冀东遵化豆荚状铬铁矿中的矿物包裹体
首发时间:2011-01-11
摘要:为了探讨豆荚状铬铁矿母岩浆成分特征以及形成的构造环境,本文研究了遵化豆荚状铬铁矿中的矿物包裹体。原生矿物包裹体主要有金云母、角闪石、单斜辉石、顽火辉石、镁橄榄石,多矿物包裹体主要为橄榄石+顽火辉石+金云母和金云母+角闪石。遵化豆荚状铬铁矿中原生矿物包裹体中单斜辉石和金云母以及角闪石中的Mg#指数较高基本在90以上,但Ti含量明显较低,此外,单斜辉石中的Al含量偏低,角闪石和金云母中的Mg#相似。通过地质温度计得出,包裹体单斜辉石的结晶温度为952-975 oC,橄榄石+斜方辉石矿物共生组合结晶温度为1308 oC,大量富水矿物包裹体的出现与母岩浆形成时大量流体有关,可能反映了与上俯冲带相关的构造环境。
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Mineral Inclusions in Podiform Chromite Exposed in Zunhua Area, Eastern Hebei Province?
Abstract:For understanding the characteristics of parental magma of the podiform chromite and its tectonic setting, the mineral inclusions of podiform occurred in Zunhua area, eastern Hebei Province were studied in this paper. The original mineral inclusions in podiform chromite include phlogopite, hornblende, clinopyroxene, enstatite, forsterite; and the multi-mineral inclusions are olivine + enstatite + phlogopite assemblage or phlogopite + hornblende assemblage. The Mg# values are generally higher than 90 for the clinopyroxene, phlogopite, and hornblende in original mineral inclusions, but the Ti content of these minerals are low. Besides these characteristics, the Al content of clinopyroxene is lower than normal value, and the Mg# value of hornblende is similar to that of phlogopite. The crystallization temperatures estimated by geothermometer are 952 ~ 975 oC for the clinopyroxene in inclusion of podiform chromite, and 1308 oC for the assemblage of olivine and orthopyroxene. The occurrence of abundant water-bearing minerals in the inclusions of podiform chromite is related to fluid activity during the formation stage of parental magma, and indicates a supra-subduction zone environment for parental magma.
Keywords: mineralogy mineral inclusion podiform chromite Zunhua
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