苏北东海石榴石二辉橄榄岩初步研究

ON THE GARNET LHERZOLITE IN THE DONGHAI,NORTHERN JIANGSU

本文研究了东海地区石榴石二辉橄榄岩岩体的矿物、化学及微量元素特征。认为该区石榴石二辉橄榄岩来源于上地幔,是一种受过交代的弱亏损型地幔岩石。

The garnet lherzolite in the Donghai county,Northern Jiangsu Province mainly distributes in the boundary of North China Plateform and Yangtze Plateform loca- ted in the east side of Tan-Lu fault.The rock body intruded into the metamo- rphic strata of Donghai Group of Lower Proterozoic Erathem contacted with the host rock by fault.According to the exposes and drilling exploration,the rock body has no root and composed of many small rock bodies.The rock contains much Mg,less Si and depletes melting composition of Al,Ca,Ti,The value of 100 Mg/(Mg+Fe)is same as the weakly depleted same rock.The trace element contents,except Co which is quite low in content,are close to the (?) mantle and the rock in Mingxi of Fujian and Chongli of Hebei,which have sim- ilar distribution curve and slope.The rare earth element contents is 4.3 times of chondrite and characteristic of concentration of LREE and depletion of HREE. The slope of distribution curve is larger than that of South Africe and Mingxi. The diagenetic temperature is 983-1031°(C),and the presure is 34-44(kb).The de- pth is more than 120 km.Therefore,the research indicates that the mantle be- longs to continentle mantle and the rock belongs to replaced weakly depleted ma- ntle rock.