Abstract

Eclogite-like rocks of the Olkhon terrane correspond to two types according to the mode of occurrence and mineral compositions, although both types developed after the same type of gabbro of a single complex. The rocks of the first type are composed of garnet, clinopyroxene, pargasite (± scapolite, ± anorthite, ± spinel) and occur as thin veins or patches in the marginal parts of several small gabbro massifs of the Tonta Zone. The garnet is of almandine–pyrope–grossular composition and contains up to 40% of the pyrope end member. The rocks of the second type have been found in the Zamogoi Island in the Maloe More Strait. The island is composed of metasomatically altered gabbro cut by numerous granite and syenite veins. Carbonate and carbonate–silicate rocks compose dismembered veins and veinlets, as well as matrix embedding variably sized fragments of metasomatized gabbro and eclogite-like rocks in the southern part of the island. Based on the mode of occurrence and the presence of calcite–anorthite symplectite in some of the rocks, we suggest that the gabbro was penetrated by carbonate fluid or fluid–melt in a tectonic zone. The zone contains veins of garnet–clinopyroxene composition (varying from monomineralic garnetite to monomineralic pyroxenite) with minor pargasite, zoisite, anorthite, scapolite, and titanite. The garnet of Zamogoi Island has a grossular–almandine composition with a minor andradite concentration (about 10%). The compositions of minerals of the Zamogoi massif differ from the compositions of minerals in Tonta Zone, and the former are much more similar to skarn minerals.

中文翻译：

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西贝加尔湖地区Olkhon Terrane的类似榴辉岩的Metagabbro

摘要

Olkhon地层的榴辉岩状岩石根据发生的方式和矿物成分而对应于两种类型，尽管两种类型都是在单个复合体的同一种辉长岩之后形成的。第一类岩石由石榴石，斜向辉石，辉石（±尖晶石，±钙长石，±尖晶石）组成，并以细脉或斑块的形式出现在通塔地区的几个小辉长岩块的边缘。石榴石的成分为金刚烷-吡啶-草状，最多含有40％的吡啶末端。在马洛莫尔海峡（Maloe More Strait）的Zamogoi岛上发现了第二类岩石。该岛由被许多花岗岩和正长岩脉切割的变质生辉长岩组成。碳酸盐和碳酸盐-硅酸盐岩石组成了破碎的脉和小脉，以及在岛的南部嵌入基质的变尺寸交变辉长岩和类似榴辉岩的岩石碎片。根据出现的方式和某些岩石中方解石-钙长石共混物的存在，我们建议辉长岩在构造区被碳酸盐岩流体或流体融化作用穿透。该区域包含石榴石–斜辉石组成的脉脉（从单矿物的石榴石到单矿物的辉石），具有少量的方铁石，膨润土，钙长石，钙皂石和钛铁矿。Zamogoi岛的石榴石有少量的–以及少量的辐射（约10％）。Zamogoi地块的矿物组成与通塔地区的矿物组成不同，前者与矽卡岩矿物更为相似。