论文部分内容阅读
在卡纳塔克约为35亿年的霍莱纳拉西普尔绿岩带的变质橄榄科马提岩、蛇纹岩和角闪岩中,发现了呈岩席和透镜体产出的极细粒的变质斜长岩—斜长岩质变质玄武岩。岩石的稀土元素图谱表现出其轻稀土元素较重稀土元素稍有富集,与球粒陨石相比,La的变化在12—7倍之间,而重稀上元素在3—4倍之间变化。(Ce/Yd)N平均比值是2.1。岩石的Eu含量是可变的。Eu/Eu~*比值范围是1.2—9.0,相对于标准角闪石呈现强的负相关。在这些方面,这些上地壳的斜长岩质岩石与格陵兰西部和挪威西北部地区的那些主要化学元素近似的高级变质区斜长岩相比较,有很大的不同,但与月球高地玄武岩相比却表现山有明显的一致性。这种一致性是通过其结构关系和其它诸如地球化学的相似性等方面来证实的.斜长玄武岩相对不分异的性质表明它可以代表斜长玄武岩熔体,并在熔体中出现了少量斜长石的堆积。根据稀土元素资料,这种熔体的成因有两种可能性:(a)由于含水的地幔橄榄岩的部分熔化程度很小所致;(b)由于有大量的橄榄石和斜方辉石从橄榄科马提岩岩浆中分异出来的结果。
In the metamorphic olive komatiites, serpentines and amphiboles of the roughly 3.5 billion-year-old Hollenara-Purpur greenstone belt in Karnataka, very fine Granular metamorphic plagioclase - anorthosite metamorphic basalts. Rare earth element spectra of rocks show a slight enrichment of the heavier REEs than their heavier REE counterparts. Compared with chondrites, La varies between 12 and 7 times, while heavy rare elements are between 3 and 4 times Variety. (Ce / Yd) N average ratio is 2.1. The Eu content of rocks is variable. Eu / Eu ~ * ratios range from 1.2 to 9.0, showing a strong negative correlation with standard amphiboles. In these respects, these upper crustal anorthositic rocks are quite different from those of the high-grade metamorphic-area plagiogranons in western Greenland and northwestern Norway, which are similar in major chemical elements, but compared with the lunar highland basalts However, the performance of the mountain has obvious consistency. This consistency is evidenced by its structural relationship and other similarities, such as geochemistry. The relatively undifferentiated nature of plagioclase basalts indicates that it represents a plagioclase basalt melt and that a small amount appears in the melt Plagioclase accumulation. Based on the REE data, there are two possible causes for this melt: (a) due to the small degree of partial melting of the water-bearing mantle peridotite; (b) due to the large amount of olivine and ettringite from the olive Komati rock magma in the results of the separation.