STAGE AND PHASE DIVISION AND BASIC FEATURES OF PRECAMBRIAN INTRUSIVE ROCKS IN THE WESTERN SHANDONG AREA

The Precambrian intrusive rocks in western Shandong area mainly fall into two parts:the Taishanian（Archean）and the Aolaishanian（early Proterozoic） intrusive rocks. The intrusive rocks of the first phase（Xinfushanian phase）of the Taishanian stage are represented by quartz diorite,tonalite, trondjemite and granodiorite, generally referred to as the TTG series and genetically assigned to syn- tectonic granite. Affected by late-stage metamorphism, they generally exhibit a gneissic structure. The intrusive rocks of the second phase（Zhongtianmenian phase）of the Taishanian stage are composed of gabbro, diorite and quartz diorite,belenging to the mantle differentiation type. The above-mentloned Taishan ian intrusive rocks are mostly widespread in the area,covering an area of 2000 km~2. The isotopic ages measured range from 2700 to 2500 Ma. Early Proterozoic Aolaishanian intrusive rocks consist mainly of biotite adamellite and Light-coloured adamellite with local K-feldspar granite. The rocks of this stage belong to crustal anatectic granite, covering an area of only 150km2, and their isotopic ages range from 2490 to 2200Ma.