Abstract

The metabasites of the Tim Formation occur in the Paleoproterozoic Orel, Tim–Yastrebovka, and Avilsky synforms in the Archean Kursk block of Eastern Sarmatia. The volcanics are picrites, picrobasalts, basalts, and basaltic andesites metamorphosed to the greenschist and epidote-amphibolite facies. Their zircon (SIMS) age is 2099 ± 8 Ma. Based on their (Gd/Yb)_n and Ti/Y ratios, the volcanics of the Tim Formation are subdivided into two types. The first one is OIB-type metabasites with (Gd/Yb)_n > 2 and Ti/Y > 500. The parental melts of these rocks corresponded to ferropicrite and were derived by melting a garnet-bearing mantle source. The rocks of the second type are MORB-type volcanics with (Gd/Yb)_n < 2 and Ti/Y < 500, which implies that the magma was derived from a garnet-free source at a relatively shallow depth. Their parental melts could be variously enriched MORB-type picrites. These magmas, which are contrastingly different in petrogenesis but had approximately equal age, were likely generated at various interaction stages between the asthenospheric mantle and eclogitized oceanic crust, subcontinental lithospheric mantle, and continental crust in the destruction environment of a subducted oceanic slab at the accretionary–collisional interaction between the Kursk domain and Volga–Don orogen.

中文翻译：

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东萨尔马提亚库尔斯克地块的古元古代OIB型和MORB型裂谷火山岩：岩石学和地球动力学

摘要

蒂姆组的变质岩发生在东萨尔马提亚的太古宙斯块中的古元古代奥勒尔，蒂姆-耶斯特雷波夫卡和阿维斯基同形体中。火山是变质为绿岩岩和显露-闪石岩相的微晶岩，微玄武岩，玄武岩和玄武安山岩。他们的锆石（SIMS）年龄为2099±8 Ma。根据它们的（Gd / Yb）_n和Ti / Y比，Tim组的火山岩可分为两种类型。第一个是OIB型变质岩，其（Gd / Yb）_n > 2和Ti / Y>500。这些岩石的母体熔体对应于亚铁锰矿，并且是通过熔化带有石榴石的地幔源而产生的。第二类岩石为MORB型火山岩，（Gd / Yb）_n<2和Ti / Y <500，这意味着岩浆是在相对浅的深度从无石榴石来源获得的。他们的父母熔体可能是各种丰富的MORB型野餐。这些岩浆在成岩作用上差异较大，但年龄大致相等，可能是在软流圈地幔和陆壳岩石圈地幔以及大陆壳在俯冲俯冲板块的破坏环境中在增生作用下的软弱圈地幔与陆化壳之间的各种相互作用阶段产生的。 – Kursk域与伏尔加河-顿造山带之间的碰撞相互作用。