The Cretaceous is among the most unusual eras in the geological past. Geoscience communities have been having great concerns with geological phenomena within this period, for example carbonate platforms and black shal...The Cretaceous is among the most unusual eras in the geological past. Geoscience communities have been having great concerns with geological phenomena within this period, for example carbonate platforms and black shales in the Early and Middle Cretaceous respectively, during the last decades. But few people have paid any attention to the set of pelagic redbeds lying on the black shales, not to mention the applications to paleoclimatology and paleoceanography. It is shown by the sedimentary records of redbeds, that they were deposited around the CCD, with both a higher content of iron and much lower concentrations of organic carbon, which implies conditions with a relatively high content of oxygen. Such redbeds occurred in the global oceans, mainly in the Tethyan realm, with different durations of deposition and a climax from the late Santonian to early Campanian. Global cooling and dramatic changes in ocean currents might help to increase the oxygen flux between the atmosphere and ocean, after the large scale organic carbon burial during the Middle Cretaceous, and therefore lead to the oxygenation of deep ocean and so the occurrence of late Cretaceous oceanic redbeds.展开更多
Eocene Fenghuoshan Group and lower Oligocene Yaxicuo Group are represented by mainly fluvial, lacustrine and fan\|deltaic redbeds cropping out in Hoh Xil basin, the largest redbed basin in northern Tibet plateau. Lith...Eocene Fenghuoshan Group and lower Oligocene Yaxicuo Group are represented by mainly fluvial, lacustrine and fan\|deltaic redbeds cropping out in Hoh Xil basin, the largest redbed basin in northern Tibet plateau. Lithic sandstone, lithic quartzose sandstone, conglomerate, as well as siltstone, consist of the major rock composition of the redbeds. The petrography of sandstone and conglomerate reveals the relationship between regional tectonic uplift events and the provenance of lower Tertiary redbeds.The outcrop rock data show that the detritus were derived from sedimentary rocks, volcanic rocks, and metamorphic rocks. Phyllite and quartzite rock fragments are most common in the metamorphic rock fragments .The sedimentary rock fragments are composed of chert, limestone, siltstone, and mudstone fragments. But volcanic rock fragments are minor and occasionally occur. In Hantaishan area, the northwestern part of Hoh Xil basin, clastic composition of sandstones and conglomerates testify to mainly southward and northeastward provenances. The metamorphic rock fragments, which are more common than volcanic and sedimentary rock fragments, can be directly correlated with metamorphic rock of Triassic metasedimentary Bayankara Group around the basin. In Fenghuoshan area, the southwestern part of the basin, there are less metamorphic rock fragment composition and more limestone fragments than in Hantaishan area.The limestone fragments were obviously derived from Carboniferous—Permian or Jurassic limestone beds. These limestone strata can not be found in the Bayankara block mass at which Hoh Xil basin locates, thus it is deduced that the limestone detritus were derived from the south, that is, Qiangtang blockmass.展开更多
We focus on early Cenozoic uplift, erosion and growth of northern Tibet plateau by reconstructing paleo\|drainage pattern in the Hoh Xil basin. Stratigraphical infilling sequences and lithic type orogenic basins are d...We focus on early Cenozoic uplift, erosion and growth of northern Tibet plateau by reconstructing paleo\|drainage pattern in the Hoh Xil basin. Stratigraphical infilling sequences and lithic type orogenic basins are determined largely by contemporaneous tectonic activity. It is therefore reasonable to infer that paleoflow variability record give useful information about regional tectonic events. We now report paleocurrent data from outcrop measurement of 4 expedition profiles across the basin during 1997—1998.The west\|east trending Hoh Xil basin is the largest redbeds basin in northern Tibet plateau. It is 400km in axial length and has maximum width of 200km, which extends along Jin zone, separated the Qiangtang from the Bayankara block. It accommodates more than 5000m of terrestrial sediments during the Eocene to Oligocene dated by preliminary magnetostratigraphy and minor fossils.Detailed sedimentological observation and lithic facies associations analysis of the Eocene Fenghuoshan Group show to have evolved vertically from alluvial fan system in the lowest part, into stacked megasequences of coarsening\|upward fan\|delta system in the middle and upper part. The braided fluvial conglomeratic deposits occur at intervals along the basin margin and grade basin ward interbedded sandstone and mudstone. The Oligocene Yaxicuo Group is locally present and forms as laterally elongate sub\|basins, which is of a maximum thickness of 2000m, as seen in the Wudaoliang and the Hantaishan area. Alluvial fan associations in this sub\|basin in the proximal part adjacent to the southern faulted border and prograded northward to floodplain in distal part.展开更多
Underground prospecting within the L ubin- Sieroszowice mining area which took place during last5 years,led to a discovery of a new type of Au,Pt and Pd mineralisation located 0 - 0 .5 m below the copper- silver orebo...Underground prospecting within the L ubin- Sieroszowice mining area which took place during last5 years,led to a discovery of a new type of Au,Pt and Pd mineralisation located 0 - 0 .5 m below the copper- silver orebody in the south- western part of the Polish Permian Basin.The gold- bearing zone lies mainly in the Weissliegendessandstone (L ower Permian) , butlocally transgresses the stratigraphic sequence into the overlying kupferschieferand Wer- ra limestone(Zechstein) .Gold deposit lies in a secondary red- coloured variety of the above mentioned sedimentary strata.The oxidation in the underlying sandstone is reflected by red spots and dots containing fine grains of hematite dispersed in a carbonate- clay matrix.The secondary oxidation is peneconcordant in relation to the reducing facies which contains cop- per sulphides and to the Rote Faule,thatis early diagenetic.Between redbeds(gold bearing zone) and black,reduced sediments (Kupferschiefer) ,a transition zone has been recognized. This transition zone is characterized by the low grade of copper mineralisation.Thickness of the gold depositvaries from few centimetresto1.5 metres with an average of about0 .2 5 me- tres.The highestthickness of Au- depositis observed in placeswhere oxide fronttransgress- es the copper- silver deposit.Gold content ranges from 0 .5 up to 10 6 ppm with an average grade of(0 .717- 3.491)× 10 -6depending on the counting block.Gold- bearing horizon is peneconcordantand is characterized by the presence of high fineness native gold,electrum, hematite,and minor pyrite,chalcopyrite,digenite,chalcocite,covellite,rammelsbergite, clausthalite and展开更多
Deterioration of the physical properties of redbeds is one of the leading causes of geological disasters,engineering problems,and ecological damage.Fabric changes are internal factors leading to the deterioration of p...Deterioration of the physical properties of redbeds is one of the leading causes of geological disasters,engineering problems,and ecological damage.Fabric changes are internal factors leading to the deterioration of physical properties.Existing research on fabric changes in redbeds is qualitative and fuzzy,and their impact on the decline of physical properties needs to be revealed urgently,making the efficient control of redbeds disasters challenging.Therefore,this study focuses on 22 types of redbeds samples and divides them into five classes based on their fabric(composition and structure).Physical property degradation experiments were conducted on different classifications of redbeds during water–rock interaction,and the impact of fabric changes on the degradation of physical properties was analyzed.The results indicate that a linear correlation exists between the internal changes in composition,structure,and physical properties under the action of static water.Moreover,the trend of changes between composition and structure,composition–physical properties,and structure–physical properties shows an exponential regression relationship.Based on this,an action mechanism between compositions such as redbeds,catastrophic minerals,elements,and oxides,as well as the void structure,was proposed,revealing the multifield degradation mechanism of the chemical reactions of the compositions,physical response of the structure,and mechanical reaction of the rock block under the influence of the fabric.The research results can provide a foundation for theoretical research and engineering practice of disaster modes,disaster mechanisms,and prevention and control principles of redbeds disasters.展开更多
The Gan-Hang Belt in Southeast China is characterized by several igneous and siliciclastic basins associated with crustal extension during Late Mesozoic. The sedimentary evolution of the red basins is still poorly und...The Gan-Hang Belt in Southeast China is characterized by several igneous and siliciclastic basins associated with crustal extension during Late Mesozoic. The sedimentary evolution of the red basins is still poorly understood. In this study, sedimentary fades analysis and pebble counting were performed on outcrop sections of the Late Cretaceous Guifeng Group in the Yongfeng-Chongren Basin in central Jiangxi Province. Thirty-five conglomerate outcrops were chosen to measure pebble lithology, size, roundness, weathering degree and preferred orientation. Results show that gravels are mostly fine to coarse pebbles and comprise dominantly quartzites, metamorphic rocks, granitoids and sandstones. Rose diagrams based on imbricated pebbles indicate variable paleocurrent directions. Combining with typical sedimentary structures and vertical successions, we suggest that the Guifeng Group were deposited in alluvial fan, river and playa lake depositional systems. The proposed depositional model indicates that the Hekou Formation represents the start-up stage of the faulted basin, accompanied by sedimentation in alluvial fan and braided river environments. Then this basin turned into a stable expansion stage during the deposition of the Tangbian Formation. Except for minor coarse sediments at the basin margin, the other area is covered with fine-grained sediments of lake and river environments. The Lianhe Formation, however, is once again featured by conglomerates, suggesting a probable tectonic event. Therefore, the study region possibly suffered two tectonic events represented by the conglomerates of the Hekou and Lianhe formations in the context of the crustal extension in Southeast China.展开更多
基金The research is jointly supported by the Key Project of the National Natural Science Foundation of China(No.40332020)Prophase Special Research of Vital Projects in the Basic Research of the Ministry of Science and Technology of China(No.2001CCA01 800)International Geological Correlation Program(IGCP463/494).
文摘The Cretaceous is among the most unusual eras in the geological past. Geoscience communities have been having great concerns with geological phenomena within this period, for example carbonate platforms and black shales in the Early and Middle Cretaceous respectively, during the last decades. But few people have paid any attention to the set of pelagic redbeds lying on the black shales, not to mention the applications to paleoclimatology and paleoceanography. It is shown by the sedimentary records of redbeds, that they were deposited around the CCD, with both a higher content of iron and much lower concentrations of organic carbon, which implies conditions with a relatively high content of oxygen. Such redbeds occurred in the global oceans, mainly in the Tethyan realm, with different durations of deposition and a climax from the late Santonian to early Campanian. Global cooling and dramatic changes in ocean currents might help to increase the oxygen flux between the atmosphere and ocean, after the large scale organic carbon burial during the Middle Cretaceous, and therefore lead to the oxygenation of deep ocean and so the occurrence of late Cretaceous oceanic redbeds.
文摘Eocene Fenghuoshan Group and lower Oligocene Yaxicuo Group are represented by mainly fluvial, lacustrine and fan\|deltaic redbeds cropping out in Hoh Xil basin, the largest redbed basin in northern Tibet plateau. Lithic sandstone, lithic quartzose sandstone, conglomerate, as well as siltstone, consist of the major rock composition of the redbeds. The petrography of sandstone and conglomerate reveals the relationship between regional tectonic uplift events and the provenance of lower Tertiary redbeds.The outcrop rock data show that the detritus were derived from sedimentary rocks, volcanic rocks, and metamorphic rocks. Phyllite and quartzite rock fragments are most common in the metamorphic rock fragments .The sedimentary rock fragments are composed of chert, limestone, siltstone, and mudstone fragments. But volcanic rock fragments are minor and occasionally occur. In Hantaishan area, the northwestern part of Hoh Xil basin, clastic composition of sandstones and conglomerates testify to mainly southward and northeastward provenances. The metamorphic rock fragments, which are more common than volcanic and sedimentary rock fragments, can be directly correlated with metamorphic rock of Triassic metasedimentary Bayankara Group around the basin. In Fenghuoshan area, the southwestern part of the basin, there are less metamorphic rock fragment composition and more limestone fragments than in Hantaishan area.The limestone fragments were obviously derived from Carboniferous—Permian or Jurassic limestone beds. These limestone strata can not be found in the Bayankara block mass at which Hoh Xil basin locates, thus it is deduced that the limestone detritus were derived from the south, that is, Qiangtang blockmass.
文摘We focus on early Cenozoic uplift, erosion and growth of northern Tibet plateau by reconstructing paleo\|drainage pattern in the Hoh Xil basin. Stratigraphical infilling sequences and lithic type orogenic basins are determined largely by contemporaneous tectonic activity. It is therefore reasonable to infer that paleoflow variability record give useful information about regional tectonic events. We now report paleocurrent data from outcrop measurement of 4 expedition profiles across the basin during 1997—1998.The west\|east trending Hoh Xil basin is the largest redbeds basin in northern Tibet plateau. It is 400km in axial length and has maximum width of 200km, which extends along Jin zone, separated the Qiangtang from the Bayankara block. It accommodates more than 5000m of terrestrial sediments during the Eocene to Oligocene dated by preliminary magnetostratigraphy and minor fossils.Detailed sedimentological observation and lithic facies associations analysis of the Eocene Fenghuoshan Group show to have evolved vertically from alluvial fan system in the lowest part, into stacked megasequences of coarsening\|upward fan\|delta system in the middle and upper part. The braided fluvial conglomeratic deposits occur at intervals along the basin margin and grade basin ward interbedded sandstone and mudstone. The Oligocene Yaxicuo Group is locally present and forms as laterally elongate sub\|basins, which is of a maximum thickness of 2000m, as seen in the Wudaoliang and the Hantaishan area. Alluvial fan associations in this sub\|basin in the proximal part adjacent to the southern faulted border and prograded northward to floodplain in distal part.
文摘Underground prospecting within the L ubin- Sieroszowice mining area which took place during last5 years,led to a discovery of a new type of Au,Pt and Pd mineralisation located 0 - 0 .5 m below the copper- silver orebody in the south- western part of the Polish Permian Basin.The gold- bearing zone lies mainly in the Weissliegendessandstone (L ower Permian) , butlocally transgresses the stratigraphic sequence into the overlying kupferschieferand Wer- ra limestone(Zechstein) .Gold deposit lies in a secondary red- coloured variety of the above mentioned sedimentary strata.The oxidation in the underlying sandstone is reflected by red spots and dots containing fine grains of hematite dispersed in a carbonate- clay matrix.The secondary oxidation is peneconcordant in relation to the reducing facies which contains cop- per sulphides and to the Rote Faule,thatis early diagenetic.Between redbeds(gold bearing zone) and black,reduced sediments (Kupferschiefer) ,a transition zone has been recognized. This transition zone is characterized by the low grade of copper mineralisation.Thickness of the gold depositvaries from few centimetresto1.5 metres with an average of about0 .2 5 me- tres.The highestthickness of Au- depositis observed in placeswhere oxide fronttransgress- es the copper- silver deposit.Gold content ranges from 0 .5 up to 10 6 ppm with an average grade of(0 .717- 3.491)× 10 -6depending on the counting block.Gold- bearing horizon is peneconcordantand is characterized by the presence of high fineness native gold,electrum, hematite,and minor pyrite,chalcopyrite,digenite,chalcocite,covellite,rammelsbergite, clausthalite and
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Numbers:42293354,42277131,42293351,42293355 and 42293350)。
文摘Deterioration of the physical properties of redbeds is one of the leading causes of geological disasters,engineering problems,and ecological damage.Fabric changes are internal factors leading to the deterioration of physical properties.Existing research on fabric changes in redbeds is qualitative and fuzzy,and their impact on the decline of physical properties needs to be revealed urgently,making the efficient control of redbeds disasters challenging.Therefore,this study focuses on 22 types of redbeds samples and divides them into five classes based on their fabric(composition and structure).Physical property degradation experiments were conducted on different classifications of redbeds during water–rock interaction,and the impact of fabric changes on the degradation of physical properties was analyzed.The results indicate that a linear correlation exists between the internal changes in composition,structure,and physical properties under the action of static water.Moreover,the trend of changes between composition and structure,composition–physical properties,and structure–physical properties shows an exponential regression relationship.Based on this,an action mechanism between compositions such as redbeds,catastrophic minerals,elements,and oxides,as well as the void structure,was proposed,revealing the multifield degradation mechanism of the chemical reactions of the compositions,physical response of the structure,and mechanical reaction of the rock block under the influence of the fabric.The research results can provide a foundation for theoretical research and engineering practice of disaster modes,disaster mechanisms,and prevention and control principles of redbeds disasters.
基金supported by China Geological Survey projects (Grant Nos.1212011120836,1212011220248)China Scholarship Council (Grant No.201308360142)+2 种基金Gan-Po Excellent Talents 555 Project of Jiangxi Province (GCZ 2012-1)Research Foundation of Jiangxi Education Department (Grant No.GJJ13438)the open fund of Fundamental Science on Radioactive Geology and Exploration Technology Laboratory (Grant No.RGET1304)
文摘The Gan-Hang Belt in Southeast China is characterized by several igneous and siliciclastic basins associated with crustal extension during Late Mesozoic. The sedimentary evolution of the red basins is still poorly understood. In this study, sedimentary fades analysis and pebble counting were performed on outcrop sections of the Late Cretaceous Guifeng Group in the Yongfeng-Chongren Basin in central Jiangxi Province. Thirty-five conglomerate outcrops were chosen to measure pebble lithology, size, roundness, weathering degree and preferred orientation. Results show that gravels are mostly fine to coarse pebbles and comprise dominantly quartzites, metamorphic rocks, granitoids and sandstones. Rose diagrams based on imbricated pebbles indicate variable paleocurrent directions. Combining with typical sedimentary structures and vertical successions, we suggest that the Guifeng Group were deposited in alluvial fan, river and playa lake depositional systems. The proposed depositional model indicates that the Hekou Formation represents the start-up stage of the faulted basin, accompanied by sedimentation in alluvial fan and braided river environments. Then this basin turned into a stable expansion stage during the deposition of the Tangbian Formation. Except for minor coarse sediments at the basin margin, the other area is covered with fine-grained sediments of lake and river environments. The Lianhe Formation, however, is once again featured by conglomerates, suggesting a probable tectonic event. Therefore, the study region possibly suffered two tectonic events represented by the conglomerates of the Hekou and Lianhe formations in the context of the crustal extension in Southeast China.
