苏鲁、秦岭和南岭三叠纪花岗岩对比研究

In the Triassic, the South China Block collided with the North China Block in the north, and with the Indochina Block in the south, this was usually referred as the Indosinian orogeny. During this period, granitoids with variable compositions were generated in South China and its neighboring regions. Because they formed in different tectonic settings, to study the source nature and genetic mechanism of these Triassic granitoids will be of great importance in understanding granitic petrogenesis. Research objects of this project are mainly Triassic granitoids in the Sulu, Qinling and Nanling regions. On the basis of systematic field investigations and petrographic observations, a combined study of whole-rock major and trace elements, Sr-Nd-Pb isotopes, in-situ zircon U-Pb dating and Lu-Hf isotopes as well as whole-rock and mineral O isotopes will be carried out for these granitoids. The results will be used to decipher the category, magma source and the geodynamic mechanism that generated them, discuss the similarity and difference in magma source and petrogenetic mechanism of the granitoids generated in different tectonic backgrounds, advance the understanding of granitic petrogenesis.

三叠纪时期，华南陆块分别与北边的华北陆块和南边的印支陆块发生大陆碰撞，在大地构造上与印支运动相对应。在这个时期，华南及其周边形成了不同成分的花岗岩。由于它们形成的地球动力学背景存在差异，研究这些三叠纪花岗岩的源区性质和形成机制，对于理解花岗岩的成因具有重要意义。本项目拟选择苏鲁、秦岭和南岭地区三叠纪花岗岩作为主要研究对象，在系统的野外观察和岩相学研究基础上，对其进行全岩主微量元素和Sr-Nd-Pb同位素分析、锆石U-Pb微区原位定年和Lu-Hf同位素分析以及全岩和单矿物O同位素分析。结果将用于确定这些花岗岩的类型、源区物质来源及其形成的地球动力学背景，探讨不同构造环境下产出的花岗岩在源区物质和形成机制等方面的异同点，深化对花岗岩岩石学成因的认识。

三叠纪华南陆块与华北陆块和印支陆块发生大陆碰撞，形成了不同成分的花岗岩，研究它们的源区性质和形成条件对于认识大陆碰撞造山带花岗岩的成因具有重要意义。对苏鲁、秦岭和南岭地区三叠纪花岗岩进行了系统的岩石学和地球化学研究，得到了如下结果：(1) 苏鲁三叠纪花岗岩为I型，新元古代残留锆石和18O亏损表明它们是同折返阶段俯冲华南陆壳减压脱水熔融的产物；(2) 秦岭三叠纪花岗岩既有S型也有I型，S型花岗岩为过铝质，具有高度富集的Sr-Nd-Hf同位素组成和高的δ18O值，是变沉积岩脱水或水致部分熔融的产物，I型花岗岩为准铝质，具有弱富集的Sr-Nd-Hf同位素组成和低的δ18O值，是大陆碰撞过程中造山带下地壳再造的产物；(3) 南岭三叠纪花岗岩主要为S型，它们普遍含有丰富的残留锆石，具有富集的Sr-Nd-Hf同位素组成和高的δ18O值，一些主量和微量元素含量与锆饱和温度之间具有相关性，表明部分熔融温度对花岗岩成分起着十分重要的作用。