【摘 要】
：
The boninite series volcanic rocks, mainly composed of basaltic andesite, andesitic lava breccia and andesite porphyrite, were recognized for the first time in
【机 构】
：
Laboratory of Continental Dynamics of Ministry of Land and Resources of China
论文部分内容阅读
The boninite series volcanic rocks, mainly composed of basaltic andesite, andesitic lava breccia and andesite porphyrite, were recognized for the first time in the Bangong Lake ophiolite mé1ange, western Tibet. These rocks have a strong boninitic affinity, with high SiO2 (55.61％-59.23％,weight percent), MgO (6.63％-13.08％, 9.13％ on average (weight percent)), A1203/1iO2 ratios (36-54), Mg# (0.61-0.74), Ni (116 ppm on average) and Cr (354 ppm on average)low TiO2 (0.23％-0.39％, weight percent), and strong LILEs enrichment relative to the depleted HFSEs. C1-chondrite normalized (La/Gd)N and (Gd/Yb)N ratios of about 1.70 and 0.83, respectively, produce prominent“U-shaped” normalized REE (rare earth element) patterns. Such a close compositional affinity to boninite indicates that these volcanic rocks were formed in a forearc setting produced by the intra-oceanic subduction.
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