Journal
JOURNAL OF SEDIMENTARY RESEARCH
Volume 92, Issue 12, Pages 1141-1168Publisher
SEPM-SOC SEDIMENTARY GEOLOGY
DOI: 10.2110/jsr.2022.047
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Funding
- [DFG Forschergruppe 1644]
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This study focuses on the Triassic Latemar isolated platform in the Dolomite Mountains of northern Italy. It explores spatial and temporal gradients in processes and products related to contact metamorphism, dolomitization, and the dedolomitization of marine limestones. The findings show that fluid mixing resulted in the precipitation of two complex carbonate successions. The data from fluid inclusions and clumped isotopes reveal the complexity of a multi-fluid system and provide answers to the controversial interpretation of dolomitizing fluid temperature in Latemar.
This work focuses on an exceptionally complex natural laboratory, the Triassic Latemar isolated platform in the Dolomite Mountains of northern Italy. It explores spatial and temporal gradients in processes and products related to contact metamorphism, dolomitization, and the dedolomitization of marine limestones. Rock samples were studied using dual fluid-inclusion thermometry and clumped-isotope thermometry. Independent of the spatial position at Latemar, D47 clumped-isotope and fluid-inclusion data provide contrasting paleotemperature estimates. An apparent lack of systematic patterns in fluid-inclusion data (homogenization temperature, salinity, density) results from analyses of micrometer-sized growth zones within a single crystal. The composition of the individual fluid inclusions represents a ``snapshot'' of fluid mixing with variable endmember elemental ratios. The bulk crush-leach data and slopes in Caexcess versus Nadeficit diagrams indicate different water-rock interactions and fluid signatures with evaporation sequences and crystalline rocks. The presence of three fluid types (crystalline basement brine, halite-dissolution brine, seawater) in all carbonates suggests that all fluids coexisted during contact metamorphism and dolomitization of Latemar carbonates. Non-equilibrium processes overruled thermodynamic controls on the precipitation of diagenetic phases. Fluid mixing resulted in the precipitation of two complex carbonate successions. The D47 data represent bulk temperatures, averaging the mixing ratio of fluids with different temperatures and their respective volume. Fluid-inclusions record patterns of remarkable complexity and shed light on the complexity of a multi-fluid system. Data shown here provide answers to the controversial interpretation of dolomitizing fluid temperature in the Latemar and exemplify the strengths of multi-proxy paleotemperature studies.
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