山东沂水雪山岩体和林家官庄岩体的同位素年代学

研究了山东沂水地区的两个太古宙花岗岩类岩体,雪山岩体是花岗闪长岩-花岗岩体。林家官庄岩体属奥长花岗岩-英云闪长岩系列。稀土元素均具轻稀土富集型的分配型式。分别具轻微到明显,和轻微负Eu异常。用质谱计双带源逐层蒸发法进行了单颗粒锆石的详细定年。确定了雪山岩体侵入时代为2530Ma(2531,2532).林家官庄岩体的侵入时代为2507Ma,两个岩体都形成于新太古代。雪山岩体中还发现了年龄为2910Ma的继承性锆石。推测这种错石来自于表壳岩包体。

STUDY ON CHRONOLOGY FOR XUESHAN AND LINJIAGUANZHUANG BODIES IN YISHUI, SHANDONG PROVINCE

This paper study on petrology, geochemistry and single-grain zircon U-Pb isotopic age for Xueshan and Linjiaguanzhuang intensive bodies in Yishui, Shandong province. The Xueshan body is varying in minerals and chemical composition, and its rock type belonges to hypersthene bearing granodiorite to chanockite. The chondite-normalized REE patterns are enriched in LREE, with negative Eu anomaly, LREE/HREE=15.15-33.57,(La/Yb)_N=31.07-188.68. The rock type of Linjiaguanzhuang body belongs to trondhjemite-tonalite senes. The chondite-normalized REE pattern of YS9531 is silimar to sample YS9573 of Xueshan body, slightly enriched in LREE , with very small negative anomaly(Eu / Eu^*=0.92). LREE/HREE=9.75,(La/Yb)_N=16.65. The isotopic age detenninated by whole grain evaporation on single zircon using a method double-filement themal ion mass spectrometer. The single-grain zircon ²⁰⁷Pb/²⁰⁶Pb age of Xueshan body is of 2531-2532Ma and the Linjiaguanzhuang body is of 2507Ma. If shows that the former is older than latter and all belong to Neoarchean. It is worth to notice that the isotopic age of 2910Ma, we consider that this zircon may be from the older supercrustal relict, but this zircon is very difficult to distinguish from orthers.