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印度伊比利亚半岛的主要岩类是由变形的硅铝质岩组成,广义地称为“伊此利亚片麻岩”。在塔尔瓦尔克拉通西部所研究的岩石组合为英云闪长质或奥长花岗质,其同位素年龄为3400—3000Ma。大量全岩同位素年龄所记录的最后地质事件是3000Ma以前,这与底胖奥长花岗岩深成体的侵位时间是一致的。片麻岩组合表现出由大量彼此分离的岩浆体组成,其中有一些岩浆体是在非常低压条件下达到平衡的,甚至可能是喷出的。低~(87)Sr/~(86)Sr初始比值,表明它们是由地幔熔融派生的,或者由部分熔融之前只有很短时间获得地壳Rb/Sr比值的物质派生的。有些年龄代表变质事件发生前不久侵位岩石的变质作用。片麻岩中几乎不含沉积组份,这可由岩石中缺乏圆形锆石、低铬(Cr)和低标准矿物刚玉含量(或含量为零)得以说明。成分上的某些变化发生在片麻岩原始定位之后。铀(U)含量的大量增加和钍(Tn)含量的一些增加,都发生在大约3000Ma以前,与此同时,其它亲石元素可能也有所活动。大约在2500Ma以前,在地壳深处发生麻粒岩相变质作用期间,没有直接证据说明由交代作用使一些元素进入片麻岩中,尽管最高级紫苏花岗岩的亲石元素有亏损。
The main rocks of the Iberian Peninsula in India are composed of deformed sillimanites, broadly termed “Ikoa gneiss.” The rock assemblage studied in the western part of Talwar Craton is an eclogitic or orthorhombic granite with an isotopic age of 3400-3000 Ma. The last geological event recorded by a large number of whole-rock isotope ages was 3000Ma, which is consistent with the emplacement time of the deep-fat granite in the basement. Gneiss assemblages appear to consist of a large number of separate magma bodies, some of which are equilibrated under very low pressure conditions and may even be ejected. The low initial ratios of (87) Sr / ~ (86) Sr indicate that they were derived from the mantle melting or derived from the crust Rb / Sr ratio for a short period of time prior to partial melting. Some ages represent the metamorphic effects of emplacement rocks shortly before metamorphic events occurred. Gneiss is almost free of sedimentary components, as demonstrated by the absence of round zircon, low chromium (Cr) and low-standard corundum (or zero) in the rock. Some of the compositional changes occur after the gneiss was originally located. Significant increases in uranium (U) content and some increases in thorium (Tn) content occur before about 3000 Ma, while other lithophile elements may also be active. Until about 2500 Ma, there was no direct evidence that during the granulite facies metamorphism in deep crust, some of the elements entered the gneisses by metasomatism, despite the loss of lithophile elements from the granite of the highest grade.