藏南仲巴地区早白垩世日朗组物源分析及其构造意义

藏南仲巴地区早白垩世日朗组出露于特提斯喜马拉雅北亚带,整体为黄绿色火山岩屑砂岩,局部层位可见页岩与泥岩,分析为一套深海海底扇沉积组合。本文仔细分析了日朗组砂岩岩石学特征及鲍马序列和槽模沉积构造等沉积学特征,结果表明:日朗组砂岩成分成熟度和结构成熟度均不高,具有近源物源的特点;槽模构造古水流数据统计表明古流向由南向北,指示物质组分来源于南侧特提斯喜马拉雅和/或印度克拉通。砂岩碎屑组分统计结果表明日朗组的物源区构造背景属于克拉通内部及石英再旋回区。碎屑锆石U-Pb年龄频谱图对比进一步表明其物源区为印度稳定大陆边缘,外加一套早白垩世火山碎屑物质的输入。仲巴地区日朗组物源特征反映了印度大陆北缘早白垩世由深部断裂引起的一次强烈的火山事件,可能与印度大陆从澳大利亚-南极大陆裂解有关。     

藏南古近纪甲查拉组物源分析及其对印度-欧亚大陆碰撞启动时间的约束

位于特提斯喜马拉雅北亚带的江孜地区古近纪甲查拉组角度不整合于晚白垩世宗卓组之上,系该地区最高(时代最晚)海相地层。运用岩石学和地球化学方法对其进行分析研究结果表明该组物源区主要为近源再旋回造山带,岩屑的母岩类型主要是岩浆弧成因的中性、中酸性安山质火山岩。新生代以前,特提斯喜马拉雅属于印度板块的被动大陆边缘,从特提斯喜马拉雅南亚带向北亚带显示了一种从浅水陆棚到深水盆地的变化,在侏罗-白垩纪时其陆源碎屑物主要是成熟度极高的石英砂岩,所以甲查拉组的碎屑物质只能来源于当时的冈底斯弧地区,所获有限的古水流证据也指示了这一点。从欧亚大陆侵蚀下来的碎屑物质被带到原印度大陆地区沉积,暗示该区的特提斯洋壳已经完全消失,印度与欧亚大陆在特提斯喜马拉雅中、东部产生了初始的陆-陆碰撞,其碰撞的启动时间为甲查拉组开始沉积的65 M a±。     

印度-亚洲大陆碰撞初期的海沟沉积:藏东南宗卓组沉积岩石学与物源分析

混杂岩是汇聚板块边缘的地质体,主要形成于俯冲和碰撞的背景下。本文对藏东南浪卡子地区宗卓组进行了详细的野外地质调查、岩石学研究和物源分析。野外调查表明,宗卓组与下伏特提斯喜马拉雅地层的原始接触关系为逐渐过渡的沉积接触,后期构造作用多呈断层接触。界线附近,宗卓组滑塌的岩块长轴沿页岩片理方向展布,显示沉积混杂的特征;宗卓组多数地层受后期构造作用的改造。宗卓组的混杂岩由岩块和"基质"组成,岩块包括砂岩、灰岩、硅质岩,"基质"以硅质页岩、泥岩为主。砂岩岩块碎屑成分多为火成岩岩屑和沉积岩岩屑;碎屑锆石U-Pb年龄主要分布在88~140 Ma,中生代的锆石εHf(t)值变化范围大(-20~17)。这些特征表明岩块的物源为亚洲活动大陆边缘。结合宗卓组的基底为印度大陆北缘的特提斯喜马拉雅地层,因此宗卓组沉积混杂岩为印度-亚洲大陆碰撞之后沉积。由于宗卓组砂岩岩块缺乏冈底斯弧中古近纪年轻(60 Ma)年龄,推测这些砂岩岩块的碎屑并非直接来自冈底斯弧及拉萨地体,而是来自洋壳俯冲时期形成的增生楔修康混杂岩。由此,宗卓组为印度-亚洲板块碰撞初期,深水环境下侧向搬运形成的一套沉积混杂岩,物源主要来自西侧的修康混杂岩。宗卓组代表了印度-亚洲大陆碰撞最早期的海沟沉积,其分布指示了印度-亚洲大陆碰撞初期的缝合带位置。     

藏南下侏罗统日当组地球化学和碎屑锆石U-Pb年代学特征及构造意义

喜马拉雅东段印度被动大陆边缘沉积的中—新生界地层是研究新特提斯大洋演化的重要载体。本文对西藏山南市错那县曲卓木乡的下侏罗统日当组粉砂岩和页岩进行碎屑锆石U-Pb定年和全岩地球化学分析。其碎屑锆石年龄有两个峰值区间，分别是546～496 Ma和952～853 Ma，峰值年龄分别为516 Ma和926 Ma，最年轻年龄为292.5±5.5 Ma。日当组的Al₂O₃含量较高，平均值为20.8%，而CaO、Na₂O和K₂O含量均较低(0.4%～4.0%)，表明日当组富含粘土矿物，其物源区成分成熟度高，风化强，代表沉积物的再循环以及构造静止期或者克拉通环境。日当页岩轻稀土元素富集，重稀土元素亏损，Eu负异常明显。本文综合古地理环境，认为日当组物质来源主要为冈瓦纳大陆北缘的印度板块和澳大利亚板块，构造背景为稳定的被动大陆边缘。     

昌宁-孟连结合带东部泥盆系—石炭系南段组研究新进展及其对特提斯洋演化的启示

原—古特提斯洋之间的构造转换方式一直是国际国内研究的热点与难点。南段组是昌宁-孟连结合带东侧地层重要组成部分,其沉积时代、沉积环境和与特提斯演化的关系均存在争议,制约了对昌宁-孟连结合带乃至东特提斯洋演化特征的认识和理解。本文对南段组变质砂岩样品开展了岩石学、岩相学、元素地球化学以及碎屑锆石U-Pb年代学研究工作,结果表明其为泥盆纪—石炭纪被动大陆边缘的浅海沉积,物源来自成熟的大陆。南段组碎屑锆石年龄谱可识别出560Ma、950Ma和1130Ma三个明显的年龄峰值,与来自澳大利亚北缘的拉萨地体上古生界碎屑锆石年龄谱可以对比。南段组物源特征具有亲冈瓦纳大陆属性,但不能据此限定所在地体泥盆—石炭纪古地理位置。保山地块东缘泥盆系曼信组碎屑锆石年龄谱可识别出440Ma和950Ma两个年龄峰值,与南段组存在显著区别。本文新获得昌宁-孟连特提斯洋两侧泥盆纪碎屑锆石年龄谱特征,为原特提斯洋与古特提斯洋之间为连续演化提供了新的沉积学证据。     

藏北南羌塘盆地二叠纪曲地组碎屑锆石LA-ICP-MSU-Pb年龄及其地质意义

南羌塘盆地是特提斯大洋俯冲削减而产生的一套构造增生地质体,也是研究青藏高原早期构造演化的关键地区,盆地内出露的石炭纪地层极少。对晚古生代曲地组2个砂岩样品进行全岩主量、微量、稀土元素的研究,并采用LA-ICP-MS同位素测定技术对其中的碎屑锆石进行U-Pb同位素测定,结果表明,碎屑锆石年龄具有6个峰值:330~270Ma、560~480Ma、880~720Ma、1750~1650Ma、2400~2000Ma和2800Ma;地球化学特征表明,曲地组源区的大地构造环境主要为被动大陆边缘及大陆岛弧环境;沉积物物源具有多源性,但仍需进一步研究。推测其物源主要为晚古生代二叠纪之前的冈瓦纳大陆北缘相关地体。     

藏南柳区砾岩的沉积环境及物源分析:对雅鲁藏布缝合带古近纪隆升的约束

沿雅鲁藏布江缝合带分布的柳区砾岩是喜马拉雅造山作用过程中重要的沉积记录。然而,目前对该套地层的构造属性仍存在不同的认识,因为尚未发现来自冈底斯中酸性的火山岩砾石,部分学者认为其是在印度和洋内岛弧碰撞形成的。本次工作对柳区出露的柳区砾岩进行了详细的剖面实测、沉积学观察和物源区分析。地层由厚层的砾级到巨砾级的砾岩以及相对较薄层的砂岩和泥岩组成,砾石包括硅质岩、基性-超基性岩、石英砂岩、岩屑砂岩以及板岩和千枚岩。砾岩分选差,磨圆差,颗粒支撑和基质支撑均发育,根据岩相组合判断其形成于冲积扇和辫状河环境。较大的砾径以及极低的结构成熟度表示为近源堆积,暗示雅鲁藏布江蛇绿岩带为该套砾岩的重要源区,而特提斯喜马拉雅带为板岩和片岩的主要源区。岩屑砂岩的碎屑颗粒统计结果显示岩屑的含量为82%~85%,其中沉积岩屑为主(82%~95%),石英颗粒以单晶石英为主。碎屑锆石U-Pb年龄有453~579Ma和737~889Ma二个主要的范围,而缺少200~400Ma的锆石年龄。上述观测都说明日喀则弧前盆地、雅鲁藏布蛇绿岩带和特提斯喜马拉雅为柳区砾岩的重要物源区。由于柳区砾岩内部含有日喀则弧前盆地提供的物源,所以柳区砾岩是印度-欧亚板块碰撞之后沉积的。而柳区砾岩内各成分的变化反应源区对物源贡献的变化,同时记录了造山带隆升的历史,具体表现为印度-欧亚板块碰撞后,首先雅鲁藏布江蛇绿岩带和日喀则弧前盆地相对较快隆升,并遭受剥蚀,为柳区砾岩的沉积提供初始的物源,随着印度板块的俯冲,特提斯喜马拉雅带开始隆升,成为了柳区砾岩的物源,主要提供板岩和千枚岩。进一步的俯冲使得蛇绿岩带大幅度隆升而阻碍了日喀则弧前盆地和冈底斯继续提供物源,使得柳区砾岩上段石英砂岩中缺少火山岩石英和再旋回的石英颗粒。     

藏南桑单林地区晚白垩世—始新世砂岩物源区分析

西藏南部桑单林地区出露一套晚白垩世-始新世深水沉积的地层,下部为晚白垩世以石英砂岩和粉砂质页岩为主的桑单林组,上部为始新世含长石岩屑砂岩、硅质岩和硅质页岩的者雅组,由于断层错断,二者之间的古新世地层缺失.砂岩的岩石学分析表明,桑单林组石英砂岩的成分成熟度和结构成熟度均较高,杂基含量少,为硅质胶结;者雅组长石岩屑砂岩中,不稳定组分明显增加,杂基含量高,主要为泥质胶结.运用重矿物组合以及全岩主量元素、微量元素和稀土元素组成对砂岩的物源区分析表明,桑单林组砂岩形成于稳定的被动大陆边缘,碎屑物质来源于印度克拉通内部,而者雅组砂岩中存在明显的火成岩物质的输入,这些火山物质只可能来自于沉积盆地北部.桑单林组和者雅组砂岩的物源区的明显变化,反映了古新世末期-早始新世的一次碰撞事件:印度大陆与亚洲大陆的碰撞或者印度大陆与洋内岛弧的碰撞.     

西藏白朗南部地区三叠纪地层沉积环境及物源

综合露头剖面、砂岩碎屑组分、地球化学、阴极发光等资料的研究,对西藏白朗地区南部三叠系沉积环境及物源开展了研究。该区三叠纪地层以灰黑色泥岩、浅灰白色石英砂岩、长石石英砂岩、灰色灰岩为主,沉积背景为拉轨岗日被动陆缘盆地的浅海-半深海环境。碎屑岩及其地球化学分析结果反映,物源总体来自克拉通内部。阴极发光结果表明,物源区石英主要为变质成因,次为火成岩成因。综合判定,研究区该套地层为下—中三叠统吕村组和上三叠统涅如组,物源区来自南部高喜马拉雅基底杂岩带。     

雅鲁藏布江周缘前陆盆地物源分析及构造演化

本文通过雅鲁藏布江缝合带南侧江孜和岗巴地区晚白垩世-古近纪沉积地层的碎屑岩岩石学、地球化学和铬尖晶石电子探针分析,揭示了碰撞前后沉积盆地的物源区变化,提供了盆地和造山带早期的演化历史.江孜地区上白垩统宗卓组属于弧-陆或陆-陆碰撞背景下的海沟沉积.日朗砾岩中的岩屑质长石砂岩地球化学特征反映有大洋岛弧物质的注入,物源区为大洋岛弧或增生楔.上古新统-下始新统甲查拉组长石质岩屑砂岩反映了冈底斯岛弧和再循环造山带物源区特征,是陆-陆碰撞背景下形成的周缘前陆盆地的前渊沉积.岗巴地区古新统基堵拉组石英砂岩表现为印度大陆内部物源区特征,而始新统遮普惹组岩屑砂岩为再循环造山带和冈底斯岛弧物源区.沉积特征和物源区综合研究表明,雅鲁藏布江周缘前陆盆地在古新世期间开始发育,它指示了印度与欧亚板块的初始碰撞时间.     

Late Triassic sedimentary records in the northern Tethyan Himalaya:Tectonic link with Greater India

The Upper Triassic flysch sediments(Nieru Formation and Langjiexue Group)exposed in the Eastern Tethyan Himalayan Sequence are crucial for unraveling the controversial paleogeography and paleotectonics of the Himalayan orogen.This work reports new detrital zircon U-Pb ages and whole-rock geochemical data for clastic rocks from flysch strata in the Shannan area.The mineral modal composition data suggest that these units were mainly sourced from recycled orogen provenances.The chemical compositions of the sandstones in the strata are similar to the chemical composition of upper continental crust.These rocks have relatively low Chemical Index of Alteration values(with an average of 62)and Index of Compositional Variability values(0.69),indicating that they experienced weak weathering and were mainly derived from a mature source.The geochemical compositions of the Upper Triassic strata are similar to those of graywackes from continental island arcs and are indicative of an acidicintermediate igneous source.Furthermore,hornblende and feldspar experienced decomposition in the provenance,and the sediment became enriched in zircon and monazite during sediment transport.The detrital zircons in the strata feature two main age peaks at 225-275 Ma and 500-600 Ma,nearly continuous Paleoproterozoic to Neoproterozoic ages,and a broad inconspicuous cluster in the Tonian-Stenian(800-1200 Ma).The detrital zircons from the Upper Triassic sandstones in the study area lack peaks at 300-325 Ma(characteristic of the Lhasa block)and 1150-1200 Ma(characteristic of the Lhasa and West Australia blocks).Therefore,neither the Lhasa block nor the West Australia blocks likely acted as the main provenance of the Upper Triassic strata.Newly discovered Permian-Triassic basalt and mafic dikes in the Himalayas could have provided the 225-275 Ma detrital zircons.Therefore,Indian and Himalayan units were the main provenances of the flysch strata.The Tethyan Himalaya was part of the northern passive margin and was not an exotic terrane separated from India during the Permian to Early Cretaceous.This evidence suggests that the Neo-Tethyan ocean opened prior to the Late Triassic and that the Upper Triassic deposits were derived from continental crustal fragments adjacent to the northern passive continental margin of Greater India.     

滇西允沟岩组碎屑锆石年龄谱对相关地块亲缘性的约束

滇西允沟岩组为一套低绿片岩相的泥质浅变质岩,岩性以云母石英片岩、云母石英千枚岩、云母片岩、细晶灰岩为主,局部夹硅质岩,一直以来被认为是前寒武纪变质基底的重要组成部分。其原岩以碎屑岩为主,含有部分灰岩、白云岩,是一套形成于特提斯洋被动大陆边缘的半深海-深海沉积物,因此,是研究特提斯洋构造演化的重要窗口。但是,对允沟岩组的形成时代至今仍存在较大争议,为此本文选取允沟岩组中的片岩进行了碎屑锆石U-Pb精确定年。分析结果表明,允沟岩组原岩沉积时代为新元古代晚期-寒武纪期间(551～491Ma),主要由新太古代、新元古代及少量古元古代碎屑物质组成。其中,大量太古宙晚期碎屑锆石表明其源区有太古宙基底的存在,而1749Ma这组碎屑锆石可能与哥伦比亚超大陆聚散有关,956Ma和848Ma这两组锆石记录的事件可能是对罗迪尼亚超大陆三阶段裂离事件的前两期的响应。此外,还含有少量泛非运动信息,但泛非运动对其源区的影响极其有限。结合前人研究成果和本文碎屑锆石年龄谱,显示允沟岩组形成于原特提斯洋的被动陆缘,与印度板块、南羌塘地块具有显著的亲缘性。     

上扬子西南盐源盆地早三叠世物源体系及构造意义

晚古生代末期至早中生代期间,上扬子西部边缘地区经历了峨眉山大火成岩省构造岩浆热事件和与古特提斯洋闭合相关的三江造山带形成事件,导致康滇古陆两侧形成了独特的盆山格局和沉积模式.由于目前人们对盐源盆地早三叠世青天堡组的物源与构造背景了解不多,故以盐源、盐塘剖面为代表,对青天堡组碎屑岩进行了砂岩组分、全岩地球化学和碎屑锆石年代学分析.结果显示,盐源盆地下三叠统青天堡组物源来自于近源搬运的火山岩,青天堡组与峨眉山大火成岩省的高钛玄武岩具有一致的元素组合配分模式,青天堡组锆石谐和加权平均年龄为261±16 Ma,与峨眉山大火成岩省形成的地幔柱活动时期一致.上述结果表明早三叠世盐源盆地青天堡组物源为其东侧的峨眉山大火成岩省,扬子西部三江造山带可能并没有为盐源盆地提供物源,上扬子西南边缘地区早三叠世时期仍然为被动大陆边缘沉积.      

柴达木盆地北缘西段下石炭统物源和构造背景：来自碎屑岩U- Pb年代学与地球化学的约束

为查明柴达木盆地北缘西段早石炭世沉积物来源和构造背景,本次研究采集小赛什腾山怀头他拉组沉积岩进行碎屑岩锆石U- Pb年代学和全岩微量元素地球化学分析。研究表明：测试样品微量元素蛛网图呈平坦型,富Th、U、Hf,贫Co、Sc、Ni、V元素;砂岩轻重稀土元素分馏明显,属轻稀土富集型,具有中等负Eu异常;Cr/Zr、Sm/Nd、Th/Sc及Th/U等微量元素比值和判别图版显示研究区怀头他拉组为上地壳长英质物源区。沉积岩微量元素、稀土元素含量及特征比值显示,研究区样品与大陆弧环境砂岩具有极为相似的地球化学特征,相关构造环境投图同样表明怀头他拉组沉积环境以大陆弧为主,兼有主动大陆边缘特征。怀头他拉组碎屑锆石U- Pb年龄可划分出3个年龄区间,480～402 Ma,1493～900 Ma和1908～1803 Ma。年龄谱呈早古生代单峰值特征,峰值年龄为414 Ma,反映物源区与柴北缘加里东期构造带内早古生代晚期的岩浆作用关系密切。结合前人区域上古地理、古水流证据,综合分析认为小赛什腾山下石炭统怀头他拉组物源主要来自于柴北缘高压—超高压变质带。     

Early Carboniferous paleogeography of the northern Verkhoyansk passive margin as derived from U–Pb dating of detrital zircons: role of erosion products of the Central Asian and Taimyr–Severnaya Zemlya fold belts

The first U–Pb dating of detrital zircons from the Lower Carboniferous sandstones in the frontal part of the northern Verkhoyansk fold-and-thrust belt showed that detrital zircon age spectra for the Lower Visean (Krestyakh Formation) and the Upper Visean–Serpukhovian (Tiksi Formation) rocks are quite different. The Early Visean sandstones contain up to 95% detrital zircons of Precambrian age, while those of Late Visean–Serpukhovian age, only 55%. The shape of age distribution plots of Precambrian zircons for both samples is similar, indicating that reworking of terrigenous sediments of the Krestyakh Formation or the same sources dominated in Early Visean time (crystalline basement of the craton, eroded Meso- and Neoproterozoic sedimentary complexes, and igneous rocks of Central Taimyr) contributed significantly to the accumulation of the Late Visean–Serpukhovian deposits. In the rocks of the Tiksi Formation, 45% of detrital zircons are of Paleozoic age, while 24% are Early Paleozoic, with prevailing Cambrian and Ordovician ages. Possible provenance areas with abundant igneous rocks of this age could be the Taimyr–Severnaya Zemlya and Central Asian fold belts extending along the northern, western or southwestern margins of the Siberia. The presence of Middle–Late Devonian zircons is thought to be related to the erosion of granitoids of the Yenisei Ridge and the Altai–Sayan region. Early Carboniferous detrital zircons probably had a provenance in igneous rocks of the Taimyr–Severnaya Zemlya fold belt, on the assumption that collision between the Kara block and the northern margin of the Siberian continent had already occurred by that time. In Early Visean time, sedimentation occurred in small deltaic fans, likely along steep fault scarps that formed as a result of Middle Paleozoic (Devonian–Carboniferous) rifting. The clastic material came from small rivers that eroded the nearby area. Late Visean–Serpukhovian time was marked by a sharp increase in the amount of clastic material and by the appearance of detrital zircons coming from new provenance regions, such as fold belts extending along the northern and southwestern margins of the Siberian continent. A large river system, which was able to transport clastic material over large distances to deposit it in submarine fans on the northern Verkhoyansk passive continental margin, had already existed by that time.     

Geochemical features,depositional settings,and provenances of Lower Paleozoic rocks in the Mamyn terrane,Central Asian Fold Belt

New data on geochemical features of the Lower Paleozoic terrigenous rocks in the Mamyn terrane (eastern Central Asian Fold Belt) and U–Pb geochronological studies of the detrital zircon from these rocks are presented. The obtained results suggest the following conclusions. 1. At present, the Kosmataya sequence includes different age Lower Cambrian terrigenous–carbonate and Lower Ordovician terrigenous rocks or represents Lower Ordovician olistostromes including limestone blocks with the Lower Cambrian fauna. Lower Ordovician terrigenous rocks were formed in an island arc or active continental margin, mainly, owing to the erosion of Cambrian–Early Ordovician plutons and volcanics that are widespread in structures of the Mamyn terrane and weakly reworked by the chemical weathering. 2. The Silurian Mamyn Formation was developed at a passive continental margin. The main sources of clastic material for this formation were the same Cambrian–Early Ordovician igneous rocks as for the Cambrian sequence, with the participation of Early Silurian and Vendian igneous complexes. The obtained data significantly refine concepts about the geological structure of the Mamyn terrane, which is a member of the Argun Superterrane, one of the largest tectonic structures in the eastern Central Asian Fold Belt.     

Stratigraphy of the upper cretaceous and lower tertiary strata in the Tethyan Himalayas of Tibet (Tingri area,China)

The 1500-m-thick marine strata of the Tethys Himalaya of the Zhepure Mountain (Tingri, Tibet) comprise the Upper Albian to Eocene and represent the sedimentary development of the passive northern continental margin of the Indian plate. Investigations of foraminifera have led to a detailed biozonation which is compared with the west Tethyan record. Five stratigraphic units can be distinguished: The Gamba group (Upper Albian - Lower Santonian) represents the development from a basin and slope to an outer-shelf environment. In the following Zhepure Shanbei formation (Lower Santonian - Middle Maastrichtian), outer-shelf deposits continue. Pebbles in the top layers point to beginning redeposition on a continental slope. Intensified redeposition continues within the Zhepure Shanpo formation (Middle Maastrichtian - Lower Paleocene). The series is capped by sandstones of the Jidula formation (Danian) deposited from a seaward prograding delta plain. The overall succession of these units represents a sea-level high at the Cenomanian/Turonian boundary followed, from the Turonian to Danian, by an overall shallowing-upward megasequence. This is followed by a final transgression — regression cycle during the Paleocene and Eocene, documented in the Zhepure Shan formation (?Upper Danian - Lutetian) and by Upper Eocene continental deposits. The section represents the narrowing and closure of the Tethys as a result of the convergence between northward-drifting India and Eurasia. The plate collision started in the Lower Maastrichtian and caused rapid changes in sedimentation patterns affected by tectonic subsidence and uplift. Stronger subsidence and deposition took place from the Middle Maastrichtian to the Lower Paleocene. The final closure of remnant Tethys in the Tingri area took place in the Lutetian.     

安哥拉东北部地区Inkisi组碎屑锆石U- Pb年龄、地球化学特征及其地质意义

Inkisi组是刚果盆地西南缘最古老的沉积地层之一,岩性主要为一套紫红色、红褐色细粒、细中粒长石砂岩、杂砂岩。通过对安哥拉东北部Inkisi组长石砂岩开展碎屑锆石测年、岩石地球化学研究,探讨其沉积时代、物质来源、沉积环境和大地构造背景,为研究刚果盆地演化提供科学依据。结果表明,碎屑锆石206Pb/238U年龄主要集中于3个年龄峰值区间2350~1900 Ma、1150~850 Ma、850~500 Ma,最年轻的锆石峰值年龄为531±9 Ma,据此,笔者等认为Inkisi组的沉积时代上限应厘定为早寒武世。Inkisi组砂岩地球化学特征显示,物源具有长英质物源近源搬运特征,沉积时期的水体为陆相开阔的淡水环境。通过碎屑锆石年龄谱特征、主微量元素物源判别及构造判别图解,本文认为,West Congo构造带为安哥拉东北部地区Inkisi组主要物源区,Lufilian构造带、Angola 地盾等是其次要物质来源,物源区构造环境主要为活动大陆边缘和被动大陆边缘构造环境背景。