INDOSINIAN SHAHEWAN-RAPAKIVI GRANITE IN QINLING AND ITS DYNAMIC SIGNIFICANCE

Rapakivi granite is a postorogenic granite mainly occurring within Pre cambrian stable blocks in the world. Shahewan rapakivi granite in Qinl ing, however, is a seldom seen young rock body occurring at the end of Indo-Chinese epoch (195-213 Ma) and intruding in an orogenic belt. Th is rock body consists of amphibole-quartz monzonite and amphibole-biot ite adamellite and shows a series of distinctive geological and geoche mical characteristics. It intruded in Shangdan faulted zone-the main s uture belt between the North China and Yangtze plates as a result of t he delamination of the lithospheric mantle occurring after collision. Presence of Shahewan rapakivi granite marked the end of orogenic stage of subduction-collision from Caledonian-Hercynian to Indo-Chinese epo ch and the transition to intracontinental orogeny in the late orogenic stage.