The Triassic granitoids and associated diorites in the Qinling orogenic belt reveal critical evidence of crust-mantle interaction during the terminal collision between the North China and Yangtze Blocks.This study pre...The Triassic granitoids and associated diorites in the Qinling orogenic belt reveal critical evidence of crust-mantle interaction during the terminal collision between the North China and Yangtze Blocks.This study presents new constraints from zircon U-Pb age,Lu-Hf isotopes,and amphibole-plagioclase-apatite geochemistry for the Maoerliang diorite in the Foping area.Zircon U-Pb dating yields a crystallization age of 212±2.8 Ma,withεHf(t)values ranging from−8.6 to+3.0 and corresponding twostage Hf model ages(T_(DM2))of 886-1479 Ma,indicative of derivation from an evolved lithospheric mantle source.Petrogenetic indicators reveal a mantle affinity:amphiboles exhibit high MgO(9.8-11.2 wt%)and elevated Nb/Ta ratios(14.3-18.1),while apatites display F-rich(2.1-2.8 wt%)and Cl-poor(0.08-0.15 wt%)characteristics.Thermobarometric calculations based on amphibole chemistry constrain crystallization conditions of 805-866℃and 211-383 MPa,corresponding to mid-crustal emplacement depths(8-14 km).Both amphibole and zircon indicate elevated oxygen fugacity(ΔNNO=−4.08 to−3.71;ΔFMQ=−1.14 to+3.96)and hydrous magma conditions(H_(2)O=4.22-4.94 wt%).Late-stage plagioclase crystallization(An21-26.5)reflects prolonged fractional crystallization in a hydrous dioritic magma.These diagnostic features-mantle-derived signatures,high f O_(2),and hydrous nature-exhibit remarkable convergence with gold-mineralized granites in the East Qinling.Our findings suggest that Triassic dioritic magmatism may have played an underappreciated role in facilitating gold enrichment processes within the South Qinling metallogenic belt.展开更多
High-Mg andesite/diorite(HMA)is useful for identifying subduction-related processes in orogenic belts,including the identification of ophiolites formed in suprasubduction zone(SSZ)environments.The E'rentaolegai hi...High-Mg andesite/diorite(HMA)is useful for identifying subduction-related processes in orogenic belts,including the identification of ophiolites formed in suprasubduction zone(SSZ)environments.The E'rentaolegai high-Mg diorite from the Diyanmiao ophiolite in central Inner Mongolia,North China,has been investigated revealing low-K tholeiitic-calc-alkaline characteristics and have SiO_(2)contents of 53.44-54.92 wt%,MgO contents of 8.44-9.54 wt%,and Mg~#of 54.35-57.60,with variable Fe_(2)O_(3)(7.51-8.61 wt%),Al_(2)O_(3)(11.95-15.09 wt%),and Na_(2)O(3.42-3.94 wt%)contents,low K_(2)O(0.34-0.97 wt%),TiO_(2)(0.35-0.67 wt%),and P2O5(0.12-0.15 wt%)contents,and high Ni(43-193 ppm)and Cr(189-556 ppm)contents.Samples collected have low total rare earth element(REE)contents(30.58-77.80 ppm),with flat or slightly right-dipping REE patterns(La_(N)/Yb_(N)=2.19-3.11)and a lack of pronounced Eu anomalies.The samples are also enriched in large-ion lithophile elements(LILEs,e.g.,K,Rb,Ba,U,and Sr)and depleted in high field strength elements(e.g.,Ta,Nb,Ti,and P).The E'rentaolegai high-Mg diorite has characteristics typical of HMA,and are similar to those of sanukites from the Setouchi Arc in SW Japan.They also display high positiveε_(Nd)(t)values(+6.32 to+7.80),comparable to the values of their host rocks.Petrogenetic analyses suggest that the E'rentaolegai HMA was probably formed by the interaction of partial melts and aqueous fluids from subducted sediments with mantle peridotite.Zircon U-Pb dating reveals that the high-Mg diorite crystallized at 313.6±2.4 Ma,i.e.,late Carboniferous.Combining our data with the temporal and spatial distribution of the Diyanmiao SSZ-type ophiolite,we propose that the eastern Paleo-Asian Ocean had not closed by the late Carboniferous,but intra-oceanic subduction was ongoing.A new model of the initiation of subduction in the eastern PAO during the late Paleozoic.展开更多
The high-Mg diorites, widely occurring in western Shandong, have important implications in the study of the relationship between the Mesozoic magmatism and the nature of the lithosphere and its thinning period in the ...The high-Mg diorites, widely occurring in western Shandong, have important implications in the study of the relationship between the Mesozoic magmatism and the nature of the lithosphere and its thinning period in the eastern North China craton （NCC）. The Tietonggou and Jinling intrusions are typically representatives. LA-ICP-MS zircon U-Pb dating, major and trace element and Sr-Nd isotopic compositions of the Mesozoic intrusive rocks from western Shandong, eastern China, were analyzed. The weighted mean 106^pb/ 238^U ages from LA-ICP-MS zircon U-Pb dating results for early norite-diorite, late pyroxene-diorite from the Tietonggou intrusion and biotite-diorite from the Jinling intrusion are （131.4±4.9） Ma（n=15）, （134. 5±2.3） Ma（n=13）, and （132.8±4. 2） Ma（n=12）, respectively, implying that they were formed in the Early Cretaceous. The weighted mean 207^pb/ 204^Pb ages for round zircons from late pyroxene-diorite in the Tietonggou intrusion is （ 2 513 ± 54） Ma（ n= 8）, suggesting that the basement of the North China craton should exist in the research area. The high-Mg diorites are characterized by enrichment in MgO, Na20, and light rare earth elements （LREE）, and they are poor in heavy rare earth elements （HREE） and high field strength elements （HFSE）, being similar to adakite. The existence of the mantle peridotite xenoliths with a high-Mg feature for these intrusive rocks implies that their primary magma should be derived from the upper mantle. However, Sr-Nd isotopic composi- tions （Is： 0.704 75--0.707 15;ENd （130 Ma） values： --3.95 to -- 13.30）, depletion in HFSE, and the occurrence of Archean inherited zircons suggest that crustal materials could be involved in the derivation of the primary magma. The compositional difference between the diorites from the Tietonggou and Jinling intrusions could be attributed to those of magma sources and degrees of partial melting. The Early Cretaceous high-Mg diorites are considered to have been formed by the mixed melting of the delaminated lithosphere （lithospheric mantle ＋ crust） and asthenosphere, based on their geochemistry, the mantlederived xenoliths, and the Early Mesozoic lithospheric evolutionary history of the eastern North China craton.展开更多
Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intru-sion is mainly composed...Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intru-sion is mainly composed of a suite of gabbro-diorite. Zircons from the intrusion display eu-hedral-subhedral in shape and have high Th/U ratios (1.23―2.87), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating results for two samples indicate that they were formed in the Early Cre-taceous, yielding weighted mean 206Pb/238U ages of 129±1Ma and 134±2Ma, respectively. Except for early cumulate such as sample QT-19, their SiO2 and MgO contents range from 50.12% to 56.37% and from 3.52% to 6.37%, respectively. Moreover, the gabbro-diorites are characterized by high Mg# (0.54―0.63), enrichment in Na (Na2O/K2O ratios more than 1), Cr (73×10-6―217×10-6) and Ni (34×10-6―241×10-6), and intensive enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Their initial 87Sr/86Sr ratios and ε Nd(t) values range from 0.70962 to 0.71081 and from-16.60 to-13.04, respectively. Taken together with the Early Creta-ceous high-Mg diorites and the mantle xenoliths from the Tietonggou and Jinling as well as basalts from the Fangcheng and Feixian, it is suggested that the primary magma for the Shangyu gab-bro-diorites should be derived from the enriched lithospheric mantle intensively modified by conti-nental crust. The Sr-Nd-Pb isotopic compositions for the Early Cretaceous high-Mg diorites in western Shandong display a trend of spatial variations, i.e., initial 87Sr/86Sr, 207Pb/204Pb and 208Pb/204Pb ratios de-creasing and ε Nd(t) values increasing from southeast to northwest in western Shandong, which is con-sistent with the tectonic model that the Yangtze Craton subducted beneath the North China Craton oriented in north-west direction in the Early Mesozoic.展开更多
Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic ma...Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic massif to understand its petrogenesis and source.The clinopyroxene composition(high Mg#,Cr-content,sum of REE and Ti/Eu ratio;depletion in HREE;negative Eu-anomaly)indicates that it formed from a reduced melt derived from a mantle source metasomatized by fluids/melts having crustal affinity.Melt compositions in equilibrium with clinopyroxene and amphibole were calculated using solid/liquid partition coefficients.The high Nb/Y and Zr/Y ratio values of a liquid simulated from clinopyroxene,which appears to have very similar characteristics to sanukitoid melts,indicate a low degree of melting of the mantle source.Melt simulated from amphibole is more evolved and more felsic(dacitic).It displays a geochemical“amphibole fractionation”signature,indicating the peritectic transformation of clinopyroxene to amphibole in the lower crust.Rock textures and major element mineral compositions suggest that further amphibole was precipitated directly from the melt in the middle crust.The results show that the Chelyabinsk highMg diorite was probably formed as a cumulate from sanukitoid-like melt during its ascent and cooling below dacitic liquidus inside the amphibole stability field.展开更多
Numerous Indosinian igneous rocks in the North Qaidam(NQ)provide crucial insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents a comprehensive study of the petrography,mineralogy,geochemis...Numerous Indosinian igneous rocks in the North Qaidam(NQ)provide crucial insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents a comprehensive study of the petrography,mineralogy,geochemistry,zircon U-Pb geochronology,and Hf isotope composition of dioritic rocks from the eastern NQ.Zircon U-Pb dating results indicate that the dioritic rocks were formed during the Middle Triassic(244-240 Ma).The rocks exhibit high-K calc-alkaline characteristics with variable SiO_(2)(55.25-65.39 wt%)and elevated K_(2)O+Na_(2)O(4.81-6.94 wt%)contents.They show enrichment in LILEs(Rb,Ba,K)and depletion in HFSEs(Nb,Ta,Ti),with slight negative Eu anomalies(Eu/Eu*=0.89-0.97).Zirconε_(Hf)(t)values(−20.93 to+5.60)and T_(DM2)ages(0.85-1.72 Ga)suggest mixed sources.Petrographic and mineralogical analysis reveals that the plagioclase phenocrysts exhibit disequilibrium textures(including reverse zoning),primarily composed of andesine and labradorite,with a small amount of oligoclase.The clinopyroxenes are all augites and have high crystallization temperatures(1111-1151℃).These features,particularly the reverse zoning of plagioclase,support a petrogenetic model involving mantle-derived magma underplating that induced melting of ancient lower crust,followed by mixing of underplated basaltic magma with crust-derived felsic magma.Our results indicate formation in a back-arc extensional setting during subduction of the Zongwulong Paleo-Tethys Ocean.展开更多
To investigate the Early Cretaceous magmatic activity and tectonic evolution in the Xiaoqinggou mining area of Jilin Province,the authors conducted petrological,geochemical,and isotopic analyses of diorite rocks.The f...To investigate the Early Cretaceous magmatic activity and tectonic evolution in the Xiaoqinggou mining area of Jilin Province,the authors conducted petrological,geochemical,and isotopic analyses of diorite rocks.The findings show that the zircons exhibit distinct magmatic growth zoning,confirming their magmatic origin.LA–ICP–MS zircon U–Pb dating yielded an age of 128.7±2.2 Ma,corresponding to Early Cretaceous.Geochemical data reveal that the diorite rocks are high and potassium but low in sodium,classifying them within the peraluminous,high-potassium calc-alkaline series.They are enriched in large ion lithophile elements(e.g.,K,Ba and Rb)and depleted in high field strength elements(e.g.,Nb,Ta and Ti).TheδEu values range from 1.07 to 1.14,indicating weakly positive Eu anomalies.Regional comparisons and integrated studies suggest that the Xiaoqinggou diorite rocks formed in a volcanic island arc setting,associated with the westward subduction of the Paleo-Pacific plate beneath the Eurasian continent in an extensional tectonic environment.This study provides a theoretical basis for further exploration of the Xiaoqinggou deposit.展开更多
The Dharwar Craton in India,as one of the oldest cratons in the world,preserves key information of early continental crust evolution.However,a~3.0 Ga tectonothermal event was previously recognized only in the Western ...The Dharwar Craton in India,as one of the oldest cratons in the world,preserves key information of early continental crust evolution.However,a~3.0 Ga tectonothermal event was previously recognized only in the Western Dharwar Craton,and the coeval tectono-thermal event has been rarely reported in the Central Dharwar Block.In this study,zircon U-Pb dating of the gabbroic diorite xenolith from Neoarchean Closepet batholith yields an age of 2995±13 Ma,confirming the~3.0 Ga magmatism in the Central Dharwar Block.The gabbroic diorite is characterized by low SiO_(2)(52.62%-53.42%)and high MgO(5.38%-5.42%),Cr(48-70)×10^(-6),and Ni(115-124)×10^(-6),with relative enrichment in LILEs and LREE and depletion in HFSEs as well as negative Nd(ε_(Nd)(t)=−4.8 to−4.5)and Hf(ε_(Hf)(t)=−6.64 to−2.36)isotopes,indicating an enriched mantle source.Furthermore,geochemical signatures of zircon,clinopyroxene,and hornblende indicate that this magmatism occurred in an environment with water enrichment and high oxygen fugacity,similar to the island-arc setting,suggesting that the gabbroic diorite was produced by partial melting of enriched mantle source under a subduction zone.Additionally,the mafic magmatism in the Dharwar Craton evidently decreased from 3.2 to 3.0 Ga,accompanied by a transition of crustal components from Na-rich to K-rich,implying that a significant tectonic regime shift had already happened in the Dharwar Craton around~3.0 Ga.Considering the enriched isotopic composition of the gabbroic diorite and previous studies on the Dharwar Craton from 3.2 to 3.0 Ga,it suggests that the Dharwar Craton might have undergone a vertical-to-lateral tectonic transition beginning at~3.2 Ga and lasting until~3.0 Ga,and the subduction related to the plate tectonic probably started in a specific scale.展开更多
The granodiorites,monzogranites and diorites are widely developed in the Balikun area of Eastern Tianshan Orogen.Of which,LA–ICP–MS zircon U-Pb isotopic dating from the diorites revealed that they were emplaced at 3...The granodiorites,monzogranites and diorites are widely developed in the Balikun area of Eastern Tianshan Orogen.Of which,LA–ICP–MS zircon U-Pb isotopic dating from the diorites revealed that they were emplaced at 327~333 Ma,representing an important period of magmatism in the Early Carboniferous.Geochemically,they are characterized by moderate SiO2(51.33–62.48 wt%),high but variable MgO(2.04–11.16 wt%,average 5.35),higher Mg#(40–73)and TiO2(0.67–1.29 wt%),Na2O/K2O(1.39–2.95)as well as variable Cr(2.49–675 ppm)and Ni(1.31–174 ppm),showing a geochemistry similar to those of high-Mg diorites or sanukitoids.In addition,they are enriched in the LILE,poor HFSE with an evident negative Nb anomalies and a REE pattern of moderate fractionator between LREE and HREE without or weak negative Eu anomalies.TheirεHf(t)are positive(+3.63–+15.65),suggesting a source from the depleted mantle.In addition,they have high TiO2 and Pb,and large quantity of amphibolite and biotite,indicating that they were most likely derived from the partial melting of depleted mantle metasomatized by the slabderived melt under a hydrous condition.Consequently,combined with the contemporary volcanics and granitoids formed in the island arc settings,we proposed that the subduction was continued till Early Carboniferous in the Bogda-Harlik tectonic belt.After that,wide occurrence of the post-collisional A-type granites and mafic-ultramafic intrusions indicate this tectonic belt entered the post-collisional environment from Late Carboniferous to Permian.展开更多
The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs c...The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold.Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials.The Re-Os isotopic data of four pyrite samples construct an isochron,yielding a weighted average age of 226±17 Ma（mean square weighted deviation=1.7）,which is considered the main mineralization age.A dioritic porphyrite vein sample,showing weaker mineralization,was also dated using the SHRIMP zircon UPb isotopic method to constrain the youngest metallogenic age of the ore deposit,because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field,but also the main ore bodies.The dioritic porphyrite sample yields a weighted mean ^（206）Pb/^（238）U age of 221±3 Ma,which is slightly younger than the Re-Os isotopic isochron age of the pyrites,considered as the upper age limit of the mineralization,namely the ending age of the mineralization.The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma-related fluid,and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle.The Erlihe Pb-Zn deposit and associated dioritic porphyrite vein,important records of Qinling tectonic-magmatism-mineralization activities,were formed during the Triassic collisional orogeny processes.展开更多
We have determined the ages of the ore-bearing Tinggong porphyries and the Eocene granites using the LA-ICPMS zircon U-Pb method.Zircons from one adamellite porphyry and two diorite porphyries yield ages of 15.54±...We have determined the ages of the ore-bearing Tinggong porphyries and the Eocene granites using the LA-ICPMS zircon U-Pb method.Zircons from one adamellite porphyry and two diorite porphyries yield ages of 15.54±0.28 Ma,15.02±0.25 Ma and 14.74±0.22 Ma,respectively.The ages of two granites are 50.48±0.71 Ma and 50.16±0.48 Ma.Light Rare Earth Elements （LREE） are enriched in the ore-bearing adamellite porphyries,which are high-K caic-alkaline and metaluminous,while Heavy Rare Earth Elements （HREE） and Y are strongly depleted,indicating an adakitic affinity.The Large Ion Lithophile Elements （LILE） of the adamellite porphyries are highly enriched,whereas some High Field Strength Elements （HFSE） are depleted.The diorite porphyry in this study is chemically similar to the adamellite porphyries,except that the Mg# of the diorite porphyry is a little higher,demonstrating more mantle contamination.Four samples from different rocks are selected for in situ zircon Hf isotopic analyses.The samples show positive εHf（t） values and young Hf model ages,indicating their derivation from juvenile crust.However,the adamellite porphyry and diorite porphyry formed in the Miocene exhibit more heterogeneous Hf isotopic ratios,with lower （Σ）Hf （t） values than the granites formed in the Eocene,suggesting the involvement of old Indian continent crust in their petrogenesis.The geochronology and geochemistry of the adamellite porphyries and the diorite porphyries indicate that they formed from the same source region in a post-collisional environment,but contaminated by crust and mantle materials in different ratios.The metallic minerals formed mainly during the older adamellite porphyry stage,but they were recycled and reactivated by the diorite porphyry intrusion.展开更多
A mass of granitoid and dioritic intrusions are distributed in the southern Yidun Arc, among which the representative Indosinian intrusions include the Dongco and Maxionggou granitoid intrusions in Daocheng County and...A mass of granitoid and dioritic intrusions are distributed in the southern Yidun Arc, among which the representative Indosinian intrusions include the Dongco and Maxionggou granitoid intrusions in Daocheng County and hypabyssal intrusions intruding into arc volcanic rocks near the Xiangcheng town. The Dongco and Maxionggou granitoid intrusions consist mainly of porphyraceous monzogranites, megacryst monzogranites and aplite granites. The Xiangcheng hypabyssal intrusions are composed dominantly of dioritic porphyries. SHRIMP zircon ages of 224±3 Ma and 222±3 Ma have been obtained for the Dongco granitoid intrusion and the Xiangcheng dioritic porphyries, respectively. The Xiongcheng dioritic porphyries show a calc-alkaline geochemical feature, and are characterized by higher Sr/Y ratios, depletive Nb, Ta, P and Ti, enriched LILEs, and lower εNd （t） （=-3.27）, suggesting that they might be derived from mantle source magmas that were obviously contaminated by continent crustal materials. However, the Dongco and Maxionggou granitoids belong to high-potassium calcalkaline series with a per-metaluminous feature, and are characterized by higher CaO/（∑FeO＋MgO） and Al2O3/（∑FeO＋ MgO） ratios, lower （La/Yb）n and Sr/Y ratios, depletive Nb, Ta, Sr, P and Ti, enriched LILEs, and very low εNd （t） （=-8.10）, indicating that the granitoids might be derived from partial melting of continental crust materials mainly of graywacke. Petrogenesis of Dongco and Maxionggou granitoids implies that there was an oceanic crust between the Zongza continental block （ZCB） and western margin of the Yangtze Craton （WMYZC）. And the oceanic crust slab subducted westward during the Indosinian Epoch, producing an Andes-type continent marginal arc and a backarc basin at the WMSCC. Then the oceanic basin closed and a sinistrally lateral collision occurred at ca. 224 Ma-222 Ma between the ZCB and the WMYZC, causing partial melting of sediments in the back-arc basin to generate granitoid magmas of the Dongco and Maxionggou intrusions.展开更多
Magmatic activities associated with tectonic events play a significant role in understanding the evolution of an orogenic belt.The Jiangnan orogenic belt has been regarded as the collisional suture zone between the Ya...Magmatic activities associated with tectonic events play a significant role in understanding the evolution of an orogenic belt.The Jiangnan orogenic belt has been regarded as the collisional suture zone between the Yangtze Block and the Cathaysia Block.Although the magmatic activities during the period of intra-plate extension after the collision have been well studied in recent years,some remaining issues,including source nature and geodynamic mechanism,need to be further addressed.In this paper,based on a detailed field geological,petrological,geochemical and geochronological study,we focus our work on diorites in the Pengshan area located at the northwestern margin of the Jiangnan orogenic belt.The mineral assemblages are mainly composed of plagioclase(55 vol.%-65 vol.%)and hornblende(35 vol.%-45 vol.%).One diorite sample yields zircon^(206)Pb/^(238)U mean age of 768±8 Ma(MSWD=0.29).The diorites have enriched large ion lithophile elements(Ba,K and Rb)and incompatible elements(Th and U),and are depleted in high field-strength elements including Ta,Ti and Nb.Diorites in this study have relatively high MgO content(6.56 wt.%-7.58 wt.%,7.07 wt.%on average)and Mg number values(65-67,65.8 on average).The diorites are metaluminous,high K calc-alkaline series rocks with high contents of K_2O(1.59 wt.%-1.97 wt.%)and total alkali(Na_2O+K_2O=5.56 wt.%-6.05 wt.%).The Nd/Th ratio(4.34-5.27)is higher than that of crust-derived rocks and lower than mantle-derived rocks.The Rb/Sr ratio(0.19-0.22)is slightly lower than crust,but significantly higher than upper mantle.Based on the above geochemical and geochronological analyses,we suggest that the diorites in the Pengshan area were mainly derived from crustal materials with a small amount of mantleoriginated materials involved,and possibly produced from an extensional tectonic setting after the collision between the Yangtze Block and Cathaysia Block.展开更多
The Wulong diorite porphyry displays a very unusual flower-like glomerophyric texture and is thus well-known as a gemstone type of ＂Luoyang peony stone＂ for non-geologists. Hereby, we present a comprehensive study i...The Wulong diorite porphyry displays a very unusual flower-like glomerophyric texture and is thus well-known as a gemstone type of ＂Luoyang peony stone＂ for non-geologists. Hereby, we present a comprehensive study in terms of petrography, zircon U-Pb geochronology, geochemistry and Sr-Nd-Pb isotope. The rock exposed as small-scale dykes in the field, intruding in the Archean migmatized biotite- plagioclase genesis at the southern margin of the North China Craton. It exhibits typical porphyrite texture with plagioclase and amphibole as dominant and subdominant phenocrysts, respectively. The diorite porphyry rocks contain 51 wt.%-59 wt.% SiO2, belonging to medium-K calc-alkaline rock series. They are characterized by enrichment of large ion lithophile elements （LILEs, e.g., Ba） and depletion of high field-strength elements （HFSEs, e.g., Nb, Ta, Zr and Hf）, resembling island arc magmatic rocks. They show high initial Sr isotopic ratios （0.710 7-0.715 8）, low eNd（t） values （-9.9 to -13.3） and variable initial Pb isotopic ratios （206pb/204Pb vary from 17.3 to 19.3）, similar to the coeval intermediate and mafic magmatic rocks of adjacent region. These geochemical features indicate that the Wulong diorite porphyry is likely to originate from an enriched mantle with contamination of crustal materials. Zircon U-Pb dating results reveal a magma crystallization age of 480-A3 Ma, consistent with the summit of the magmatic events of the Qinling orogenic belt and reflecting the northernmost Paleozoic magmatic activity of the belt. This may indicate the influence of northward subduction of Paleotethyan oceanic slab can extend a distance of ca. 200 km to the north and reach Luoyang-Songshan region in the East Qinling Orogen.展开更多
This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of Lhasa.Our research goals are to provide further constrain...This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of Lhasa.Our research goals are to provide further constraints on pre-collisional structure of the southern margin of Asia and the onset of the India-Asia collision.Magnetite is identified as the main magnetic carrier in our study.The magnetite shows no evidence of metamorphism or alteration as determined from optical and scanning electron microscope observations.A strong mineral orientation is revealed by anisotropy of magnetic susceptibility analysis both for the intruded dykes and the country rocks.The authors interpret this AMS fabric to have formed during intrusion rather than deformation.Fifteen of 23 sites yield acceptable site mean characteristic remanences with dual polarities.A scatter analysis of the virtual geomagnetic poles suggests that the mean result adequately averaged paleosecular variation.The paleomagnetic pole from the Gangdese dykes yields a paleolatitude of 14.3°N±5.8°N for the southern margin of Asia near Lhasa.The paleolatitude corresponds to an in-between position of the Lhasa terrane during about 130‒60 Ma.Furthermore,the mean declination of the characteristic remanent magnetization reveals a significant counterclockwise rotation of 18°±9°for the sampling location since about 83 Ma.In the light of tectonic setting of the dykes,the strike of the southern margin of Asia near Lhasa is restored to trend approximately about 310°,which is compatible with the hypothesis that the southern margin of Eurasia had a quasi-linear structure prior to its collision with India.展开更多
LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within...LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within errors.It is the first time that the microgranular enclaves age in Kalamaili area was determined.Petrochemistry and geochemistry research shows the characteristics of host rock as follows:展开更多
The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt,which is a tectonic joint among Alxa Block,Ordos Block,and North Qilian orogenic belt.However,...The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt,which is a tectonic joint among Alxa Block,Ordos Block,and North Qilian orogenic belt.However,the tectonic evolution of this area remains unclear due to the lack of magmatic information.This paper conducted researches on geochronology,geochemistry,and Sr-Nd-Hf isotopes of the diorite porphyrites exposed in the Weining Beishan area.The zircon U-Pb dating yields two ages of 145.0±1.1 and 146.2±1.5 Ma,and the whole-rock geochemical data indicate that the diorite porphyrites are metaluminous to weakly peraluminous and high-K calc-alkaline series.The characteristics of highly initial^(87)Sr/^(86)Sr ratios(0.70816 to 0.71047),negativeε_(Nd)(t)(−8.9 to−8.4),and negativeε_(Hf)(t)(−13.8 to−21.2)indicate that the diorite porphyrites originated from partial melting of the middle-lower ancient crust related to the North China Craton.Combined with the regional geology,we suggested that partial melting was triggered by a tectonic activity of deep faults cutting through the crust under the regional stress transformation from compressing to extension during the Late Jurassic–Early Cretaceous,which is probably related to the westward subduction of the Paleo-Pacific Plate.展开更多
LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion...LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion of Early Cambrian. Geochemistry analysis indicates that the rocks belong to high-K calc-alkaline series,with low content of SiO_2( 52.24%-53.64%) and high Mg( MgO = 5.67%-6.56%,Mg~#= 61. 05-65. 46).The rocks are characterized by the enrichment of LREE and LILE( e.g. Rb,Ba,Pb),and relative depletion in HREE and HFSE( e.g. Ta,Nb,P,Ti),and with a high content of Sr( 442. 3-622. 3) × 10^(-6),Yb( 2.49-3.42) ×10^(-6) and Y( 25.64-35.49) ×10^(-6),and slightly negative Eu anormaly( δEu= 0.60-0.81). Based on Rb/Sr( 0.15-0.25) and Rb/Nb( 8.27-15.12),it is concluded that the primary magma of diorite was derived from the mixture of the crust and mantle. Combined with background of regional tectonic evolution,it is suggested that diorite was formed in the extensional environment after the collage of the EGM with the Siberian.展开更多
The Masjed Daghi mineralization is located 30 km southeast of Jolfa city at the bank of Araxes River, northwest Iran. This area is situated in the Alborz-Azarbaijan structural zone of Iran. The most widespread rocks i...The Masjed Daghi mineralization is located 30 km southeast of Jolfa city at the bank of Araxes River, northwest Iran. This area is situated in the Alborz-Azarbaijan structural zone of Iran. The most widespread rocks in the mineralization area are andesite and trachyandesite, while there are rock units of latite tuff, andesitic agglomerate, and hornblende porphyry basalt in eastern hills and Eocene flysch in the southern part of the area. Several intrusive bodies are present in the study area, from which the dominant intrusive rock hosting the mineralization is diorite porphyry. The mineralized rock units of the area are cut by different diorite ad mafic dikes. The most prevalent texture of mineralization is dissemination, while open space filling textures including veins and veinlets, are common as well. Diverse types of alteration including potassic, phyllic, argillic, silicification, and a little of carbonatization were recognized in the field and microscopic observations as well as by XRD. In addition to thick silica veins and stockwork zones, some silica, barite, sulfide, and calcite veins and veinlets have occurred in the Masjed Daghi mineralization area. In this research, 26 doubly polished thin sections (wafers) were prepared and investigated. Four samples were taken from surface veins, while 22 samples were chosen from core samples (of 6 boreholes) of white and grey-white silica, and silica-barite veins. The fluid inclusion studies on 105 primary fluid inclusions indicated five phases for inclusions including: 1) liquid or gas, 2) liquid and gas, 3) liquid, gas, and solid, 4) liquid, gas, halite, and solid, and 5) liquid, gas, halite, and two types of solids. The data gained from fluid inclusions approved two mineralization fluids which caused porphyry and epithermal mineralizations. The porphyry fluid inclusions were homogenized in temperatures of 122°C to 550°C with a maximum of 700°C and average salinity of 55 wt% NaCl equivalent, while the epithermal inclusions indicated an average homogenization temperature of 186°C with an average salinity of 6.23 wt% NaCl equivalent.展开更多
The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region, with the aim to constraining its formation age, magma source and tectonic setting. LA-ICP-MS U-Pb dating...The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region, with the aim to constraining its formation age, magma source and tectonic setting. LA-ICP-MS U-Pb dating results of zircons from the diorites indicate that the rocks were formed in the Middle Jurassic （171 ±2 Ma, MSWD = 1. 19）. Geochemically, these rocks have Si02 concentrations of 52. 52%-54. 90%,K20 of 2. 14%-3.84% , Na20 of 3. 17%-3. 35% , MgO of 7. 43%-9. 34% and high Mg# of 68. 57-72. 57. These rocks are characterized by enrichment in large ion lithophile elements（ LILE,such as K, Ba, Rb and Sr） and light rare earth elements （ LREE） , relatively depletion in high field strength elements （ HFSE, such as Ta, Nb, Ti and Zr） , and heavy rare earth elements （HREE）. These characteristics suggest that primary magma of the rocks were derived from the partial melting of mantle with miner crustal contamination, which may related to partial melting of mantle wedge by addition of sediment melt from subducting oceanic crust. Based on former and present studies, the authors consider that the Nancha ore deposit high-Mg diorites were formed in compres- sional structural setting which is similar to volcanic arc. It could be related to the subduction of the Paleo-Paci- fic plate beneath the Eurasian continent.展开更多
基金supported by the National Natural Science Foundation of China(42372071,41102037)Shaanxi public welfare geological survey project(202409)the Foundation for the Author of National Excellent Doctoral Dissertation of China(201324).
文摘The Triassic granitoids and associated diorites in the Qinling orogenic belt reveal critical evidence of crust-mantle interaction during the terminal collision between the North China and Yangtze Blocks.This study presents new constraints from zircon U-Pb age,Lu-Hf isotopes,and amphibole-plagioclase-apatite geochemistry for the Maoerliang diorite in the Foping area.Zircon U-Pb dating yields a crystallization age of 212±2.8 Ma,withεHf(t)values ranging from−8.6 to+3.0 and corresponding twostage Hf model ages(T_(DM2))of 886-1479 Ma,indicative of derivation from an evolved lithospheric mantle source.Petrogenetic indicators reveal a mantle affinity:amphiboles exhibit high MgO(9.8-11.2 wt%)and elevated Nb/Ta ratios(14.3-18.1),while apatites display F-rich(2.1-2.8 wt%)and Cl-poor(0.08-0.15 wt%)characteristics.Thermobarometric calculations based on amphibole chemistry constrain crystallization conditions of 805-866℃and 211-383 MPa,corresponding to mid-crustal emplacement depths(8-14 km).Both amphibole and zircon indicate elevated oxygen fugacity(ΔNNO=−4.08 to−3.71;ΔFMQ=−1.14 to+3.96)and hydrous magma conditions(H_(2)O=4.22-4.94 wt%).Late-stage plagioclase crystallization(An21-26.5)reflects prolonged fractional crystallization in a hydrous dioritic magma.These diagnostic features-mantle-derived signatures,high f O_(2),and hydrous nature-exhibit remarkable convergence with gold-mineralized granites in the East Qinling.Our findings suggest that Triassic dioritic magmatism may have played an underappreciated role in facilitating gold enrichment processes within the South Qinling metallogenic belt.
基金supported by the Ministry of Science and Technology of the People’s Republic of China(Grant No.2022FY101704)the National Natural Science Foundation of China(Grant No.41972061)+1 种基金Science and Technology Innovation Team of Hebei GEO University(30801071)the China Geological Survey(Grant Nos.1212011120701 and 1212011120711)。
文摘High-Mg andesite/diorite(HMA)is useful for identifying subduction-related processes in orogenic belts,including the identification of ophiolites formed in suprasubduction zone(SSZ)environments.The E'rentaolegai high-Mg diorite from the Diyanmiao ophiolite in central Inner Mongolia,North China,has been investigated revealing low-K tholeiitic-calc-alkaline characteristics and have SiO_(2)contents of 53.44-54.92 wt%,MgO contents of 8.44-9.54 wt%,and Mg~#of 54.35-57.60,with variable Fe_(2)O_(3)(7.51-8.61 wt%),Al_(2)O_(3)(11.95-15.09 wt%),and Na_(2)O(3.42-3.94 wt%)contents,low K_(2)O(0.34-0.97 wt%),TiO_(2)(0.35-0.67 wt%),and P2O5(0.12-0.15 wt%)contents,and high Ni(43-193 ppm)and Cr(189-556 ppm)contents.Samples collected have low total rare earth element(REE)contents(30.58-77.80 ppm),with flat or slightly right-dipping REE patterns(La_(N)/Yb_(N)=2.19-3.11)and a lack of pronounced Eu anomalies.The samples are also enriched in large-ion lithophile elements(LILEs,e.g.,K,Rb,Ba,U,and Sr)and depleted in high field strength elements(e.g.,Ta,Nb,Ti,and P).The E'rentaolegai high-Mg diorite has characteristics typical of HMA,and are similar to those of sanukites from the Setouchi Arc in SW Japan.They also display high positiveε_(Nd)(t)values(+6.32 to+7.80),comparable to the values of their host rocks.Petrogenetic analyses suggest that the E'rentaolegai HMA was probably formed by the interaction of partial melts and aqueous fluids from subducted sediments with mantle peridotite.Zircon U-Pb dating reveals that the high-Mg diorite crystallized at 313.6±2.4 Ma,i.e.,late Carboniferous.Combining our data with the temporal and spatial distribution of the Diyanmiao SSZ-type ophiolite,we propose that the eastern Paleo-Asian Ocean had not closed by the late Carboniferous,but intra-oceanic subduction was ongoing.A new model of the initiation of subduction in the eastern PAO during the late Paleozoic.
文摘The high-Mg diorites, widely occurring in western Shandong, have important implications in the study of the relationship between the Mesozoic magmatism and the nature of the lithosphere and its thinning period in the eastern North China craton （NCC）. The Tietonggou and Jinling intrusions are typically representatives. LA-ICP-MS zircon U-Pb dating, major and trace element and Sr-Nd isotopic compositions of the Mesozoic intrusive rocks from western Shandong, eastern China, were analyzed. The weighted mean 106^pb/ 238^U ages from LA-ICP-MS zircon U-Pb dating results for early norite-diorite, late pyroxene-diorite from the Tietonggou intrusion and biotite-diorite from the Jinling intrusion are （131.4±4.9） Ma（n=15）, （134. 5±2.3） Ma（n=13）, and （132.8±4. 2） Ma（n=12）, respectively, implying that they were formed in the Early Cretaceous. The weighted mean 207^pb/ 204^Pb ages for round zircons from late pyroxene-diorite in the Tietonggou intrusion is （ 2 513 ± 54） Ma（ n= 8）, suggesting that the basement of the North China craton should exist in the research area. The high-Mg diorites are characterized by enrichment in MgO, Na20, and light rare earth elements （LREE）, and they are poor in heavy rare earth elements （HREE） and high field strength elements （HFSE）, being similar to adakite. The existence of the mantle peridotite xenoliths with a high-Mg feature for these intrusive rocks implies that their primary magma should be derived from the upper mantle. However, Sr-Nd isotopic composi- tions （Is： 0.704 75--0.707 15;ENd （130 Ma） values： --3.95 to -- 13.30）, depletion in HFSE, and the occurrence of Archean inherited zircons suggest that crustal materials could be involved in the derivation of the primary magma. The compositional difference between the diorites from the Tietonggou and Jinling intrusions could be attributed to those of magma sources and degrees of partial melting. The Early Cretaceous high-Mg diorites are considered to have been formed by the mixed melting of the delaminated lithosphere （lithospheric mantle ＋ crust） and asthenosphere, based on their geochemistry, the mantlederived xenoliths, and the Early Mesozoic lithospheric evolutionary history of the eastern North China craton.
基金the National Natural Science Foundation of China (Grant No. 40472033)the State Key Laboratory of Continental Dynamics, Northwest Uni-versity
文摘Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intru-sion is mainly composed of a suite of gabbro-diorite. Zircons from the intrusion display eu-hedral-subhedral in shape and have high Th/U ratios (1.23―2.87), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating results for two samples indicate that they were formed in the Early Cre-taceous, yielding weighted mean 206Pb/238U ages of 129±1Ma and 134±2Ma, respectively. Except for early cumulate such as sample QT-19, their SiO2 and MgO contents range from 50.12% to 56.37% and from 3.52% to 6.37%, respectively. Moreover, the gabbro-diorites are characterized by high Mg# (0.54―0.63), enrichment in Na (Na2O/K2O ratios more than 1), Cr (73×10-6―217×10-6) and Ni (34×10-6―241×10-6), and intensive enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Their initial 87Sr/86Sr ratios and ε Nd(t) values range from 0.70962 to 0.71081 and from-16.60 to-13.04, respectively. Taken together with the Early Creta-ceous high-Mg diorites and the mantle xenoliths from the Tietonggou and Jinling as well as basalts from the Fangcheng and Feixian, it is suggested that the primary magma for the Shangyu gab-bro-diorites should be derived from the enriched lithospheric mantle intensively modified by conti-nental crust. The Sr-Nd-Pb isotopic compositions for the Early Cretaceous high-Mg diorites in western Shandong display a trend of spatial variations, i.e., initial 87Sr/86Sr, 207Pb/204Pb and 208Pb/204Pb ratios de-creasing and ε Nd(t) values increasing from southeast to northwest in western Shandong, which is con-sistent with the tectonic model that the Yangtze Craton subducted beneath the North China Craton oriented in north-west direction in the Early Mesozoic.
文摘Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic massif to understand its petrogenesis and source.The clinopyroxene composition(high Mg#,Cr-content,sum of REE and Ti/Eu ratio;depletion in HREE;negative Eu-anomaly)indicates that it formed from a reduced melt derived from a mantle source metasomatized by fluids/melts having crustal affinity.Melt compositions in equilibrium with clinopyroxene and amphibole were calculated using solid/liquid partition coefficients.The high Nb/Y and Zr/Y ratio values of a liquid simulated from clinopyroxene,which appears to have very similar characteristics to sanukitoid melts,indicate a low degree of melting of the mantle source.Melt simulated from amphibole is more evolved and more felsic(dacitic).It displays a geochemical“amphibole fractionation”signature,indicating the peritectic transformation of clinopyroxene to amphibole in the lower crust.Rock textures and major element mineral compositions suggest that further amphibole was precipitated directly from the melt in the middle crust.The results show that the Chelyabinsk highMg diorite was probably formed as a cumulate from sanukitoid-like melt during its ascent and cooling below dacitic liquidus inside the amphibole stability field.
基金supported by China Geological Survey Project(DD20190069 and DD20221636)Science and Technology Plan Project in Shaanxi Province,China(2023-JC-ZD-14,2023-JC-YB-236,2024JC-YBQN-0249,and 2022JQ-286).
文摘Numerous Indosinian igneous rocks in the North Qaidam(NQ)provide crucial insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents a comprehensive study of the petrography,mineralogy,geochemistry,zircon U-Pb geochronology,and Hf isotope composition of dioritic rocks from the eastern NQ.Zircon U-Pb dating results indicate that the dioritic rocks were formed during the Middle Triassic(244-240 Ma).The rocks exhibit high-K calc-alkaline characteristics with variable SiO_(2)(55.25-65.39 wt%)and elevated K_(2)O+Na_(2)O(4.81-6.94 wt%)contents.They show enrichment in LILEs(Rb,Ba,K)and depletion in HFSEs(Nb,Ta,Ti),with slight negative Eu anomalies(Eu/Eu*=0.89-0.97).Zirconε_(Hf)(t)values(−20.93 to+5.60)and T_(DM2)ages(0.85-1.72 Ga)suggest mixed sources.Petrographic and mineralogical analysis reveals that the plagioclase phenocrysts exhibit disequilibrium textures(including reverse zoning),primarily composed of andesine and labradorite,with a small amount of oligoclase.The clinopyroxenes are all augites and have high crystallization temperatures(1111-1151℃).These features,particularly the reverse zoning of plagioclase,support a petrogenetic model involving mantle-derived magma underplating that induced melting of ancient lower crust,followed by mixing of underplated basaltic magma with crust-derived felsic magma.Our results indicate formation in a back-arc extensional setting during subduction of the Zongwulong Paleo-Tethys Ocean.
文摘To investigate the Early Cretaceous magmatic activity and tectonic evolution in the Xiaoqinggou mining area of Jilin Province,the authors conducted petrological,geochemical,and isotopic analyses of diorite rocks.The findings show that the zircons exhibit distinct magmatic growth zoning,confirming their magmatic origin.LA–ICP–MS zircon U–Pb dating yielded an age of 128.7±2.2 Ma,corresponding to Early Cretaceous.Geochemical data reveal that the diorite rocks are high and potassium but low in sodium,classifying them within the peraluminous,high-potassium calc-alkaline series.They are enriched in large ion lithophile elements(e.g.,K,Ba and Rb)and depleted in high field strength elements(e.g.,Nb,Ta and Ti).TheδEu values range from 1.07 to 1.14,indicating weakly positive Eu anomalies.Regional comparisons and integrated studies suggest that the Xiaoqinggou diorite rocks formed in a volcanic island arc setting,associated with the westward subduction of the Paleo-Pacific plate beneath the Eurasian continent in an extensional tectonic environment.This study provides a theoretical basis for further exploration of the Xiaoqinggou deposit.
基金funded by the National Science Foundation of China(grant Nos.41890831 and 41772189)the Most Special Fund from State Key Laboratory of Continental Dynamics,Northwest University,Xi’an,China(grant No.201210133).
文摘The Dharwar Craton in India,as one of the oldest cratons in the world,preserves key information of early continental crust evolution.However,a~3.0 Ga tectonothermal event was previously recognized only in the Western Dharwar Craton,and the coeval tectono-thermal event has been rarely reported in the Central Dharwar Block.In this study,zircon U-Pb dating of the gabbroic diorite xenolith from Neoarchean Closepet batholith yields an age of 2995±13 Ma,confirming the~3.0 Ga magmatism in the Central Dharwar Block.The gabbroic diorite is characterized by low SiO_(2)(52.62%-53.42%)and high MgO(5.38%-5.42%),Cr(48-70)×10^(-6),and Ni(115-124)×10^(-6),with relative enrichment in LILEs and LREE and depletion in HFSEs as well as negative Nd(ε_(Nd)(t)=−4.8 to−4.5)and Hf(ε_(Hf)(t)=−6.64 to−2.36)isotopes,indicating an enriched mantle source.Furthermore,geochemical signatures of zircon,clinopyroxene,and hornblende indicate that this magmatism occurred in an environment with water enrichment and high oxygen fugacity,similar to the island-arc setting,suggesting that the gabbroic diorite was produced by partial melting of enriched mantle source under a subduction zone.Additionally,the mafic magmatism in the Dharwar Craton evidently decreased from 3.2 to 3.0 Ga,accompanied by a transition of crustal components from Na-rich to K-rich,implying that a significant tectonic regime shift had already happened in the Dharwar Craton around~3.0 Ga.Considering the enriched isotopic composition of the gabbroic diorite and previous studies on the Dharwar Craton from 3.2 to 3.0 Ga,it suggests that the Dharwar Craton might have undergone a vertical-to-lateral tectonic transition beginning at~3.2 Ga and lasting until~3.0 Ga,and the subduction related to the plate tectonic probably started in a specific scale.
基金co-funded by the Land and Resources Survey Project of China(Grant no.12120113042200)MOST Special Funds from the State Key Laboratory of Continental Dynamics,Northwest University,Xi’an,China
文摘The granodiorites,monzogranites and diorites are widely developed in the Balikun area of Eastern Tianshan Orogen.Of which,LA–ICP–MS zircon U-Pb isotopic dating from the diorites revealed that they were emplaced at 327~333 Ma,representing an important period of magmatism in the Early Carboniferous.Geochemically,they are characterized by moderate SiO2(51.33–62.48 wt%),high but variable MgO(2.04–11.16 wt%,average 5.35),higher Mg#(40–73)and TiO2(0.67–1.29 wt%),Na2O/K2O(1.39–2.95)as well as variable Cr(2.49–675 ppm)and Ni(1.31–174 ppm),showing a geochemistry similar to those of high-Mg diorites or sanukitoids.In addition,they are enriched in the LILE,poor HFSE with an evident negative Nb anomalies and a REE pattern of moderate fractionator between LREE and HREE without or weak negative Eu anomalies.TheirεHf(t)are positive(+3.63–+15.65),suggesting a source from the depleted mantle.In addition,they have high TiO2 and Pb,and large quantity of amphibolite and biotite,indicating that they were most likely derived from the partial melting of depleted mantle metasomatized by the slabderived melt under a hydrous condition.Consequently,combined with the contemporary volcanics and granitoids formed in the island arc settings,we proposed that the subduction was continued till Early Carboniferous in the Bogda-Harlik tectonic belt.After that,wide occurrence of the post-collisional A-type granites and mafic-ultramafic intrusions indicate this tectonic belt entered the post-collisional environment from Late Carboniferous to Permian.
基金supported by the National Scientific and Technological Support Program of China (grant no:2006BAB01A11)
文摘The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold.Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials.The Re-Os isotopic data of four pyrite samples construct an isochron,yielding a weighted average age of 226±17 Ma（mean square weighted deviation=1.7）,which is considered the main mineralization age.A dioritic porphyrite vein sample,showing weaker mineralization,was also dated using the SHRIMP zircon UPb isotopic method to constrain the youngest metallogenic age of the ore deposit,because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field,but also the main ore bodies.The dioritic porphyrite sample yields a weighted mean ^（206）Pb/^（238）U age of 221±3 Ma,which is slightly younger than the Re-Os isotopic isochron age of the pyrites,considered as the upper age limit of the mineralization,namely the ending age of the mineralization.The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma-related fluid,and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle.The Erlihe Pb-Zn deposit and associated dioritic porphyrite vein,important records of Qinling tectonic-magmatism-mineralization activities,were formed during the Triassic collisional orogeny processes.
基金supported by the "Researches of tectonics, magmatism evolution, and metallogeny in the Gangdese belt, Tibet" Program of China Geological Survey (1212010818098)
文摘We have determined the ages of the ore-bearing Tinggong porphyries and the Eocene granites using the LA-ICPMS zircon U-Pb method.Zircons from one adamellite porphyry and two diorite porphyries yield ages of 15.54±0.28 Ma,15.02±0.25 Ma and 14.74±0.22 Ma,respectively.The ages of two granites are 50.48±0.71 Ma and 50.16±0.48 Ma.Light Rare Earth Elements （LREE） are enriched in the ore-bearing adamellite porphyries,which are high-K caic-alkaline and metaluminous,while Heavy Rare Earth Elements （HREE） and Y are strongly depleted,indicating an adakitic affinity.The Large Ion Lithophile Elements （LILE） of the adamellite porphyries are highly enriched,whereas some High Field Strength Elements （HFSE） are depleted.The diorite porphyry in this study is chemically similar to the adamellite porphyries,except that the Mg# of the diorite porphyry is a little higher,demonstrating more mantle contamination.Four samples from different rocks are selected for in situ zircon Hf isotopic analyses.The samples show positive εHf（t） values and young Hf model ages,indicating their derivation from juvenile crust.However,the adamellite porphyry and diorite porphyry formed in the Miocene exhibit more heterogeneous Hf isotopic ratios,with lower （Σ）Hf （t） values than the granites formed in the Eocene,suggesting the involvement of old Indian continent crust in their petrogenesis.The geochronology and geochemistry of the adamellite porphyries and the diorite porphyries indicate that they formed from the same source region in a post-collisional environment,but contaminated by crust and mantle materials in different ratios.The metallic minerals formed mainly during the older adamellite porphyry stage,but they were recycled and reactivated by the diorite porphyry intrusion.
文摘A mass of granitoid and dioritic intrusions are distributed in the southern Yidun Arc, among which the representative Indosinian intrusions include the Dongco and Maxionggou granitoid intrusions in Daocheng County and hypabyssal intrusions intruding into arc volcanic rocks near the Xiangcheng town. The Dongco and Maxionggou granitoid intrusions consist mainly of porphyraceous monzogranites, megacryst monzogranites and aplite granites. The Xiangcheng hypabyssal intrusions are composed dominantly of dioritic porphyries. SHRIMP zircon ages of 224±3 Ma and 222±3 Ma have been obtained for the Dongco granitoid intrusion and the Xiangcheng dioritic porphyries, respectively. The Xiongcheng dioritic porphyries show a calc-alkaline geochemical feature, and are characterized by higher Sr/Y ratios, depletive Nb, Ta, P and Ti, enriched LILEs, and lower εNd （t） （=-3.27）, suggesting that they might be derived from mantle source magmas that were obviously contaminated by continent crustal materials. However, the Dongco and Maxionggou granitoids belong to high-potassium calcalkaline series with a per-metaluminous feature, and are characterized by higher CaO/（∑FeO＋MgO） and Al2O3/（∑FeO＋ MgO） ratios, lower （La/Yb）n and Sr/Y ratios, depletive Nb, Ta, Sr, P and Ti, enriched LILEs, and very low εNd （t） （=-8.10）, indicating that the granitoids might be derived from partial melting of continental crust materials mainly of graywacke. Petrogenesis of Dongco and Maxionggou granitoids implies that there was an oceanic crust between the Zongza continental block （ZCB） and western margin of the Yangtze Craton （WMYZC）. And the oceanic crust slab subducted westward during the Indosinian Epoch, producing an Andes-type continent marginal arc and a backarc basin at the WMSCC. Then the oceanic basin closed and a sinistrally lateral collision occurred at ca. 224 Ma-222 Ma between the ZCB and the WMYZC, causing partial melting of sediments in the back-arc basin to generate granitoid magmas of the Dongco and Maxionggou intrusions.
基金supported by the Fundamental Research Funds for the Central Universities,China University of Geosciences,Wuhan(CUGW)(Nos.CUGCJ1707 and CUGL180406)NNSFC fund(No.41602234)+1 种基金China Geological Survey’s projects(Nos.DD20160036 and DD20190261)Open Fund from the State Key Laboratory of Geological Processes and Mineral Resources,CUGW(No.GRMR201901)
文摘Magmatic activities associated with tectonic events play a significant role in understanding the evolution of an orogenic belt.The Jiangnan orogenic belt has been regarded as the collisional suture zone between the Yangtze Block and the Cathaysia Block.Although the magmatic activities during the period of intra-plate extension after the collision have been well studied in recent years,some remaining issues,including source nature and geodynamic mechanism,need to be further addressed.In this paper,based on a detailed field geological,petrological,geochemical and geochronological study,we focus our work on diorites in the Pengshan area located at the northwestern margin of the Jiangnan orogenic belt.The mineral assemblages are mainly composed of plagioclase(55 vol.%-65 vol.%)and hornblende(35 vol.%-45 vol.%).One diorite sample yields zircon^(206)Pb/^(238)U mean age of 768±8 Ma(MSWD=0.29).The diorites have enriched large ion lithophile elements(Ba,K and Rb)and incompatible elements(Th and U),and are depleted in high field-strength elements including Ta,Ti and Nb.Diorites in this study have relatively high MgO content(6.56 wt.%-7.58 wt.%,7.07 wt.%on average)and Mg number values(65-67,65.8 on average).The diorites are metaluminous,high K calc-alkaline series rocks with high contents of K_2O(1.59 wt.%-1.97 wt.%)and total alkali(Na_2O+K_2O=5.56 wt.%-6.05 wt.%).The Nd/Th ratio(4.34-5.27)is higher than that of crust-derived rocks and lower than mantle-derived rocks.The Rb/Sr ratio(0.19-0.22)is slightly lower than crust,but significantly higher than upper mantle.Based on the above geochemical and geochronological analyses,we suggest that the diorites in the Pengshan area were mainly derived from crustal materials with a small amount of mantleoriginated materials involved,and possibly produced from an extensional tectonic setting after the collision between the Yangtze Block and Cathaysia Block.
基金the National Natural Science Foundation of China(Nos.41530211,41502046)the China Geological Survey(No.DD20160030)The Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUGCJ1711)is also acknowledged for partial financially support
文摘The Wulong diorite porphyry displays a very unusual flower-like glomerophyric texture and is thus well-known as a gemstone type of ＂Luoyang peony stone＂ for non-geologists. Hereby, we present a comprehensive study in terms of petrography, zircon U-Pb geochronology, geochemistry and Sr-Nd-Pb isotope. The rock exposed as small-scale dykes in the field, intruding in the Archean migmatized biotite- plagioclase genesis at the southern margin of the North China Craton. It exhibits typical porphyrite texture with plagioclase and amphibole as dominant and subdominant phenocrysts, respectively. The diorite porphyry rocks contain 51 wt.%-59 wt.% SiO2, belonging to medium-K calc-alkaline rock series. They are characterized by enrichment of large ion lithophile elements （LILEs, e.g., Ba） and depletion of high field-strength elements （HFSEs, e.g., Nb, Ta, Zr and Hf）, resembling island arc magmatic rocks. They show high initial Sr isotopic ratios （0.710 7-0.715 8）, low eNd（t） values （-9.9 to -13.3） and variable initial Pb isotopic ratios （206pb/204Pb vary from 17.3 to 19.3）, similar to the coeval intermediate and mafic magmatic rocks of adjacent region. These geochemical features indicate that the Wulong diorite porphyry is likely to originate from an enriched mantle with contamination of crustal materials. Zircon U-Pb dating results reveal a magma crystallization age of 480-A3 Ma, consistent with the summit of the magmatic events of the Qinling orogenic belt and reflecting the northernmost Paleozoic magmatic activity of the belt. This may indicate the influence of northward subduction of Paleotethyan oceanic slab can extend a distance of ca. 200 km to the north and reach Luoyang-Songshan region in the East Qinling Orogen.
基金financially supported by the National Science Foundation of China(92055205,41672223)the start-up funding from Sun Yat-sen University(74110-18841244).
文摘This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of Lhasa.Our research goals are to provide further constraints on pre-collisional structure of the southern margin of Asia and the onset of the India-Asia collision.Magnetite is identified as the main magnetic carrier in our study.The magnetite shows no evidence of metamorphism or alteration as determined from optical and scanning electron microscope observations.A strong mineral orientation is revealed by anisotropy of magnetic susceptibility analysis both for the intruded dykes and the country rocks.The authors interpret this AMS fabric to have formed during intrusion rather than deformation.Fifteen of 23 sites yield acceptable site mean characteristic remanences with dual polarities.A scatter analysis of the virtual geomagnetic poles suggests that the mean result adequately averaged paleosecular variation.The paleomagnetic pole from the Gangdese dykes yields a paleolatitude of 14.3°N±5.8°N for the southern margin of Asia near Lhasa.The paleolatitude corresponds to an in-between position of the Lhasa terrane during about 130‒60 Ma.Furthermore,the mean declination of the characteristic remanent magnetization reveals a significant counterclockwise rotation of 18°±9°for the sampling location since about 83 Ma.In the light of tectonic setting of the dykes,the strike of the southern margin of Asia near Lhasa is restored to trend approximately about 310°,which is compatible with the hypothesis that the southern margin of Eurasia had a quasi-linear structure prior to its collision with India.
文摘LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within errors.It is the first time that the microgranular enclaves age in Kalamaili area was determined.Petrochemistry and geochemistry research shows the characteristics of host rock as follows:
文摘The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt,which is a tectonic joint among Alxa Block,Ordos Block,and North Qilian orogenic belt.However,the tectonic evolution of this area remains unclear due to the lack of magmatic information.This paper conducted researches on geochronology,geochemistry,and Sr-Nd-Hf isotopes of the diorite porphyrites exposed in the Weining Beishan area.The zircon U-Pb dating yields two ages of 145.0±1.1 and 146.2±1.5 Ma,and the whole-rock geochemical data indicate that the diorite porphyrites are metaluminous to weakly peraluminous and high-K calc-alkaline series.The characteristics of highly initial^(87)Sr/^(86)Sr ratios(0.70816 to 0.71047),negativeε_(Nd)(t)(−8.9 to−8.4),and negativeε_(Hf)(t)(−13.8 to−21.2)indicate that the diorite porphyrites originated from partial melting of the middle-lower ancient crust related to the North China Craton.Combined with the regional geology,we suggested that partial melting was triggered by a tectonic activity of deep faults cutting through the crust under the regional stress transformation from compressing to extension during the Late Jurassic–Early Cretaceous,which is probably related to the westward subduction of the Paleo-Pacific Plate.
基金Supported by Project of China Geological Survey(No.12120113098300)
文摘LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion of Early Cambrian. Geochemistry analysis indicates that the rocks belong to high-K calc-alkaline series,with low content of SiO_2( 52.24%-53.64%) and high Mg( MgO = 5.67%-6.56%,Mg~#= 61. 05-65. 46).The rocks are characterized by the enrichment of LREE and LILE( e.g. Rb,Ba,Pb),and relative depletion in HREE and HFSE( e.g. Ta,Nb,P,Ti),and with a high content of Sr( 442. 3-622. 3) × 10^(-6),Yb( 2.49-3.42) ×10^(-6) and Y( 25.64-35.49) ×10^(-6),and slightly negative Eu anormaly( δEu= 0.60-0.81). Based on Rb/Sr( 0.15-0.25) and Rb/Nb( 8.27-15.12),it is concluded that the primary magma of diorite was derived from the mixture of the crust and mantle. Combined with background of regional tectonic evolution,it is suggested that diorite was formed in the extensional environment after the collage of the EGM with the Siberian.
文摘The Masjed Daghi mineralization is located 30 km southeast of Jolfa city at the bank of Araxes River, northwest Iran. This area is situated in the Alborz-Azarbaijan structural zone of Iran. The most widespread rocks in the mineralization area are andesite and trachyandesite, while there are rock units of latite tuff, andesitic agglomerate, and hornblende porphyry basalt in eastern hills and Eocene flysch in the southern part of the area. Several intrusive bodies are present in the study area, from which the dominant intrusive rock hosting the mineralization is diorite porphyry. The mineralized rock units of the area are cut by different diorite ad mafic dikes. The most prevalent texture of mineralization is dissemination, while open space filling textures including veins and veinlets, are common as well. Diverse types of alteration including potassic, phyllic, argillic, silicification, and a little of carbonatization were recognized in the field and microscopic observations as well as by XRD. In addition to thick silica veins and stockwork zones, some silica, barite, sulfide, and calcite veins and veinlets have occurred in the Masjed Daghi mineralization area. In this research, 26 doubly polished thin sections (wafers) were prepared and investigated. Four samples were taken from surface veins, while 22 samples were chosen from core samples (of 6 boreholes) of white and grey-white silica, and silica-barite veins. The fluid inclusion studies on 105 primary fluid inclusions indicated five phases for inclusions including: 1) liquid or gas, 2) liquid and gas, 3) liquid, gas, and solid, 4) liquid, gas, halite, and solid, and 5) liquid, gas, halite, and two types of solids. The data gained from fluid inclusions approved two mineralization fluids which caused porphyry and epithermal mineralizations. The porphyry fluid inclusions were homogenized in temperatures of 122°C to 550°C with a maximum of 700°C and average salinity of 55 wt% NaCl equivalent, while the epithermal inclusions indicated an average homogenization temperature of 186°C with an average salinity of 6.23 wt% NaCl equivalent.
文摘The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region, with the aim to constraining its formation age, magma source and tectonic setting. LA-ICP-MS U-Pb dating results of zircons from the diorites indicate that the rocks were formed in the Middle Jurassic （171 ±2 Ma, MSWD = 1. 19）. Geochemically, these rocks have Si02 concentrations of 52. 52%-54. 90%,K20 of 2. 14%-3.84% , Na20 of 3. 17%-3. 35% , MgO of 7. 43%-9. 34% and high Mg# of 68. 57-72. 57. These rocks are characterized by enrichment in large ion lithophile elements（ LILE,such as K, Ba, Rb and Sr） and light rare earth elements （ LREE） , relatively depletion in high field strength elements （ HFSE, such as Ta, Nb, Ti and Zr） , and heavy rare earth elements （HREE）. These characteristics suggest that primary magma of the rocks were derived from the partial melting of mantle with miner crustal contamination, which may related to partial melting of mantle wedge by addition of sediment melt from subducting oceanic crust. Based on former and present studies, the authors consider that the Nancha ore deposit high-Mg diorites were formed in compres- sional structural setting which is similar to volcanic arc. It could be related to the subduction of the Paleo-Paci- fic plate beneath the Eurasian continent.
