辽北—吉南早前寒武纪大陆壳的地质特征和演化

GEOLOGICAL FEATURE AND EVOLUTION OF THE EARLY PRECAMBRIAN CONTINENTAL CRUST IN NORTHERN LIAONING PROVINCE AND SOUTHERN JILIN PROVINCE

辽北—吉南地区是中国典型的早前寒武纪大陆壳出露区之一，由花岗岩—绿岩带和高级变质区构成，赋存有丰富的Ａｕ、Ｃｕ、Ｚｎ、Ｆｅ矿产资源。单颗粒锆石ＵＰｂ、４０Ａｒ／３９Ａｒ、ＳｍＮｄ和ＲｂＳｒ等时线年龄表明绿岩带形成时代为２７００～２８００Ｍａ，三类同构造期花岗岩的形成时代分别为（２５５５±３５）Ｍａ、（２５１５±４）Ｍａ和２５００～２４００Ｍａ。高级区表壳岩和花岗岩的形成时代分别为３０１８Ｍａ和２９５０Ｍａ。绿岩带同构造期和后构造期金矿床的成矿时代分别为２４０９～２４７５Ｍａ和１８０～９０Ｍａ。本区早前寒武纪地壳可划分为两种类型，一类是地幔部分熔融直接添加而形成的初始地壳，另一类是先存地壳深熔或部分熔融的活化再造地壳。其造壳时代可划分为３５００～３７００Ｍａ、３０００Ｍａ、２７００～２９００Ｍａ和２５００～２６００Ｍａ。

The region of northern Liaoning Province and southern Jilin Province is one of the regions where typical Early Precambrian continental crust is exposed.It is composed of the granite greenstone belt and high grade metamorphic terrain,which contain abundant mineral resources such as gold,copper,zinc and iron.Single zircon U Pb, 40 Ar / 39 Ar,Sm Nd and Rb Sr isochron ages suggest that the greenstone belt was formed 2700—2800 Ma ago.The ages of three types of syntectonic granites associated with the greenstone belt are (2555±35)Ma,(2515±4)Ma and 2505—2400Ma,respectively.The formation ages of supracrustal rocks and granites in the high grade terrain are 3018 Ma and 2950 Ma.Metallogenic epochs of syntectonic and post tectonic gold deposits in the greenstone belt are 2409—2475 Ma and 180—190 Ma.The Early Precambrian crust can be divided into two types in the study area:one type is primaty crust which was formed by direct mantle partial melting,while the other is reworked crust which was formed by anatexis or partial melting of preexisting crust.Four periods of Early Precambrian continental crust formation may be distinguished,they are 3500—3700Ma,3000 Ma,2700—2900 Ma,respectively.