Insights into the Tethyan mantle heterogeneity: Trace element evidence from the Karakaya Complex, Central Anatolia

Kaan Sayit
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引用次数: 1

Abstract

The Nilüfer Unit of the Karakaya Complex (northern Turkey) preserves the remnants of the voluminous Triassic Tethyan magmatism. In the Imrahor area (Ankara), the Nilüfer Unit is characterized by a megablock consisting of hydrothermally altered basalts, gabbros, and subordinate wehrlitic cumulates. These lithologies display marked positive Nb anomalies with depleted Th/La ratios and varying degrees of LREE enrichment. They can be subdivided into two groups based on Nb/Nb*, which are not related to each other via fractional crystallization or extent of partial melting. With their strong Nb-kick and broad La/Sm range, the Imrahor lithologies are more akin to FOZO (Focus Zone)- or C (common component)-type melts than EM (Enriched Mantle) and HIMU (high μ). The Zr-Nb systematics reveals that melt mixing was an essential process in the petrogenesis of these mafic rocks. Based on geochemical modeling, the trace element systematics of the İmrahor lithologies can be explained by melting metasomatized oceanic lithospheric mantle (OLM) infiltrated by very low-degree melt fractions. The metasomatized OLM may represent a recycled, plume-related material that has generated Nb-enriched melts during the Triassic Tethyan magmatism.

特提斯地幔非均质性研究:来自安纳托利亚中部卡拉卡亚杂岩的微量元素证据
卡拉卡亚杂岩的Nilüfer单元(土耳其北部)保存了大量三叠纪-特提斯岩浆活动的残余。在Imrahor地区(安卡拉),Nilüfer单元的特征是由热液蚀变玄武岩、辉长岩和次级Wehritic堆积体组成的巨型块体。这些岩性显示出明显的正Nb异常,Th/La比值贫化,LREE富集程度不同。它们可以基于Nb/Nb*细分为两组,这两组通过分级结晶或部分熔融的程度彼此无关。Imrahor岩性具有较强的Nb井涌和较宽的La/Sm范围,与EM(富集地幔)和HIMU(高μ)相比,更类似于FOZO(聚焦带)或C(常见成分)型熔体。Zr-Nb系统学表明,熔融混合是镁铁质岩石形成的重要过程。基于地球化学模型,伊姆拉霍尔岩性的微量元素系统学可以用极低程度熔融组分渗透的熔融交代海洋岩石圈地幔(OLM)来解释。交代OLM可能代表一种回收的、与羽流相关的物质,在三叠纪特提斯岩浆作用期间产生了富含Nb的熔体。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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CiteScore
4.70
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