کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4688901 1636018 2016 18 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Controls on reflux dolomitisation of epeiric-scale ramps: Insights from reactive transport simulations of the Mississippian Madison Formation (Montana and Wyoming)
ترجمه فارسی عنوان
کنترل های دولومیتیزاسیون ریفلاکس رمپ های مقیاس ایپی: مقیاس های شبیه سازی حمل و نقل واکنشی سازند مدیسون می سی پی (مونتانا و وایومینگ)
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی


• Large scale brine reflux across epeiric ramps is unfeasible.
• Pervasive dolomitisation of extensive ramps requires local-scale flow systems.
• Fluid flow is always focussed in coarse grained more permeable beds.
• Interbedded reactive but less permeable beds are preferentially dolomitised.

Prediction of the geometry and petrophysical properties of dolomite geobodies depends on understanding both the hydrological system supplying reactive fluids and the chemistry of these fluids. However, patterns are complicated by the non-linear response of the diagenetic system to depositional texture, which controls both fluid flux via permeability architecture and reaction rate via effective surface area. This study explores interactions between extrinsic controls (spatial distribution of brine composition and temperature) and intrinsic controls (permeability and reactivity) using local and regional scale reactive transport models of sequential episodes of brine reflux that resulted in partial dolomitisation of the Mississippian Madison ramp.Inter-well scale models show preferential early dolomitisation of fine grained, more reactive beds. Pervasive dolomitisation can occur most readily beneath the brine pool where flow is perpendicular to bedding, and is most rapid at high brine fluxes. Down-dip of the brine pool, bedding-parallel flow is focused in relatively permeable coarse grained beds, providing reactants for strongly preferential alteration of intervening more reactive fine grained beds. In contrast, thicker sequences of fine grained beds dolomitise more slowly, limited by the rate of supply of magnesium. Regional-scale models, with injection of brines of increasing salinity towards the ramp interior, reproduce the observed pattern of dolomitisation. However, more realistic simulations in which reflux is driven by lateral density contrasts, generate flow rates orders of magnitude too low for significant dolomitisation. Simulations suggest pervasive dolomitisation of epeiric-scale ramps by a platform-wide reflux circulation, as often invoked, is not feasible. Rather, dolomitisation of such extensive systems critically requires local-scale flow systems, such as may result from topographically-controlled variations in restriction of platform-top seawater circulation.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Sedimentary Geology - Volume 345, November 2016, Pages 85–102
نویسندگان
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