The Dynamic Process Mesozoic-cenozoic Igneous in Tibetan Plateau, China

Abstract

Tibetan Plateau, China has intensive magmatic activity with widely magmatic rocks distribution, in the exposed area of about 300,000 km2. Isotopic dating method has been the most important means in the determination of rock formation age, the inversion of history and mechanism of Tibetan Plateau and the establishment of patterns of magma there. Whereas the most outstanding natural laboratory on the Earth for studying continental collision orogensis (Allegre et al.,1984; Molnar et al.,1993), investigations on Tibetan plateau have been conducting. The Chinese and foreign geologists had long-term research on geochronology of igneous rocks in Tibet since 1964 when the first K-Ar isotopic age data on Tibet has been published by Prof. Li, who worked in a scientific expedition of Tibet Academy Sciences. Study areas have spanned the various district of the plateau and the means of geochronology are constantly updated with the progress of isotopic dating techniques. However, owing to over 4500 m altitude and poor traffic system, a few areas have are studed, remaining 1,520,000 km2 to do geological servey before 1999. After 2005, China Geological Survey has conducted the one hundred and one 1/250,000 scale region mapping on the western and the northern Tibet. Consequently, numerous radiometric age data of its magmatisms have been accumulated, including the most acive long half-life period radioisotope dating method, such as the K-Ar, fast neutron activation of 40Ar-39Ar, Rb-Sr, zircon and monazite U-Pb and SHRIMP. It is both important scientific and practical significance to make full use of these valuable data collested from nature condition scurviness areas, clean up and dig out some useful information among them. It has been shown that the climax and valley of magmatic activity just corresponds to that of tectonic activity and vice versa. Furthermore, the tectonic magmatic process is often accompanied by relevant metamorphism, mineralization and uplift cooling of geological body or belt. Therefore, the statistical isotopic age data of igneous rocks is the concentrated expression of the geological process, which reflects the regional characteristics of major geological events recorde better than the application of a single age of geological body in some way (Bi et al.,, 1999). The increased isotope age data about its magmatism enable us to identifie the formation and distribution of the main magmatism in Tibetan Plateau and fine a new approach to trace the geology process of Tibetan Plateau. To this end, the chapter collects the Mesozoic and Cenozoic isotopic age of all kinds of igneous rocks in the Tibetan Plateau from the literature and the latest region geological