| Autor: |
Chen, Jiangfeng, Zhou, Taixi, Foland, K. |
| Zdroj: |
Chinese Journal of Geochemistry; 1985, Vol. 4 Issue 3, p220-235, 16p |
| Abstrakt: |
The geochronology and genesis of the Qingyang batholith were investigated usingAr/Ar and Rb-Sr isotopic techniques. The Qingyang is a composite batholith consisting of two major rock types granodiorite and granite in the Yangtze fold belt.Ar/Ar spectra for biotite and amphibole separates are internally concordant. The concordance of the minerals and spectra indicate no thermal disturbance of the ages, and rapid cooling of the rocks. The granodiorite has an age of 137.6±1.4 m.y. and the granite 122.7±1.2 m.y. Whole-rock Rb-Sr analysis yields ages consistent with theAr/Ar dates. Thus, the Qingyang batholith was formed in two major stages in the late Jurassic and early Cretaceous. The batholith is not Triassic as was previously proposed. SpecialAr/Ar analysis of two granodiorite samples has precisely documented a 1.0 m.y. apparent age difference between these samples. Several factors could account for this difference, but different emplacement times seem most convincible. The granodiorite and granite show little variation in initialSr/Sr ratio (about 0.7085). The high initial Sr ratios suggest that the magmas were formed by anatexis of older crustal materials. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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