桐柏北部燕山期花岗岩对地壳深部物质组成的地球化学示踪

Geochemical study of deep crustal composition from Yansanian granitesof northern Tongbai area

通过对桐柏北部（相当于北秦岭构造块体）燕山期老湾岩体和梁湾岩体花岗岩主元素、微量元素和Ｐｂ－Ｓｒ－Ｎｄ同位素地球化学的研究，分析了岩浆的物质来源，并用来指示地壳深部组成。结果表明，老湾和梁湾花岗岩均属壳源型花岗岩，岩浆物质并不来自于北秦岭基底和华北克拉通南缘基底，而是来自南秦岭构造块体中桐柏杂岩的部分熔融。这表明在桐柏北部的深部地壳中，含有南秦岭的地壳物质，从而进一步证明了早期南秦岭陆壳向北俯冲并叠置于北秦岭块体之下的认识。

Major element, trace element and Pb-Sr-Nd isotope composition of Yansanian Laowan andLiangwan granites, which distributed in northern Tongbai area, North Qinling, are analyzed.The results show that the geochemical characteristics of Laowan granite are much similar tothose of Liangwan granite, and both of them are crust-derived granites. Their source study isused to probe the deep crust composition and tectonic nature. The source of the Laowan andLiangwan granitic magmas was not related to the basements of North Qinling and the southernmargin of North China Craton. Both the magmas were derived from the partial melting ofTongbai complex of South Qinling. Therefore, the deep crust in northern Tonghai contains thecrust material of South Qinling, which further confirms the underthrusting of South Qinlingcontinental crust beneath North Qinling block in early period.