新疆阿尔泰山西段乞格拉塔乌岩体LA-ICP-MS锆石U-Pb同位素年龄及其地质意义     

王星  蔺新望  张亚峰  何元方  赵端昌  菅坤坤  陈光庭 《地质论评》2019,65(2):370-385

新疆阿尔泰山西段发育的花岗岩体缺乏精确地锆石U-Pb同位素年龄资料。本次在乞格拉塔乌岩体中获得了425.1±4.4Ma的LA-ICP-MS锆石U-Pb同位素年龄数据,将其形成时代厘定为中志留世。岩石SiO_2含量在64.07%～73.77%之间,Al_2O_3含量为12.40%～15.71%, A/CNK值为1.02～1.10,全碱(ALK)含量为5.85%～7.93%,里特曼指数(σ)为1.62～2.24,具有弱过铝质、高钾钙碱性系列花岗岩特征;稀土总量介于166.3×10~(-6)～197.2×10~(-6)之间,轻、重稀土分馏明显,δEu值介于0.47～0.63之间,具明显负Eu异常。微量元素富集Rb、Th、U等大离子亲石元素及La、Ce、Sm等,亏损Nb、Zr等高场强元素及Sr、P、Ti等,具有低Sr高Yb的特征(Sr含量在93.7×10~(-6)～211×10~(-6),Yb含量在2.1×10~(-6)～3.9×10~(-6))。研究表明,古亚洲洋从奥陶纪开始向北俯冲,一直持续到晚古生代中晚期。早古生代末期形成的乞格拉塔乌岩体,既有俯冲环境特征,又显示了后碰撞花岗岩类特点,其复杂的成因可能与古亚洲洋存在洋中脊俯冲作用有关。  相似文献   

巴颜喀拉地块当俄花岗岩体地球化学特征及锆石年龄          下载免费PDF全文

邓金贤  冯平  周云龙  彭健  齐兵德  邓良武  沙浩 《地质找矿论丛》2019,34(2):242-248

巴颜喀拉地块夹持于昆南缝合带、金沙江缝合带及龙门山断裂带之间,出露了较多的花岗岩体。当俄花岗岩体的岩石地球化学特征表明,当俄岩体具有较高SiO_2含量(w(SiO_2)=65.78%～70.22%)、过铝质(A/CNK=1.58～1.95,1.1)特征,属过铝质高钾钙碱性A型花岗岩;该岩体总体形成温度为700℃—800℃,总体形成压力为0.05GPa—0.2GPa,为低压高温环境;岩石具有Rb、Th强正异常,Ba、Nb、Sr、P、Ti强烈亏损,轻稀土强烈富集特征,且具有一定的负Eu异常,显示出有壳源的特征;花岗岩锆石SHRIMP U-Pb测年为211.9 Ma±1.9Ma,表明岩浆侵位时代为中生代晚三叠世。当俄花岗岩体形成于碰撞造山后期地壳减薄环境中,属于印支晚期岩浆活动的产物。  相似文献   

Kerr场中缓慢粒子的运动     

刘麟仲  彭秋和 《天文学报》1994,35(4):371-379

本文用后－后牛顿近似讨论Ｋｅｒｒ场中缓慢粒子的运动，我们用Ｂｏｙｅｒ－Ｌｉｎｄｑｕｉｓｔ坐标，导出试验粒子的运动方程，把它与有心力场中粒子作二体运动之球坐标形式下的运动方程对比，得出由于Ｋｅｒｒ场的作用而引起的试验粒子的等效摄动加速度，利用球面三角公式把它换算到行星运动摄动方程的形状，对摄动方程进行积分，我们得出了试验粒子绕中心天体运动一周后粒子轨道根数的变化以及单位时间中轨道根数的平均变化，运用  相似文献   

Tectonic controls on gold deposits and their environmental impact, New Zealand     

D. Craw   《Journal of Geochemical Exploration》2001,73(1):129

New Zealand is an active orogenic belt which varies along its length from continental collision to continent–ocean subduction tectonics. Mesothermal gold deposits, with rare mercury, have formed in collisional settings from late Mesozoic to Pleistocene, with youngest deposits along the axis of the actively rising Southern Alps mountain chain. Epithermal gold and mercury deposits have formed, and are still forming associated with calcalkaline volcanism above the subduction zone, and with basaltic volcanism associated with extensional faulting. The environmental impact of mineral deposits is related to tectonic setting, mineralogy, and climate, all of which are governed by the geometry of the orogen. Mesothermal mineralisation added carbonates to calcite-bearing host rocks in what is now cool semiarid or extreme Alpine settings, and oxidation of sulphides does not result in significant acidification of the environment. Arsenic is the principal metal of environmental significance, and is readily mobilised from these deposits at neutral to alkaline pH. Mercury may be leached from cinnabar and/or gold on geological time scales. In contrast, epithermal mineral deposits have hydrothermal clay alteration, locally further clay-altered by deep temperate to subtropical weathering, and calcite is generally subordinate to sulphides. Acidification accompanies oxidation of these deposits, and copper, cadmium, lead and zinc are readily mobilised into the environment. Mercury can be mobilised by these acid solutions as well, where mercury occurs in minerals other than cinnabar.  相似文献   

Metallogenesis of the Ertix gold belt, Xinjiang and its relationship to Central Asia-type orogenesis   总被引：11，自引：0，他引：11  

CHEN Huayong  CHEN Yanjing  Liu Yulin 《中国科学D辑(英文版)》2001,44(3):245-255

The Ertix gold belt is located on the boundary of the Kalatongke arc and the Kelan back-arc basin of D-C1. Most scholars used to interpret the formation and distribution of the gold deposits in the Ertix tectonic belt in terms of the petrogenic and metallogenic models for active continental margins. However, enormous data of isotopic dating and geologic research show that the mineralization was obviously later than the oceanic subduction, whereas exactly simultaneous with the collisional orogenesis during C₂-P, especially at the transition stage from collisional compression to extension. Based on study of metallogenic time, tectonic background, ore geology, ore fluid nature, ore material source, etc., we reveal that all the gold deposits possess the character of orogenic deposits formed in collisional orogenic system, and that their ore-forming materials mainly have derived from the stratigraphic terranes south to individual deposits. Accordingly, the theoretical tectonic model for collisional metallogenesis and petrogenesis is employed to explain the formation of the Ertix gold belt and to determine the gold exploration directions.  相似文献   

河南康山金矿同位素地球化学及其对成岩成矿及流体作用模式的印证   总被引：18，自引：1，他引：18  

王海华  陈衍景  高秀丽 《矿床地质》2001,20(2):190-198

康山金矿位于华北克拉通南缘熊耳山区，矿化类型介于蚀变破碎带于石英脉型矿床之间，为硅化体型金矿。蚀变矿化过程分为早期石英－黄铁矿阶段、中期多金属硫化物阶段和晚期碳酸盐阶段；温度分别集中在300－380℃、180-240℃和100－140℃；碳氢氧同位素研究揭示成矿流体由变质热液经混合热液，向大气降水热液演化。流体混合导致矿化中期成矿物质快速沉淀，多金属硫化物等多种矿物爆发形成，且结晶程度低（以玉髓和烟灰状黄铁矿为标志），含矿性好，是大规模成矿的关键。碳铅硫同位素研究表明成矿物质主要来自马超营断裂南侧由官道口群、栾川群、太华超群等地层构成的储冲板片，而赋矿围岩熊耳群提供成矿物质的可能性最小，因此认为中生代时沿马超营断裂倾向北的陆内俯冲诱发了流体成矿作用，导致康山金矿等熊耳山区10多处大中型矿床的形成和规律性分带，马超营断裂北侧是寻找金、银等矿床的有利地带。本文印证了同碰撞矿床的存在和成岩成矿及流体作用（CPMF）模式。  相似文献   

The Racialization of Difference: Enlarging the Story Field     

Kay Anderson 《The Professional geographer》2002,54(1):25-30

In this article, I explore ways of loosening the interpretive grid of “race” in critical geographical analysis without obscuring that concept's efficacy as a social force. In recent years, social constructivist perspectives on race have brought much evidence to bear on the logics of race/power formations in America and other British settler societies. The risk of petrifying “race” in the analysis of social life and reinscribing the very power that antiracists wish to undo has, however, prompted efforts to reframe the geographical study of race and racism. This article takes up that challenge by exploring an alternative modality of representational power that can be tracked to figurations of humanity and animality in Western cultural process. Such discursive formations take us some way toward understanding the norms and interiorised anxieties out of which racialized whiteness and its subjugated others were, and continue to be, constructed.  相似文献   

GRAPES模式后处理技术改进应用研究     

佟华  胡江林  张玉涛 《气象科技》2020,48(4):511-517

详细梳理了GRAEPS模式后处理系统的计算方案,进行了GRAPES模式后处理中海平面气压计算方案的改进,温度垂直插值方案的改进以及位势高度的垂直插值外插方案的改进等。假定温度廓线随地形高度变化并满足静力平衡条件,对海平面气压及位势高度外插进行改进,改进后海平面气压和低层等压面的位势高度场在青藏高原和南美洲西部等大地形处改进明显,均方根误差和距平相关系数改进较大并通过显著性检验。对温度垂直插值采用的原始插值层进行改进,使得高层等压面温度场的准确性进一步提高,统计检验评分在各区域都有不同程度的提高,尤其是热带地区和东亚地区高层温度场改善明显。这些都为模式产品用户提供了更可靠的数值模式产品。  相似文献   

Collision Event during 177-135 Ma on the Eastern Marginof the Qinghai-Tibet Plateau: Evidence from ~(40)Ar/ ~(39)Ar Dating for Basaltson the Western Margin of the Yangtze Platform   总被引：2，自引：0，他引：2  

HOU Zengqian  CHEN Wen  LU Jiren Institute of Mineral Resources  Chinese Academy of Geological Sciences Beijing  Institute of Geology  Chinese Academy of Geological Sciences  Beijing College of Earth Sciences  China University of Geosciences  Beijing Hao Ziguo Liu Xinzhu 《《地质学报》英文版》2002,76(2):194-204

Geochronology of continental flood basalts sampled from the Emei large igneous province (LIP) on the western margin of the Yangtze platform was investigated by the laser microprobe 40Ar/39Ar dating technique. These basalts yield a fairly wide range of 40Ar/39Ar ages, varying from 259 to 135 Ma. One basalt sample, at least altered, recorded the oldest 40Ar/39Ar age of about 259 Ma, corresponding to a peak eruption age of the Emei LIP continental flood basalts. Most of the samples yield much younger ages from 135 to 177 Ma, which are consistent with the K-Ar ages for the same samples (122.8-172.1 Ma). The dating data suggest that these Permian basalts had been widely affected by the regional tectonothermal event at 177-135 Ma. The event was probably caused by the convergence and collision among the Laurasia, Yangtze and Qiangtang-Qamdo continental blocks on the eastern margin of the Qinghai-Tibet plateau after the late Triassic. The age of the event reflects the timing of the peak collisional orogeny.  相似文献   

云南巍山-永平矿集区碰撞成矿流体系统成矿物理化学条件分析   总被引：1，自引：1，他引：1  

王勇  莫宣学  董方浏  毕先梅  喻学惠  曾普胜  杨伟光 《矿物岩石》2004,24(3):72-81

云南巍山-永平矿集区有铜金多金属中小型矿床及矿化点140余处，位于兰坪走滑拉分盆地南段，盆地发育和成矿作用与印度-亚洲板块碰撞密切相关。矿集区可分为紫金山背斜与公郎弧两个成矿流体系统。紫金山背斜成矿流体系统成矿流体的pH值为5．3～7．1，Eh值为-0．11V～2．84V，成矿压力为30MPa-130MPa，成矿温度为228℃～255℃，成矿深度在1．05km～6．67km。公郎弧成矿流体系统成矿流体的pH值为6．7～7．9，Eh值为-0．83V～0．11V，成矿压力为100MPa～225MPa，成矿温度为317℃～346℃，成矿深度为3．51km～7．89km。与紫金山背斜成矿流体系统相比，公郎弧成矿流体系统具有较高的成矿压力、成矿温度、成矿深度、pH值和较低的Eh值。但二者均属弱还原的中性-弱碱性成矿环境。  相似文献