Peridotites and Chromitites from the Dingqing Ophiolite in the Eastern Segment of Bangong–Nujiang Suture Zone,Tibet: Occurrence Characteristics and Classifications     

LI Guanlong  YANG Jingsui  BO Rongzhong  LIU Fei  RUI Huichao  XIONG Fahui  GUO Tengfei 《《地质学报》英文版》2020,94(Z1):23-25

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大洋地幔橄榄岩-铬铁矿中的金刚石和深地幔再循环     

杨经绥 《地质力学学报》2020,26(5):731-741

全球多地蛇绿岩型地幔橄榄岩和铬铁矿中发现微粒金刚石,并在中国西藏南部和俄罗斯乌拉尔北部的蛇绿岩铬铁矿中发现原位产出的金刚石,认为是地球上金刚石的一种新的产出类型,不同于金伯利岩型金刚石和超高压变质型金刚石。它们与呈斯石英假象的柯石英、高压相的铬铁矿和青松矿等高压矿物以及碳硅石和单质矿物等强还原矿物伴生,指示蛇绿岩中的这些矿物组合形成于深度150~300 km或者更深的地幔。金刚石具有很轻的C同位素组成（δ13C-18‰~-28‰）,并出现多种含Mn矿物和壳源成分包裹体。研究认为它们曾是早期深俯冲的地壳物质,达到>300 km深部地幔或地幔过渡带后,经历了熔融并产生新的流体,后者在上升过程中结晶成新的超高压、强还原矿物组合,通过地幔对流或地幔柱作用被带回到浅部地幔,由此建立了一个俯冲物质深地幔再循环的新模式。蛇绿岩型地幔橄榄岩和铬铁矿中发现金刚石等深部矿物,质疑了蛇绿岩铬铁矿形成于浅部地幔的已有认识,引发了一系列新的科学问题,提出了新的研究方向。   相似文献   

Ultramafic Blocks in Sumdo Region, Lhasa Block, Eastern Tibet Plateau: An Ophiolite Unit     

Chen Songyong  Yang Jingsui  Li Yuan  Xu Xiangzhen 《中国地质大学学报(英文版)》2009,20(2)

Recently, an over 100 kin long MORB-type eclogite belt of Permian was discovered in the Sumdo (松多) region of the Lhasa block, Tibet. A critical question thus is: what is the tectonic setting of the eclogite belt and is it related to an unrecognized suture in the region? Further investigations show that there are some mafic and ultramafic rocks spatially associated with the eclogite belt in the region. Three ultramafic massifs were recognized in the Sumdo region, and called the Luomaling (罗马岭),Gongbupala (贡布爬拉) and Qiazhasumdo (卡扎松多) massifs. All the massifs are fault-contacted with greenschist (Chasagang (岔萨岗) Formation) or muscovite-quartz schist (Mabuku (马布库) Formation), and individuals are about 100 m×50 m in size extending in EW as the regional structure. All the ultramafic rocks have been entirely serpentinized, and the Gongbupala massif has been selected for study in geochemistry. Eleven chemical analyses of the rocks from the Gongbupala massif show a narrow range in contents: SiO2(35.97-40.63) wt.%, MgO (37.02-38.60) wt.%, TiO2(0.01-0.08) wt.%, Al2O3 (0.80-1.64) wt.%, (Na2O+K2O) less than 0.1 wt.%, with high volatile contents (H2O+CO2) (11.24-14.91) wt.%. After recalculation without H2O+CO2, the mean values are SiO2 45.24 wt.%, MgO 43.54 wt.%, FeOT(7.45-9.97) wt.% (8.55 wt.% in average), (MgO+FeOT) 52.09 wt.%, Mg# (100×Mg/(Mg+Fe*), where Fe* represents total Fe)=89.42-90.08, (m+f)/Si ((atomicity Mg+atomicity Fe) /atomicity Si)=1.53-1.75 (1.59 in average), respectively. The mean M/F (atomicity Mg/atomicity Fe) ratio of the rocks is 9.05, which is classified as magnesium enriched-type of ultramafic rocks. The compositional features, depleted in K, Na, Ca, Al and Ti and enriched in Mg#, indicate the characteristics of peridotite originated from a depleted mantle. The rocks have low ∑ REE with (1.60-2.68)×10-6 similar to those of the primitive mantle. The chondrite-normalized REE patterns of all samples show slightly enrichment in LREE, with (Ce/Yb)N 1.03-2.46, but a little depleted in HREE. Most samples show a slight negative anomaly in Eu, a feature In REE from a relic mantle and common features In highly serpentinized ultramafic rocks in the Yarlung-Zangbo (雅鲁藏布) ophiolite and the Bangong (班公)-Nnjiang (怒江)ophiolite in Tibet. The primitive mantle-normalized spiderdiagram of trace elements for Gongbupala ultramafic rocks yields uniform distributed pattern. They are relatively enriched in Rb, Ba, La, P element (LHSE) and depleted in Sin, Ti, Y, Yb element (HFSE), a feature of metasomatic mantle peridotite. The geochemical features of the rocks suggest that the protofith of Gongbupala serpentinite in Sumdo region is harzburgite, a typical depleted mantle rock, and may represent a dismembered ophiolite unit in the region.  相似文献   

Records of Indosinian Orogenesis in Lhasa Terrane, Tibet     

Li Huaqi  Xu Zhiqin  Yang Jingsui  Cai Zhihui  Chen Songyong  Tang Zemin 《中国地质大学学报(英文版)》2009,20(2)

Based on the deformation characteristics of the ductile shear zones in Sumdo (松多) Group, the quartz fabric by EBSD (electron backscatter diffraction), the data of muscovite 40Ar-39Ar geochronology (220-230 Ma) from ductile shear zones and the zircon SHRIMP U-Pb chronology (190 Ma) of granites in Snmdo region, Lhasa (拉萨) terrane is thought to have experienced an important Indosinian orogenic event at 220-230 Ma, which caused the closure of the paleo-Tethys Ocean along the tectonic zone of eclogite and the collision between northern part and southern part of the Lhasa terrane. The zircon SHRIMP U-Pb chronology of 190 Ma for biotite adamellite, with the distributing characteristics of the granite massif intruding in Sumdo Group, indicates that the biotite adamellitc should be the late orogenic or post-orogenic granite resulting from the lndosinian orogenesis. The discovery of Indosinian orogenic belt in Lhasa terrane expansed the southern boundary of lndosinian orogenic belt in Qinghai (青海)-Tibet plateau to Lhasa terrane from Qiangtang (羌塘) terrane, which changed the understanding about the distribution of Indosinian orogenic belt in Qinghai-Tibet plateau and extended the "T" type lndosinian orogenic belt in China. The study is very important for the formation and distribution of paleo-Tethys Ocean in Tibet. The ancient terrane framework and evolution of Qinghai-Tibet plateau need further research.  相似文献   

Geochronology and Geochemistry of the Magmatic Rocks from Zedong Ophiolite, Eastern Yarlung-Zangbo Suture Zone, Tibet     

XIONG Fahui  YANG Jingsui  Paul T. ROBINSON  GAO Jian  ZHANG Lan  CHEN Yanhong  LAI Shengming 《《地质学报》英文版》2017,91(Z1):45-45

The Yarlung Zangbo suture zone extends more than2000 km along southern Tibet and marks the boundary between the Indian subcontinent and Eurasia.The Zedong terrane has been not suggested to represent the vestige of such an intra-oceanic arc developed within the Neo-Tethys Ocean,as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic.In this study,we present detailed geochemical and geochronological data of various types of magmatic rocks widely exposed in the Zedong terrane to constrain the formation age and tectonic setting of the Zedong terrane.We found that the Zedong volcanic rocks belong to high K2O calc-alkaline series,whereas the diabase and gabbro plotted in the low-K calcalkline.The basalt rocks are highly enriched in LREE and LILE,but strongly depleted in HFSE,indicating they were derived from a metasomatized mantle.Both gabbros and diabase have similar N-MORB geochemistry indicates that the cumulates were produced from MOR setting.Zircons from four samples,including the basalt rocks(158-161Ma)are older than the gabbro(131 Ma),certificate the gabbro are as the vein intrude into the basalt rocks.This suggests that the volcanic eruption and plutonic emplacement were coevally developed in the Zedonghave similar positiveεHf(t)values(+2.0 to+15.6)and(+8.6 to+18.4),indicating they were stemmed from similarly depleted mantle sources,same with the gabbro and granitic rocks from the Gangdese arc.Therefore,we proposed that the basalt rocks in the Zedong terrane were formed through partial melting of the mantle wedge metasomatized by slab-released fluids/melts.A part of hydrous basalts were underplated in the thickened lower crust beneath the Zedong terrane,which gave rise to the cumulate and granitic rocks.This suggests that the Zedong terrane represents a slice of the active continental margin developed on the southern margin of the Lhasa terrane as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic,although a possible intra-oceanic arc setting cannot be excluded.  相似文献   

青藏高原南部与东南部重要成矿带的大地构造定格与找矿前景   总被引：4，自引：0，他引：4  

许志琴  杨经绥  李文昌  曾令森  许翠萍 《地质学报》2012,86(12):1857-1869

印度/亚洲汇聚-碰撞过程经历了新特提斯洋盆滋生、消减和俯冲、亚洲南缘增生造山以及印度/亚洲碰撞造山和青藏高原的隆升,在青藏高原南部和东南部造就了"冈底斯火山岩浆带"、"雅鲁藏布江缝合带"、"喜马拉雅碰撞造山带"和大量物质向南东逃逸的"三江侧向挤出地体群",以及相应形成具有重大找矿突破战略前景的"冈底斯成矿带"、"雅鲁藏布江成矿带"、"特提斯喜马拉雅成矿带"和"三江成矿带"。本文通过对四大成矿带的大地构造定格讨论了与资源前景相关的科学问题,提出"冈底斯成矿带"中的岛弧型斑岩铜金矿具有找矿的重大潜力、重视藏东—滇西地区的俯冲-碰撞型岩浆成矿专属性研究;提出扩大西藏罗布莎铬铁矿矿集区的开发规模,以及在西部阿里地区的大型超基性岩体中寻找新的铬铁矿远景地的思路;在三江多阶段成矿作用的叠合型矿床中,集中古特提斯和新特提斯成矿类型,关注与斜向碰撞有关的走滑剪切带对成矿作用的制约机制;需进一步确定特提斯喜马拉雅矿化带与藏南拆离系关系和重视始—中新世高Sr/Y花岗(斑)岩的成矿专属性及找矿前景。  相似文献   

Origin of the Dongbo Peridotite Massif from the Western Part of the Yarlung Zangbo Suture Zone, Tibet: Evidence from Petrological and Os Isotopic Geochemical Data     

NIU Xiaolu  YANG Jingsui  XU Jifeng  LI Jie  CHEN Songyong  FENG Guangying  LIU Fei  XIONG Fahui  LIU Zhao 《《地质学报》英文版》2013,87(Z1):192-193

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An Eocene magmatic belt across central Tibet: mantle subduction triggered by the Indian collision?   总被引：2，自引：0，他引：2  

F. Roger  P. Tapponnier  N. Arnaud  U. Schärer  M. Brunel  X. Zhiqin  & Y. Jingsui 《地学学报》2000,12(3):102-108

Mountain domes rising to ≈ 6600 m along Tibet's Tanggula range herald the Eocene intrusion of calcalkaline granites into terranes accreted much earlier. Together with coeval, cogenetic volcanics, such intrusives, which have similar crystallization and cooling ages, may be part of an ESE-trending belt cutting central Tibet in half. This magmatic belt may have marked a former northern boundary of the plateau, testifying to S-directed subduction of the Asian mantle. Such subduction would have developed soon after India's collision but long before the rise of the plateau's present rims, along one of central Tibet's Mesozoic sutures.  相似文献   

NORTH QAIDAM ULTRAHIGH PRESSURE METAMORPHIC (UHPM) BELT ON THE NORTHEASTERN QINGHAI-TIBET PLATEAU AND ITS EASTWARD EXTENSION     

Yang Jingsui  Song Suguang  Wu Cailai  Shi Rendeng  Marc Jalivet 《地学前缘》2000,(Z1)

NORTH QAIDAM ULTRAHIGH PRESSURE METAMORPHIC (UHPM) BELT ON THE NORTHEASTERN QINGHAI-TIBET PLATEAU AND ITS EASTWARD EXTENSION1　YangJS ,XuZQ ,LiHB ,etal.DiscoveryofeclogiteatnorthernmarginofQaidambasin ,NWChina[J] .ChineseScienceBulletin,1998,4 3:1755～ 176 0 . 2　ZhangJX ,ZhangZM ,XuZQ ,etal.TheagesofU PbandSm NdforeclogitefromthewesternsegmentofAltynTaghtectonicbelt—theevidencesforexistenceofCaledonianorogenicroot[J] .ChineseScienc…  相似文献   

The Bangong Lake ophiolite (NW Tibet) and its bearing on the tectonic evolution of the Bangong–Nujiang suture zone     

Rendeng Shi  Jingsui Yang  Zhiqin Xu  Xuexiang Qi 《Journal of Asian Earth Sciences》2008,32(5-6):438

The Jurassic Bangong Lake ophiolite, NW Tibet, is a key element within the western part of the Bangong–Nujiang suture zone, which marks the boundary between the Lhasa and Qiangtang blocks. It is a tectonic mélange consisting of numerous blocks of peridotite, mafic lavas and dikes. The mantle peridotites include both clinopyroxene-bearing and clinopyroxene-free harzburgites. The Cpx-bearing harzburgite contains Al-rich spinel with low Cr#s (20–25), resembling peridotites formed in mid-ocean ridge settings. On the other hand, the Cpx-free harzburgite is highly depleted with Cr-rich spinel (Cr# = 69–73), typical of peridotites formed in subduction zone environments. Mafic rocks include lavas of N-MORB and E-MORB affinity and boninites. The N-MORB rocks consist of pillow lavas and mafic dikes, whereas the E-MORB rocks are brecciated basalts. The boninites have high SiO₂ (53.2–57.9 wt%), MgO (6.5–12.5 wt%), Cr (166–752 ppm) and Ni (63–213 ppm) and low TiO₂ (0.22–0.37 wt%) and Y (5.34–8.10 ppm), and are characterized by having U-shaped, chondrite-normalized REE patterns. The N-MORB and E-MORB lavas probably formed by different degrees of partial melting of primitive mantle, whereas the boninites reflect partial melting of depleted peridotite in a suprasubduction zone environment. The geochemistry of the ophiolite suggests that it is a fragment of oceanic lithosphere formed originally at a mid-ocean ridge (MOR) and then trapped above an intraoceanic subduction zone (SSZ), where the mantle peridotites were modified by boninitic melts. The Bangong–Nujiang suture zone is believed to mark the boundary between two blocks within Gondwanaland rather than to separate Gondwanaland from Eurasia.  相似文献