新疆伊犁地块早二叠世的古地磁结果

作者对新疆伊宁地区早二叠世地层的古地磁进行了研究。结果表明:1)早二叠世时,伊犁地块已增生到欧亚大陆之上并同塔里木地块连在一起;2)早二叠世后伊犁地块相对欧亚大陆北部稳定区发生过大规模顺时针旋转运动。     

新疆早二叠世古气候

新疆早二叠世古气候可以划分为两个不同的气候区，即准噶尔温带气候区和塔里木热带—亚热带气候区。准噶尔早二叠世的气候特点是间歇性地出现炎热气候，这些气候变化大致可以划出两个气候旋回。塔里木早二叠世由潮湿环境转变为比较干旱的环境，晚期。红层普遍发育。影响准噶尔早二叠世气候的主要因素为全球气候变暖和火山作用。影响塔里木早二叠世气候的主要因素包括处于偏低纬度的地理位置、古特提斯洋暖流、周缘火山活动，海退使整个塔里木运动远离海洋。     

从古气候探讨新疆北部石炭—二叠纪生油层位

不同沉积矿产的形成经常有不同的古气候背景。石油的生成与炎热气候关系密切。炎热气候和长期稳定的还原环境对油气的形成最有利。新疆北部早石炭世、早二叠世处于炎热气候条件下 ,克拉麦里以南的南准噶尔在晚石炭世也基本处于炎热气候条件下。早石炭世晚期北准噶尔、伊犁地区都有稳定的弱氧化环境下的碳酸盐沉积 ,早石炭世晚期—晚石炭世早期的准噶尔 ,晚石炭世—早二叠世早期准噶尔南缘、西北缘海相沉积都有深水宁静的还原环境。早二叠世晚期准噶尔南缘、东准噶尔、吐鲁番有深水湖泊。上述地区和层位对生油是有利的     

新疆三叠纪古地理

1 早三叠世古地理 三叠纪开始,由于印度板块由经向运动转变为纬向运动,印度板块开始裂解成印度－喜马雅地块、冈底斯－羌塘地块和昆仑地块等地体。昆仑、羌塘地块快速向北漂移,以独立地块存在于古特提斯洋中。早三叠世塔里木在晚二叠世沉积基础上,沉积范围扩大,局部经受了古特提斯洋海侵,在杜瓦和满加尔坳陷中形成海泛区1,2。天山山前和准噶尔除局部地区为连续沉积外,广大地区均为不整合或平行不整合接触3。康西瓦－阿尔金断裂带以南的古特提斯北缘海相沉积区与晚二叠世基本一致（附图24）。1．1 剥蚀区 （1）天山中－低山…     

准噶尔盆地的类型和构造演化

准噶尔盆地的早二叠世属于裂谷还是前陆盆地 ,存在意见分歧 ;晚二叠世—老第三纪盆地的性质也不确定。文中通过对盆地构造几何学、沉降史、热史及火山岩的综合分析研究 ,对盆地类型和构造演化获得了一些新的认识 :( 1)准噶尔盆地在早二叠世为裂谷 ,晚二叠世为热冷却伸展坳陷 ,三叠纪—老第三纪为克拉通内盆地 ,新第三纪至今 ,由于印度板块与亚洲大陆碰撞才形成陆内前陆盆地。 ( 2 )对石炭纪—早二叠世的岩浆活动结合区域构造资料的研究表明 ,准噶尔地区古生代的板块运动和造山作用具软碰撞特点 ,早二叠世的裂谷盆地是在软碰撞背景下造山带伸展塌陷的产物。 ( 3)地幔热对流作用可能是软碰撞造山后伸展塌陷的主要深部动力学机制。     

塔里木盆地古董山地区早二叠世古地磁特征 及其地质意义

通过对塔里木盆地内古董山地区早二叠世玄武岩的古地磁测定,揭示了1组高温特征剩磁分量。实验结果表明,其特征剩磁方向为：Dg=213.7°, Ig=26.9°,κg=19.7, N=9,α95=13.7°; Ds=217.7°, Is=-37.5°, κs=15.4,α95=13.6°,相对应的古地磁极位置为：53.2°N、 187.5°E,A95=12.3°,古纬度为21.0°N。由于采样剖面所获得的早二叠世古地磁结果全部为反极性特征,认为这一高温特征剩磁分量很可能代表了研究区早二叠世时期的原生特征剩磁。对比塔里木地块西北缘早二叠世的古地磁结果,认为研究地区与塔里木地块西北缘之间在古地磁误差范围内并未发生明显的相对构造运动。依据塔里木早二叠世古地磁极与哈萨克斯坦地块同时期古地磁极的一致性,结合二者的古生物资料,提出早二叠世时期塔里木地块可能已经与哈萨克斯坦地块碰撞相连,至晚二叠世,二者之间的海水完全退出,碰撞造山使得天山雏形基本形成。结合前人古地磁研究成果,对塔里木地块及周边主要块体早二叠世的古地理进行了重建。     

西藏和云南三江地区特提斯洋盆演化历史的古地磁分析

通过对华南、思茅、保山、缅泰、印支、羌塘、拉萨和喜马拉雅地块进行了古纬度和纬度运移量的对比分析,以确定西藏和云南西部三江地区主要地块的碰撞拼合历史,以及相应的特提斯洋盆演化时限。结果表明:①分隔保山和思茅地块的古特提斯洋可能于早志留世张开;②保山与思茅地块于晚二叠世碰撞,然后继续和华南地块、缅泰地块一起向北漂移,直到晚三叠世;③古特提斯洋年龄范围在早志留世至晚二叠世之间;④中特提斯洋年龄范围在早二叠世至早白垩世之间,在晚三叠世达到其最大纬度宽度,约42°;⑤雅鲁藏布江缝合带所代表的新特提斯洋于晚三叠世张开。     

新疆南天山缝合带的形成时限 ——来自阔克萨彦岭花岗岩体的锆石年龄新证据

南天山缝合带位于塔里木克拉通与中天山-伊犁-哈萨克斯坦地块之间,其形成时限对于研究古亚洲洋西南缘的南天山洋最终闭合具有重要的意义.利用LA-ICP-MS锆石U-Pb法对南天山阔克萨彦岭地区的花岗岩体进行测试,结果表明花岗岩体的形成时代为早二叠世(273～283Ma),而且大量早二叠世侵入体同时出现在中天山-伊犁-哈萨克斯坦地块和塔里木克拉通.其中,巴雷公蛇绿岩也被早二叠世侵入体所侵入,限定了南天山缝合带的形成时限应早于早二叠世.研究结果进一步支持南天山洋的最终闭合应发生在300Ma之前.     

新疆准噶尔盆地和塔里木盆地二叠纪孢粉组合的比较及其植物区系和地层意义

根据二十年来积累的准噶尔和塔里木盆地二叠纪孢粉组合序列资料 ,结合其他动植物化石证据 ,初步做了两地二叠纪孢粉生物地层对比 ,并讨论了植物区系性质 ,指出准噶尔盆地在晚石炭世早期已属亚安加拉区 ,塔里木盆地在早二叠世虽总体上属欧美区 ,但已混生若干安加拉—亚安加拉成分 ,中、晚二叠世基本上已属亚安加拉区。孢粉证据支持准噶尔板块在早石炭世已与哈萨克斯坦板块—西伯利亚板块对接、塔里木板块在早二叠世与准噶尔板块对接的假说。二叠纪时 ,两地处于亚热带—暖温带 (4 0°N以南 ) ,气候总体上为半干旱气候 ,但干旱程度并不严酷 ,局部地区或层位偶尔还形成薄煤层或煤线 ,准噶尔盆地还有干湿的周期性变化和年度的季节变化     

新疆准噶尔盆地东缘中—晚二叠世植物群及其地质意义

本文首次报道了新疆准噶尔盆地东缘胜利沟中二叠世平地泉组植物化石11属19种和晚二叠世黄梁沟组植物化石7属9种,并结合前人对这一地区中—晚二叠世植物化石记录,讨论了两个植物群的地质时代。研究认为：中二叠世平地泉组植物群以安加拉植物群为主,混生个别欧美植物群分子;晚二叠世黄梁沟组植物群为混生少量华夏植物群分子的安加拉植物群。在此基础上,探讨了中—晚二叠世植物群演替、植被变化、植物群混生与中亚造山带板块聚合之间的关系,认为中二叠世的暖温带温湿气候在晚二叠世转变为季节性干热气候,准噶尔盆地东缘中—晚二叠世植物群混生与准噶尔—吐哈地块、塔里木板块、佳蒙地块、华北板块的拼合和古亚洲洋的关闭密切相关。     

思茅地块西缘龙洞河组放射虫动物群及其地质意义

思茅地块西缘的龙洞河组为一套火山—沉积岩系 ,原定时代为晚石炭世 ,被认为属南澜沧江洋弧后盆地沉积。现在龙洞河组层状硅质岩断片中发现了晚泥盆世放射虫化石 ,在细碧角斑岩之硅质岩夹层中发现了早石炭世放射虫动物群 ,表明龙洞河组不全是晚石炭世地层 ,而是由晚古生代的一些地层断片组成。思茅地块西缘深水沉积盆地的演化始于泥盆纪 ,应为滇西南古特提斯多岛洋的一个分支 ,向南可能与泰国难河带对比。     

黑龙江省东部古生代—早中生代的构造演化:火成岩组合与碎屑锆石U-Pb年代学证据

黑龙江省东部松嫩—张广才岭地块与佳木斯地块之间的演化历史以及古亚洲洋构造体系与环太平洋构造体系的叠加与转化一直是地学领域研究的热点问题之一。依据该区古生代—早中生代火成岩的年代学与岩石组合研究,结合碎屑锆石的年代学研究成果,讨论了松嫩—张广才岭地块与佳木斯地块之间的演化历史以及两大构造体系叠加与转化的时间。锆石U-Pb定年结果表明:黑龙江省东部古生代—早中生代岩浆作用可划分成8期:早奥陶世(485Ma)、晚奥陶世(450Ma)、中志留世(425Ma)、中泥盆世(386Ma)、早二叠世(291Ma)、中二叠世(268 Ma)、晚三叠世(201～228 Ma)以及早侏罗世(184 Ma)。早奥陶世—中志留世,岩浆作用主要分布在松嫩—张广才岭地块的东缘,并呈南北向带状展布,主要由闪长岩-英云闪长岩-二长花岗岩组成,显示活动陆缘—碰撞的构造演化历史,揭示松嫩—张广才岭地块与佳木斯地块于中志留世(425Ma)已经拼合在一起,这也得到了早泥盆世地层碎屑锆石年代学的支持。中泥盆世,火山作用分布在佳木斯地块东缘和松嫩—张广才岭地块上,前者为双峰式火山岩组合,后者为A型流纹岩,它们共同揭示该区处于一种碰撞后的伸展环境。早二叠世,佳木斯地块东缘发育一套钙碱性火山岩组合,揭示古亚洲洋俯冲作用的存在,而同期的张广才岭地区则发育一套典型的双峰式火成岩组合,揭示了陆内伸展环境的存在。中二叠世,同碰撞型火山岩分布于佳木斯地块东缘及东南缘,其形成可能与佳木斯地块和兴凯地块的碰撞拼合有关。晚三叠世,张广才岭地区存在的双峰式火山岩和敦—密断裂东南区发育的A型流纹岩均显示陆内的伸展环境,其形成应与古亚洲洋最终闭合后的伸展环境相联系。此外,结合牡丹江断裂两侧均发育中—晚二叠世花岗岩以及佳木斯地块上晚三叠世—早侏罗世岩浆作用的缺失,暗示松嫩—张广才岭地块与佳木斯地块在三叠纪早期沿牡丹江断裂可能存在一次裂解事件。而早—中侏罗世陆缘(东宁—汪清—珲春)钙碱性火山岩和陆内(小兴安岭—张广才岭)双峰式火成岩组合的出现,结合牡丹江断裂两侧"张广才岭群"和"黑龙江群"构造混杂岩的就位,暗示松嫩—张广才岭地块与佳木斯地块在早—中侏罗世再次拼合,这也标志着环太平洋构造体系的开始。     

滇西北羊拉铜矿区地层划分

通过滇西北羊拉矿区7.5km实测地层剖面的岩石地层划分,矿区原定二叠纪嘎金雪山群巨厚洋盆沉积实际由泥盆纪至二叠纪构造岩块高度混杂而成。因矿区经历了金沙江洋盆的初始裂开、扩张、俯冲消减、碰撞造山的洋－陆转换过程,岩石普遍发生绿片岩相变质作用,缺少古生物化石,原岩层序难以恢复。基于前人成果和本次工作发现的牙形石,结合矿区沉积特征和金沙江洋演化历史,将地层修订为下泥盆统江边组岩块、中泥盆统－石炭系岩块、二叠系岩块,并讨论了其构造演化。     

Zirconology of serpentinites from Nyashevo massif (Southern Urals)

Zircons in serpentinites from Nyashevo massif of the Ilmenogorskii complex were dated for the first time by means of the SHRIMP technique. The maximum date of 1892 ± 23 Ma for the zircons accounts for the minimum age of their mantle substrate probably constituting the restite residue. The date is comparable to those for metamorphic rocks of the Selyankino group, as well as of fenite–sand amphibolites of the Ilmenogorskii complex. The Upper Ordovician age limit of 443 ± 12 Ma is adequate for formation of the massif and conforms to the age of the Buldym massif and miaskites. The Early Permian dates of zircons (275.8 ± 2.1 Ma) represent late shear processes in the Ilmenogorskii complex.     

黑龙江省东南部张广才岭群新兴组的形成时代及物源

为确定张广才岭群新兴组的形成时代和物源,本文测定了其碎屑锆石和岩浆锆石的年龄。在新兴组中测得的两组碎屑锆石(LA- ICP- MS U- Pb)产生多组谐和年龄,BP18R15样品91个测点最小峰值(谐和)年龄为260Ma (41个点),BP18R83样品100个分析点最小峰值(谐和)年龄为253Ma (52个点)。锆石绝大多数呈自形—半自形晶,显示典型振荡岩浆生长环带或条痕状吸收,且Th/U值相对较高,暗示其岩浆成因。以此确定新兴组沉积下限为晚二叠世之后。结合侵入于新兴组的正长花岗岩年龄为210 ±1Ma,表明张广才岭群新兴组形成于晚二叠世—晚三叠世之间,而非前人所确定的新元古代。从新兴组中碎屑锆石的年龄频数可看出,新兴组的沉积物主要来源于周边晚古生代地质体以及次要的中元古代、新元古代、早古生代和早中生代地质体。前寒武纪碎屑锆石的存在暗示新兴组沉积时,区域地表或浅部曾存在一些具有类似年龄的前寒武纪残余地质体。新兴组几乎所有沉积物源来自松嫩- 张广才岭地块,暗示松嫩- 张广才岭地块与佳木斯- 兴凯地块及华北地块的拼合应晚于晚二叠世。     

北淮阳梅山群的隶属及其地质构造若干问题

摘　 要　 结合 1∶5 万区调工作, 经过对安徽境内的梅山群和河南境内的杨山煤系的系统剖面 观察、 研究与对比, 认为梅山群相当于杨山煤系中上部(胡油坊组、 杨小庄组、 灰冲组)的东 延部分, 其时代归属于晚石炭世—早二叠世。 同时对梅山群的变质作用、 糜棱岩的形成期次、 “ 前寒武纪岩块” 等地质构造问题进行了论述和探讨。     

The Songpan-Garzê Massif: Its Relation to the QinlingFold Belt and Yangtze Platform and Developmental History1

Abstract Whether there existed the Songpan-Garzê massif is a controversial problem. This paper expounds and proves that the old basement of the massif is represented by the pre-Sinian granitic rock series. This massif and the South Qinling fold belt might both be a part of the old Yangtze platform. Rifting generated by the Caledonian orogeny in the terminal Early Palaeozoic caused the massif to be disintegrated from the northwestern part of the Yangtze platform. This disintegration, however, was not thorough, and the rift troughs were later gradually closed and filled up. The Emei taphrogeny that was initiated in the Early Permian Maokou'an Stage involved a second disintegration of this massif from the Yangtze platform. The rift line largely goes along the Muli-Pingwu line. This rifting belongs to synchronous extensional rifting at peripheries of the Yangtze platform and in its interior, showing that the posterior, lateral and interior extension resulting from rapid northward shift of the Yangtze platform led to isolation of this massif together with South Qinling from their adjacent areas. During the Ladinian Stage, the Songpan-Garzê massif and southern Qinling sank strongly en masse. This subsidence continued till the end of the Late Triassic when the late Indosinian movement caused the sea trough to be closed and Songpan-Garzê and southern Qinling to be folded and uplifted and become mountains.     

Paleozoic magmatic events in the Strandja Massif,NW Turkey

The Strandja massif consists of metamorphic basement intruded by large Early Permian plutons of the Kirklareli type and overlain by Triassic metasedimentary cover. Together with its continuation in Bulgaria this massif forms an important link between the Pontides and the orogenic belts of Europe. Various types of orthogneisses constitute a significant part of the metamorphic basement however these rocks have until now escaped a particular study and therefore the Paleozoic history of the massif is essentially unknown. In this study these rocks are classified and mapped as hornblende-biotite, biotite-muscovite, and leucocratic orthogneisses. Their modal compositions correspond to quartz diorite, tonalite, granodiorite and trondhjemite. Geochemical data suggest a calc-alkaline trend of differentiation and metaluminous character of the parent magmas. Isotopic dating using the single zircon evaporation method has shown that magmatic ages of these orthogneisses cluster within a short time interval between 312±2 and 315 ±5 Ma in the Carboniferous. At the same time inherited ages of magmatic zircons in these rocks record a long lived magmatic activity between 340 and 650 Ma. We infer that the Carboniferous orthogneisses were formed in a magmatic arc that evolved atop of a mature continental basement. Previously established ([1, 2]) Early Permian magmatic event has been confirmed by additional age determinations constraining it at 257±6 Ma. Tectonic setting of this episode is also interpreted as subduction related taking into consideration its geochemical features and relationships with surrounding tectonic units.     

The Songpan-Garze Massif: Its Relation to the QinlingFold Belt and Yangtze Platform and Developmental History

Whether there existed the Songpan-Garze massif is a controversial problem. This paper expounds and proves that the old basement of the massif is represented by the pre-Sinian granitic rock series. This massif and the South Qinling fold belt might both be a part of the old Yangtze platform. Rifting generated by the Caledonian orogeny in the terminal Early Palaeozoic caused the massif to be disintegrated from the northwestern part of the Yangtze platform. This disintegration, however, was not thorough, and the rift troughs were later gradually closed and filled up. The Emei taphrogeny that was initiated in the Early Permian Maokou' an Stage involved a second disintegration of this massif from the Yangtze platform. The rift line largely goes along the Muli-Pingwu line. This rifting belongs to synchronous extensional rifting at peripheries of the Yangtze platform and in its interior, showing that the posterior, lateral and interior extension resulting from rapid northward shift of the Yangtze platform led t     

Detrital Zircon U‐Pb Dating of Nanshuangyashan Formation in the Jiamusi Massif,NE China and its Tectonic Implications

A suite of the fossil-rich marine-land interbedded strata(Nanshuangyashan Formation) is distributed at the eastern margin of the Jiamusi massif in the eastern Heilongjiang Province, NE China. The authors had recently discovered a suite of arkose beneath the marine-land interbedded strata, which overlays unconformably on the Permain granite in the eastern margin of the Jiamusi massif. The LA-ICP-MS zircon U-Pb dating indicate that all detrital zircons from the analysed four arkose samples show the four population ages of 800 Ma, 538–481 Ma, 269–250 Ma and 223–215 Ma. The former three population ages are widely recorded in the Jiamusi-Khanka massif and the Songnen massif. The later group is the minimal age population in the analyzed samples, limiting the sedimentation time of the arkoses occurred after the Late Triassic. At present, the minimal age population is not recorded in the Jiamusi massif, but the granites with the ages of 228–210 Ma are widely distributed in the Songnen-Zhangguangcai Range massif and the Khanka massif. The predominantly Permian zircons are characterized by oscillatory zoning and euhedral shapes, with variable zircon ε_(Hf)(t) values(-5.5 to +11.2), indicating that they were derived from mixture sources, possibly mixed with components of the Songnen-Zhangguangcai Range massif and the Jiamusi-Khanka massif. These results, combined with regional analyses, indicate that the closing of Mudanjiang ocean and Panthalassa ocean possibly existed from Early Permian to Late Triassic.