Characteristics and geological significance of olivine xenocrysts in Cenozoic volcanic rocks from western Qinling  

作　　者：SU Benxun ZHANG Hongfu XIAO Yan ZHAO Xinmiao 

机构地区：[1]State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029,China [2]Graduate School of Chinese Academy of Sciences, Beijing 100039, China

出　　处：《Progress in Natural Science:Materials International》2006年第12期1300-1306,共7页自然科学进展·国际材料（英文版）

基　　金：Supported by National Natural Science Foundation of China (Grant Nos .40534022 and 40421202)

摘　　要：Cenozoic volcanic rocks from the Haoti, Dangchang County of the western Qinling Mountains, contain a few clearlyzoned olivines. These olivines are relatively big in grain sizes and usually have cracks or broken features. Their cores have similar compositions （Mg^# = 90.4 - 91.0） to those for the peridotitic xenoliths entrained in host volcanic rocks and their rims are close to the compositions of olivine phenocrysts （Mg^# = 85.5 - 81.9）. The CaO contents in these zoned olivines are lower than 0. 1%, These features demonstrate that the clearly-zoned olivines are xenocrysts and disaggregated from mantle peridotites. The zoned texture was the result of the interaction between the olivine and host magma. Available data show that the volcanic rocks would have been derived from the mantle source metasomatized by subducted hydrathermally-altered oceanic crust. The formation of these Cenozoic volcanic rocks was perhaps related to the rapid uplift of the Tibetan Plateau.从 Haoti 的新生代暴烈的岩石，西方的 Qinling 山的 Dangchang 县，包含一些地区得清楚地的橄榄石。这些橄榄石在谷物尺寸相对大并且通常有裂缝或破特征。他们的核心有类似的作文(Mg <SUP>#</SUP> 90.4-91.0 ) 到那些因为 peridotitic 捕虏体在暴烈的岩石和他们的边界接近的主人乘火车橄榄石斑晶的作文(Mg <SUP>#</SUP>=85.5-51.9) 。在这些 zoned 橄榄石的 CaO 内容比 0.1% 低。这些特征证明地区得清楚地的橄榄石从披风 periodotites 是 xenocrysts 和 disaggregated。zoned 质地是在橄榄石和主人岩浆之间的相互作用的结果。暴烈的岩石将被潜水艇 ducted 从披风来源 metasomatized 导出的可得到的数据表演改变 hydrathermally 的海洋的外壳。这些新生代暴烈的岩石的形成也许与有关快速西藏的高原高举。

关 键 词：Western Qinling Dangchang Haoti Cenozoic volcanic rocks olivine xenocrysts zoned texture 

分 类 号：P58[天文地球—岩石学]