Sedimentologic to metamorphic processes recorded in the high-pressure/low-temperature Mesozoic Rosetta Marble of Anatolia
Sedimentologic to metamorphic processes recorded in the high-pressure/low-temperature Mesozoic Rosetta Marble of Anatolia
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DOI：
10.1007/s00531-015-1214-y
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发表时间：
2015
影响因子：
2.3
通讯作者：
F. Scheffler;R. Oberhänsli;A. Pourteau;A. Immenhauser;O. Candan
中科院分区：
文献类型：
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作者：
F. Scheffler;R. Oberhänsli;A. Pourteau;A. Immenhauser;O. Candan
安纳托利亚高压变质带的部分特征是新特提斯地层演替，其中包括白垩纪中期的半远洋大理石层序。该单元在其地层顶部含有1米至1米长的辐射钙质棒，形成玫瑰花状结构。在这里，我们把这些特征称为“罗塞塔大理石”。罗塞塔大理岩中非变质亚硒酸盐晶体与辐射方解石棒状结构的显著相似性表明，这些结构是亚硒酸盐之后的伪形态。以Rosetta亚硒酸盐伪晶为主的变质半中上层灰岩与含有残余放射虫试验的硅质元沉积物交替存在。这种地层模式表明了一个过渡阶段，其特征是盆地盐水的蒸发岩沉淀与正常海洋海水的非蒸发半远洋沉积交替发生。600 km以上罗塞塔大理岩暴露的区域分布指示了盆地尺度的蒸发间隔。高压、低温变质作用表现为富sr（高达3500ppm）、文石后的纤维方解石假晶和石英中孤立的文石包裹体。高硅白云母热气压测定证实了1.2 GPa和300-350℃的峰值变质条件。罗塞塔大理石棺的例子检验了揭示变质沉积岩从沉积到成岩和变质的完整历史的潜力。
Anatolia’s high-pressure metamorphic belts are characterized in part by a Neotethyan stratigraphic succession that includes a mid-Cretaceous hemi-pelagic marble sequence. This unit contains, towards its stratigraphic top, dm-to-m-long radiating calcitic rods forming rosette-like textures. Here, we refer to these features as “Rosetta Marble”. The remarkable textural similarity of non-metamorphic selenite crystals and radiating calcite rods in the Rosetta Marble strongly suggests that these textures represent pseudomorphs after selenites. Metamorphosed hemi-pelagic limestones, dominated by Rosetta selenite pseudomorphs, are alternating with siliceous meta-sediments containing relictic radiolaria tests. This stratigraphic pattern is indicative of transient phases characterized by evaporites precipitated from basinal brines alternating with non-evaporative hemi-pelagic deposition from normal-marine seawater. The regional distribution of Rosetta Marble exposures over 600 km is indicative of basin-scale evaporitic intervals. High-pressure, low-temperature metamorphism of these rocks is witnessed by Sr-rich (up to 3500 ppm), fibrous calcite pseudomorphs after aragonite and isolated aragonite inclusions in quartz. Peak metamorphic conditions of 1.2 GPa and 300–350 °C are attested by high-Si white mica thermobarometry. The Rosetta Marble case example examines the potential to unravel the complete history from deposition to diagenesis and metamorphism of meta-sedimentary rocks.