Geochemistry of post-collisional mafic lavas from the North Anatolian Fault zone, Northwestern Turkey
- 作者：Biltan Kü ; rkcü ; oğ ; lu ; Tanya Furman ; Barry Hanan
- 关键词：Basalt Geochemistry ; Northwestern Anatolia ; Geochemical melting model ; Mafic lavas ; Northern Anatolian Fault (NAF)
- 刊名：Lithos
- 出版年：2008
- 期刊代码：54_00244937
- 类别：ear
- 出版时间：March 2008
- 卷：101
- 期：3-4
- 页码：416-434
- 文件大小：1499 K
摘要
Extensive magmatic activity developed at the northwestern part of the Anatolian block and produced basaltic lavas that are situated along and between the two segments of the North Anatolian Fault zone. This region is a composite tectonic unit formed by collision of continental fragments after consumption of Neotethyan ocean floor during the late Cretaceous. Northwestern Anatolian basalts and evolved lavas exhibit both tholeiitic and calc-alkaline characteristics. Mafic lavas are moderately enriched in LILE (except depleted part of Yuvacık and İznik samples) and depleted in HFSE (but not Zr, Hf) relative to primitive mantle values, suggesting derivation from a MORB-like mantle source that is unexpected in this subduction environment. Sr and Nd isotopes are close to the mantle array and vary beyond analytical error (87Sr/86Sr 0.70404–0.70546, 143Nd/144Nd 0.51270–0.51289). These geochemical features may result from two possible processes: (1) melting of a MORB-like mantle source that was modified by subduction-released fluids and melts or (2) modification of mafic liquids derived from a dominantly MORB-like source by crustal or lithospheric mantle material. Geochemical characteristics of the lavas (e.g., Ba/Rb, Rb/Sr, Ba/Zr, 87Sr/86Sr, Sr/P) vary systematically along the fault zone from east to west, consistent with a decrease in the degree of melting from east to west or a change in the nature of the source composition itself. Thus, the difference in incompatible elements and Sr–Nd isotopic ratios seems to result from small-scale mantle heterogeneity in a post-collisional tectonic environment.