新疆阿斯喀尔特铍钼矿床中辉钼矿Re-Os定年及成因意义   总被引：2，自引：0，他引：2  

刘文政  张辉  唐红峰  唐勇  吕正航 《地球化学》2015,(2):145-154

阿斯喀尔特铍钼矿床位于中亚成矿域阿尔泰成矿省哈龙-青河成矿带的东南部。7件辉钼矿样品Re-Os同位素年龄介于(224.6±3.1)Ma与(235.7±3.4)Ma之间,加权平均年龄为(229.0±3.0)Ma,等时线年龄为(228.7±7.1)Ma,表明成矿作用发生于印支期。辉钼矿样品Re含量为38.26~56.45μg/g,指示成矿元素Re具有壳幔混合来源特征。由于阿斯喀尔特铍-钼矿床成矿时代晚于古亚洲洋闭合时间(约250 Ma),并且花岗岩-伟晶岩体系中的晚期伟晶岩以低的锆石Hf同位素组成(–1.50~+1.69)为特征,相似于区域中侵入的三叠纪伟晶岩中锆石Hf同位素组成,如可可托海3号脉、柯鲁木特112号脉,因此,推测与阿斯喀尔特铍钼矿床具有成因联系的花岗岩-伟晶岩体系,其成因与哈萨克斯坦-西伯利亚板块在晚古生代发生陆-陆碰撞造山作用,在三叠纪构造体系由挤压转为伸展背景下,先期存在幔源物质的古老地壳物质发生减压部分熔融有关。  相似文献   

辽宁小佟家堡子金矿床成矿流体特征及来源讨论   总被引：1，自引：0，他引：1  

王一存 《地质与勘探》2015,51(1):79-87

小佟家堡子金矿床地处辽宁青城子矿田东南部,为一大型蚀变岩型矿床。矿床产于辽河群大石桥组三段白云石大理岩中,矿体呈层状、似层状产出。矿床由热液叠加改造作用形成,历经石英-黄铁矿、石英-碳酸盐两个阶段。流体包裹体研究表明,该矿床成矿流体属中低温、低盐Na Cl-H2O型体系热液。碳氢氧同位素地球化学的研究表明,石英-黄铁矿阶段成矿流体氧同位素δ18O组成在15.2‰~18.4‰,碳同位素δ13CV-PDB组成在-7.4‰~-13.2‰,氢同位素δD组成为-89.3‰~-92.2‰,反应该阶段成矿流体主要来自岩浆水并伴有少量的大气降水。石英-碳酸盐阶段成矿流体氧同位素δ18O组成在17‰~17.8‰,碳同位素δ13CV-PDB组成在-12.3‰~-13.5‰,氢同位素组成δD为-87.7‰~-90.4‰,表明该阶段成矿流体主要来自大气降水。  相似文献   

咸化湖盆白云岩碳氧同位素特征及古环境意义:以柴西地区始新统下干柴沟组为例   总被引：4，自引：0，他引：4  

袁剑英  黄成刚  曹正林  李智勇  万传治  徐丽  潘星  吴丽荣 《地球化学》2015,44(3)

近年来,柴西地区始新统致密碳酸盐岩中的油气勘探获得了重要进展,其中白云岩为最优质的储集岩。系统的岩石学、矿物学和地球化学特征研究表明,该套白云岩主要为泥晶结构,白云石晶间孔广泛发育,孔径多小于1μm。泥晶白云岩的δ13CPDB值变化范围为-4.5‰~0.2‰,平均值为-2.4‰,相对于典型湖相碳酸盐岩偏负,反映了周缘辫状三角洲供给富含轻碳的地表水在一定程度上改变了白云岩的碳同位素组成,且湖水中的溶解碳部分来源于有机质氧化解体产生的CO2,通过改变湖水中溶解碳的碳同位素组成从而间接影响了湖相白云岩的碳同位素组成。泥晶白云岩的δ18OPDB值变化范围为-6.1‰~0.4‰,平均值为-2.6‰,相对于典型湖相碳酸盐岩偏正,明显受咸化湖沉积环境影响。碳氧同位素相关关系投点图及其计算出的盐度、温度数据反映了泥晶白云岩是在准同生阶段、半开放-半封闭的咸化环境下、于水/沉积物界面附近由方解石交代而成的低温白云岩,这类准同生交代成因白云岩在区域上分布较广,且孔径极小的白云石晶间孔抗压实能力强,这一重要发现无论是平面展布上还是纵向深度上均开拓了柴达木盆地致密油勘探的新领域。  相似文献   

西藏改则洞错地区白垩纪火山岩锆石U-Pb年代学、Hf同位素组成及对班公-怒江洋俯冲闭合的制约   总被引：1，自引：0，他引：1       下载免费PDF全文

付佳俊  丁林  许强  蔡福龙  岳雅慧  郭钰 《地质科学》2015,50(1):182-202

班公湖—怒江缝合带是青藏高原内一条重要的缝合带,其俯冲极性和闭合时限一直存在着争议,这无疑限制了我们对青藏高原演化历史的认识。本文对仲岗安山玄武岩和一套新发现的晚白垩世安山岩进行研究,获得了其锆石U-Pb年龄分别为123.75±0.92 Ma和74.23±0.76 Ma。仲岗安山玄武岩锆石的ε_(Hf)(t)值为-7.3~+4.4,具有岛弧玄武岩特征,指示班公湖—怒江洋盆在该地区仍然继续向北俯冲;晚白垩世安山岩锆石的ε_(Hf)(t)值为+3.1~+11.1,其可能是亏损地幔混熔了部分的陆壳物质而形成的,且不整合在蛇绿岩之上。结合区域资料本文认为班公湖—怒江洋盆在改则地区的闭合时限在100~75 Ma之间。  相似文献   

Response and recovery of the Comanche carbonate platform surrounding multiple Cretaceous oceanic anoxic events,northern Gulf of Mexico     

《Cretaceous Research》2015

The ubiquity of carbonate platforms throughout the Cretaceous Period is recognized as a product of high eustatic sea-level and a distinct climatic optimum induced by rapid sea-floor spreading and elevated levels of atmospheric carbon-dioxide. Notably, a series of global oceanic anoxic events (OAEs) punctuate this time-interval and mark periods of significantly reduced free oxygen in the world's oceans. The best records of these events are often from one-dimensional shelf or basin sections where only abrupt shifts between oxygenated carbonates and anoxic shales are recorded. The Comanche Platform of central Texas provides a unique opportunity to study these events within a well-constrained stratigraphic framework in which their up-dip and down-dip sedimentologic effects can be observed and the recovery of the platform to equilibrium states can be timed and understood. Stable isotope data from whole cores in middle Hauterivian through lower Campanian mixed carbonate-siliciclastic strata are used to construct a 52-myr carbon isotope reference profile for the northern Gulf of Mexico. Correlation of this composite curve to numerous global reference profiles permits identification of several anoxic events and allows their impact on platform architecture and facies distribution to be documented. Oceanic anoxic events 1a, 1b, 1d, and 2 occurred immediately before, after, or during shale deposition in the Pine Island Member, Bexar Member, Del Rio Formation, and Eagle Ford Group, respectively. Oceanic anoxic event 3 corresponds to deposition of the Austin Chalk Group. Platform drowning on three occasions more closely coincided with globally recognized anoxic sub-events such as the Fallot, Albian-Cenomanian, and Mid-Cenomanian events. This illustrates that the specific anoxic event most affecting a given carbonate platform varied globally as a function of regional oceanographic circumstances.Using chemo- and sequence-stratigraphic observations, a four-stage model is proposed to describe the changing facies patterns, fauna, sedimentation accumulation rates, platform architectures, and relative sea-level trends of transgressive-regressive composite sequences that developed in response to global carbon-cycle perturbations. The four phases of platform evolution include the equilibrium, crisis, anoxic, and recovery stages. The equilibrium stage is characterized by progradational shelf geometries and coral-rudist phototrophic faunal assemblages. Similar phototrophic fauna typify the crisis stage; however, incipient biocalcification crises of this phase led to retrogradational shelf morphologies, transgressive facies patterns, and increased clay mineral proportions. Anoxic stages of the Comanche Platform were coincident with back-ground deposition of organic-rich shale on drowned shelves and heterotrophic fauna dominated by oysters or coccolithophorids. Eustatic peaks of this stage were of moderate amplitude (∼30 m), yet relative sea-level rises were greatly enhanced by reduced sedimentation rates. In the recovery stage, heterotrophic carbonate factories re-established at the shoreline as progradational ramp systems and sediment accumulation rates slowly increased as dysoxia diminished. Full recovery to equilibrium conditions may or may not have followed. Geochemical and stratigraphic trends present in the four stages are consistent with increased volcanism along mid-ocean ridges and in large-igneous provinces as primary drivers of Cretaceous OAEs and the resulting transgressive-regressive composite sequences.  相似文献   

Performance of the seasonal forecasting of the Asian summer monsoon by BCC_CSM1.1(m)   总被引：1，自引：0，他引：1  

Xiangwen Liu  Tongwen Wu  Song Yang  Weihua Jie  Suping Nie  Qiaoping Li  Yanjie Cheng  Xiaoyun Liang 《大气科学进展》2015,32(8):1156-1172

This paper provides a comprehensive assessment of Asian summer monsoon prediction skill as a function of lead time and its relationship to sea surface temperature prediction using the seasonal hindcasts of the Beijing Climate Center Climate System Model, BCC_CSM1.1(m). For the South and Southeast Asian summer monsoon, reasonable skill is found in the model's forecasting of certain aspects of monsoon climatology and spatiotemporal variability. Nevertheless, deficiencies such as significant forecast errors over the tropical western North Pacific and the eastern equatorial Indian Ocean are also found. In particular, overestimation of the connections of some dynamical monsoon indices with large-scale circulation and precipitation patterns exists in most ensemble mean forecasts, even for short lead-time forecasts. Variations of SST, measured by the first mode over the tropical Pacific and Indian oceans, as well as the spatiotemporal features over the Niño3.4 region, are overall well predicted. However, this does not necessarily translate into successful forecasts of the Asian summer monsoon by the model. Diagnostics of the relationships between monsoon and SST show that difficulties in predicting the South Asian monsoon can be mainly attributed to the limited regional response of monsoon in observations but the extensive and exaggerated response in predictions due partially to the application of ensemble average forecasting methods. In contrast, in spite of a similar deficiency, the Southeast Asian monsoon can still be forecasted reasonably, probably because of its closer relationship with large-scale circulation patterns and El Niño-Southern Oscillation.  相似文献   

沂水县高庄地区铜铅矿地质特征及成矿模式探讨          下载免费PDF全文

亓希强  张晶  郭加朋  刘鹏磊  徐东来  肖丙建 《山东国土资源》2015,31(9)

沂水县高庄铜铅矿赋存于张夏组盘车沟段灰绿色页岩夹薄层泥灰岩和张夏组下灰岩段鲕粒灰岩之间的构造角砾岩中,在形态上和空间位置上严格受蚀变角砾岩带控制的似层状矿体。通过对矿区内地层、控矿构造、矿体特征和矿石质量的分析论述,认为该矿床为碳酸盐型中低温热液充填—交代矿床,并建立了成矿模式。  相似文献   

吉尔吉斯斯坦布丘克造山型金矿床：来自流体包裹体、H- O- S同位素证据     

史鹏亮  屈海浪  鄂建新  刘春发  缪广  马麒镒  戴毅 《地质学报》2023,97(3):738-752

吉尔吉斯斯坦北天山构造带的矿床学数据缺乏,制约了天山造山带境内外成矿对比。布丘克金矿床位于吉尔吉斯斯坦北天山构造带中部。金矿体为石英复脉,呈带状发育于NWW向韧性剪切带中。矿体倾向SSW,倾角60°～70°,赋矿围岩主要为侵入于早古生代变质碎屑杂岩中的正长斑岩。布丘克金矿床成矿期石英流体包裹体观察、石英H-O同位素、硫化物S同位素测试结果显示,布丘克金矿床石英脉中包裹体大小集中在2～10μm之间,类型以H₂O-CO₂型、富CO₂型、水溶液型包裹体为主,成分以富CO₂、含CH₄为特征。成矿流体具有中温(200～320℃)、低盐度(3%～7%NaCl_eqv)特征;石英δD_V-SMOW值介于-108.1‰～-90.2‰之间,δ¹⁸O_流体值介于4.86‰～9.26‰之间;黄铁矿δ³⁴S分布在0‰左右(-0.9‰～1.6‰)。综合本文数据、矿床地质特征、区域地质资料,本文认为布丘...  相似文献   

内蒙古扎拉格阿木铜矿成矿流体与成矿机制     

车东  王建平  吴起鑫  张照志  邢恩袁  沈存利  杨文海  郭海蛟 《地质学报》2023,97(8):2575-2592

扎拉格阿木铜矿床位于锡林浩特地块北部边缘,矿体赋存于二叠纪砂质板岩和角砾岩中,受NE向断裂控制,为中温热液脉型铜矿床。本文通过流体包裹体和C?H?O?S?Pb同位素地球化学研究手段,来探讨扎拉格阿木铜矿成矿机制。成矿热液期存在5个成矿阶段：钾长石阶段、石英?绢云母阶段、石英?黄铁矿阶段、石英?多金属硫化物阶段、石英?方解石阶段。其中石英?多金属硫化物阶段为主成矿阶段,本阶段主要发育富液相、富气相、含子矿物包裹体;富液相包裹体均一温度与盐度分别为：138～289℃和2.06%～16.11% NaCl eqv;含子矿物包裹体均一温度与盐度分别为：320～374℃和32.68%～39.81% NaCl eqv,包裹体气体成分除少量CO2以外,均为H2O。H?O同位素分析表现为,石英中的〖δO〗^18值变化范围－8.5‰～7.5‰,流体的δD值变化范围为－116‰～－98‰,暗示早阶段成矿流体主要为岩浆热液,晚期伴有大气降水混入。C?O同位素分析表明,δ13C值为-6.9‰~ -10.1‰,δ18OSMOW介于2.5‰~11.7‰,在δ18O?δ13C 图上数据点落在岩浆水与大气水的中间区域。矿石硫化物的δ34S值介于-4.5‰~1.5‰,指示具有幔源岩浆硫的特征。矿石硫化物Pb同位素的208Pb/204Pb、207Pb/204Pb和206Pb/204Pb比值分别为38.034~38.609、15.497~15.655和18.141~18.446,推测Pb具有地幔来源的特点并伴有地壳或造山带Pb混入。成矿过程中伴随着流体沸腾作用,成矿物质沉淀受早期形成的岩浆热液与后加入大气降水混合的影响。  相似文献   

滇东南老君山矿集区北部长田W(Sn)矿床成矿时代：来自白钨矿和萤石 Sm- Nd同位素定年的制约     

杜胜江  温汉捷  张锦让  杨光树 《地质学报》2023,97(10):3347-3362

滇东南是我国重要的钨锡多金属成矿区,老君山矿集区是其重要组成部分,围绕燕山期老君山复式花岗岩体,分布有都龙、南秧田、新寨大型-超大型Sn-W多金属矿床及多个中小型矿床(点)。该区地质演化复杂,Sn、W多金属可能存在多期成矿作用,包括燕山期、印支期和加里东期。由于目前该区发现的Sn-W矿化多分布于老君山岩体南、东侧,而岩体北部Sn-W成矿作用的研究相对较薄弱,特别是成矿年代学方面,多数矿床依然缺少精确同位素年代学数据,制约了该区Sn-W多金属成矿作用的认识和地质勘探的深入。长田是老君山岩体北缘代表性W (Sn)多金属矿床,区内加里东期和燕山期花岗岩均有分布,由于缺少年代学数据和地质地球化学研究,W(Sn)成矿作用的认识尚缺少实际地质地球化学依据,难以建立合理的成矿模式,制约了区内地质勘探的深入和突破。基于此,本文通过对长田W (Sn)矿床中白钨矿及共生萤石的Sm-Nd同位素定年,分别获得97 Ma和79 Ma两个年代学数据,显示该矿床钨矿化主成矿期应为燕山晚期,与老君山花岗岩活动时限一致,表明长田钨成矿作用与燕山期老君山花岗岩的侵入活动关系密切,而与加里东期岩浆活动关系不大。该成果丰富了...  相似文献