| 新疆西准噶尔地区阿尔卑斯型超基性岩中铬铁矿矿物包裹体研究 |
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| A STUDY ON INCLUSION IN CHROMITE OF ALPINE-TYPE ULTRABASIC ROCKS IN WESTERN JUNGAR AREA OF XINJIANG,CHINA |
| Chromite deposits in magnesian ultrabasic rocks of Alpine-type lying in the lower part of Palaeozoic ophiolite suite in west Jungar occur mostly in dunites marked by high basicity, low M/F ratio and rich content of Al2O3 and Cr2O3. The orebadies are distributed in clusters or/and in zones. Most of them are composed of densely disseminated-compactly massive ores and a few consist of pisolitic ores. The ore-forming chrome spinel belongs to magnesian alu-mino-chromite and chromite.From ore-forming chrome spinel in various ores, are discovered, for the first time, evolutionary primary totally crystallized silicate melt inclusions and primary fluid inclusions. The former can be found in all the ores, but the latter is mainly present in the intensively disseminated ores, especially in-the pisolitic ores, and coexist with the melt inclusions, suggesting non-conso-lution of ore-forming melt.The melt inclusions have daughter minerals: olivine (Fo 96.1-98.3), enstatite (En 93.1-93.9), diopside (En46.1-50. 1, Fs 2.3-2.9, Wo 46.5-50.9), spinel and magnesite, and they are obviously different from the main rock-forming minerals of ultrabasic rocks, in which olivine is Fo 90-94, enstatite is En 90-92 and diopside is En 46-51,Fs 2.4-7,Wo 44-50. The crystal-fluid inclusions have crystalloid daugher minerals of olivine, pyroxene, spinels and magnesites, and volatile components like H2O, CO2, CO, N2, H2, and CH4.The data of determined temperature of inclusions and mineralogy indicate that sparse-medium disseminated ores were formed at 1000-1200℃ densely-compactly massive and pisolitic ores at 713-1000℃. They might be the main, ore-forming temperatures in the region.According to the above mentioned evidence, these chromite deposits were formed by volatile-enriched ore-bearing melts generated by means of molton differentiation of ultrabasic magmas at temperatures of 713-1200℃ under an abyssal setting where physical-chemical condition was relatively stable and the temperature dropped very slowly. |
| PENG Li-gui.1987.A STUDY ON INCLUSION IN CHROMITE OF ALPINE-TYPE ULTRABASIC ROCKS IN WESTERN JUNGAR AREA OF XINJIANG,CHINA[J].Acta Geoscientica Sinica,9(3):103-119. |
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