Evolution and provenance of Neoproterozoic basement and Lower Paleozoic siliciclastic cover of the Menderes Massif (western Taurides): Coupled U-Pb-Hf zircon isotope geochemistry
Evolution and provenance of Neoproterozoic basement and Lower Paleozoic siliciclastic cover of the Menderes Massif (western Taurides): Coupled U-Pb-Hf zircon isotope geochemistry
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DOI：
10.1016/j.gr.2012.05.006
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发表时间：
2013-03
影响因子：
6.1
通讯作者：
O. Zlatkin;D. Avigad;A. Gerdes
中科院分区：
文献类型：
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作者：
O. Zlatkin;D. Avigad;A. Gerdes
在Menderes地块（西部Taurides），新元古代基底包括变质沉积物和侵入花岗岩，叠瓦状分布在古生代台地沉积物之间。本文利用LA-ICP-MS对Menderes岩石单元进行了U-Pb-Hf锆石分析。新元古代变质沉积物的U-Pb碎屑锆石信号与东北非洲冈瓦纳大陆的物源基本一致。最古老的单元是副片麻岩，含有大量（~30%）太古代锆石，其新元古代锆石中约一半的εHf（t）值为负值，表明来自以旧地壳改造为主的泛非碎屑岩。在上覆的矿物学上未成熟的岩芯片岩（仍为新元古代）中，大部分碎屑锆石为新元古代的，表现出正εHf（t）值，表明源自近端的幼年源，类似于阿拉伯-努比亚地盾。分析变质沉积物的沉积时期，被限制在570和550马（晚埃迪卡拉纪）。岩芯片岩沉积物厚约9 km，在不到20 Ma的时间内堆积，这意味着受构造控制的沉积盆地在受侵蚀的幼年碎屑岩附近演化。花岗岩（现为正片麻岩）于550 Ma侵入盆地充填物，其±0 εHf（t= 550 Ma）和TDM1.4Ga年龄与新元古代和晚太古代碎屑组分的各种混合物的深熔作用一致。北方阿拉伯-努比亚地盾花岗岩的年龄不超过580 Ma，εHf（t）值通常较正。这意味着门德雷斯并不代表阿拉伯-努比亚地盾的直接延续。Menderes基底的前石炭纪硅质岩盖层的下部包括一个淡黄色石英岩，其U-Pb-Hf碎屑锆石信号类似于约旦的远距离奥陶纪砂岩（包括0.9- 1.1 Ga碎屑锆石），支持前三叠纪的古恢复，将Tauride与非洲阿拉伯半岛结合起来。上覆含碳酸盐石英岩序列的碎屑信号表明来自不同的源区：其大部分碎屑锆石的550 Ma和±0 εHf（t= 550 Ma）值与下伏花岗质片麻岩的一致，表明源区出露了类似门德斯的花岗岩。在基底和盖层单元中发现了260- 250 Ma的铅丢失和部分锆石U-Pb系统的重置。它被解释为已知的三叠纪花岗岩侵入之前的二迭纪-早三叠世热事件的结果。
In the Menderes Massif (western Taurides) a Neoproterozoic basement comprising metasediments and intrusive granites is imbricated between Paleozoic platform sediments. U–Pb–Hf zircon analyses of Menderes rock units were performed by us using LA-ICP-MS. The U–Pb detrital zircon signal of the Neoproterozoic metasediments is largely consistent with a NE African (Gondwana) provenance. The oldest unit, a paragneiss, contains significant amounts (~30%) of Archean-aged zircons and εHf (t) values of about a half of its Neoproterozoic zircons are negative suggesting contribution from Pan-African terranes dominated by reworking of an old crust. In the overlying, mineralogically-immature Core schist (which is still Neoproterozoic), the majority of the detrital zircons are Neoproterozoic, portraying positive εHf (t) values indicating derivation from a proximal juvenile source, resembling the Arabian–Nubian Shield. The period of sedimentation of the analyzed metasediments, is constrained between 570 and 550Ma (Late Ediacaran). The Core schist sediments, ~9km thick, accumulated in less than 20My implying a tectonic-controlled sedimentary basin evolved adjacent to the eroded juvenile terrane. Granites, now orthogneisses, intruded the basin fill at 550Ma, they exhibit ±0 εHf (t=550Ma) and TDMages of 1.4Ga consistent with anatexis of various admixtures of juvenile Neoproterozoic and Late Archean detrital components. Granites in the northern Arabian–Nubian Shield are no younger than 580Ma and their εHf (t) are usually more positive. This implies that the Menderes does not represent a straightforward continuation of the Arabian–Nubian Shield. The lower part of the pre-Carboniferous silisiclastic cover of the Menderes basement, comprises a yellowish quartzite whose U–Pb–Hf detrital zircon signal resembles that of far-traveled Ordovician sandstones in Jordan (including 0.9–1.1Ga detrital zircons), supporting pre-Triassic paleorestorations placing the Tauride with Afro-Arabia. The detrital signal of the overlying carbonate-bearing quartzitic sequence indicates contribution from a different source: the majority of its detrital zircons yielded 550Ma and ±0 εHf (t=550Ma) values identical to that of the underlying granitic gneiss implying exposure of Menderes-like granites in the provenance. 260–250Ma lead-loss and partial resetting of the U–Pb system of certain zircons in both basement and cover units was detected. It is interpreted as a consequence of a Permian–Early Triassic thermal event preceding known Triassic granitoid intrusions.