The Gangdese Batholith, Southern Tibet: Ages, Geochemical Characteristics and Petrogenesis
Date Issued
2007
Date
2007
Author(s)
Wen, Da-Ren
DOI
en-US
Abstract
The Gangdese Batholith, which emplaced extensively in the Lhasa terrane of southern Tibet, is widely regarded as the major constituent of an Andean-type convergent margin resulting from northward subduction of the Neo-Tethyan oceanic lithosphere under Asia. It is the largest Trans-Himalayan plutonic complex. However, the duration, composition and evolution of the Gangdese arc magmatism that spanned the accretion to collision of Asia with India, remain poorly investigated. In fact, knowledge of this continental arc is fundamental for constraining the geodynamics of the northward Neo-Tethyan subduction, particularly its consequential effect on the magmatic evolution. This thesis reports new results of a systematic study, including SHRIMP zircon dating of 25 samples, 83 geochemical and 65 Sr–Nd isotopic analyses. The data are used to delineate the source characteristics and draw implications for the orogenic evolution and crustal growth in southern Tibet. The geochronologic results suggest two distinct stages of plutonism in the Late Cretaceous (ca. 103-80 Ma) and early Paleogene (ca. 65-46 Ma). The results also confirm, if not refine, the notion that a magmatic gap or quiescent period existed between ca. 80 and 68 Ma. With diverse lithologies from gabbros to granites, the plutonic complex shows a large range of SiO2 contents from 43 to 79 wt.%, and typical geochemical characteristics in the medium-K to high-K calc-alkaline series arc magmas, such as enrichment in LILE (e.g., Cs, Rb, U, Th, K, and Ba) and depletion in some HSFE (Nb, Ta, and Ti). The differentiation from mafic to intermediate intrusives is most likely achieved by fractional crystallization, but the felsic granitoids are produced by partial melting of pre-exsiting gabbroic lower crust, or with some crustal contamination. The intrusives are predominantly characterized by depleted mantle sources with
Subjects
岡底斯岩體
西藏
年代學
地球化學
The Gangdese Batholith
Tibet Geochronology Geochemistry
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-D89224006-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):5788d687ed99446daa52515670b6cb48