江西庐山─星子地区早前寒武纪片麻岩基底的初步研究

庐山-星子地区原称的混合花岗岩和混合岩实为以奥长花岗质片麻岩为主体的灰色片麻岩（TTG岩套）和花岗质片麻岩．后者是前者经钾质成分改造交代的结果。其常量元素和微量元素特征与早前寒武纪低铝型灰色片麻岩一致，构成扬子克拉通的晚太古代基底。其上的星子群属表壳岩，与赣北片麻岩一起构成花岗-绿岩地体，因燕山运动和新构造而出露地表。

A PRELIMINARY STUDY ON EARLY PRECAMBRIAN GNEISSOSE BASEMENT IN LUSHAN-XINGZI REGION, JIANGXI

The formerly called migmatitic granitoids and migmatite in the Lushan-Xingzi region,north Jiangxi. are renamed the Ganbei (North Jiangxi) Gneiss, which is composed of gray gneiss (TTG suite) with trondhjemitic one as their principal part and granitic gneiss. The latter may result from potassium metasomatism and reformation of the trondhjemitic gneiss.The relationships between Ca and K/Na ratio show a cafe alkaline trend in the granitic gneiss and a tonalite-trondhjemite one in gray gneiss respectively. The increasing Al2O3 with in creasing alkaline metals comprehends that the mineral controlling the changes of Al2O3,Na2O, K2O and CaO contents should be feldspar. The gneiss is classified the low-Al2O3 type, with relatively lower contents of Al2O3. MgO. CaO, P2O5, Sr and higher contents of Ba and Rb. Different from the high Al2O3 type gneiss, the Ganbei Gneiss is characterized by BEE pattern of few Eu negative anomaly and slightly increasing Y with Increasing SiO2.The Ganbei Gneiss. whose petrochemical features are relevant to the Yakou Gneiss in the region bordering Sichuan and Yunnan. the Kangding Gneiss in west Sichuan and the Kongling Gneiss in west Hubei. is the oldest basement rocks of the Yangtze Craton.The Xingzi group. with an amphiboliate facies metamorphism and from which the Early Precambrian ages are dated. is supercrust rocks deposited on the basement. The relics of Early Precambrian granite-greenstone terranes are discovered in northeast Jiangxi. Their uplifting and outcropping may result from the Yanshanian orogenesis and neotectonic movement.