南秦岭铁瓦殿岩体的成岩时代及地质意义

Emplacing Age of the Tiewadian Pluton in the South Qinling Tectonic Belt and Its Geological Implications

铁瓦殿岩体位于陕西省南部汉阴县、石泉县和紫阳县交界部位,大地构造位置属于南秦岭构造带南部,主要由闪长岩、石英闪长岩、石英二长闪长岩、石英二长岩和二长花岗岩组成。LA-ICP-MS锆石U-Pb同位素定年结果表明铁瓦殿岩体存在3阶段的岩浆侵位:早期阶段的石英二长岩形成于742±5Ma,中期阶段的石英闪长岩、石英二长闪长岩及二长花岗岩形成于～722Ma;晚期阶段的石英闪长岩形成于704±4Ma。通过与扬子北缘汉南杂岩中的中酸性火山岩及侵入岩的岩石组合和形成时代对比,发现铁瓦殿深成侵入岩与扬子克拉通北缘汉南杂岩中中酸性侵入岩具有相似的岩石组合和形成时代,表明它们经历了相似的构造-岩浆演化。铁瓦殿岩体是南秦岭地区新元古代俯冲作用相关的重要地质记录。

Tiewadian pluton is located in the contact borders between Hanyin, Shiquan and Ziyang countries in the South Qinling Tectonic Belt （SQTB）, Shaanxi Province, and consists chiefly of diorite, quartz diorite, quartz monzodiorite, quartz monzonite and monzogranite. LA-ICP-MS zircon U-Pb isotopic dating reveals three magmatic emplacement stages： early stage quartz monzonite emplaced at 742± 5 Ma, middle stage quartz diorite, quartz monzodiorite and monzogranite at ～722 Ma, late stage quartz diorite at 704±4 Ma. The Tiewadian pluton shows comparable lithological assemblage, emplacing ages and geochemical features with felsie rocks of Hannan complex in the north margin of Yangtze Craton, indicating that they experienced similar magmatic and tectonic evolution in the similar geodynamic background, and that the Tiewadian Dluton is an important geological record relating to the Neoproterozoic subduction in the SQTB.