Syn-rift hydrothermal circulation in the Mesozoic carbonates of the western Adriatic continental palaeomargin (Western Southalpine Domain, NW Italy),Basin Research

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Syn-rift hydrothermal circulation in the Mesozoic carbonates of the western Adriatic continental palaeomargin (Western Southalpine Domain, NW Italy)
Basin Research ( IF 2.8 ) Pub Date : 2021-08-16 , DOI: 10.1111/bre.12594
L. Barale ₁ , C. Bertok ₂ , A. d’Atri _{1,

2} , A. Mantovani ₂ , L. Martire ₂ , S. Agostini ₃ , S.M. Bernasconi ₄ , A. Gerdes ₅ , S. Ferrando ₂

Affiliation

Evidence of hydrothermal activity is reported for the Mesozoic pre- and syn-rift successions of the western Adriatic palaeomargin of the Alpine Tethys, preserved in the Western Southalpine Domain (NW Italy). The products of hydrothermal processes are represented by vein and breccia cements, as well as dolomitization and silicification of the host rocks. In the eastern part of the study area, interpreted as part of the necking zone of the continental margin, Middle Triassic dolostones and Lower Jurassic sediments are crossed by veins and hydrofracturing breccias cemented by saddle dolomite. The precipitation of dolomite cements occurred within the stratigraphic succession close to the sediment–water interface. Despite the shallow burial depth, fluid inclusion microthermometry and clumped isotopes show that hydrothermal fluids were relatively hot (80–150°C). In the western part of the study area, interpreted as part of the hyperextended distal zone, a polyphase history of host-rock fracturing is recorded, with at least two generations of veins cemented by calcite, dolomite and quartz. Vein opening and cementation occurred at shallow burial depth around the time of deposition of the syn-rift clastic succession. Fluid inclusion microthermometry on both quartz and dolomite cements indicates a fluid temperature of 90–130°C, again pointing to hydrothermal fluids. Both in Fenera-Sostegno and Montalto Dora areas, O, C and Sr isotope values, coupled with fluid inclusion and clumped isotope data, indicate that hydrothermal fluids derived from seawater interacted with crustal rocks during hydrothermal circulation. Stratigraphic and petrographic evidence, and U–Pb dating of dolomitized clasts within syn-rift sediments, document that hydrothermal fluids circulated through sediments from the latest Triassic to the Toarcian, corresponding to the entire syn-rift evolution of the western portion of the Adriatic palaeomargin. The documented hydrothermal processes are temporally correlated with regional-scale thermal events that took place in the same time interval at deeper crustal levels.

中文翻译：

亚得里亚海西部大陆古边缘中生代碳酸盐岩中的同裂谷热液环流（西南高山域，意大利西北部）

据报道，保存在西南高山域（意大利西北部）的高山特提斯亚得里亚海西部古边缘的中生代前裂谷和同裂谷序列存在热液活动的证据。热液过程的产物以脉和角砾胶结物以及主岩的白云石化和硅化为代表。在研究区东部，解释为大陆边缘颈缩带的一部分，中三叠统白云岩和下侏罗统沉积物被鞍状白云岩胶结的脉和水力压裂角砾岩穿过。白云石胶结物的沉淀发生在靠近沉积物-水界面的地层序列内。尽管埋藏很浅，流体包裹体显微温度测量和成簇同位素表明热液流体相对较热（80-150°C）。在研究区的西部，被解释为超伸展远侧带的一部分，记录了主岩压裂的多相历史，至少有两代由方解石、白云石和石英胶结的脉。脉张开和胶结发生在同裂谷碎屑序列沉积前后的浅埋深处。石英和白云石胶结物的流体包裹体显微温度测量表明流体温度为 90-130°C，再次指向热液流体。在 Fenera-Sostegno 和 Montalto Dora 地区，O、C 和 Sr 同位素值，加上流体包裹体和成簇同位素数据，表明源自海水的热液流体在热液循环过程中与地壳岩石相互作用。同裂谷沉积物中白云石化碎屑的地层学和岩相学证据以及 U-Pb 测年表明，热液流体在从最近三叠纪到托阿尔阶的沉积物中循环，对应于亚得里亚海古边缘西部部分的整个同裂谷演化. 记录的热液过程在时间上与更深地壳水平在同一时间间隔内发生的区域尺度热事件相关。对应于亚得里亚海古边缘西部部分的整个同裂谷演化。记录在案的热液过程在时间上与更深地壳水平在同一时间间隔内发生的区域尺度热事件相关。对应于亚得里亚海古边缘西部部分的整个同裂谷演化。记录在案的热液过程在时间上与更深地壳水平在同一时间间隔内发生的区域尺度热事件相关。

更新日期：2021-08-16

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