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Diagenetic minerals from saline diapirs as thermodynamic, chemical and isotopic tracers of evolution in the North Tunisian sedimentary basin and their impacts on ore deposits genesis
Carbonates and Evaporites ( IF 1.4 ) Pub Date : 2020-10-11 , DOI: 10.1007/s13146-020-00643-z
Mohja Dermech , Abdelkrim Charef , Mariem Trifi

To suggest the impacts of diapir evolutions on the ore deposits genesis, combined mineralogical, Raman spectrometry and C-, O- and H- isotopes studies of fluid inclusions trapped by their minerals were studied. In diapir zone, the evolution of hydrothermal fluids has been distinguished: type I hot fluids (365 °C) had formation water origin (δD ≈ − 21‰) and moderate salinity (12–23% wt% eq. NaCl) which were trapped by minerals where Mg/Ca ≥ 1, in particular, magnesite and secondary by dolomite 1. later, type II fluids less hot which were divided into two members. The first was the N2-dominant fluids (≈ 250 °C) and more saline (23–43 wt% eq. NaCl and/or KCl) which were trapped in particular by some dolomite 1, dolomite 2 and quartz. The end member was CO2-rich fluids; their trapping temperatures varying from 150 to 270 °C and salinities > 35 wt% eq. NaCl and/or KCl were trapped by minerals where Mg/Ca < 1, in particular in dolomite 2. These type II fluids were of formation water origin (− 52 < δD < − 16‰) which came probably from the dehydration of Triassic materials (mainly gypsum). All CO2 could be previously provided by thermal decomposition of Triassic carbonate. But N2 was of deep origin. The major halokinetic stages that happened at lower Cretaceous period and during the end of Tethysian rifting (associated to basic magmatism) had generated type I and II fluids. the last hydrothermal fluids (type III) derived from organic matter (− 80 < δD < − 65‰). Their temperature and salinity ranges were from 50 to 160 °C and 18.4–23 wt% eq. NaCl, respectively. type I hot fluids (365 °C) had formation water origin (δD ≈ − 21‰) and moderate salinity (12–23% wt% eq. NaCl) which were trapped by minerals where Mg/Ca ≥ 1, in particular, magnesite and secondary by dolomite 1. later, type II fluids less hot which were divided into two members. The first was the N2-dominant fluids (≈ 250 °C) and more saline (23–43 wt% eq. NaCl and/or KCl) which were trapped in particular by some dolomite 1, dolomite 2 and quartz. The end member was CO2-rich fluids; their trapping temperatures varying from 150 to 270 °C and salinities > 35 wt% eq. NaCl and/or KCl were trapped by minerals where Mg/Ca < 1, in particular in dolomite 2. These type II fluids were of formation water origin (− 52 < δD < − 16‰) which came probably from the dehydration of Triassic materials (mainly gypsum). All CO2 could be previously provided by thermal decomposition of Triassic carbonate. But N2 was of deep origin. The major halokinetic stages that happened at lower Cretaceous period and during the end of Tethysian rifting (associated to basic magmatism) had generated type I and II fluids. the last hydrothermal fluids (type III) derived from organic matter (− 80 < δD < − 65‰). Their temperature and salinity ranges were from 50 to 160 °C and 18.4–23 wt% eq. NaCl, respectively. The last halokinetic stage occurred during the dominant compressive and transpressive pyrenean and Alpine collision period. The similarities observed between geochemistry characteristics of type III and ore-bearing fluids of some peridiapiric mineralizations implying that only the last hydrothermal events had contributed to the genesis of ore deposits in the diapir zone.

中文翻译:

来自盐底辟的成岩矿物作为北突尼斯沉积盆地演化的热力学、化学和同位素示踪剂及其对矿床成因的影响

为了表明底辟演化对矿床成因的影响,研究了矿物学、拉曼光谱和 C-、O- 和 H- 同位素对被其矿物捕获的流体包裹体的组合研究。在底辟带,热液的演化已被区分:I 型热流体(365 °C)具有地层水来源(δD ≈ − 21‰)和中等盐度(12-23% wt% eq. NaCl)被困由 Mg/Ca ≥ 1 的矿物组成,特别是菱镁矿和次生由白云岩 1. 后来,II 类流体不太热,分为两部分。第一个是 N2 主导流体(≈ 250 °C)和更多的盐水(23-43 wt% eq. NaCl 和/或 KCl),它们特别被一些白云岩 1、白云岩 2 和石英捕获。最终成员是富含 CO2 的流体;它们的捕集温度从 150 到 270 °C 不等,盐度 > 35 重量%当量 NaCl 和/或 KCl 被 Mg/Ca < 1 的矿物质捕获,特别是在白云岩 2 中。这些 II 类流体是地层水来源 (- 52 < δD < - 16‰),可能来自三叠纪物质的脱水(主要是石膏)。以前可以通过三叠碳酸盐的热分解来提供所有 CO2。但是 N2 的起源很深。发生在下白垩纪和特提斯裂谷末期(与基本岩浆作用有关)的主要盐动力阶段产生了 I 型和 II 型流体。来自有机质的最后一种热液流体(III 型)(− 80 < δD < − 65‰)。它们的温度和盐度范围为 50 至 160°C,重量百分比为 18.4-23%。分别为氯化钠。I 型热流体 (365 °C) 具有地层水来源 (δD ≈ − 21‰) 和中等盐度 (12-23% wt% eq. NaCl) 被 Mg/Ca ≥ 1 的矿物,特别是菱镁矿和次生的白云岩 1. 后来,II 类流体不太热,分为两个成员。第一个是 N2 主导流体(≈ 250 °C)和更多的盐水(23-43 wt% eq. NaCl 和/或 KCl),它们特别被一些白云岩 1、白云岩 2 和石英捕获。最终成员是富含 CO2 的流体;它们的捕集温度从 150 到 270 °C 不等,盐度 > 35 wt% eq。NaCl 和/或 KCl 被 Mg/Ca < 1 的矿物质捕获,特别是在白云岩 2 中。这些 II 类流体是地层水来源 (- 52 < δD < - 16‰),可能来自三叠纪物质的脱水(主要是石膏)。以前可以通过三叠碳酸盐的热分解来提供所有 CO2。但是 N2 的起源很深。发生在下白垩纪和特提斯裂谷末期(与基本岩浆作用有关)的主要盐动力阶段产生了 I 型和 II 型流体。源自有机质的最后一种热液流体(III 型)(− 80 < δD < − 65‰)。它们的温度和盐度范围为 50 至 160°C,重量百分比为 18.4-23%。分别为氯化钠。最后一个晕动力学阶段发生在主要的压缩和反压作用的比利牛斯和阿尔卑斯碰撞时期。观察到的 III 型地球化学特征与一些周缘矿化的含矿流体之间存在相似性,这意味着只有最后一次热液事件才促成了底辟带矿床的成因。
更新日期:2020-10-11
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