海南岛西部戈枕含金剪切带花岗质糜棱岩中锆石SHRIMP U-Pb年代学及其地质意义     

李宝龙  王丹丹  张建  毛景文  马波 《岩石学报》2018,34(9):2687-2702

海南岛西部的中元古代抱板群混合岩主要沿北东向戈枕剪切带展布,近年来的研究逐渐揭示混合岩的原岩为花岗质岩石,是遭受强烈剪切作用改造的糜棱岩。本文选择土外山金矿的花岗质糜棱岩和不磨金矿的糜棱岩化花岗岩进行锆石SHRIMP U-Pb年代学测试,3件样品的锆石SHRIMP U-Pb谐和线年龄值分别为1439.1±8.4Ma(样品13JC-8-1,MSWD=0.85,n=14)、1436.9±8.3Ma(样品13JC-41,MSWD=0.54,n=10)和1448±13Ma(样品BM-3,MSWD=0.56,n=10),代表其原岩的侵位时代。结合研究区已有的研究成果,本文认为海南岛西部花岗质岩类和沿戈枕剪切带出露的糜棱岩原岩结晶年龄为~1450Ma,之后于~1400Ma经历一期构造-热变质事件;海南岛应为华夏地块的一部分,在Rodinia超大陆聚合前,华夏地块(包括海南岛,至少包括海南岛北西部)最有可能位于劳伦大陆南缘的西南延伸部分,华夏地块(包括海南岛)所经历的格林威尔造山事件可能较扬子板块偏早。  相似文献   

Metamorphic convergence of the upper and lower plates of the Vincent thrust, San Gabriel Mountains, southern California, USA     

C. E. JACOBSON 《Journal of Metamorphic Geology》1997,15(1):155-165

The Vincent thrust of the San Gabriel Mountains, southern California, separates eugeoclinal Pelona Schist from overlying Precambrian to Mesozoic igneous and metamorphic rocks of North American continental affinity. The thrust is generally considered to be synmetamorphic because of similarity in structural orientations and mineral assemblages between the Pelona Schist and mylonites at the base of the upper plate. In this study, compositions of calcic amphibole and plagioclase in the upper plate and structurally high Pelona Schist were compared to further test this interpretation. Amphibole in the schist is mostly actinolite to actinolitic hornblende with high Na/Al ratio, indicating relatively high-P/low-T metamorphism. Individual grains are zoned, with concentrations of both Na and Al decreasing from cores to rims. Premylonitic amphibole in the upper plate is hornblende, tschermakite and pargasite with compositions indicative of low- or medium-P metamorphism. During mylonitization, this amphibole was replaced by actinolite to actinolitic hornblende with a similar range of Na and Al as amphibole rims in the Pelona Schist, but with slightly lower Na/Al ratio. This is consistent with the decrease of Na/Al up-section previously noted within the Pelona Schist of this area, and is considered to be the result of an inverted thermal gradient during thrusting. Convergence of composition between schist and upper plate also occurs for K and Ti contents of amphibole and An content of plagioclase. These features provide strong evidence that mylonitization of the upper plate is closely related in space and time to metamorphism of the Pelona Schist and therefore that the Vincent thrust is a remnant of the primary fault along which the Pelona Schist and correlative units were subducted beneath North America. Nonetheless, very fine-scale differences in amphibole composition between the schist and upper plate may indicate that metamorphic re-equilibration could not quite keep pace with movement on the fault.  相似文献   

小秦岭构造岩及其与金矿化关系     

盛吉虎  徐莉  尉向东  刘长命 《河南国土资源》1996,(4)

根据小秦岭地区含金石英脉与糜棱岩的空间分布关系可将石英脉分为交代脉、拉张脉、剪切脉、角砾岩脉和裂隙脉等五种类型，它们是不同构造阶段的产物。脉体宏观构造、微观构造、包体测压数据及石英Ｘ射线研究表明，脉体的充填、定位与容矿空间扩张同时形成，容矿空间的形成是含金热液液压致裂作用的直接结果。本文详细研究了构造岩的岩石学、岩相学特征，并对构造岩的形成条件及与金矿化关系等做了初步探讨  相似文献   

Metamorphism and tectonic evolution of the Shangdan fault zone, Shaanxi, China     

HU NENGGAO  YANG JIAXI  AN SANYUAN  HU JIANMIN 《Journal of Metamorphic Geology》1993,11(4):537-548

Abstract The Shangdan fault in the Qinling Orogenic Belt of China is an important boundary between the Caledonian North Qinling Fold Belt and the Hercynian South Qinling Fold Belt. In the Danfeng area, the fault zone strikes WNW–ESE and comprises four strongly deformed zones and three weakly deformed domains parallel to each other. The fault zone has a complex history of multiple deformation and each domain has a different tectonic style that was formed at different stages of the deformation.
The rocks exposed in the weakly deformed domains belong to the Qinling, Danfeng and Liuling Groups. In this paper, the mineral chemistry and mineral assemblages are used to infer the metamorphic conditions and the P–T paths of these units. The metamorphic units in and near the fault zone have different metamorphic conditions and histories that are correlated with the tectonic evolution of the fault zone. Caledonian–Hercynian uplift and southward thrusting of the Proterozoic Qinling Group, over the Danfeng and the Liuling Groups, produced the main metamorphic and tectonic features of the fault zone. Folding of both the Liuling Group and the thrust faults during the Hercynian–Indosinian was accompanied by northward thrusting.  相似文献   

Sulphur Isotope Compositions of Shibaqinghao Gold Deposit in Central Inner Mongolia, China   总被引：1，自引：0，他引：1  

Zhang Hongying  Liu Xiang 《东北亚地学研究》2001,(1)

1 IntroductionSince the 1980, s, as a response to the upsurgein gold exploration in China, many go1d dep0sitshave been found in central Inner Mongolia. On< ofthem is Shibaqinghao gold deposit that is situate6 inBaliang Township, Guyang County, in the West…  相似文献   

焦家断裂带对成矿的制约          下载免费PDF全文

梁学明 《山东国土资源》2020,36(7):26-31

焦家金矿田内矿体稳定、规模巨大,勘查深度已超过2000m,探获金金属量已超千吨,是我国重要的金矿产地。矿体严格受NNE向焦家断裂带控制,产状与构造面产状基本一致。从断层岩岩性和构造面表面形态入手,构建了三维构造模型,研究了断层面形态和断层岩岩性差异对成矿的约束作用。系统收集焦家金矿田内500个钻孔地质资料,通过二维三维相结合方式,发现断层岩岩性从浅部向深部发生明显变化,由断层泥渐变为糜棱岩,而上盘矿体数量和蚀变分带也随着断层岩的改变发生明显变化。对构造面进行表面坡度分析,发现矿体主要赋存在表面坡度较小部位,且沿倾向上表面坡度由陡急速变缓部位易于形成厚大矿体。  相似文献   

黑龙江嫩江地区三合屯金矿区糜棱岩锆石LA- ICP- MS U- Pb 年龄与成矿的关系   总被引：1，自引：0，他引：1  

刘宝山  寇林林  张春鹏  李成禄  罗健  韩仁萍  李博文 《地质学报》2022,96(3):954-970

三合屯金矿位于黑龙江省嫩江县境内，普遍认为其是韧性剪切带型金矿。本次对采自韧性剪切带中花岗质糜棱岩样品进行了锆石LA- ICP- MS U- Pb 定年，以约束剪切带的活动时代，并为金矿化事件提供依据，获得糜棱岩中热液锆石增生边加权平均年龄为162 Ma。因此，矿区在燕山期晚侏罗世经历剪切变形，并且这期变形事件与前人研究的科洛镇- 新开岭杂岩变形时间是吻合的，也与八大罕- 嫩江断裂左行走滑运动时间基本一致。结合前人对邻区金矿床矿化时间的研究，三合屯金矿的成矿时间为燕山期早白垩世，晚于韧性剪切带的形成时间晚侏罗世。样品中继承性锆石（花岗质糜棱岩中核部锆石）最晚年龄显示晚三叠世岩浆侵入活动时间，因此认为，三合屯矿区原岩侵位时间为晚三叠世，变形时间为晚侏罗世,为三合屯金矿床的形成提供了基础条件。另外，本次测试锆石的Lu- Hf 同位素结果表明：花岗质糜棱岩成岩物质主要来源于亏损地幔的新生地壳。  相似文献   

高精度磁法在大板金矿勘查中的应用     

张立军  高飞 《国土资源》2000,(4)

大板金矿位于华北地台北缘 ,山海关—北镇隆起北段,空间上分布于排山楼金矿北东端。应用高精度磁测结果对大板金矿区的基底构造、断裂构造格架进行分析,追索和圈定含金糜棱岩带,结果表明,从构造格架上看大板金矿与排山楼金矿既有可比性,又具其独特性;高磁推断的近东西向糜棱岩带为本区金成矿有利地段。大板金矿高精度磁测找矿实践证明,在提高信息密度的前提下,利用高磁对金矿直接进行圈定是可行的。  相似文献   

青川地区青川断裂带的显微构造及其变形条件研究   总被引：8，自引：0，他引：8  

王全伟  梁斌  谢启兴  何文劲 《矿物岩石》2000,20(1):87-90

青川断裂带是一条位于龙门山构造带与摩天冷构造带之间的重要构造边界。通过对其宏观变形及其显微构造的详细研究,本文探讨了断裂带形成的温压条件、古应力值、有限应变量等特征。  相似文献   

辽宁北票宝国老金矿地质特征和成矿作用     

骆辉  郭进京  初占武 《华北地质》2000,(3)

宝国老金矿产于辽西太古宙高变质绿岩带 ,受近东西向韧性剪切带控制 ,多金属硫化物石英脉型 ,银金矿为主要含金矿物 ,矿石品位高。成矿经历火山 -沉积作用、区域变质作用和动力变质三个阶段 ,成矿时间中含古元古代的信息 ,成矿流体可能为变质热液混合岩浆热液 ,成矿温度在 160～ 310℃之间。  相似文献