中国38亿年古陆壳锆石的成因矿物学研究

A STUDY ON THE MINEROGENY OF ZIRCONS FROM THE REMMANTS OF 3 800 Ma-OLD CRUST IN CHINA

本文从锆石晶体形态、环带及晶体从核部至边缘的成分演化等特点，论述了中国最老（38亿年）两个锆石样品的岩浆成因属性，并发现它们的母岩在成因上存在差异；鞍山花岗靡棱岩是地幔或地幔来源为主的花岗质岩石，而冀东铭云母夕线石英岩中铁石的母岩则属壳源或壳幔混合型花岩质岩石，这些差别表明38亿年华北古陆壳岩石类型具有多样性。

3 800 Ma-old zircons are obtained from Jidong sillimanite quartzite in the Qianxi complexof eastern hebei and mylonite granite in the Anshan complex of Liaoning Province respectively.Both of them process enhedral growth zoning and such chemical composition variation is regardedas that of zircons in granites, i. e., the contents of HfO2, and ((UO2+ThO2) increase and theZrO2/HfO2 ratio decreases gradually from the core to the rim of zircon crystal , showing that thetwo 3 800 Ma-old zircons are the product of crystallization of granitic magma. According to theirchemical composition, crystal form and typology, the host rock of 3 800 Ma-old zircons in Anshanmylonite granite is trondhjemite, which has a high crystallization temperature and is mainly ofmantle origin. On the other hand, the host rock of 3 800 Ma-old zircons in Jidong sillimanitequatzite is granitic rock of crustal or crustal+mantle origin.The difference in host rock origin between the 3 800 Ma-old zircons of Jidong quartzite andAnshan mylonite granite indicates the diversity of petrological types in the 3 800 Ma-old crust ofChina.