东秦岭地区石宝沟和火神庙岩体的时代及岩浆物质来源

Ages and Magma Sources of Shibaogou and Huoshenmiao Complexes in East Qinling

东秦岭地区石宝沟和火神庙岩体的时代及岩浆物质来源杨荣勇徐兆文任启江（中山大学地球科学系，广州５１０２７５）（南京大学地球科学系，南京２１００９３）关键词东秦岭花岗岩岩体的时代岩浆物质来源东秦岭地区沿华北大陆板块边缘发育了大量的中生代花岗岩体，许多岩体...

Shibaogou and Huoshenmiao complexes belong to the Mesozoic granite belt in East Qinling and situated at the southern margin of North China continental plate. Shibaogou complex consists of monzonite granite,potassium feldspar granite and granite porphyry,and intrudes in the strata of Middle Proterozoic (Pt 2) Luanchuan group.Huoshenmiao complex,intermediate and intermediate basic rock body,is composed of augite monzonite,quartz monzonite,granodiorite and granite porphyry vein and also intrudes in Luanchuan group. Rb Sr ages and initial ratios of 87 Sr/ 86 Sr of Shibaogou and Huoshenmiao complexes are 142.7±6.2 Ma,0.70828±0.00004 and 162.8±6.2 Ma,0.70813±0.00029,respectively.The former is very similar with the mineralization period of the molybdenum (130￣145 Ma) and the latter is earlier than the mineralization,but the Sr initial ratios of them are similar,showing that they are derived from crust. The calculations of Rb Sr,Sm Nd isotopes show that ε Sr ( T) and ε Nd ( T ) of Shibaogou and Huoshenmiao complexes are 42.46￣67.60,-11.6￣18.0,56.02￣61.31,-14.7,respectively. The ε Nd ( T ) of Huoshenmiao is different from that of Precambrian diabase vein ( -3.33 ),demonstrating that it is derived from crust. Diagrams of δ 18 O vs. ε Sr and ε Sr vs ε Nd also show that both complexes are within low crust and also for Precambrian low crust with the low degree of differentiation and low grade geochemical province. Based on the disscussion of isotope,collision orogene belt,tectonic evolution and distribution of ore deposits,both complexes and metallogenetic material of molybdenum ore belt of East Qinling are derived from middle low crust.