西秦岭中生代中基性火山岩的岩石成因及构造指示

The mafic-intermediate volcanic rocks erupted at Tongren-Zeku-Xiahe area in West Qinling orogenic belt are previously considered to be formed during the late Triassic, middle Jurassic and early Cretaceous period. They provide the important carrier for better understanding the tectonic evolution and geodynamics of the Qinling-Dabie intraconitnental orogeny. Much attentions have been paid to the regional investigation, petrography and petrochemistry so far. This project will document detailed field investigation and a set of geochronological, geochemical and Sr-Nd-Pb-Os isotopic composition for the Mesozoic intermediate- mafic volcanic rocks in West Qinling orogenic belt. The aims for this project is to (1) obtain the systematic geochemical data, (2) to determine the precise eruption ages and its temporal-spatial pattern, (3) trace the source nature and its origin, (4) constrain the tectonic setting and geodynamic mechanism of the volcanic sequence, and (5) compare with early Cretaceous igneous rocks of the Dabie Orogenic belt and better understand the different dynamic setting of the intracontinental orogenic process between the Dabie and West Qinling belt from late Triassic to middle Jurassic and then to early Cretaceous period.

已有资料表明，在西秦岭同仁-泽库一带发育被划属上三叠统、中侏罗统和下白垩统的中基性火山岩，这些岩石能为西秦岭中生代陆内造山过程的深部动力学背景提供重要约束，但以往的研究多局限于区域地质调查、岩相学和岩石化学研究。本项目拟以区内中基性火山岩为研究对象，系统开展详细的野外地质调查、岩石(相)学、同位素年代学、元素和Sr-Nd-Pb-Os同位素地球化学等研究，以精确限定其喷发时代和归属层位，获知其地球化学属性及时空分布，示踪其岩石成因并理解其源区属性和构造背景，并与大别造山带中生代火山岩的源区属性和时空分布进行综合对比，探讨秦岭-大别造山带不同区段陆内造山动力学背景的差异性。