Red bed and basement sourced fluids recorded in hydrothermal Mn–Fe–As veins, Sailauf (Germany): A LA-ICPMS fluid inclusion study
Red bed and basement sourced fluids recorded in hydrothermal Mn–Fe–As veins, Sailauf (Germany): A LA-ICPMS fluid inclusion study
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DOI：
10.1016/j.chemgeo.2013.10.026
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发表时间：
2014-01
期刊：
影响因子：
3.9
通讯作者：
T. Fusswinkel;T. Wagner;T. Wenzel;M. Wälle;J. Lorenz
中科院分区：
文献类型：
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作者：
T. Fusswinkel;T. Wagner;T. Wenzel;M. Wälle;J. Lorenz
德国赛洛夫的热液Mn-Fe-As脉状矿化具有复杂的氧化物和碳酸盐矿物序列，记录了漫长的流体历史。成矿作用与将二叠系(泽克斯坦)沉积岩与华力西结晶基底隔开的主要不整合有关。热液矿脉包括两个主要矿化阶段，即与方解石共生的锰氧化物和与锰方解石共生的赤铁矿。通过流体包裹体岩相学、显微测温和LA-ICPMS显微分析，结合碳酸盐和氧化物矿物的稳定同位素地球化学，重建了热液系统的流体演化。流体包裹体为高盐度钠钙卤水，其整体流体性质与赤铁矿阶段无明显差异。主量元素和微量元素的LA-ICPMS分析表明，矿化形成于不同的化学流体脉冲，其特征是K、Li、B、铅和锌的浓度变化。沉淀锰氧化物阶段的流体具有异常的铅/锌和锂/硼比值，这与二叠纪ROTLIEND盆地红层裂隙充填物中的流体非常相似。相比之下，与赤铁矿阶段有关的流体具有典型的地壳流体的铅/锌和锂/硼比值，这些流体来自于与结晶基底的相互作用。这两种流体都具有特有的元素比例，包括氯/溴，但大多数金属的绝对浓度是可变的。这表明，这两种流体都是通过与一种具有相似氯/溴比的普通贫金属卤水混合而得到改性的，这种卤水最有可能是来自上复Zechstein沉积岩的地层水。SAILAUF矿化提供了对基底-盖层界面上华力西期后长期流体演化的洞察。沉淀锰氧化物的成分异常流体类似于与红层相互作用形成的卤水，可能代表了库普费舍夫型沉积容矿铜矿床的成矿流体。相反，沉积赤铁矿矿化的流体类似于通常形成基底和沉积物赋存的铅锌矿床的流体。
The hydrothermal Mn–Fe–As vein mineralization at Sailauf (Germany) hosts a complex sequence of oxide and carbonate minerals that record a protracted fluid history. The mineralization is related to a major unconformity that separates Permian (Zechstein) sedimentary rocks from underlying Variscan crystalline basement. The hydrothermal veins contain two principal mineralization stages, which are Mn oxides associated with calcite and hematite associated with Mn-calcite. The fluid evolution of the hydrothermal system has been reconstructed from fluid inclusion petrography, microthermometry, and LA-ICPMS microanalysis, coupled with stable isotope geochemistry of carbonate and oxide minerals. The fluid inclusions are high salinity sodic–calcic brines and the bulk fluid properties show no major differences between the Mn oxide and the hematite stage. LA-ICPMS analysis of major and trace elements demonstrates that the mineralization formed from chemically distinct fluid pulses characterized by variations in their K, Li, B, Pb and Zn concentrations. The fluid that precipitated the Mn oxide stage has anomalous Pb/Zn and Li/B ratios, which closely resemble fluids found in fracture fillings in red beds of the Permian Rotliegend basin. By contrast, the fluids associated with the hematite stage have Pb/Zn and Li/B ratios typical of crustal fluids that were derived from interaction with crystalline basement. Both fluids possess characteristic element ratios including Cl/Br, but variable absolute concentrations of most metals. This suggests that both fluids were modified by mixing with a common metal-depleted brine that had a similar Cl/Br ratio, most likely a formation water from the overlying Zechstein sedimentary rocks. The Sailauf mineralization provides insight into the protracted post-Variscan fluid evolution at the basement–cover interface. The compositionally anomalous fluid that precipitated the Mn oxides is comparable to brines derived from interaction with red beds and likely represents the ore fluid of Kupferschiefer-type sediment-hosted Cu deposits. Conversely, the fluid that deposited the hematite mineralization resembles fluids that typically form basement- and sediment-hosted Pb–Zn deposits.