广西云开地区区域成矿模式     

安国英  雷英凭 《矿产与地质》2012,26(2):89-94

通过对广西云开地区区域成矿特点和区域构造演化阶段的讨论,选择区内主要矿床的控矿地质因素、成矿时代、物质来源等特征进行对比,并根据典型矿床成矿模式概括区域成矿模式。指出加里东期、华力西-印支期、燕山期为本区矿床的成矿期,这是对广西云开地区成矿环境的认识进一步深化,以期指导区域矿产评价和找矿部署工作。  相似文献   

保山镇康地块矽卡岩型铅锌矿床成因初探   总被引：4，自引：0，他引：4  

杨玉龙  叶霖  程增涛  鲍谈  高伟 《岩石矿物学杂志》2012,31(4):554-564

保山镇康地块是"三江"南段重要的铅锌多金属成矿区之一,地质构造复杂,铅锌成矿地质条件优越,其中核桃坪与芦子园是近年发现的两个大型铅锌矿床,矿床受近NE向断裂、背斜轴部和地层控制明显,上寒武统核桃坪组与沙河床组大理岩化灰岩为主要赋矿地层,近矿围岩矽卡岩化强烈,流体包裹体,Pb、S、H、O同位素和微量元素等地球化学对比研究表明:核桃坪和芦子园铅锌矿床均经历了中温、高温两个矿化阶段;核桃坪铅锌矿床矿石铅同位素较芦子园铅锌矿床有较高的比值和较大的变化范围,均以高μ值为特征,属于放射性成因铅,暗示其成矿物质以壳源铅为主;硫化物硫同位素均多为较低正值并呈塔式分布,具有岩浆硫特征,两者均无生物硫酸盐热化学还原作用的参与,其中硫同位素分馏已达平衡;与硫化物共生的石英δDH2O(-109‰~-91‰)和δ18OH2O(-4.3‰~2.3‰)同位素研究表明核桃坪矿床成矿流体主要来自深部岩浆水,并遭受后期大气降水或地层水的混合;核桃坪矿床与芦子园矿床的微量元素具有岩浆热液型矿床特征,不同于VMS型、MVT型铅锌矿床。因此,笔者认为两个矿床应属于与深部隐伏岩体有关的中-高温矽卡岩型铅锌矿床,矿区深部隐伏岩体的侵入产生岩浆热液并携带Pb、Zn等成矿物质与地层水或大气降水混合,在背斜轴部与NE向断裂的交汇处形成该类型矿床。  相似文献   

Refertilization of serpentinites in the Sulu UHP terrane,Eastern China: constraints from geochronology,mineral composition,geochemistry, and Re–Os isotopes     

《International Geology Review》2012,54(15):1897-1913

ABSTRACT

Serpentinites from Junan (JN), Rizhao (RZ), and Rongcheng (RC) in the Sulu ultra-high-pressure (UHP) terrane, China, were analysed for U–Pb zircon geochronology, mineral chemistry, whole-rock major and trace element chemistry (including rare-earth elements (REEs) and platinum-group elements (PGEs)), and Re–Os isotopes, in order to better constrain their petrogenesis and geodynamic process. The serpentinite zircons yield two age groups: 731 ± 10 to 780 ± 10 Ma for relic magmatic zircon cores, which may indicate early crystallization and emplacement of the peridotite in the Yangtze crust, and 209 ± 2 to 218 ± 3 Ma for metamorphic zircon, which coincides with Triassic UHP metamorphism. The spinels in the serpentinites exhibit significant Cr# variation (0.6–0.91) and have undergone multi-stage metamorphism. The serpentinites are characterized by enrichment in incompatible trace elements, low Ni and IPGE concentrations, and high Pd/Ir ratios, and the bulk-rock major elements plot in the ultramafic cumulate region. Their Re and Os concentrations are similar to those of typical orogenic peridotite, but they have high ¹⁸⁷Os/¹⁸⁸Os ratios (0.12433–0.14423). We believe that the serpentinite’s protolith consisted of cumulates from an asthenosphere-derived melt that intruded into the continental crust of the Yangtze craton in the Neoproterozoic. These cumulates were later subducted and metamorphosed during the subduction of the Yangtze craton in the Triassic. The serpentinites underwent melt–rock interactions and fluid enrichment, both prior to and during serpentinization.  相似文献   

The tectono-magmatic evolution of the West Junggar terrane (NW China) unravelled by U–Pb ages of detrital zircons in modern river sands     

《International Geology Review》2012,54(5):607-621

ABSTRACT

The West Junggar terrane (WJT) is an outstanding laboratory for studying the tectonic evolution of the Junggar–Balkhash Ocean, because it contains widespread Paleozoic magmatism in different tectonic settings. We attempt to reconstruct the tectono-magmatic evolution of WJT through U–pb analysis of detrital zircons from three modern river sand samples from the Harabura, Baibuxie, and Aletengyemule rivers in the Barleik Mountains of the central WJT. A total of 232 concordant spots show Th/U ratios of 0.14–1.69, typical of igneous origin, and they contain abundant Paleozoic (96%) and few Precambrian (4%) ages, with major age populations at 450–530, 400–430, 320–380, and 265–320 Ma. The first two groups may be derived from the early subduction- and accretion-related magmatic rocks of the WJT, whereas the third group is congruent with magmatic activities related to the final subduction and basin-filling processes within a framework of the remnant Junggar–Balkhash Ocean. By combining with the regional data, the last group of magmatic events is referred to as post-subduction magmatism. The missing Mesozoic–Cenozoic magmatism clearly indicates a pre-Permian closure for the Junggar–Balkhash Ocean, nearly coeval with the closure of other oceans in the southwestern Palaeo-Asian Ocean.  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   

From back-arc rifting to arc accretion: the Late Jurassic–Early Cretaceous evolution of the Guerrero terrane recorded by a major provenance change in sandstones from the Sierra de los Cuarzos area,central Mexico     

《International Geology Review》2012,54(11):1377-1394

The Guerrero terrane is composed of Middle Jurassic–Lower Cretaceous arc assemblages that were rifted from the North American continental mainland during Late Jurassic–Early Cretaceous back-arc spreading within the Arperos Basin, and subsequently accreted back to the continental margin in the late Aptian. The Sierra de los Cuarzos area is located just 50 km east of the Guerrero terrane suture belt and, therefore, its stratigraphic record should be highly sensitive to first-order tectonic changes. Two Upper Jurassic–Lower Cretaceous clastic units were recognized in the Sierra de los Cuarzos area. The Sierra de los Cuarzos Formation is the lowermost exposed stratigraphic unit. Petrographic data and U-Pb zircon ages suggest that the Sierra de los Cuarzos Formation was derived from quartz-rich sedimentary and igneous sources within the North American continental mainland. The Sierra de los Cuarzos Formation is overlain by the Pelones Formation, which is composed of volcanoclastic sandstones derived from a mix of sources that include the mafic arc assemblages of the Guerrero terrane and quartz-rich sedimentary and volcanic rocks exposed in the continental mainland. The provenance change documented in the Sierra de los Cuarzos area suggests that the Pelones Formation was deposited when the Arperos Basin was closed and the Guerrero terrane was colliding with the North American continental mainland. Based on these data, we interpret the Pelones Formation as the syn-tectonic stratigraphic record associated with the accretion of the Guerrero terrane.  相似文献   

广西云开地区地球化学特征和找矿远景预测     

安国英  雷英凭  代晓莉 《物探与化探》2012,36(4):539-545

利用广西云开地区1∶20万化探扫面成果,研究该区成矿元素的地球化学特征及分布规律,并选择了主要成矿元素Ag、Au、Pb、Zn、W、Mo、Sn进行讨论,研究它们在空间、时间上的分散、富集规律,为区域矿床地球化学预测提供理论依据;提出Ⅰ级找矿远景区8个,Ⅱ级远景区5个,Ⅲ级远景区3个,作为下一步矿产勘查工作的靶区。  相似文献   

华南板块南缘早中生代的逆冲推覆构造及其相关的动力学背景   总被引：5，自引：0，他引：5       下载免费PDF全文

林伟  Michel Faure  Claude Lepvrier  陈泽超  禇杨  王清晨  N'guyen Van Vuong  Vu Van Tich 《地质科学》2011,46(1):134-145

作为理解华南构造演化的关键地区,在华南板块南缘的云开地体和越北的Song Chay地体发育了早中生代的向北东逆冲推覆的韧性变形.在云开地体,经历角闪岩相和绿片岩相变质的矿物指示了产状平缓的面理上发育明显的北东-南西向矿物拉伸线理.沿着这些矿物拉伸线理,具有上部指向北东的剪切变形.同位素年代学的定年结果指示了变形事件发生...  相似文献   

缅甸联邦MTT金铜矿床成矿地质特征          下载免费PDF全文

徐强 《江苏地质》2011,35(4):375-378

缅甸联邦实皆省MTT金铜矿床位于曼德勒以西约200km新生代安山岩中,属块状硫化物金铜矿床。对其成矿地质特征进行了研究,有助于在新生代安山岩中发现相同类型的矿床。矿体产在缅甸中部盆地地体之西缘,赋矿地层(即含矿岩系)为陆相安山岩,硫化物矿体呈层状、似层状和透镜体状。矿石具块状构造,矿石中主要成矿元素为Cu、Au、S;铜矿石品位较高,属富铜矿。该类型矿床的找矿标志是:具有低阻高极化的物探异常。  相似文献   

三维古地貌重建技术在中生代羌塘地体古地理演化分析中的应用     

于淼  陈建平  严琼  武瞾  王春女  于萍萍 《地质通报》2011,30(5):694-701

近年来,从古地貌-沉积组合与油藏关系的角度进行油气远景评价成为研究热点。针对古地貌的复原研究,提出一种建立三维古地貌模型的方法,将二维平面古地理图通过对资料的整理、挖掘与转换,并结合GIS技术生成了三维立体模型,补充了区域地形地貌的相关信息。利用该方法,建立了青藏高原油气资源潜力最大的区域——羌塘地体在三叠纪和侏罗纪的一系列三维古地貌模型,进而对其古环境和演化过程进行分析,这对于该区域的沉积矿产资源的预测与评价有重要的参考价值。  相似文献