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首页> 外文期刊>Journal of Asian earth sciences >P-T-f_(O_2) controls on a partly inverse chromite-bearing ultramafic intrusive: an evaluation from the Sukinda Massif, India
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P-T-f_(O_2) controls on a partly inverse chromite-bearing ultramafic intrusive: an evaluation from the Sukinda Massif, India

机译：P-T-f_（O_2）控制部分含亚铬铁矿的超镁铁质侵入岩：印度Sukinda Massif的评估

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摘要

The chromites from the alpine type ultramafic intrusive of Sukinda, India, display a typical partly inverse spinel form and occur in two distinct zones: Brown Ore Zone (BOZ) and Grey Ore Zone (GOZ). The host ultramafites are mostly altered and are represented by the serpentinite, tremolite-talc(chlorite) schist, talc-serpentine schist and chlorite rock. The less altered variants are dunite, harzburgite and websterite. A dyke of orthopyroxenite runs through the main ultramafic body. The composition of olivine (Fo_(92)), orthopyroxene (En_(92-89)) and Al_2O_3 contents of the parental liquid (10.40-11.45%) determined from chromites, suggest that the parent melt is of boninitic affinity. The chemical plot of TiO_2 content against cr# of chromites corroborates a boninitic parental melt. The Fe-Mg partitioning in olivine and chromite depicts the temperature for chromitites as 1200℃. A compositional plot of mg# and cr# suggests crystallization at high pressure conditions, corresponding to the kimberlite xenolith field. From the P-T diagram of pyrolite melting and mineral assemblage, the pressure of crystallization is stipulated to be ≥ 1.2 GPa. The f_(O_2) values estimated from Fe~(3+)/Cr + Al + Fe~(3+) ratios range from 10~(-8.3) to 10~(-9) for the GOZ and 10~(-7.1) to 10~(-7.3) for the BOZ. The f_(O_2) values together with the pressure range suggest crystallization at upper mantle conditions. The heterogeneity in chemical composition and f_(O_2) conditions for the GOZ and BOZ could be linked to heterogeneity in the upper mantle.
机译：来自印度Sukinda的高山型超镁铁质侵入体的亚铬铁矿显示出典型的部分反尖晶石形式，并出现在两个不同的区域中：棕色矿带（BOZ）和灰色矿带（GOZ）。寄主超黑胶岩大部分被改变，以蛇纹岩，透闪石-滑石片岩，滑石-蛇纹岩片岩和绿泥石岩为代表。改变较少的变体是辉光岩，哈兹伯格岩和韦氏石。钙钛矿的堤坝贯穿主要的超镁铁质岩体。由亚铬铁矿测定的母液中橄榄石（Fo_（92）），邻苯二酚（En_（92-89））和Al_2O_3的组成（10.40-11.45％）表明母熔体具有亲和力。 TiO_2含量对亚铬酸铬cr＃的化学图证实了亲本的母体熔体。 Fe-Mg在橄榄石和铬铁矿中的分配表明铬铁矿的温度为1200℃。 mg＃和cr＃的组成图表明，在高压条件下会发生结晶，这与金伯利岩异种石场相对应。从黄铁矿熔融和矿物组合的P-T图，结晶压力规定为≥1.2 GPa。根据Fe〜（3 +）/ Cr + Al + Fe〜（3+）的比值估算的f_（O_2）值在GOZ范围从10〜（-8.3）到10〜（-9），在10〜（-7.1） ）至BOZ的10〜（-7.3）。 f_（O_2）值与压力范围一起表明在上地幔条件下结晶。 GOZ和BOZ的化学成分和f_（O_2）条件的异质性可能与上地幔的异质性有关。

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