluorite mineralization at the Bayan Obo deposit.
基金This study was funded by Jiangxi Provincial Natural Science Foundation(20202BABL211019)the National Science and Technology Major Project(2016ZX05026007)+2 种基金the National Major Fundamental Research and Development Project(2009CB219400)Open Fund Project of Key Laboratory of Sedimentary Mineralization and Sedimentary Mineral Resources in Shandong Province(DMSM 2019008)National Natural Science Foundation of China(41502081).
文摘North Carnarvon Basin is a gas province with minor oily sweet spots in deepwater area with water depth more than 500 m,which is one of the hot spots of global petroleum exploration for its series of giant hydrocarbon discoveries in recent years.However,the degree of oil and gas exploration in deepwater area is still low,and the conditions for oil and gas accumulation are not clear.Based on the current exploration situation and latest database of fields,applying multidisciplinary analysis of hydrocarbon geology,hydrocarbon accumulation elements and its exploration direction of North Carnarvon Basin in deepwater area are analyzed.The results show that there are three sets of main source rocks in deepwater area of North Carnarvon Basin,which are Triassic marine shale in Locker Formation and delta coal-bearing mudstone with thin carbonaceous mudstone in Mungaroo Formation,Lower–Middle Jurassic paralic carbargilite and coal measure strata in Athol Formation and Murat Formation,Cretaceous delta mudstone in Barrow Group and marine shale in Muderong Formation.Most source rock samples show gas-prone capability.The coarse sandstone of delta facies in Middle–Upper Triassic Mungaroo Formation is the most important reservoir in deepwater area,Lower Cretaceous Barrow Group deep-water gravity flow or underwater fan turbidite sandstone is the secondly main reservoir.Lower Cretaceous marine shale in Muderong Formation is most important regional caprock.Triassic mudstone in Mungaroo Formation is an important interlayer caprock in deepwater area.There are two main reservoir accumulation assemblages in deepwater area,one is Triassic structural-unconformity plane reservoir accumulation assemblage of Locker Formation to Mungaroo Formation,and the other is Lower–Middle Jurassic Athol Formation and Murat Formation–Lower Cretaceous stratigraphic lithology-structural reservoir accumulation assemblage of Barrow Group to Muderong Formation.There are three main control factors of hydrocarbon Accumulation:One is coupling of source and seal control hydrocarbon distribution area,the second is multi-stage large wave dominated deltas dominate accumulation zone,the third is direction of hydrocarbon migration and accumulation in hydrocarbon-rich generation depression was controlled by overpressure.The south of Exmouth platform in deepwater area is adjacent to hydrocarbon rich depression zone,reservoir assemblage is characterized by“near source rocks,excellent reservoir facies,high position and excellent caprocks”,which is the main battlefield of deepwater oil and gas exploration in North Carnarvon Basin at present.There are a lot of fault block traps in the northern structural belt of Exmouth platform,and the favorable sedimentary facies belt at the far end of delta plain in Mungaroo Formation is widely distributed,which is the next favorable exploration zone.The Lower Cretaceous,which is located at the concave edge uplift adjacent to the investigator depression and the Exmouth platform,also has a certain exploration prospect in northwest of deepwater area.
基金supported by Vietnam National Foundation for Science and Technology Development under grant number 105.01–2012.06supported by Ministry of Natural Resources and Environment of The Socialist Republic of Vietnam for Science and Technology Development,Project TNMT.03.50 to Tran My Dung+1 种基金National Key Basic Research and Development(973)Project of China(2015CB452600)China Geological Survey(1212011120343)
文摘The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits associated with granitic intrusion. The deposit consists of ore bodies in altered granite or along the contact zone between granite and Proterozoic meta-sedimentary rocks. The Cu-bearing intrusion is sub-alkaline I-type granite. It has a zircon U-Pb age of ~776 Ma, and has subduction-related geochemical signatures. Geochemical analysis reveals that the intrusion may be formed by melting of mafic lower crust in a subduction regime. Three stages of alteration and mineralization are identified in the Suoi Thau deposit, i.e., potassic alteration; silicification and Cu mineralization; and phyllic alteration. Two-phase aqueous fluid inclusions in quartz from silicification stage show wide ranges of homogenization temperatures （140-383℃） and salinities （4.18wt%- 19.13wt%）. The high temperature and high salinity natures of some inclusions are consistent with a magmatic derivation of the fluids, which is also supported by the H-O-S isotopes. Fluids in quartz have JD values of-41.9‰ to -68.8%. The fluids in isotopic equilibrium with quartz have j180 values ranging from 7.9‰ to 9.2%. These values are just plotted in the compositional field of magmatie- hydrothermal fluids in the ~Dwater versus jlSOwater diagram. Sulfide minerals have relatively uniform j34S values from 1.84%o to 3.57%0, which is supportive of a magmatic derivation of sulfur. The fluid inclusions with relatively low temperatures and salinities most probably represent variably cooled magmatic-hydrothermal fluids. The magmatic derivation of fluids and the close spatial relationship between Cu ore bodies and intrusion suggest that the Cu mineralization most likely had a genetic association with granite. The Suoi Thau deposit, together with other deposits in the region, may define a Neoproterozoic subduction-related ore-forming belt.
文摘Iran is a country that benefits from nice nature, diverse continent, areas full of unique geological phenomena. Thus, it is necessary to study these attractions for better recognition of them. In this regard, Hormoz Island with valuable geoheritage, biodiversity, cultural, historical and political diversity is very important. The accumulation of these attractions and its being located in Persian Gulf strategic area made it of considerable significance in national and international communities. Hormoz Island is a spherical salt dome which is located in Hormoz strait. This Island is composed of evaporites, igneous rocks and sedimentary rocks, and sediments mainly belong to Mishan and Aghajari formations and salt, gypsum and, to a lesser extent, limestone evaporites. In sedimentary formations of Hormoz, Aouthigenic minerals such as Pyrite, Dolomite, quartz, Anhydrite, gypsum and halite are frequently seen. Mineralization of volcanic leads to formation of high temperature minerals, such as oligiste, pyroxene, amphibole and low temperature and hydrothermal minerals such as Pyrite, quartz... in the tracks of igneous rocks. This unique geodiversity in rocks and mineral which made various colors in Hormoz Island made it a mineraogical reservoir. Beside considerable mineralogical attractions, there are other potentials like ochre mine, coral reefs, rock seashore, sea caves, salt caves, plant cover and wild life which have added to various tourism capabilities of this Island and made it a unique place in the world. This paper studies Hormoz Island in terms of geological features and geotourism potentials.
基金Acknowledgements The authors wish to thank Dr. K. Shibata of Niigata University, for isotopic analyses. We also thank Prof. Nakashima of Niigata University, for his valuable comments on the manuscript. We are deeply indebted to Prof. M.Bommari for his great help with sample analysis. We thank the Institute of Analytical Chemistry of Canada for major and trace-element analysis. Dr. A. Ahmadi of University of Sistan and Baluchestan, is also sincerely thanked for providing geological information on the study area. We also acknowledge Dr. SH. Varkouhi of Islamic Azad University, for reviewing and improving the manuscript.
基金jointly provided by the National Natural Science Foundation of China(Grant Nos.41421002,41730426,41272092,and 41030423)MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest UniversityNorthwest University Graduate Innovation and Creativity Fund(YZZ17190)
文摘The Liziyuan gold deposit,situated on the south side of the Shangdan suture zone,West Qinling Orogen,occurs in metamorphic volcanic rocks(greenschist facies)of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite.Orebodies in the Liziyuan gold field are controlled by the ductile-brittle shear zone,and by thrusting nappe faults related to the Indosinian orogeny.In detail,this paper analyzed the geological characteristics of the Liziyuan gold field,and the Pb isotopes of the Lziyuan host rocks,granitoids(Tianzishan monzogranite and Jiancaowan syenite porphyry),sulfides,and auriferous quartz veins by multiple-collector inductively coupled plasma mass spectrometry(MC-ICPMS).In addition,previous data on the sulfur,hydrogen,and oxygen isotopes were employed to discuss the possible sources of the ore-forming fluids and materials,and to further understand the tectonic setting of the Liziyuan gold deposit.The sulfides and their host rocks(Lziyuan Group),Tianzishan monzogranite and Jiancaowan syenite porphyry,and auriferous quartz veins have similar Pb isotopic compositions.Zartman’s plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves.In the△β-△γdiagram,which genetically classifies the lead isotopes,most of the data fall within the range of the subduction-zone lead mixed with upper crust and mantle.This indicates that a complex source of the ore lead formed in the orogenic environment.Theδ34S values of the sulfides range from 3.90 to 8.50‰(average6.80‰),with a pronounced mode at 5.00‰-8.00‰.These values are consistent with that of orogenic gold deposits worldwide,indicating that the sulfur sourced mainly from reduced metamorphic fluids.The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the oreforming fluids,with possible mixing of minor magmatic fluids,but the late stage was dominated by meteoric water.The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide.
文摘Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, erosion by ephemeral streams shortly after the eruption disrupted the lateral continuity of the 270 to 300 cm-thick pumice deposit. Co-evolution of the surface- and ground-water systems in a low-relief, low-slope landscape allowed diffuse groundwater discharge from the banks of the evolving stream system. Accumulation of organic material from groundwater dependent ecosystems at these sites of discharge allowed peat deposits to form on gently sloping erosion surfaces cut into the pumice deposit. Following early stream incision, fine-grained, silt-rich deposits accumulated in valleys and contributed permeability barriers to the lateral migration of water in the pumice aquifer. Fens discharge from the pumice aquifer through gently sloping surfaces patterned after the slope of the erosion surface cut into the pumice deposit and overlain by approximately 1 m of peat on the sloping surface and alluvium or iron-cemented pumice overlain by alluvium at the toe of the slope. The predominant source of groundwater is snowmelt which infiltrates the pumice deposit during the freshet. However, shallow groundwater flow also takes place along permeable pathways in bedrock units. Locally, low volume discharge takes place along faults. The snowmelt-dependent hydrologic system that supports the fens of the Walker Rim study area occurs at elevations primarily above 1585 m.
基金supported by Natural Science Foundation of China (Project No. 41630312)The National Nature Science Foundation of China (Project No. 41372208 and 40534019)The Open Found of the State Key Laboratory of Ore Deposit Geochemistry, CAS(Project No. 201304)
文摘1 Introduction The Weibei Uplift is located in the southwest of the North China Plate,where is the stable block(the Ordos Block)in the north and the active belt(the QinlingOrogenic Belt)in the south(Ren et al,2014,2015).And the belt is separated from the Weihe basin.The Weibei uplift has a uniform crystalline basement with the North
文摘Extensive thickly folded sedimentary sequences are exposed onshore of the Rio del Rey Basin contrary to previous reports of their rarity. Shales predominate, frequently intercalated by marlstones, sandstones, mudstones, limestones and marls and have been intruded in places by volcanic rocks of the Cameroon Volcanic Line (CVL). An integration of lithostratigraphic, paleontologic, granulometric and petrographic data generated from field and laboratory studies, permitted the identification of eleven (11) lithofacies which were subsequently grouped into three facies associations to facilitate the reconstruction of the paleo-depositional environment. Graphic logs constructed from the different outcrops studied revealed general coarsening upward sequences. Mega body fossils recovered from these sediments include severely altered, ferruginized fish and turtle-like heads, bivalve shells and moulds. Two bivalve taxa were identified: Exogyra ponderosa (Roemer) and members of theVenericardiinae sub-family. Textural and mineralogical details were obtained from granulometric and thin sections (microscopy). Interpretation of these data inferred an open relatively deeper marine, probably middle neritic to near shore transitional intertidal environments into which these sediments previously dated as Lower to Upper Cretaceous were deposited. Elements of a possible petroleum system: source and reservoir rocks, migratory pathways and trapping conditions, have been pointed out and thought to exist in space and time.
文摘This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered by the weak regulations, pollution, increasing user population and industrialization coupled with the present limited knowledge of the true geological condition prevailing within the groundwater domain of the Niger Delta are the considerations that compelled this review study. The hydraulic properties of the region’s aquifers are discussed. The Niger Delta is characterized by a complex multilayered aquifer system hosted in the Benin Formation with the main body of fresh water, with increasing occurrence of intercalating clay units towards the coast. Lithological analysis indicates the prevalence of unconsolidated sand and sandy gravels in the aquiferous horizons, presenting them as pervious and prolific aquifers. Reported hydrochemical data gathered from wells drilled suggest that the quality of groundwater in the Niger Delta is considered generally very good and compares favorably with WHO standards for drinking water. However, relatively high iron/manganese and chloride values are localized in time and space. In the coastal areas however, seawater intrusion has been identified as one of the major influences on hydrochemistry of groundwater in the shallow unconfined aquifers. Regional groundwater flow direction is from north to south. Changes in groundwater flow directions which occur at some places generally serve localized discharge areas. The resultant flow path eventually joins and feeds the major regional north-south flow direction. The increasing pressure on groundwater, the need for urgent attention and the absence of strong institutions and regulations have made the management of groundwater resources in the region a difficult task. Therefore, future ground water resources development in the Niger Delta requires adequate observational data, investments in infrastructure and an integrated management approach to ensure optimal basin-wide benefits.
文摘The NW-SE trending Santanghu basin is located in Xinjiang,NW China,between Tianshan Mountains and Altai Mountains.The tectonic evolution history of north Xinjiang has long been debated,especially the question when did that area began its intraplate rift evolution stage.This abstract discusses the features and possible origin of the hydrothermal exhalative dolostone of Lucaogou Formation in Santanghu basin,aiming to provide relevant information about this question.The target dolostone are characterized by extreme thin lamina of 0.3cm–1 cm thick.Dolomite,ankerite,potassium feldspar and analcite are dominant composition.Most dolomite is poor crystallized and is in anhedral or subhedral shapes.Ankerite is generally porphyritic,few is in irregular shapes.It has to be noted that the porphyritic ankerite commonly develop zonal textures characterized by rings with various Fe O content.Potassium feldspar and analcite（<50%）are commonly observed in dolostones.Thin sections show some analcite is tetragonal trisoctahedron with harbour–like corrosion rims.Besides,few fragments of carbonatite rocks are observed in Lucaogou Formation and they perform intermittent or scattered distribution in rock layers.Previous work done by our study team showsδ13C PDB values are 4.8‰;1.4‰,6.93‰on average.Theδ18 O PDB values are between-5‰;21.1‰,-10.94‰on average.Paleosalinity calculated byδ13C andδ18 O is between 128.35 and 136.81,134.42 on average.Sr content of dolostones in study area reaches to164×10-6;37×10-6（379.1×10-6 on average）,most dolostone in target area are between 0.70457;.706194, average at 0.705360.Considering either accompanying residual tuff or residual leucite is found via electron probe,this indicates the analcite may derive form analcime phonolite.Furthermore,fragments of carbonatite rocks proves mantle-derived magmatism exist.The rapid variation ofδ18 O indicates multiple interactions of hydrothermal fluids with lake water during Lucaogou sedimentary period.87Sr/86Sr values are much lower than that of crustal silica rocks while are more close to mantle derived rocks,which indicates diagenetic hydrothermal fluid is mantle-origin.It has been reported that dolostone does not intergrow with iron-rich dolostone in study area.According to the latest X diffraction results of cores,iron-rich dolostone distributes rather locally.Given that ankerite commonly develop zonal textures characterized by various Fe O content,we confirm it is due to multiple hydrothermal fluids activities in different hydrothermal vents.There should be abundant hydrothermal vents during Lucaogou period.Deep faults and its relevant fractures built plenty paths for mantle-origin hydrothermal fluids to run up.Different vents owned various fluid properties,so did relevant sedimentation products.Hence we inclined to believe Santanghu basin was at intraplate rift evolution stage,under regional extension condition in late Carboniferous.During early-mid Permian the basin was a starved,deep lacustrine intracontinental rift basin.Accordingly,in northern Xinjiang,ocean basin may close in late Carboniferous and started continental sedimentary development in early Permian.
文摘The discovery of patches of a coal deposit and other associated sedimentary and volcanic rocks in Tabenken North West Cameroon has raised the question of the geology and palaeoenvironment of that area. This Region, which is predominantly characterized by a granitoid basement of Precambrian age is in most parts overlain by Cenozoic basalts, hawaite, mugearite, trachyte and rhyolites. Volcanic outpours modified the geomorphology of the area into a series of hills and valleys. We investigated the geological setting in view of reconstituting the palaeodepositional environment of the Tabenken Coal Seam. Field studies show that the coal occurs in form of inclusions within sandstones, high grade coal bed, massive beds exposed by landslides and in alkali rhyolites. The results of Ultimate analyses of the coal indicate bituminous coal with 58% Carbon, sulfur content as low as 0.12% and ash content of 17%. The occurrence of a well stratified dark volcanic ash bed in the area is interpreted to be an interactive product of the explosive volcanic activity and weathering. Field examination of the area suggests that it was a micro-continental sedimentary palaeo-basin which was later infilled with Cenozoic volcanic outpours which probably modified the chemistry of the coal to meta-anthracites. The actual ages of the coal as well as the associated sedimentary units have not been established, meanwhile, the volcanism started some 31 ma ago.
文摘The Yinyan porphyry tin deposit is a blind deposit associated with a small granite porphyry stock.The petrology and geochemistry of the Yinyan granite porphyry suggest that it is genetically of the transfor-mation type,emplaced at the late stage of fractional crystallization within a high-level magma chamber.Ore-forming fluids are derived predominantly from the granitic magma and they interact with the wall rocks intensely when finding their way upwards through the granite porphyry.From the lower part of the porphyry upwards the following alteration zones can be distinguished(a)slightly altered granite porphyry (with weak potash feldspathization),(b)protolithionite-quartz greisenization zone,(c)to-paz-quartz greisenization zone,(d)senicite-quartz sericitization zone,and （e）silicification zone (quartz core at the surface).Tin mineralization is related to greisenization,especially to topaz-quartz greisenization.Rock and ore-forming temperatures and oxygen fugacities are estimated,respectively.There are significant differences in many aspects between the Yinyan porphyry tin deposit and volcan-ic-subvolcanic porphyry tin deposits.
