南秦岭旬阳盆地东部晚泥盆世岩浆成因钠长岩及其构造意义

发布时间：2018-06-07 06:27

本文选题：南秦岭 + 旬阳盆地　；参考：《地质学报》2017年02期

【摘要】：南秦岭旬阳盆地的钠长岩此前被认为是热水沉积或热液交代作用的产物。本文对南秦岭旬阳盆地东端黄石板地区侵入于下志留统梅子亚组浅变质岩中的钠长岩体进行了地球化学和锆石U-Pb LA-ICP-MS年代学研究,结果表明钠长岩具有富钠贫钾、铝不饱和、亏损大离子亲石元素K和Rb、高场强元素(Nb、Ta、Th、Hf)显著富集的地球化学特点,主体属于钙碱性系列岩石,反映幔源成因的特征。钠长岩中获得最年轻的锆石U-Pb年龄为364~376Ma,该年龄代表岩体的形成年龄,反映晚泥盆世时南秦岭旬阳盆地处于强烈的伸展构造环境。此项研究结果表明,在旬阳盆地的志留系中,岩浆成因与热水沉积成因的钠长岩可能是共存的。黄石板岩浆成因钠长岩岩体中含有大量前寒武纪和早古生代的捕获锆石,在捕获锆石中测得迄今为止在研究区及其邻区获得的最古老的锆石U-Pb年龄(3291Ma)。这些捕获锆石的测年数据说明,研究区所在的南秦岭地区可能从古太古代开始就与扬子地块具有明显的亲缘性。
[Abstract]:The sodium feldspar in Xunyang Basin of the South Qinling Mountains was previously considered to be the product of hydrothermal deposition or hydrothermal metasomatism. In this paper, geochemistry and zircon U-Pb LA-ICP-MS chronology of the sodium feldspar intruded into the shallow metamorphic rocks of the Lower Silurian Meiziya formation in the eastern end of Xunyang Basin, South Qinling are studied. The results show that the sodium feldspar is rich in sodium and poor in potassium and is not saturated in aluminum. Large ion lithophile elements K and Rb, and high field strength elements NbTa-Th Hf) are characterized by their significant enrichment in geochemistry and belong to the calc-alkaline series rocks, which reflect the characteristics of mantle origin. The youngest zircon U-Pb age obtained from the sodium feldspar is 36440? 376Ma. this age represents the age of the formation of the rock mass, which indicates that the Xunyang basin in the southern Qinling Mountains was in a strong extensional tectonic environment during the late Devonian. The results show that magmatic and hydrothermal sedimentary sodium feldspar may coexist in Silurian system of Xunyang basin. A large amount of Precambrian and early Paleozoic caught zircons were found in the Huangshi plate magmatic sodium feldspar, and the oldest zircon U-Pb dating obtained in the studied area and its adjacent area has been obtained by now. These zircon dating data suggest that the southern Qinling area in which the study area is located may have been closely related to the Yangtze block since PaleoArchean.
【作者单位】：大陆动力学国家重点实验室(西北大学)西北大学地质学系;白河县大湾银矿有限责任公司;
【基金】：陕西省自然科学基金项目(编号2014JM5206)资助成果
【分类号】：P588.3;P534.44

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