豫西小秦岭地区太华杂岩斜长角闪岩Sm-Nd等时线年龄及其地质意义

Sm-Nd ISOCHRON FOR THE AMPHIBOLITES WITHIN TAIHUA COMPLEX FROM XIAO QINLING AREA, WESTERN HENAN AND ITS GEOLOGICAL IMPLICATIONS

小秦岭地区太华杂岩以多种产状出露于表壳岩系和花岗质片麻岩中，经历了角闪岩相变质作用。其空间上的密切共生和地球化学演化特征说明它们是弧后盆地扩张不同阶段的产物。不同产状的斜长角闪岩几乎具有一致的Sm－Nd等时线年龄（2542±57）Ma，表明斜长角闪岩形成于新太古代，不支持太华杂岩时代二分为太古古和古元古代的观点。（2542±57）Ma代表了华北地由南缘新太古代张裂事件的年代。

Taihua complex from the Xiaoqinling area western Henan, consists of supracrustal sequence and granitic gneisses. The amphibolites occur as enclaves or bands within the supracrustal sequence (A-type amphibolites) and granihc gneisses (B-type amphibolites)of the Taihua complex. Their mineral assemblages suggest that they may have been subject to amphibolite factes metamorphism. A whole rock Sin-Nd isochron age of (2542±57) Ma was obtained, with, suggeshng that the formation of the Taihua complex must be (2542±57)Ma (2a). The whole rock Sm-Nd isochron age of three analyzed specimens of A-type amphibolites was the same as that of five of B-type arnphibolites. The Sin-Nd isotopic composition, combined with available petrological, geological and geochemical, indicates that amphibolites from the south margin of Sino-Korean craton are Late Archean in emplacement age. The whole rock Sin-Nd isochron age of (2542±57)Ma was the age of extention event in the south margin of Sincr-Korean craton. Their positive Nd(t) value suggests an extended event of depletion of subeonhnental mantle sources in the south margin of Sino-Korean craton in Late Arehean of (2542±57)Ma.