BASIC FEATUES OF THREE YANSHANIAN COMPOSITE ROCK MASSES IN JIANGSU PROVINCE AND THEIR ORE BEARING CHARACTERS

The Liguo, Ningzhen and Suzhou composite rock masses are respectively composed of rock masses of three phases of Yanshanian intrusion. They account for more than 50% of intrusive rocks of the entire province and the rocks thereof form three rock associations, i. e. the association of intermediate rocks-intermediate-acid rocks-acid rocks, the association of basic and intermediate rocks-intermediate-acid rocks-acid rocks and the association of acid rocks. With respect to the petrological and petrochemical features, they all exhibit the features of late acid magmatic differentiation very clearly. With respect of origin, it has been considered according to the strontium isotope data that the Liguo and Ningzhen composite rock masses originated from the intermediate-acid magma formed by mixing of basaltic magmas and sialic substances. According to the K-Na-Ca atomic weight diagram combined with the measurements of the temperatures of the melt inclusions（that range from 920°—940℃）, the Suzhou composite rock mass has been determined to be derived from granitic magmas of magmatic origin. So both belong to the I-type magma. Through plotting the average values of normative minerals on the diagram, it has been estimated that the pressure in the Suzhou composite rock mass was close to 1200 kb and a magma depth of 4 km has been thus found prelimiminarily. It has been inferred that the magma depths of the Liguo and Ningzhen composite rock masses were slightly greater than 4 km. The polyphase intrusion of the three composite rock masses is related to the endogenic metallic ore deposits in Jiangsu province, and they exhibit distinct ore-bearing characters.