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Geology and geochemistry of carbonate-hosted Pb–Zn–F mineralizations from Jebel Lassel and Bou-Izem in the Kherrata area (Nappe zone of the Tellian Atlas Mountains, northern Algeria)
Carbonates and Evaporites ( IF 1.4 ) Pub Date : 2021-07-29 , DOI: 10.1007/s13146-021-00727-4
Djamel Eddine Mazari 1, 2 , Omar Kolli 1 , Abdelhak Boutaleb 1
Affiliation  

The Jebel Lassel (JL) and Bou Izem (BIZ) Pb–Zn–F mineralizations are widely found in the Djamila nappe which is the dominant structural unit in the Kherrata area (northern Algeria). They are hosted respectively in Upper Cretaceous limestone and marly limestone and in dolomite from a Triassic complex at the contact of the thrust sheets. They occur in tension veins of different fillings and directions which can be divided into several types: (i) galena-calcite veins, (ii) sphalerite-calcite veins, and (iii) fluorite-calcite veins. The mineralizations consist mainly of galena or sphalerite, fluorite, and pyrite. Supergene oxidation minerals include cerusite, smithsonite, and iron oxides. Calcite, dolomite, and to a lesser extent quartz are the main gangue minerals. Fluid inclusions (FI) from Bou Izem fluorite samples occur in three phases at room temperature (L + V + halite) and homogenize by the dissolution of the halite crystal after the vapor bubble has disappeared. They are characterized by high salinities (28–39% wt% NaCl equiv.) and high homogenization temperatures (Th) (222–299 °C). Single-phase fluid inclusions are very abundant in quartz crystals from the Bou Izem borehole samples. These inclusions contain a CO2 and CH4 mixture and are nearly pure methane with less than 10% CO2. At the Jebel Lassel anticline, FIs in fluorite and sphalerite exhibit low ice-melting temperatures (– 11 and – 37 °C) and homogenization temperatures in the liquid phase of 103–174 °C. Primary FIs in calcite studied in late crystals associated with sulfides and fluorite have Th of 141–196 °C, with the final ice-melting temperatures (Tm(ice)), ranging from − 37 to − 8 °C, corresponding to salinity values ranging between 14 and more than 23.2 wt% NaCl equiv. δ13CV-PDB values of the calcite gangue, which vary between − 1 and + 2‰, indicate an inorganic carbon origin and are consistent with a marine origin of the host rocks and heritage. Most δ18OV-SMOW values of calcites are between + 16 and + 25‰ and indicate that the oxygen isotopic compositions of the fluids varied between + 5 and + 16 ‰. These values are typical of deep brines in sedimentary basins. δ34SV-CDT values vary from 9.5 to 9.8 (galena) and from 12.7 to 14.5‰ (sphalerite), and the high temperature of the fluid exclude all possibilities of bacterial sulfate reduction and indicate that the source of the sulfur is the thermochemical reduction of sulfate from Triassic evaporites (δ34S = + 15‰). The fluorite samples from JL and BIZ reveal that all patterns fit into two different types without (Eu) and (Ce) anomalies. Combined, geological, mineralogical, isotopic, and geochemical data of vein mineralization at Jebel Lassel and Bou Izem confirm the epigenetic character of the mineralization and enable us to classify them as Mississippi Valley-type deposits.



中文翻译:

来自 Kherrata 地区(阿尔及利亚北部 Tellian Atlas 山脉的推覆带)的 Jebel Lassel 和 Bou-Izem 的碳酸盐岩 Pb-Zn-F 矿化的地质和地球化学

Jebel Lassel (JL) 和 Bou Izem (BIZ) Pb-Zn-F 矿化广泛存在于 Djamila 推覆岩中,该推覆岩是 Kherrata 地区(阿尔及利亚北部)的主要构造单元。它们分别赋存于上白垩统灰岩和泥灰岩以及冲断层接触的三叠系杂岩中的白云岩中。它们出现在不同充填物和方向的张拉脉中,可分为几种类型:(i)方铅矿-方解石脉,(ii)闪锌矿-方解石脉,和(iii)萤石-方解石脉。矿化主要由方铅矿或闪锌矿、萤石和黄铁矿组成。表生氧化矿物包括铜辉石、菱锌矿和氧化铁。方解石、白云石和少量石英是主要的脉石矿物。Bou Izem 萤石样品中的流体包裹体 (FI) 在室温下呈三相(L + V + 岩盐),并在蒸汽泡消失后通过岩盐晶体的溶解而均匀化。它们的特点是高盐度(28-39% wt% NaCl equiv.)和高均质温度(Th)(222-299 °C)。Bou Izem 钻孔样品的石英晶体中含有非常丰富的单相流体包裹体。这些内含物含有 CO2和 CH 4混合物,几乎是纯甲烷,CO 2少于 10% 。在杰贝尔拉塞尔背斜,萤石和闪锌矿中的 FIs 表现出较低的融冰温度(– 11 和 – 37 °C),液相中的均质温度为 103–174 °C。在与硫化物和萤石相关的晚期晶体中研究的方解石中的初级 FIs 的 Th 为 141–196 °C,最终的冰融化温度 (Tm (ice) ),范围从 − 37 到 − 8 °C,对应于盐度值范围在 14 和超过 23.2 wt% NaCl 当量之间。δ 13 C V-PDB方解石脉石的值在 - 1 到 + 2‰ 之间变化,表明无机碳来源并且与主岩和遗产的海洋来源一致。大多数方解石的δ 18 O V-SMOW值在 + 16 到 + 25 ‰ 之间,表明流体的氧同位素组成在 + 5 到 + 16 ‰ 之间变化。这些值是沉积盆地中深层盐水的典型值。δ 34 S V-CDT值在 9.5 到 9.8(方铅矿)和 12.7 到 14.5‰(闪锌矿)之间变化,流体的高温排除了细菌硫酸盐还原的所有可能性,表明硫的来源是热化学从三叠纪蒸发岩中还原硫酸盐 ( δ 34S = + 15‰)。来自 JL 和 BIZ 的萤石样品表明,所有图案都适合两种不同的类型,没有 (Eu) 和 (Ce) 异常。Jebel Lassel 和 Bou Izem 矿脉矿化的综合地质、矿物学、同位素和地球化学数据证实了矿化的表观遗传特征,使我们能够将它们归类为密西西比河谷型矿床。

更新日期:2021-07-29
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