ABSTRACT

Provenance analysis including sandstone modal compositions, heavy mineral assemblages, and LA-ICP-MS U-Pb dating with in-situ Hf isotopic compositions of detrital zircons defines two types of Late Cretaceous-Eocene turbiditic sequences separated by the Siah Cheshmeh-Khoy-Misho-Tabriz Fault in the Azerbaijan Province, Northwest Iran: (1) Volcaniclastic turbidites to the southwest and (2) terrigenous turbidites to the northeast. The first appearance of Cr-spinel in Upper Cretaceous sandstones of both sequences indicates the erosion of ophiolites at that time. The southwestern volcaniclastic sandstones contain few Late Triassic and dominantly Late Cretaceous zircon grains whose Hf isotopic compositions suggest a continental magmatic arc provenance. In the northeastern terrigenous sandstones, detrital zircon U-Pb ages cluster in five main age groups from Paleoproterozoic-Neoproterozoic with Hf isotopic compositions typical of continental crust to Late Cretaceous-Palaeocene zircon grains with Hf isotopic compositions similar to those of the southwest turbidites. The provenance characteristics define, along with sedimentary structures, two separate basins, a marginal basin to the northeast, and a deep oceanic basin to the southwest. We conclude that the Siah Cheshmeh-Khoy-Misho-Tabriz Fault overprints a boundary between two lithospheres separated by ophiolite outcrops; therefore, the Siah Cheshmeh-Khoy-Misho-Tabriz Fault is a reworked suture. The Cretaceous arc, witnessed by clastic material, has been largely eroded and/or subducted.

摘要

物源分析包括砂岩模态组成，重矿物组合和LA-ICP-MS U-Pb以及碎屑锆石的原位Hf同位素组成，定义了两种类型的晚白垩世-始新世湍流序列，由Siah Cheshmeh-Khoy-Misho分隔-伊朗西北部阿塞拜疆省的塔布里兹断层：（1）西南的火山碎屑浊度和（2）东北的陆源性浊度。Cr-尖晶石在这两个层序的上白垩统砂岩中的首次出现表明当时蛇绿岩的侵蚀。西南火山碎屑砂岩几乎不含三叠纪晚期和白垩纪晚期的锆石颗粒，其H同位素组成表明其具有大陆性岩浆弧源。在东北陆源砂岩中，碎屑锆石的U-Pb年龄集中在从古陆界典型的Hf同位素组成的古元古生界-新元古界到Hf同位素组成类似于西南浊石的晚白垩世-古新世锆石晶粒。物源特征连同沉积结构一起定义了两个独立的盆地，东北部的边缘盆地和西南部的深海盆地。我们得出的结论是，Siah Cheshmeh-Khoy-Misho-Tabriz断层覆盖了由蛇绿岩露头隔开的两个岩石圈之间的边界。因此，Siah Cheshmeh-Khoy-Misho-Tabriz断层是重做的缝合线。白垩纪弧在碎屑物质的作用下已被很大程度上侵蚀和/或俯冲。