滇东—黔西南泥盆纪构造格局及岩相古地理演化

滇东-黔西南泥盆纪时位于古特提斯洋东缘,构造格局可划分为特提斯洋板块的哀牢山大洋裂谷系,扬子板块的滇东南-黔南被动陆缘裂谷系和滇东北-黔南陆内裂谷系三个构造单元。三裂谷系中发育有三个性质和内部结构不同的沉积盆地。盆地中晚古生代沉积建造和火山活动受盆内同沉积断裂拉张和走滑控制,在每一盆地中泥盆纪沉积相展布格局和岩相古地理演化与裂谷系中同沉积断裂活动相对应。     

新疆富蕴扎河坝地区蛇绿岩带基本特征及大地构造意义

扎河坝地区蛇绿岩带属扎河坝—阿尔曼太蛇绿岩带之组成部分，主要由无序的蛇纹岩、变辉长岩、变辉绿岩及少量变质基性火山岩、硅质岩构成其主体。常见外来混杂岩块。据其组合特征可分为蛇绿岩、混杂岩两亚带。经初步研究认为：蛇绿岩为残留洋壳的一部分，其形成时代为奥陶纪—志留纪。加里东晚期洋壳发生转化，至泥盆纪发育一套中基性海相沟弧型火山岩组合。因此，该带及其北部至额尔齐斯带南缘地区，应为西伯利亚板块华力西增生带。     

蛇绿岩套研究现状、科学问题及新思考

蛇绿岩套是运用板块构造理论解释造山带构造演化的关键,合理理解蛇绿岩套的形成、演化有助于构建与板块构造理论吻合的造山带演化模型。经典的蛇绿岩套发育由地幔橄榄岩、堆晶辉长岩、枕状玄武岩-深海沉积岩组成的“三位一体”岩石组合,与现代洋中脊新形成的大洋岩石圈具有相同的岩石组合及岩石空间分布样式。地球化学家们在经典蛇绿岩套定义基础上,根据玄武质岩石地球化学特征的变化,提出了“俯冲带之上(SSZ)蛇绿岩套”概念,并对其划分亚类、构建相应的概念性成因模型,从而引发了“在俯冲汇聚阶段能否发生岩石圈裂解、形成新生洋壳”的“蛇绿岩难题”。针对阿尔卑斯-喜马拉雅造山系内的两个典型SSZ型蛇绿岩套的详细解剖表明,部分SSZ型蛇绿岩套的定义可能存在玄武质岩石“年代误植”、“构造背景误植”问题。前人定义的伊朗克尔曼沙赫弧前蛇绿岩套、巴基斯坦拉斯科赫弧间蛇绿岩套均由两部分组成：下部为形成于洋中脊环境、时代较老的大洋岩石圈残片;其上分别被年轻的弧前盆地和岛弧相关火山-沉积岩组合不整合覆盖。显然,大部分SSZ型蛇绿岩套是经典洋中脊蛇绿岩套残片与形成于其他构造环境(如大陆裂谷、俯冲带)的火山-沉积岩序列的组合体,并不存在...     

对北祁连中段皇城一带蛇绿岩的初步认识

北祁连造山带是我国蛇绿岩保存较为完整的地区,空间分布有南北两个带,南带西自鹰嘴山经川刺沟至白银,发育寒武纪末—早奥陶世洋脊环境蛇绿岩,北带自昌马经民乐童子坝至景泰老虎山,以奥陶世蛇绿岩为主。在野外地质调查的基础上,对北祁连中段皇城南直河一带发育的蛇绿岩地质特征、火山岩组合及其成矿特征提出初步认识,以引起对该区地质研究和勘查找矿的关注。     

蛇绿岩研究新进展及其定义和分类的再讨论

蛇绿岩保存于大陆造山带中,在地质历史上产于洋--陆过渡区多种构造背景(活动大陆边缘、被动大陆边缘、弧前、弧后、弧内、弧问、板块三联点、转换断层、大陆裂谷或它们的复合背景等)的洋盆扩张脊.蛇绿岩以超镁铁质岩、镁铁质岩为主,是一套彼此具有成因演化亲缘关系的、古洋壳 大洋地幔岩石的有机组合.我们把蛇绿岩概括为产于洋盆扩张脊的洋壳 大洋地幔岩石组合.蛇绿岩按构造背景有红海萌芽型洋壳和大洋中脊型洋壳两个端元,可三分为近陆的活动大陆边缘型--科迪勒拉型、东地中海型(新特提型)过渡型、西地中海型--大洋中脊古特提斯型.科迪勒拉型和东地中海型均属俯冲带(SSZ)上叠型,更近陆靠俯冲带;环太平洋型和被动大陆边缘型属特提斯型.     

西藏雅鲁藏布江一带中生代沉积盆地的演化

经过研究证实,在雅鲁藏布江蛇绿岩的南北两侧,有两套形成于雅鲁藏布江洋底盆地的沉积组合,它们不但形成于不同时代,而且属于不同构造环境下的产物。时代属于晚侏罗世到早白垩世的南侧沉积组合为放射虫硅质岩-层状玄武岩,其沉积特征类似于太平洋洋隆类型,反映了它可能是属于西藏特提斯快速扩张的产物。根据最近所发现的圆笠虫化石确定北侧一套的时代属于中白垩世,它是蛇绿质碎屑岩-枕状玄武岩组合,反映了一种类似于大西洋洋脊类型的、慢速扩张的板块构造环境。它是正常沉积接触关系覆于雅鲁藏布江蛇绿岩套之上。雅鲁藏布江蛇绿岩套是这个时期形成的洋壳的残留体。在晚白垩世时,雅鲁藏布江蛇绿岩被捕获在北部的冈底斯山弧前并且变为冈底斯南缘弧前盆地的基底。随后日喀则群浊积岩在其上堆积。     

甘肃省肃南地区蛇绿岩岩石单元地质特征

通过对肃南地区发育的理想蛇绿岩包括的岩石单元的阐述,并与理想蛇绿岩进行了对比,在对比的基础上,也对E.M.穆尔斯扩大了的蛇绿岩组合所涉及到的其它岩石单元进行了解释,表明在肃南地区结晶基底之上早奥陶纪存在较为完整的蛇绿岩组合模式。     

狮泉河蛇绿混杂岩带早侏罗世辉长岩锆石年代学及地质意义

西藏狮泉河-申扎-嘉黎蛇绿混杂岩带紧邻班公湖-怒江蛇绿混杂岩带南侧,出露有较为完整的蛇绿岩岩石组合。嘎铃辉长岩出露于拉梅拉山口地区,野外实测剖面显示其具有明显的混杂增生特征。样品富集Ba、U、K、Pb、Sr等大离子亲石元素,亏损Nb、P等高场强元素,稀土配分模式属于轻稀土元素弱亏损的总体平坦型,判断其可能形成于俯冲背景下的弧后裂谷环境。LA-ICP-MS锆石U-Pb年龄为(189±1)Ma。结合区域构造背景,认为狮泉河蛇绿岩代表的特提斯洋可能是一个早侏罗世开始俯冲,早白垩世闭合的具有独立演化历程的局限性洋盆。     

塔里木盆地周缘洋盆开合在盆地内部的构造沉积响应

依据塔里木盆地周缘蛇绿岩年龄及盆内钻井岩性、古生物、地球物理等资料,以古天山洋和古昆仑洋的开合演化为线索,将盆地构造沉积响应划分为五个期次。南华纪-震旦纪早世Rodinia泛大陆开始裂解,塔里木陆块北部发育南天山海槽、南部发育库地小洋盆,同期塔里木盆地只有中北部地区沉积碎屑物,塘古孜巴斯至古城墟地区为古隆起无沉积;震旦纪晚世-奥陶纪中世南天山洋和北昆仑洋(原库地小洋盆)进入成年期,塔里木陆块西部高地发育快速生长的碳酸盐岩台地,东部低地(满加尔)发育饥饿盆地,塔里木陆块形成了西台东盆的沉积格局;奥陶纪晚世-泥盆纪北昆仑洋和南天山洋分别向中昆仑和中天山微陆块俯冲(最终与塔里木陆块拼贴),塔里木陆块边缘逐渐出现不同规模的陆源剥蚀区,陆块内碳酸盐台地逐渐消亡;石炭纪-二叠纪中世北天山洋和南昆仑洋-阿尼玛卿洋关闭造山,塔里木陆块内部实际处于广义的弧后扩张状态,期间接受了海陆交互相碎屑岩沉积及海相碳酸盐岩沉积;二叠纪晚世至今金沙江洋、澜沧江洋、班公-怒江洋和雅鲁藏布江洋等先后关闭,受此影响天山、昆仑造山带强烈抬升,塔里木盆地发育库车和塔西南2个前陆盆地。     

两类蛇绿岩剖面及其成因的探讨

研究表明，蛇绿岩剖面是多种多样的，至少可分为两类，第一类以特罗多斯为代表，为具有序性的，厚度较大的洋壳，特征是有席状岩墙群和较厚的堆晶岩单元，第二类以及双沟为代表，仅出现镁铁质的喷出岩和侵入岩，洋壳厚度较小，缺少席状岩墙群和堆晶超镁铁岩或堆晶岩不发育，不同的蛇绿岩剖面反映了洋脊之下不同的动力学过程。     

U-Pb zircon dating of Early Paleozoic gabbro from the Nantinghe ophiolite in the Changning-Menglian suture zone and its geological implication

The Nantinghe ophiolite is located in the northern part of the Changning-Menglian suture zone in southeast Tibet. It is composed of meta-peridotite, cumulative gabbro, meta-gabbro, plagioclase amphibolite and meta-basalt. Zircon U-Pb dating of the cumulative gabbro gives concordant ages of 473.0±3.8 Ma and 443.6±4.0 Ma respectively, indicating the early and late episodes of mafic magmatisms during the Paleo-Tethys oceanic rifting. The 16 LA-ICPMS zircon U-Pb analyses of meta-gabbro yield a weight mean age of 439±2.4Ma. The gabbro shows relatively low contents of SiO2 (46.46%-52.11%), TiO2 (0.96%-1.14%) and K2O (0.48%-0.75%). Its trace element distribution patterns are partly similar to those of the mid-ocean ridge basalts, and part is depleted in high field strength elements such as Nb, Ta, Zr, Hf and Ti. These features suggest that the mafic rocks were probably formed in a MORB-like or backarc rift basin setting. The zircon U-Pb age of gabbro is consistent with a late crystallization age of the cumulative gabbro from the Nantinghe ophiolite, suggesting that the Paleo-Tethys oceanic basin was opened during 444-439 Ma, possibly as a backarc basin. It is the first precise age which defines the formation time of the early Paleozoic ophiolite in the Changning-Menglian suture zone. These geochronological and geochemical characteristics of the Nantinghe ophiolite are consistent with those from the Guoganjianianshan and Taoxinghu of the Longmu Co-Shuanghu suture in the Qiangtang region. Thus, we suggest that the both Changning-Menglian and Longmu Co-Shuanghu sutures were probably transformed from the relic oceanic crust of the uniform Paleo-Tethys, which likely represents the original and main Paleo-Tethys oceanic basin.     

大陆造山带古洋盆恢复的有关问题讨论

对涉及古洋盆恢复的有关问题，诸如蛇绿岩的内涵与外延、造山带的结构构造特征、岩浆活动的特征、性质及时空分布规律等进行讨论。认为古洋盆恢复应以构造活动为主线，结合造山带地质体的变形、变质、岩浆活动、地球化学和同位素年龄等进行综合研究。     

Zircon SHRIMP U-Pb dating on plagiogranite from Kuerti ophiolite in Altay,North Xinjiang

The geochronological study on ophiolites is of great interest due to its tectonic significance. Previous studies have shown that ophiolites can form in various tectonic settings including middle ocean ridge, island arc, forearc and backarc basins; most of them are found in the suprasubduction zone[1,2]. Although the hypothesis that high SiO2 and low K2O granitoid rocks in ophiolites are produced by the fractional crystallization of mafic magma has been proved by experimental simulations[3,4],…     

博格达山下二叠统塔什库拉组沉积特征及古地理分析

博格达山属于晚古生代的陆间裂谷。在早二叠世晚期,它为走向近东西的槽型盆地。盆地轴部位于博格达北坡及主峰一带,南北两侧为构造控制的高角度斜坡。斜坡上发育块体搬运的重力流沉积和内陆棚粗粒风暴岩。块体搬运的重力流顺斜坡演化为浊流,进入盆地轴部后转为由东往西顺盆地走向流动,并在轴部形成一套经典浊积岩。     

Discovery of ophiolite in southeast Yunnan, China

The Babu ophiolite in Malipo County, SE Yunnan, consists of three units: ultramafic, mafic and basaltic rocks. Studies of geological mapping, petrology and geochemistry reveal that the gabbro is similar to that in the Troodos ophiolite, and the diabase and basalt belong to a normal MORB-type, analogous to the Shuanggou ophiolite in west Yunnan. The ophiolite studied as a thrust tectonic slab, was overthrust northwards onto the Late Paleozoic-Triassic deep marine deposits of continental margin. It is inferred to be relics of Paleotethyan ocean; namely, a branch of Paleotethys occurs in South China, where the tectonic nature and evolutional history of the area should be reconsidered.     

兰坪-思茅中生代盆地性质及构造演化

兰坪－思茅盆地位于澜沧江缝合线与金沙江缝合线之间，它是在澜沧江洋和金沙江洋消亡后发展起来的一个中新生代陆内盆地。在中生代，该盆地的形成与演化受特提斯构造带的控制。对盆地地层格架和区内碎屑岩的骨架矿物成分、化学成分、微量元素以及火山岩化学成分的分析表明，兰坪－思茅中生代盆地是由两个不同类型的盆地叠置而成的多旋回叠合盆地，其早期为一后造山裂谷盆地，晚期为坳陷盆地。兰坪－思茅中生代盆地的形成和演化可反馈滇西特提斯构造演化的信息。     

中国边缘海盆地构造演化与油气分布富集规律

中国边缘海盆地处在欧亚、印度-澳大利亚及太平洋三大板块相互作用之新生代最活跃区域,其中,南部边
缘海盆地尚受南海裂解扩张作用等多种因素的深刻影响,形成了具有断拗双层结构不同类型伸展型或伸展、走滑、挤
压复合型盆地,沉积充填了古近纪断陷裂谷早期中深湖相地层及其烃源岩、古近纪断陷晚期煤系地层及烃源岩、新近
纪拗陷期海相地层及其烃源岩,为油气形成奠定了雄厚的物质基础。受区域地质背景影响,边缘海盆地地壳性质及厚
度从陆缘区到深海洋盆区具有逐渐递变的特点;盆地沉降沉积中心亦逐渐向深海洋盆迁移,导致其大地热流及地热场
向洋盆区逐渐升高增强,加之与晚期新构造运动和烃源供给系统时空上的相互耦合配置,最终控制了边缘海盆地油气
分布富集规律。     

A new interpretation of the tectonic setting and age of meta-basic volcanics in the Ondor Sum Group, Inner Mongolia

The Ondor Sum Group in the central Inner Mongolia is mainly composed of meta-basic volcanics intercalated with ferruginous quartzite and quartz schist, and has been interpreted as slices of oceanic crust or an ophiolite suite of the Early Paleozoic or much older ages. This paper presents new LA-ICP-MS zircon U-Pb dating and geochemical data for the meta-basic volcanics. The results show that zircons in the meta-basic volcanics were derived from complicated sources, most of which may be captured by basic magma from the country rocks or other sources. They yield a large age range from the Late Archean to Early Mesozoic with the youngest age group between 246 and 261 Ma, constraining the protolith of the meta-basic volcanics formed in the Late Permian to Early Triassic. The meta-basic volcanics have an affinity to E-MORB in geochemistry, and also a similarity toward OIB, representing a tectonic setting of limited intra-continental ocean basin. This limited basin might have been related to the continuous extension of the area since the Early Permian and finally closed in the Early Mesozoic.     

塔里木盆地深部构造与震旦纪裂谷

塔里木盆地是一个发育在塔里木反块中部的大型克拉通盆地，它位于一近东西向展布的地幔隆起之上，其地壳厚度为４１～５０ｋｍ。盆地基底结构复杂，由太古界—下元古界深变质岩系和中上元古界浅变质岩系经８００Ｍａ前的热构造事件拼合固结而成。基底四周被深大断裂切割，控制和影响着盆地的形成与演化。震旦纪，岩石圈伸展分裂，塔里木盆地南北缘均为被动大陆边缘，其裂谷作用具有北强南弱东强西弱的特点。因此，在盆地部形成夭折裂谷，盆地西南则表现为克拉通内坳陷