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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Geomorphic and hydrological controls on groundwater dolocrete formation in the semi-arid Hamersley Basin, northwest Australia
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Geomorphic and hydrological controls on groundwater dolocrete formation in the semi-arid Hamersley Basin, northwest Australia

机译：澳大利亚西北半干旱地下水哈尔默斯利地区地貌与水文控制

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摘要

Groundwater dolocretes may exert an important geomorphic control on landscape evolution within sub-humid to arid regions. However, the geomorphic and hydrogeological settings of dolocrete remain poorly described. The hydrochemical conditions of dolomite precipitation in groundwater environments are also not well known. Classic models of dolocrete formation explain dolomite precipitation from highly evolved groundwaters at the terminus of major drainage but do not explain dolocrete distributed in regionally elevated landscapes, upgradient of major drainage. This study investigated the mineralogy, micromorphology and stable carbon and oxygen isotope compositions of three dolocrete profiles within a regionally elevated sub-basin of the Hamersley Ranges in the Pilbara region of northwest Australia. We sought to establish the environmental and hydrochemical conditions and present a model for dolocrete formation. We found that dolocrete formed within zones of emerging groundwater under saline-evaporitic conditions within internally draining sub-basins, most likely during the Late Miocene and Pliocene. Saline-evaporitic conditions were indicated by: (i) the mineralogy, dominated by dolomite, palygorskite and smectite; (ii) desiccation features and the presence of phreatic and vadose cements, indicative of a shallow fluctuating water table, and; (iii) dolomite delta O-18 values (median = -5.88 parts per thousand). Dolomite precipitation was promoted by evaporation and carbon dioxide degassing from shallow magnesium (Mg)-rich groundwater. These factors appear to have been the major drivers of dolocrete development without a requirement for significant down-dip hydrochemical modification. Primary dolomite precipitation was possible due to the presence of microbial extracellular polymeric substances (EPS). EPS provided negatively charged nucleation sites, which bound Mg2+, overcoming kinetic effects. High microbial activity within groundwater systems suggest these processes may be important for dolocrete formation worldwide and that groundwater dolocretes may be more pervasive in landscapes than currently recognized. (c) 2019 John Wiley & Sons, Ltd.
机译：地下水Dolocretes可能对潜伏地区的景观演变产生重要的几制控制。然而，Dolecrete的地貌和水文地质环境仍然差。白云岩沉淀在地下水环境中的水化学条件也不是众所周知的。 Dolocrete地层的经典模型解释了主要排水末端高度发展的地下水的白云石降水，但不要解释在区域升高的景观中分布的Dolocrete，主要排水升级。该研究研究了三个Doolocrete曲线在澳大利亚西北部Pilbara地区的区域升高的亚盆地内部盆地内的矿物学，微晶和稳定碳和氧同位素组成。我们试图建立环境和水化学条件，并提出了一种典型的Dolocrete地层模型。我们发现，在内部排水亚盆地内的盐水蒸发条件下，在新出现的地下水中形成的Dolecrete，最有可能在晚期内肾上腺和全环中。盐水蒸发条件是指：（i）矿物学，由白云石，甲岩和蒙脱土支配; （ii）干燥特征和潜水和散滤水泥的存在，指示浅波动水位，和; （iii）白云石ΔO-18值（中位数= -5.88份零份）。通过蒸发和二氧化碳从浅镁（Mg） - richwater脱气脱气，促进了白云石沉淀。这些因素似乎是Dolecrocrete发展的主要驱动因素，而无需显着下降浸的水化改性。由于存在微生物细胞外聚合物（EPS），初级白云石沉淀是可能的。 EPS提供带负电荷的成核位点，其结合MG2 +，克服动力学效果。地下水系统中的高微生物活动表明这些过程对于全球的Dolecrocrete地层可能是重要的，并且地下水Dolocretes可能比目前认可的景观更普遍。 （c）2019 John Wiley＆Sons，Ltd。

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