鲁西地区泰山群地层划分及其原岩特征

THE STRATIGRAPHIC DIVISION OF THE TAISHAN GROUP IN WESTERN SHANDONG AND THE CHARACTERISTICS OF ITS PROTOLITHS

据近几年来最新的研究资料,重新厘定了鲁西地区泰山群的层序,自下而上分为雁翎关组、山草峪组,柳杭组。其中雁翎关组以斜长角闪岩为主,原岩为基性—超基性熔岩,测得 Sm-Nd 等时线年龄为2684.9士278.1Ma;山草峪组以黑云更长变粒岩为主,其原岩为含少量中酸性火山岩成分的泥、砂质沉积岩,测得锆石 U-Pb一致曲线上交点年龄为2498Ma;柳杭组下亚组为斜长角闪岩,上亚组为变质砾岩,其胶结物中锆石 U-Pb一致曲线上交点年龄为2599Ma。此外,侵入泰山群的花岗闪长岩,其全岩 Rb-Sr 等时线年龄为2586Ma,英云闪长岩锆石U-Pb 年龄为2628Ma.从上述情况推断,泰山群的形成时代大约在2700Ma 以前。

According to the latest data of research,the author has re-established the stratigraphical sequence of the Taishan Group in the western Shandong area. From below upwards the group is divided into the Yanlingguan,Shaneaoyu and Liuhang Formations.The Yanlingguan Formation consists mainly of plagioclase amphibolite,whose protolith is basic-ultrabasic lavas,with Sm-Nd isochron age of 2684.9+278.1 Ma.The Shancaoyu Formation is dominated by biotite- oligoclase granulitite,whose protolith is argillo-arenaceous sedimentary rocks containing small amounts of intermediate-acid volcanic rocks,with a zircon U-Pb concordia upper intercept age of 2498 Ma.The Lower Subformatiou of the Liuhang Formation is made up of plagioclase amphibolite (intermediate- basic volcanic rocks) and its Upper Subformation consists of metaconglomerate (intermediate-acid volcanic rocks).The zircon in its cements gave a U-Pb concordia upper intercept age of 2599 Ma.Besides,the granodiorite intruding the Taishan Group has a whole-rock Rb-Sr isochron age of 2586 Ma and tonalite has a zircon U-Pb age of 2628 Ma.Through synthesizing the above- mentioned data,it may be inferred that the Taishan Group was formed roughly at 2700 Ma ago.