Trace and rare earth elements as indicators of provenance and depositional environments of Lias cherts in Gumushane, NE Turkey
Trace and rare earth elements as indicators of provenance and depositional environments of Lias cherts in Gumushane, NE Turkey
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DOI：
10.1016/j.chemer.2011.11.004
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发表时间：
2012-01-01
影响因子：
--
通讯作者：
Kaygusuz, Abdullah
中科院分区：
文献类型：
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作者：
Eker, Cigdem Saydam;Sipahi, Ferkan;Kaygusuz, Abdullah
对 Gumushane 地区 Lias 龄燧石的微量元素和稀土元素 (REE) 进行了研究，以了解其起源和沉积环境。通过电感耦合等离子体质谱、X 射线衍射和矿物学研究对来自 5 个地层剖面的 23 个燧石样品进行了分析。研究区的利亚燧石根据矿物含量分为微晶质、隐晶质石英和兆石英。燧石微量元素与PAAS相比，Co、Y、Th在5个剖面中的损耗较强，而V、Ni、Zr、Nb、Hf的损耗较小。 Zr、Hf 和 Ta 的分布产生 Zr/Hf、Zr/Ta 和 Hf/Ta 比率（分别为 25/645、37/665 和 0.18/3），与球粒陨石和平均上大陆地壳的比率不同，表明这些元素可能不是碎屑元素，但来自海水。 Th/U 比率范围为 0.04 至 0.45，低于上大陆壳的比率（平均值：3.9）。在 PAAS 和球粒陨石归一化图的五个部分中，连接燧石的 REE 总丰度较低，且消耗较强。燧石的特点是正 Eu 异常（平均：4.9）和轻稀土富集（La-N/Yb-N = 平均：3.5）。此外，大约一半的燧石表现出正Ce异常（范围：0.25-2.58）、球粒状Y/Ho值（范围：3.3-60）和低（La/Ce）（N）值（平均值：1.8）。 Lias燧石中的稀土元素和微量元素丰度表明这些元素可能来自热液、陆源和海水。燧石的稀土元素模式表明它们可能沉积在靠近大陆边缘的地方。 (C) 2011 爱思唯尔有限公司。版权所有。
Trace elements and rare earth elements (REEs) of Lias-aged cherts in the Gumushane area were studied in order to understand their origin and depositional environment. Twenty three chert samples from five stratigraphic sections were analysed by inductively coupled plasma-mass spectrometry, X-ray diffraction, and mineralogical investigation. Lias cherts in the study area are microcrystalline, cryptocrystalline quartz, and megaquartz depending on mineralogical content. Trace elements of the cherts were compared with PAAS, Co, Y, and Th had stronger depletions in the five sections, whereas V, Ni, Zr, Nb, and Hf had smaller depletions. The distribution of Zr, Hf, and Ta yields Zr/Hf, Zr/Ta and Hf/Ta ratios (25/645, 37/665, and 0.18/3, respectively) that differ from those of chondrites and average upper continental crust, suggesting that these elements are likely non-detrital but are sourced from seawater. Th/U ratios range from 0.04 to 0.45 and are lower than those of the upper continental crust (average: 3.9). Liasaged cherts have low total REE abundances and stronger depletions in five sections of the PAAS and chondrite-normalised plots. The cherts are characterised by a positive Eu anomaly (average: 4.9) and LREE-enrichment (La-N/Yb-N = average: 3.5). In addition, about one-half of the cherts exhibit positive Ce anomaly (range: 0.25-2.58), chondritic Y/Ho values (range: 3.3-60), and low (La/Ce)(N) values (average: 1.8). REE and trace element abundance in Lias cherts indicate that these elements were likely derived from hydrothermal solutions, terrigenous sources, and seawater. The REE patterns of the cherts show that they were probably deposited close to a continental margin. (C) 2011 Elsevier GmbH. All rights reserved.