PDF(543 KB)
Petrogenesis of Early Cretaceous riebeckite granophyres in southern Da Hinggan Mts.
WANG Jianguo, HE Zhonghua*, CHAO Lin, WU Qing and JIN Ling
Global Geology ›› 2013, Vol. 16 ›› Issue (1) : 26-34.
PDF(543 KB)
PDF(543 KB)
Petrogenesis of Early Cretaceous riebeckite granophyres in southern Da Hinggan Mts.
This paper reports lithologic features,K--Ar age and geochemical data of riebeckite granophyres from Aliwula area in the southern Da Hinggan Mts.,aiming to reveal the petrogenesis of riebeckite granophyres. K-- Ar age of riebeckite granophyres is 126 ± 2 Ma,implying that the riebeckite granophyres formed in the Early Cretaceous. The granophyres are rich in riebeckites and with a lot of melt-fluid inclusion in its quartz phenocrysts. The granophyres are characterized by extensive enrichment in SiO2 ,FeO,and ( Na2O + K2O) and depletion in MgO and CaO,strong negative Eu anomalies and strong positive Ce anomalies. Additionally,the riebeckite granophyres not only have high total REE contents and display enrichment of HFSEs ( for example Zr, Hf,Nb,Ta) ,but also are strong in depletion of LILEs ( e. g. Ba,Sr) as well as high Ga /Al ratios. Primitive mantle-normalized REE pattern significantly displays REE M--W tetrad effect. REEs fractionate evidently and highly enrich in LREE,but are uneven distribution in the rocks. Taken together,we conclude that the riebeckite granophyres are similar to typical A-type granite,which could be derived from stretching environments in the Early Cretaceous. The granophyres originated from residual melt which underwent highly differentiation process, and were formed in magmatic-hydrothemal transition stage at last.
petrogenesis / geochemistry / riebeckite granophyres / southern Da Hinggan Mts.
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