Magmatic oxide deposits in the～260 Ma Emeishan Large Igneous Province（ELIP）,SW China and northern Vietnam,are important sources of Fe,Ti and V.Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua,Hongg...Magmatic oxide deposits in the～260 Ma Emeishan Large Igneous Province（ELIP）,SW China and northern Vietnam,are important sources of Fe,Ti and V.Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua,Hongge,and Baima deposits,are well described in the literature and are hosted in layered mafic-ultramafic intrusions in the Panxi region,the central ELIP.The same type of ELIP- related deposits also occur far to the south and include the Anyi deposit,about 130 km south of Panzhihua,and the Mianhuadi deposit in the Red River fault zone.The Anyi deposit is relatively small but is similarly hosted in a layered mafic intrusion.The Mianhuadi deposit has a zircon U-Pb age of～260 Ma and is thus contemporaneous with the ELIP.This deposit was variably metamorphosed during the Indosinian orogeny and Red River faulting.Compositionally,magnetite of the Mianhuadi deposit contains smaller amounts of Ti and V than that of the other deposits,possibly attributable to the later metamorphism.The distribution of the oxide ore deposits is not related to the domal structure of the ELIP.One major feature of all the oxide deposits in the ELIP is the spatial association of oxide-bearing gabbroic intrusions,syenitic plutons and high-Ti flood basalts.Thus,we propose that magmas from a mantle plume were emplaced into a shallow magma chamber where they were evolved into a field of liquid immiscibility to form two silicate liquids,one with an extremely Fe-Ti-rich gabbroic composition and the other syenitic.An immiscible Fe-Ti-（P） oxide melt may then separate from the mafic magmas to form oxide deposits.The parental magmas from which these deposits formed were likely Fe-Ti-rich picritic in composition and were derived from enriched asthenospheric mantle at a greater depth than the magmas that produced sulfide-bearing intrusions of the ELIP.展开更多
The western margin of Yangtze Craton is known as a significant sediment-hosted base-metal aggregate cluster,especially for Pb-Zn deposits in China,e.g.Jinding,Daliangzi,Tianbaoshan, Kuangshanchang and Qinlinchang depo...The western margin of Yangtze Craton is known as a significant sediment-hosted base-metal aggregate cluster,especially for Pb-Zn deposits in China,e.g.Jinding,Daliangzi,Tianbaoshan, Kuangshanchang and Qinlinchang deposits.In comparison with the classic MVT deposits in the world, based on the basic geology of the sediment-hosted Pb-Zn deposits,this paper focuses on temporal-spatial distribution of this deposit to further discuss its large scale mineralization and tectonic evolution history.In the SW Sanjiang Thethys,Jinding deposit is typically thrust fault-controlled and hosted mainly in the sandstones and breccia-bearing sandstones,whereas MVT-type deposits are controlled by lithology and faulting/fracturing with a strong preference for carbonate-hosted rocks.Most importantly,Jinding Pb-Zn deposit differs from the other types of sediment-hosted Pb-Zn deposits in which it was formed in a strongly deformed foreland basin within a continental collision zone.In the Kangdian area,the sediment-hosted Pb-Zn deposits were formed in the extensional basin on the side of the continental orogenic belt along the Yangtze Craton.Compared with classic MVT deposits,the Pb-Zn deposits in the Kangdian area belong to MVT deposits.This paper is significant not only for interpretation of the genesis of sediment-hosted Pb-Zn deposits but also for exploiting large base metal deposits in large sedimentary target areas.展开更多
SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neoproterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857±13)...SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neoproterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857±13) Ma. Geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (late Mesoproterozoic to early Neoproterozoic) low-K tholeiitic protolith within an intraplate anorogenic setting. The Guandaoshan pluton probably records the earliest magmatism induced by the proposed ca. 860-750 Ma mantle superplume beneath the supercontinent Rodinia.展开更多
Located on the western Yangtze Block, the Sichuan （四川）-Yunnan （云南）-Guizhou （贵州） （SYG） Pb-Zn metallogenic province has been a major source of base metals for China. In the south- eastern SYG province, str...Located on the western Yangtze Block, the Sichuan （四川）-Yunnan （云南）-Guizhou （贵州） （SYG） Pb-Zn metallogenic province has been a major source of base metals for China. In the south- eastern SYG province, structures are well developed and strictly control about 100 Pb-Zn deposits. Al- most all the deposits are hosted in Devonian to Permian carbonate rocks. Lead-zinc ores occur either as veinlets or disseminations in dolomitic rocks with massive and disseminated textures. Ore minerals are composed of pyrite, sphalerite and galena, and gangue minerals are calcite and dolomite. Sulfide min- erals from four typical Pb-Zn deposits are analyzed for sulfur isotope compositions to trace the origin and evolution of hydrothermal fluids. The results show that 034S values of sulfide minerals range from ＋3.50%0 to ＋20.26%0, with a broad peak in ＋10%0 to ＋16%0, unlike mantle-derived sulfur （0±3%0）. How- ever, the mean δ34Ssulflde and δ34S∑s-fluids values are similar to that of sulfate-bearing evaporites in the host rocks （gypsum： -＋15%0 and barite： ＋22%0 to ＋28%0） and Cambrian to Permian seawater sulfate （＋15%0 to ＋35%0）. This suggests that reduced sulfur in hydrothermal fluids was likely derived from evaporates in the host rocks by thermo-chemical sulfate reduction （TSR）. Calculated δ34S∑s-fluids values of the Shanshulin （杉树林）, Qingshan （青山）, Shaojiwan （筲箕湾） and Tianqiao （天桥） Pb-Zn deposits are ＋21.59‰, ＋18.33‰, ＋11.4‰ and ＋10.62‰, respectively, indicating sulfur-bearing hydrothermal fluids may be evolved from the Shanshulin to Qingshan and then the Shaojiwan to Tianqiao deposition sites along the Yadu （垭都）-Ziyun （紫云） lithospheric fracture in the southeastern SYG province.展开更多
Olivine phenocryst compositions and whole-rock chemical compositions are used to identify primitive picrite basalts from the early part of flood basalt successions in the western part of the Emeishan large igneous pro...Olivine phenocryst compositions and whole-rock chemical compositions are used to identify primitive picrite basalts from the early part of flood basalt successions in the western part of the Emeishan large igneous province （ELIP）, southwestern China. The Fo contents of olivine phenocrysts of komatiites with MgO-21.79 wt% range from 85.2% to 91.4%. The composition of unerupted parental melts is calculated from the compositions of the most Fo-rich olivine phenocrysts. These melts had -22 wt% MgO, and originated in mantle with a potential temperature of -1600℃ and at about 4.2 GPa pressure, supporting the conclusion that the generation of ELIP can be attributed to melting of a plume head beginning at -138 km depth.展开更多
The Early Cretaceous-Early Eocene granitoids in the Tengchong Block record the evolutionary history of the Mesozoic-Cenozoic tectono-magmatic evolution of Eastern Tethys.(a)The Early Cretaceous granitoids with relativ...The Early Cretaceous-Early Eocene granitoids in the Tengchong Block record the evolutionary history of the Mesozoic-Cenozoic tectono-magmatic evolution of Eastern Tethys.(a)The Early Cretaceous granitoids with relatively low(^(87)Sr/^(86)Sr)iratios of 0.7090-0.7169 andε_(Nd)(t)values of-9.8 to-7.8 display metaluminous,calc-alkaline dominated by I-type granite affinity and hybrid mantle-crust geochemical signatures.They may have been derived from melting of the subducted Meso-Tethyan BangongNujiang oceanic crust with terrigenous sediments in an arc-continent collisional setting.(b)The Late Cretaceous-Paleocene granitoids with relatively high(^(87)Sr/^(86)Sr)iratios of 0.7109-0.7627,andε_(Nd)(t)values of-12.1 to-7.9 exhibit metaluminous to peraluminous,calc-alkaline dominated by S-type granite affinity and hybrid Lower-Upper crust geochemical signatures,which may be originated from partial melting of the Meso-Proterozoic continental crust in the collision setting between the Tengchong Block and Baoshan Block.(c)The Early Eocene granitoids have metaluminous,calc-alkaline I-type and S-type granites dual affinity,with relatively high(^(87)Sr/^(86)Sr)iratios of 0.711-0.736,ε_(Nd)(t)values of-9.4 to-4.7,showing crust-mantle mixing geochemical signatures.They may have been originated from partial melting of the late Meso-Proterozoic upper crustal components mixed with some upper mantle material during the ascent process of mantle magma caused by the subduction of the Neo-Tethyan Putao-Myitkyian oceanic crust,and collision between the Western Burma Block and the Tengchong Block.It is these multi-stage subductions and collisions that caused the spatial and temporal distribution of the granitic rocks in the Tengchong Block.展开更多
An early Paleozoic Proto-Tethys ocean in western Yunnan has long been postulated although no robust geological evidence has been identified.Here we investigated the recently-identified Mayidui and Wanhe ophiolitic m&#...An early Paleozoic Proto-Tethys ocean in western Yunnan has long been postulated although no robust geological evidence has been identified.Here we investigated the recently-identified Mayidui and Wanhe ophiolitic mélanges in SW Yunnan,which occurs in a N-S trending belt east of the late Paleozoic Changning-Menglian suture zone.The ophiolites consist mainly of meta-basalts(amphibole schists),meta-(cumulate)gabbros and gabbroic diorites,and meta-chert-shale,representing ancient oceanic crust and pelagic and hemipelagic sediments,respectively.Six samples of gabbros and gabbroic diorites from 3 profiles(Mayidui,Kongjiao and Yinchanghe)yielded zircon U-Pb ages between 462±6 Ma and 447±9 Ma,constraining the formation of the Mayidui and Wanhe ophiolites to Middle Ordovician.Gabbros from the Mayidui and Kongjiao profiles share similar geochemical characteristics with affinities to tholeiitic series,and are characterized by depleted to slightly enriched LREEs relative to HREEs with(La/Sm)N=0.69-1.87,(La/Yb)N=0.66-4.72.These,along with their predominantly positive wholerock eNd(t)and zircon eHf(t)values,indicate a MORB-like magma source.By contrast,the meta-mafic rocks from the Yinchanghe profile show significantly enriched LREEs((La/Sm)N=0.97-3.33,(La/Yb)N=1.19-14.93),as well as positive whole-rock eNd(t)and positive to negative zircon eHf(t)values,indicating an E-MORB-type mantle source.These geochemical features are consistent with an intra-oceanic setting for the formation of the Mayidui-Wanhe ophiolites.Our data,integrated with available geological evidence,provide robust constraints on the timing and nature of the Mayidui-Wanhe ophiolitic mélange,and suggest that the ophiolites represent remnants of the Proto-Tethys Ocean,which opened through separation of the Indochina and Simao blocks from the northern margin of Gondwana before the Early Cambrian,and evolved through to the Silurian.展开更多
The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of N...The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations, and are structurally controlled by EW-trending fault. It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb. Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks. The ore minerals include chalcopyrite, galena and pyrite, and gangue minerals are quartz, sericite and chlorite. The H-O isotopic compositions of quartz, S-Cu-Pb isotopic compositions of sulfide minerals, Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit. The oSCUNBs values of chalcopyrite range from -0.09% to ＋0.33%0, similar to basic igneous rocks and chalcopyrite from magmatic deposits. J6SCUNBS values of chalcopyrite from the early, middle and final mineralization stages show an increasing trend due to 63Cu prior migrated in gas phase when fluids exsolution from magma, ja4ScDT values of sulfide minerals range from -2.7‰ to ＋2.8‰, similar to mantle-derived sulfur （0±3‰）. The positive correlation between J65CUNBs and ja4SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma. JDu2o- SMOW and JlSOH2O-SMOW values of water in fluid inclusions of quartz range from -60.7‰ to -44.4‰ and ＋7.9‰ to ＋9.0%0 （T=260℃）, respectively and fall in the field for magmatic and metamorphic waters, implicating that mixed sources for H20 in hydrothermal fluids. Ores and sulfide minerals have a small range of Pb isotopic compositions （208Pb/204pb=38.152 to 38.384, 207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049） that are close to orogenic belt and upper crust Pb evolution curve, and similar to Neoproterozo展开更多
将Holland风场与ERA5风场相结合,通过引入一个随风速半径变化的权重系数,构建了混合风场,进而利用MIKE21 SW建立了浙江海域台风浪模型。使用Holland风场、ERA5风场、混合风场作为输入风场模拟1918号台风“米娜”期间的风速和有效波高,...将Holland风场与ERA5风场相结合,通过引入一个随风速半径变化的权重系数,构建了混合风场,进而利用MIKE21 SW建立了浙江海域台风浪模型。使用Holland风场、ERA5风场、混合风场作为输入风场模拟1918号台风“米娜”期间的风速和有效波高,验证结果说明Holland风场和ERA5风场均无法准确反映真实风场和有效波高,而本文构建的混合风场弥补了两种风场的不足。为验证混合风场在浙江海域是否具有普适性,选取近5年影响浙江海域最为严重的5个典型台风进行台风浪数值模拟实验,并开展误差统计分析。结果表明:Holland风场在台风中心周围的风速模拟表现较好,最大风速的平均相对误差为8.62%~10.19%,但10 m s以下风速的平均相对误差较大,为29.76%~44.29%;ERA5风场在台风中心周围的风速偏小,最大风速的平均相对误差为17.64%~25.77%,但10 m s以下风速的平均相对误差比Holland风场小,为19.64%~32.00%。对5个台风的模拟中,由Holland风场、ERA5风场和混合风场驱动得到的台风浪有效波高平均相对误差的平均值分别为29.92%、25.62%和22.82%,均方根误差的平均值分别为0.46 m、0.42 m和0.39 m,一致性指数分别为0.94、0.95和0.96。上述结果说明本文构建的混合风场在浙江海域具有普适性,能够提高台风浪的模拟准确度。展开更多
The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolutio...The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto-and Paleo-Tethys.In this paper,we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic,based on stratigraphic,sedimentologic,and magmatic evidences.The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys.The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian(about 505 Ma).From the late Late Ordovician to the ealiest Silurian(about 450–442 Ma),the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean.The main collision stage occurred in the early Silurian(about 442–430 Ma)and the postcollision stage lasted from the mid-Silurian to the early Carboniferous(430–355 Ma).The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian,and the ocean was then subducted in an eastward direction in the middle Late Carboniferous(about 310 Ma).The initial collision stage in the Paleo-Tethys took place at the end of the Permian(about 253Ma),and the main stage of the collision persisted into the early Ladinian(about 253–238 Ma).This was followed by postcollision extension from the late Ladinian to the early Jurassic(ca.238–196 Ma).We suggest that the opening of Paleo-Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys.Additionally,the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean.展开更多
基金supported by the Research Grant Council of Hong Kong(HKU707012P)to MFZfrom a Chinese National "973" project (2011CB808903)+1 种基金a "CAS Hundred Talents" project under Chinese Academy of Sciences to CYWSouth African National Science Foundation Grant SA/China Project 67220 to SP and MFZ
文摘Magmatic oxide deposits in the～260 Ma Emeishan Large Igneous Province（ELIP）,SW China and northern Vietnam,are important sources of Fe,Ti and V.Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua,Hongge,and Baima deposits,are well described in the literature and are hosted in layered mafic-ultramafic intrusions in the Panxi region,the central ELIP.The same type of ELIP- related deposits also occur far to the south and include the Anyi deposit,about 130 km south of Panzhihua,and the Mianhuadi deposit in the Red River fault zone.The Anyi deposit is relatively small but is similarly hosted in a layered mafic intrusion.The Mianhuadi deposit has a zircon U-Pb age of～260 Ma and is thus contemporaneous with the ELIP.This deposit was variably metamorphosed during the Indosinian orogeny and Red River faulting.Compositionally,magnetite of the Mianhuadi deposit contains smaller amounts of Ti and V than that of the other deposits,possibly attributable to the later metamorphism.The distribution of the oxide ore deposits is not related to the domal structure of the ELIP.One major feature of all the oxide deposits in the ELIP is the spatial association of oxide-bearing gabbroic intrusions,syenitic plutons and high-Ti flood basalts.Thus,we propose that magmas from a mantle plume were emplaced into a shallow magma chamber where they were evolved into a field of liquid immiscibility to form two silicate liquids,one with an extremely Fe-Ti-rich gabbroic composition and the other syenitic.An immiscible Fe-Ti-（P） oxide melt may then separate from the mafic magmas to form oxide deposits.The parental magmas from which these deposits formed were likely Fe-Ti-rich picritic in composition and were derived from enriched asthenospheric mantle at a greater depth than the magmas that produced sulfide-bearing intrusions of the ELIP.
基金supported by the National Basic Research Program(No.2009CB421008)the Fundamental Research Funds for the Central Universities (No.2010ZY02)+2 种基金China Postdoctoral Science Foundation (No.20090460400)Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)the 111 Project(No.B07011)
文摘The western margin of Yangtze Craton is known as a significant sediment-hosted base-metal aggregate cluster,especially for Pb-Zn deposits in China,e.g.Jinding,Daliangzi,Tianbaoshan, Kuangshanchang and Qinlinchang deposits.In comparison with the classic MVT deposits in the world, based on the basic geology of the sediment-hosted Pb-Zn deposits,this paper focuses on temporal-spatial distribution of this deposit to further discuss its large scale mineralization and tectonic evolution history.In the SW Sanjiang Thethys,Jinding deposit is typically thrust fault-controlled and hosted mainly in the sandstones and breccia-bearing sandstones,whereas MVT-type deposits are controlled by lithology and faulting/fracturing with a strong preference for carbonate-hosted rocks.Most importantly,Jinding Pb-Zn deposit differs from the other types of sediment-hosted Pb-Zn deposits in which it was formed in a strongly deformed foreland basin within a continental collision zone.In the Kangdian area,the sediment-hosted Pb-Zn deposits were formed in the extensional basin on the side of the continental orogenic belt along the Yangtze Craton.Compared with classic MVT deposits,the Pb-Zn deposits in the Kangdian area belong to MVT deposits.This paper is significant not only for interpretation of the genesis of sediment-hosted Pb-Zn deposits but also for exploiting large base metal deposits in large sedimentary target areas.
基金supported by the National Climbing Project(Grant No.95-Y-25)the National Natural Science Foundation of China(Grant Nos.40032010-B and 49725309)the Chinese Academy of Sciences(Grant No.KZCX2-101).
文摘SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neoproterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857±13) Ma. Geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (late Mesoproterozoic to early Neoproterozoic) low-K tholeiitic protolith within an intraplate anorogenic setting. The Guandaoshan pluton probably records the earliest magmatism induced by the proposed ca. 860-750 Ma mantle superplume beneath the supercontinent Rodinia.
基金supported by the National Natural Science Foundation of China(Nos.41102055,41272111 and 41102053)
文摘Located on the western Yangtze Block, the Sichuan （四川）-Yunnan （云南）-Guizhou （贵州） （SYG） Pb-Zn metallogenic province has been a major source of base metals for China. In the south- eastern SYG province, structures are well developed and strictly control about 100 Pb-Zn deposits. Al- most all the deposits are hosted in Devonian to Permian carbonate rocks. Lead-zinc ores occur either as veinlets or disseminations in dolomitic rocks with massive and disseminated textures. Ore minerals are composed of pyrite, sphalerite and galena, and gangue minerals are calcite and dolomite. Sulfide min- erals from four typical Pb-Zn deposits are analyzed for sulfur isotope compositions to trace the origin and evolution of hydrothermal fluids. The results show that 034S values of sulfide minerals range from ＋3.50%0 to ＋20.26%0, with a broad peak in ＋10%0 to ＋16%0, unlike mantle-derived sulfur （0±3%0）. How- ever, the mean δ34Ssulflde and δ34S∑s-fluids values are similar to that of sulfate-bearing evaporites in the host rocks （gypsum： -＋15%0 and barite： ＋22%0 to ＋28%0） and Cambrian to Permian seawater sulfate （＋15%0 to ＋35%0）. This suggests that reduced sulfur in hydrothermal fluids was likely derived from evaporates in the host rocks by thermo-chemical sulfate reduction （TSR）. Calculated δ34S∑s-fluids values of the Shanshulin （杉树林）, Qingshan （青山）, Shaojiwan （筲箕湾） and Tianqiao （天桥） Pb-Zn deposits are ＋21.59‰, ＋18.33‰, ＋11.4‰ and ＋10.62‰, respectively, indicating sulfur-bearing hydrothermal fluids may be evolved from the Shanshulin to Qingshan and then the Shaojiwan to Tianqiao deposition sites along the Yadu （垭都）-Ziyun （紫云） lithospheric fracture in the southeastern SYG province.
文摘Olivine phenocryst compositions and whole-rock chemical compositions are used to identify primitive picrite basalts from the early part of flood basalt successions in the western part of the Emeishan large igneous province （ELIP）, southwestern China. The Fo contents of olivine phenocrysts of komatiites with MgO-21.79 wt% range from 85.2% to 91.4%. The composition of unerupted parental melts is calculated from the compositions of the most Fo-rich olivine phenocrysts. These melts had -22 wt% MgO, and originated in mantle with a potential temperature of -1600℃ and at about 4.2 GPa pressure, supporting the conclusion that the generation of ELIP can be attributed to melting of a plume head beginning at -138 km depth.
基金funded by the National Natural Science Foundation of China(Grant Nos.41972312,41672329,41272365)the National Key Research and Development Project of China(Grant No.2016YFC0600509)。
文摘The Early Cretaceous-Early Eocene granitoids in the Tengchong Block record the evolutionary history of the Mesozoic-Cenozoic tectono-magmatic evolution of Eastern Tethys.(a)The Early Cretaceous granitoids with relatively low(^(87)Sr/^(86)Sr)iratios of 0.7090-0.7169 andε_(Nd)(t)values of-9.8 to-7.8 display metaluminous,calc-alkaline dominated by I-type granite affinity and hybrid mantle-crust geochemical signatures.They may have been derived from melting of the subducted Meso-Tethyan BangongNujiang oceanic crust with terrigenous sediments in an arc-continent collisional setting.(b)The Late Cretaceous-Paleocene granitoids with relatively high(^(87)Sr/^(86)Sr)iratios of 0.7109-0.7627,andε_(Nd)(t)values of-12.1 to-7.9 exhibit metaluminous to peraluminous,calc-alkaline dominated by S-type granite affinity and hybrid Lower-Upper crust geochemical signatures,which may be originated from partial melting of the Meso-Proterozoic continental crust in the collision setting between the Tengchong Block and Baoshan Block.(c)The Early Eocene granitoids have metaluminous,calc-alkaline I-type and S-type granites dual affinity,with relatively high(^(87)Sr/^(86)Sr)iratios of 0.711-0.736,ε_(Nd)(t)values of-9.4 to-4.7,showing crust-mantle mixing geochemical signatures.They may have been originated from partial melting of the late Meso-Proterozoic upper crustal components mixed with some upper mantle material during the ascent process of mantle magma caused by the subduction of the Neo-Tethyan Putao-Myitkyian oceanic crust,and collision between the Western Burma Block and the Tengchong Block.It is these multi-stage subductions and collisions that caused the spatial and temporal distribution of the granitic rocks in the Tengchong Block.
文摘An early Paleozoic Proto-Tethys ocean in western Yunnan has long been postulated although no robust geological evidence has been identified.Here we investigated the recently-identified Mayidui and Wanhe ophiolitic mélanges in SW Yunnan,which occurs in a N-S trending belt east of the late Paleozoic Changning-Menglian suture zone.The ophiolites consist mainly of meta-basalts(amphibole schists),meta-(cumulate)gabbros and gabbroic diorites,and meta-chert-shale,representing ancient oceanic crust and pelagic and hemipelagic sediments,respectively.Six samples of gabbros and gabbroic diorites from 3 profiles(Mayidui,Kongjiao and Yinchanghe)yielded zircon U-Pb ages between 462±6 Ma and 447±9 Ma,constraining the formation of the Mayidui and Wanhe ophiolites to Middle Ordovician.Gabbros from the Mayidui and Kongjiao profiles share similar geochemical characteristics with affinities to tholeiitic series,and are characterized by depleted to slightly enriched LREEs relative to HREEs with(La/Sm)N=0.69-1.87,(La/Yb)N=0.66-4.72.These,along with their predominantly positive wholerock eNd(t)and zircon eHf(t)values,indicate a MORB-like magma source.By contrast,the meta-mafic rocks from the Yinchanghe profile show significantly enriched LREEs((La/Sm)N=0.97-3.33,(La/Yb)N=1.19-14.93),as well as positive whole-rock eNd(t)and positive to negative zircon eHf(t)values,indicating an E-MORB-type mantle source.These geochemical features are consistent with an intra-oceanic setting for the formation of the Mayidui-Wanhe ophiolites.Our data,integrated with available geological evidence,provide robust constraints on the timing and nature of the Mayidui-Wanhe ophiolitic mélange,and suggest that the ophiolites represent remnants of the Proto-Tethys Ocean,which opened through separation of the Indochina and Simao blocks from the northern margin of Gondwana before the Early Cambrian,and evolved through to the Silurian.
基金supported by Science Foundation of Guizhou province (No. 2012-2334)Open Foundation of State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (Nos. 2011001 and 2009014)National Natural Science Foundation of China (Nos. 41102055 and 41102053)
文摘The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations, and are structurally controlled by EW-trending fault. It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb. Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks. The ore minerals include chalcopyrite, galena and pyrite, and gangue minerals are quartz, sericite and chlorite. The H-O isotopic compositions of quartz, S-Cu-Pb isotopic compositions of sulfide minerals, Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit. The oSCUNBs values of chalcopyrite range from -0.09% to ＋0.33%0, similar to basic igneous rocks and chalcopyrite from magmatic deposits. J6SCUNBS values of chalcopyrite from the early, middle and final mineralization stages show an increasing trend due to 63Cu prior migrated in gas phase when fluids exsolution from magma, ja4ScDT values of sulfide minerals range from -2.7‰ to ＋2.8‰, similar to mantle-derived sulfur （0±3‰）. The positive correlation between J65CUNBs and ja4SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma. JDu2o- SMOW and JlSOH2O-SMOW values of water in fluid inclusions of quartz range from -60.7‰ to -44.4‰ and ＋7.9‰ to ＋9.0%0 （T=260℃）, respectively and fall in the field for magmatic and metamorphic waters, implicating that mixed sources for H20 in hydrothermal fluids. Ores and sulfide minerals have a small range of Pb isotopic compositions （208Pb/204pb=38.152 to 38.384, 207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049） that are close to orogenic belt and upper crust Pb evolution curve, and similar to Neoproterozo
文摘将Holland风场与ERA5风场相结合,通过引入一个随风速半径变化的权重系数,构建了混合风场,进而利用MIKE21 SW建立了浙江海域台风浪模型。使用Holland风场、ERA5风场、混合风场作为输入风场模拟1918号台风“米娜”期间的风速和有效波高,验证结果说明Holland风场和ERA5风场均无法准确反映真实风场和有效波高,而本文构建的混合风场弥补了两种风场的不足。为验证混合风场在浙江海域是否具有普适性,选取近5年影响浙江海域最为严重的5个典型台风进行台风浪数值模拟实验,并开展误差统计分析。结果表明:Holland风场在台风中心周围的风速模拟表现较好,最大风速的平均相对误差为8.62%~10.19%,但10 m s以下风速的平均相对误差较大,为29.76%~44.29%;ERA5风场在台风中心周围的风速偏小,最大风速的平均相对误差为17.64%~25.77%,但10 m s以下风速的平均相对误差比Holland风场小,为19.64%~32.00%。对5个台风的模拟中,由Holland风场、ERA5风场和混合风场驱动得到的台风浪有效波高平均相对误差的平均值分别为29.92%、25.62%和22.82%,均方根误差的平均值分别为0.46 m、0.42 m和0.39 m,一致性指数分别为0.94、0.95和0.96。上述结果说明本文构建的混合风场在浙江海域具有普适性,能够提高台风浪的模拟准确度。
基金supported by the National Natural Science Foundation of China (Grant Nos.92055201,41672222,and 41873062)the China Geological Survey (Grant No.2011-03-04-02)。
文摘The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto-and Paleo-Tethys.In this paper,we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic,based on stratigraphic,sedimentologic,and magmatic evidences.The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys.The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian(about 505 Ma).From the late Late Ordovician to the ealiest Silurian(about 450–442 Ma),the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean.The main collision stage occurred in the early Silurian(about 442–430 Ma)and the postcollision stage lasted from the mid-Silurian to the early Carboniferous(430–355 Ma).The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian,and the ocean was then subducted in an eastward direction in the middle Late Carboniferous(about 310 Ma).The initial collision stage in the Paleo-Tethys took place at the end of the Permian(about 253Ma),and the main stage of the collision persisted into the early Ladinian(about 253–238 Ma).This was followed by postcollision extension from the late Ladinian to the early Jurassic(ca.238–196 Ma).We suggest that the opening of Paleo-Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys.Additionally,the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean.
