Extremely low-Al orthopyroxene in the Horoman peridotite,Japan
Extremely low-Al orthopyroxene in the Horoman peridotite,Japan
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日本霍罗马橄榄岩中的极低铝斜方辉石
DOI：
10.2465/jmps.96.48
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发表时间：
2001
影响因子：
0.7
通讯作者：
S. Arai
中科院分区：
文献类型：
--
作者：
T. Morishita;T. Morishita;S. Arai
我们在日本霍罗曼橄榄岩杂岩的尖晶石二辉橄榄岩中发现了极低铝斜方辉石。低铝斜方辉石以两种方式赋存，第一种赋存于与橄榄石接触的大型斜方辉石碎斑岩的边缘，第二种赋存于单斜辉石与橄榄石之间的晶界。低铝斜方辉石中的Al_2O_3、Cr_2O_3和CaO含量均小于0.2wt.%，明显低于斜方辉石斑岩中的含量。岩石学观察结合推断的霍罗曼橄榄岩的P-T历史表明，低铝斜方辉石是通过橄榄岩与水流体的非常局部的反应形成的，这并没有渗透地改变前体矿物学。
We report an occurrence of extremely low-alumina orthopyroxenes in a spinel lherzolite from the Horoman Peridotite Complex, Japan. The low-Al orthopyroxenes occur in two modes; the first occurs at the margin of a large orthopyroxene porphyroclast in contact with olivine and the second occurs at grain boundaries between clinopyroxene and olivine. Al2O3, Cr2O3 and CaO contents in the low-Al orthopyroxenes are less than 0.2 wt.% and are distinctively lower than those in orthopyroxene porphyroclasts. Petrographic observations combined with a inferred P-T history of the Horoman peridotite reveal that the low-Al orthopyroxenes were formed through a very local reaction between peridotite with aqueous fluids, which were not pervasively altering the precursor mineralogy.