Neoarchaean TTG Petrogenesis in Mazhuang,Songshan Area and Its Geological Significance
Received date: 2015-08-24
Revised date: 2016-01-20
Online published: 2016-05-30
Songshan is one of the typical area where the Neoarchean TTG rocks are well exposed.Neoarchean TTG rocks in Mazhuang which are mainly distributed in Songshan with the features of grayish-white colour,medium-grained structure,gneissic and banded structure.Geochemical study shows that Mazhuang TTG rocks are featured with high concentration of Na2O(4.34%~6.49%) and SiO2(>69.24%),poor in iron and magnesium,and with high Na2O/K2O (2.0~3.2) ratio.The average content of Al2O3 is 16.51%(>15%,its range is 14.35%~17.68%),this phenomenon shows the characteristics of TTG gneiss with weak peraluminous.Trace elements analysis indicates that ΣREE is 11.57×10-6~30.94×10-6,depleted in HREE,with strong differentiation in LREE and HREE.Eu positive abnormality is obviously,high contents of Sr and Sr/Y ratio,low contents of Cr,Yb and Y,reflect that it has the similar geochemical characteristics with high silicon adakite in Cenozoic era.The formation environment of Mazhuang TTG rocks is similar with island arc volcano rock according to the environment discrimination diagram of trace element geochemical.It is concluded that Mazhuang TTG rock mass is formed by the partial melting of subducted oceanic crust which is aqueous basaltic under the high pressure.
Key words: Neoarchean; TTG gneisses; geochemical; Songshan area; Neoarchean; TTG gneisses; geochemical; Songshan area
LI Xinglong , SI Rongjun , MAO Guangyu , XIE Xiang . Neoarchaean TTG Petrogenesis in Mazhuang,Songshan Area and Its Geological Significance[J]. Gold Science and Technology, 2016 , 24(2) : 51 -58 . DOI: 10.11872/j.issn.1005-2518.2016.02.051
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