Petrogenesis of the Mesozoic intrusive rocks in the Tongling area, Anhui Province, China and their constraint on geodynamic process  

作　　者：王强 许继峰 赵振华 熊小林 包志伟 

机构地区：[1]Guangzhou Institute of Geochemistry,Chinese Academy of Sciences

出　　处：《Science China Earth Sciences》2003年第8期801-815,共15页中国科学（地球科学英文版）

基　　金：the People’s Republic of China(Grant Nos.2002CB412601,G1999043202);the Knowledge Innovation Program of Chinese Academy of Sciences(Grant Nos.KZCX2-102,KZCX2-SW-117 , KZCX3-SW-122);the National Climbing Program of China(Grant No.95-Y-25); theNational Natural Science Foundation of China(Grant Nos.40273019,40172028).

摘　　要：Petrology, element and isotopic geochemistry of the Mesozoic intrusive rocks in the Tongling area were systematically investigated in this study. The intrusive rocks can be divided into two groups, one contains shoshonitic rocks with SiO2 ? 55%, the other consists mainly of high-potassic calc-alkaline rocks with SiO2 > 55%. The shoshonitic rocks (SiO2 ? 55%) were generated by the fractional crystallization of the primary basaltic magma sourced from an enriched mantle, then the evolved basaltic magma likely experienced low-degree contamination with the lower crust materials when they ascended. On the other hand, although the intrusive rocks with SiO2 > 55% show most elemental geochemical characteristics similar to an adakite, such as high Na2O, AI2O3, Sr contents, high Sr/Y and La/Yb ratios, they have isotopic compositions much different from an adakite, such as low σNd(t) (-9.16—16.55) and high (87Sr/86Sr), (0.7068—0.7105), and some of them show relatively high Y and Yb contents than those of an adakite. We propose that the intrusive rocks with SiO2 > 55% were most probably produced by mixing of the mantle-derived basaltic magma and adakite-like magma derived from the melting of basaltic lower crust that was heated by the underplating mantle-derived shoshonitic magmas. The delamination of lower crust likely took place after or during the formation of these adakite-like rocks in the Tongling area.Petrology, element and isotopic geochemistry of the Mesozoic intrusive rocks in the Tongling area were systematically investigated in this study. The intrusive rocks can be divided into two groups, one contains shoshonitic rocks with SiO2≤55%, the other consists mainly of high-potassic calc-alkaline rocks with SiO2>55%. The shoshonitic rocks (SiO2≤55%) were generated by the fractional crystallization of the primary basaltic magma sourced from an enriched mantle, then the evolved basaltic magma likely experienced low-degree contamination with the lower crust materials when they ascended. On the other hand, although the intrusive rocks with SiO2>55% show most elemental geochemical characteristics similar to an adakite, such as high Na2O, Al2O3, Sr contents, high Sr/Y and La/Yb ratios, they have isotopic compositions much different from an adakite, such as low e Nd(t) (-9.16—16.55) and high (87Sr/86Sr)i (0.7068—0.7105), and some of them show relatively high Y and Yb contents than those of an adakite. We propose that the intrusive rocks with SiO2>55% were most probably produced by mixing of the mantle-derived basaltic magma and adakite-like magma derived from the melting of basaltic lower crust that was heated by the underplating mantle-derived shoshonitic magmas. The delamination of lower crust likely took place after or during the formation of these adakite-like rocks in the Tongling area.

关 键 词：MAGMA mixing  adakite  underplating  delamination  shoshonite  Tongling. 

分 类 号：P534.5[天文地球—古生物学与地层学]