赣北景德镇韧性剪切带两类剪切指向及其构造意义          下载免费PDF全文

徐先兵  汤帅  林寿发 《高校地质学报》2016,22(2):308

景德镇韧性剪切带位于新元古代江南造山带的核部,其构造变形特征和形成时代对华南新元古代至早古生代构造演 化具有重要的制约意义。景德镇韧性剪切带呈北东向展布,全长约180 km,最大出露宽度为~7 km。通过详细的野外地质 调查和室内定向薄片鉴定,在景德镇韧性剪切带中识别出了两期韧性走滑构造变形,并研究了其运动学指向和形成时的温 压条件。早期构造变形表现为左旋韧性走滑兼逆冲作用,形成温度为420~530℃,差应力为40~300 MPa;晚期变形主要表 现为右旋走滑,形成温度为300~420℃,差应力为120~350 MPa。结合前人资料,景德镇韧性剪切带左旋走滑兼逆冲作用形 成于新元古代造山作用的晚期（810~800 Ma）,是由同造山挤压到后造山伸展调整的结果;而右旋走滑形成于早古生代,是 华南早古生代陆内造山作用的产物。  相似文献   

Recurrent mesoproterozoic continental magmatism in South-Central Norway     

Svend Pedersen  Tom Andersen  Jens Konnerup-Madsen  William L. Griffin 《International Journal of Earth Sciences》2009,98(5):1151-1171

We report U–Pb dates and Lu–Hf isotope data, obtained by LAM-ICPMS, for zircons from metamorphic rocks of the Setesdalen valley, situated in the Telemark block south of the classic Telemark region of southern Norway. The samples include infracrustal rocks from the metamorphic basement, metaigneous rocks and metasediments from the Byglandsfjorden supracrustal cover sequence, and metaigneous rocks which intruded the whole succession. The main crustal evolution took place from 1,550–1,020 Ma, beginning with the emplacement of juvenile tonalitic melts; the contribution of older crustal material increased with time. Around 1,320 Ma, further addition of juvenile material occurred, involving both mafic and felsic melts, metamorphism and deformation. Acid magmas with high FeO*/MgO were intruded at 1,215 Ma, coinciding with underplating elsewhere in South Norway. The period starting at 1,215 Ma is represented by supracrustal rocks, principally metarhyolites with minor mafic material and immature sediments of the Byglandsfjorden Group. The crust generation processes ended with the intrusion of diorites and granodiorites at 1,030 Ma, late in the Sveconorwegian orogeny. Regional processes of metamorphism and deformation (around 1,290 and 1,000 Ma) can be related to the assembly of Rodinia. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

胶东金矿成矿构造背景探讨     

李洪奎  禚传源  耿科  梁太涛 《山东地质》2012,(1):5-13

在编制1∶50万山东省大地构造相图基础上,通过对大地构造相研究显示：胶东微地块是经多期增生和碰撞而形成的,其漫长的板块构造演化明显具有阶段性。侏罗纪是该区板块构造演化史上的一个重要转换期,构造演化由原来的南、北分异转变为东、西分异,胶东地区NE向新生构造起了主要作用。胶东地区中生代有2次重要的碰撞造山事件,印支造山作用主要表现为扬子板块向华北板块俯冲,形成苏鲁高压-超高压变质带及同造山花岗岩及后造山高碱正长岩;燕山造山作用的大陆动力学环境起源于中亚-特提斯构造域向滨太平洋构造域转化和太平洋板块的俯冲,在胶东地区表现为3次造山和3次伸展。晚侏罗世造山早期玲珑片麻状花岗岩组合是区域构造挤压导致地壳增厚引起地壳重熔的产物,代表了大陆弧花岗岩特征;早白垩世造山中期郭家岭花岗闪长岩-花岗岩组合代表了造山期大陆弧花岗岩的特点;造山晚期伟德山闪长岩-花岗闪长岩-花岗岩组合表现为大陆弧花岗岩,后造山A型崂山晶洞过碱性碱长花岗岩-正长花岗岩组合为大陆造陆隆升花岗岩与后造山花岗岩,代表燕山构造的结束。胶东地区构造-岩浆事件和金矿成矿作用受控于特提斯、古亚洲洋和太平洋三大构造域的相互作用,金矿形成的动力学背景是中生代构造体制转折和岩石圈减薄,起因与太平洋板块向华北板块的俯冲机制有关。  相似文献   

江南古陆中段沧水铺群锆石U-Pb年龄和构造演化意义   总被引：5，自引：2，他引：3       下载免费PDF全文

高林志刘燕学  丁孝忠张传恒  王自强陈 俊 刘耀荣 《中国地质》2012,39(1):12-20

江南古陆中段湖南益阳地区沧水铺群发育在冷家溪群和板溪群之间,其在地层柱中的位置一直是中国地质学家解疑江南造山带何时启动的关键层位。笔者在沧水铺群中的火山集块岩中获得锆石SHRIMP U-Pb年龄(821±13)Ma,再次验证了沧水铺群中的火山岩是820 Ma武陵运动之前的火山事件的产物,与武陵运动的启动有关,也说明该期火山岩与冷家溪群中大量的火山凝灰岩为同一构造运动的产物。  相似文献   

南盘江盆地中三叠统碎屑锆石地质年代学:物源及其地质意义   总被引：1，自引：0，他引：1  

杨宗永  何斌 《大地构造与成矿学》2012,36(4)

南盘江盆地的物源及其构造性质至今尚未取得较为一致的认识。目前主要的观点认为其物源主要来自盆地东南面的云开大山地区,盆地的性质为古太平洋板块俯冲所形成的前陆盆地。本文采用碎屑锆石年代学方法,首次报道该盆地中三叠统碎屑锆石年龄组成,分析了该盆地的沉积物源,并基于物源分析探讨了成盆机制和板块间动力学关系。该盆地中三叠统碎屑锆石年龄组成最主要的特征性的年龄分布在320～250Ma之间,此区间内存在280Ma和250Ma两个峰值。通过与相邻各块体锆石年龄谱对比,本研究认为:(1)南盘江盆地的主要物源区应为古特提斯北缘(华南一侧)的石炭-二叠纪岩浆弧,SongMa构造带可能是三叠纪的缝合线,而不是因Sibumasu板块增生到印支板块而导致的板内活化带;(2)该盆地三叠纪时为古特提斯闭合在华南形成的前陆盆地,与古特提斯沿SongMa带向北俯冲闭合有关,前人认为的南盘江盆地形成于古太平洋板块向西北俯冲作用的观点值得商榷。  相似文献   

Sedimentary response to the intracontinental orogenic process: insight from the anatomy of a small Mesozoic basin in western Yanshan,northern North China     

《International Geology Review》2012,54(12):1528-1556

ABSTRACT

The intra-continental orogeny and tectonic evolution of the Mesozoic Yanshan fold-thrust belt (YFTB) in the northern North China Craton (NCC) have been strongly debated. Here, we focus on the Shangyi basin, located in the centre of the YFTB. An integrated analysis of sedimentary facies, palaeocurrents, clast compositions, and detrital zircon dating of sediments was adopted to determine the palaeogeography, provenance, basin evolution, and intra-continental orogenic process. The Shangyi basin comprises the well-exposed Early–early Middle Jurassic Xiahuayuan Formation and the Longmen Formation, and the Late Jurassic–Early Cretaceous Tuchengzi Formation. Based on the 18 measured sections, five facies associations – including alluvial fan, fluvial, delta, lacustrine, and eolian facies – have been identified and described in detail. The onset of the Shangyi basin was filled with fluvial, deltaic, and lacustrine deposits controlled by the normal fault bounding the northern basin, corresponding to the pre-orogeny. In the Middle Jurassic, the cobble–boulder conglomerates of alluvial fan, as molasse deposits, were compatible with the syn-orogeny of the Yanshan movement, which played a critical role in northern North China and even East Asia. After the depositional break in the Middle–Late Jurassic, the Shangyi basin, controlled by the normal fault present in the north of the basin, re-subsided and quickly expanded southward with thick sedimentation, which is correlative with the post-orogeny. Combined with A-type granites, metamorphic core complexes, mafic dikes, and rift basins of the Late Jurassic–early Early Cretaceous present in the northern NCC and Mongolia, significant extension was widespread in the northern NCC and even in northeast Asia. Moreover, vertical changes of provenance indicate that the Taihang Mountain and the Inner Mongolia palaeo-uplift (IMPU) present at the west and north of the basin, respectively, experienced uplift twice in the Middle–Late Jurassic and Early Cretaceous, resulting in a regional depositional break.  相似文献   

江南造山带西南段梵净山地区镁铁质-超镁铁质岩:形成时代、地球化学特征与构造环境   总被引：1，自引：0，他引：1  

薛怀民  马芳  宋永勤 《岩石学报》2012,28(9):3015-3030

梵净山地区位于江南造山带的西南缘,这里新元古代的镁铁质-超镁铁质岩浆岩广泛发育,岩性包括枕状熔岩、超镁铁质-镁铁质岩床群以及浅成侵入的辉长岩,成分属拉斑玄武岩系列。其中枕状熔岩以富集轻稀土元素和Rb、Ba、Th、U等强不相容元素,亏损高场强元素Nb和Ta,低的εNd(t)值为特征,明显不同于洋脊玄武岩,推测其成因可能与富集型地幔的部分熔融有关,形成于与俯冲有关的弧后小洋盆环境。超镁铁质-镁铁质岩床群主要由辉绿岩和碳酸辉橄岩组成,其中超镁铁质岩床群中出现大量的原生碳酸盐矿物,指示它们形成于拉张(甚至裂谷)的构造环境。辉长岩可能是区内最晚形成的岩浆岩,其SHRIMP锆石U-Pb年龄为821±4Ma。由枕状熔岩经超镁铁质-镁铁质岩床群到辉长岩,高场强元素Nb和Ta的亏损程度减弱、轻稀土元素的富集程度降低、εNd(t)值由负值变为正值,指示随时间的由早到晚,来自亏损地幔的物质不断增加。推测梵净山地区新元古代岩浆作用的顺序大致为:枕状熔岩(～840Ma)→白云母花岗岩(～838Ma)→碳酸超镁铁质岩床群→镁铁质岩床群→辉长岩(～821Ma),构造环境由俯冲-碰撞到拉张-裂谷。  相似文献   

Large-scale gold mineralization in eastern China induced by an Early Cretaceous clockwise change in Pacific plate motions     

《International Geology Review》2012,54(3):311-321

Orogenic gold (Au) deposits are the most important type, accounting for more than half of the world's proven Au reserves. They are mainly controlled by three key factors: (1) abundant andesitic rocks (SiO₂ of 55–60 wt.%) at depth, which have systematically higher Au contents than other rock types; (2) a pervasive transition from greenschist facies to amphibolite facies metamorphism within a short period, which releases S^2?-rich fluids that may scavenge Au from host rocks; and (3) deformation and fracturing under a compressive/transpressive tectonic regime. Orogenic belts at convergent margins are the best places for such mineralization because convergent margins are rich in andesites; the transition from greenschist to amphibolite facies recrystallization commonly occurs as a result of collision, compression, and thickening at convergent margins, forming large amounts of Au-rich fluids within a short period of time; and strong deformation and fracturing during orogenic processes provide channels for fluid transportation. Moreover, the overlying plate is injected and enriched by auriferous fluids released during amphibolite facies metamorphism of the subducting plate. The Pacific plate changed course by ～80° (from SW to NW) at approximately 125–122 Ma, reflecting an altered thermal structure and the elevation of the South Pacific plate attending the appearance of the plume head that formed the Ontong Java large igneous province. Consequently, the tectonic regime changed from extension to compressive/transpressive in eastern China, causing deformation, thickening, and metamorphism of the overriding plate, especially along weak crustal belts (e.g. overlying plates of palaeosutures), which resulted in world-class mineralization of orogenic Au deposits. During this process, pyrite changed to pyrrhotite during the transition from greenschist to amphibolite facies, releasing sulphur. Sulphur mobilized and scavenged Au and other chalcophile elements into metamorphic ore-forming fluids. A series of NE-trending compressive faults were formed at ?120 Ma as a result of continuous compression of the subducting Pacific plate, releasing these ore-forming fluids. Auriferous carbonate-rich quartz veins and/or metasomatized Au-bearing wall rocks were formed due to the decompression of the ascending ore-forming fluids. Orogenic belts along the margins of the North China craton and the Jiangnan block were the most favourable regions for mineralization. Compared with the former, the latter has much smaller proven Au reserves. However, more exploration is needed along the margins of the Jiangnan block. Promising targets include accessory faults and kink points of large, NE-trending Cretaceous faults that transect greenschist facies metamorphic rocks of the Niuwu and Jingtan Groups, etc.  相似文献   

Kinematics of the Guerrero terrane accretion in the Sierra de Guanajuato,central Mexico: new insights for the structural evolution of arc–continent collisional zones     

《International Geology Review》2012,54(5):574-589

The Guerrero terrane comprises Middle Jurassic–Early Cretaceous arc successions that were accreted to the North American craton in the late Early Cretaceous, producing closure of the Arperos oceanic basin and the formation of an approximately 100 km-wide fold–thrust belt. Such a suture is key to investigating the structural evolution related to Guerrero terrane accretion and, in general, to arc–continent collisional zones. The Sierra de Guanajuato is an exposure of the Guerrero terrane suture belt and consists of a complex tectonic pile that formed through at least three major shortening phases: D1SG, D2SG, and D3SG (SG, Sierra de Guanajuato). During the D1SG and D2SG phases, the Upper Jurassic–Lower Cretaceous successions of the Arperos Basin piled up, forming a doubly vergent imbricate fan of thrust sheets that accommodated substantial NE–SW shortening. Mylonite microtextures, as well as syntectonic minerals, indicate that the D1SG and D2SG deformation events took place under low greenschist-facies metamorphic conditions. We relate these deformation phases to the progressive NE migration of the Guerrero terrane, which triggered the collapse and closure of the Arperos Basin. During D3SG, the El Paxtle arc assemblage of the Guerrero terrane was tectonically emplaced onto the previously deformed successions of the Arperos Basin. However, D3SG structures indicate that during this deformational stage, the main shortening direction was oriented NW–SE and that contraction was accommodated mostly by SE-vergent ductile thrusts formed under low greenschist-facies metamorphic conditions. We suggest that the top-to-the-SE emplacement of the El Paxtle assemblage may be a result of the tectonic escape of the arc produced by the continuous NE impingement of the Guerrero terrane during its collisional addition to the Mexican mainland.  相似文献   

浙江诸暨地区石角-璜山侵入岩LA-ICP-MS锆石U-Pb年龄——对超镁铁质球状岩成因的启示   总被引：2，自引：0，他引：2  

王孝磊  舒徐洁  邢光福  谢思文  张春晖  夏晗 《地质通报》2012,31(1):75-81

对分布于江南造山带东段江绍断裂带附近的浙江诸暨地区石角-璜山侵入岩进行了LA-ICP-MS锆石U-Pb定年工作,石角角闪辉石岩和璜山石英闪长岩的结晶年龄分别为844Ma±3Ma和818Ma±6Ma。该年龄结果表明,石角村附近的超镁铁质岩(包括球状辉闪岩)与其外围的闪长岩可能并非同时形成。江绍断裂带附近分布的多个闪长岩体的形成时代介于930~820Ma之间。对这些超镁铁质岩和闪长岩的精细岩石成因研究将有助于揭示扬子和华夏在新元古代时期的拼接过程。  相似文献