Abstract：
Cr(VI) is a carcinogen with proven mutagenic and genotoxic effects. The effects of the depositional environment (e.g., paleoweathering, paleoclimate, and paleoredox condition) on Cr enrichment in non-ultramafic aquifer solids are unclear. In this study, we presented the sedimentary characteristics of a borehole from a typical non-ultramafic aquifer with high Cr groundwater in Jingbian, central Ordos Basin, China. Chromium was enriched in the K1h sandstone aquifer, especially at depths of 400-500 m, with the highest value of mass transport coefficient (τAl,Cr) up to 92.13% and τAl,Fe up to 33.5%. The provenance of aquifer Cr was predominantly intermediate and felsic igneous rocks with a mafic rock mixture. This mafic source was inferred from Cr-rich granodiorite and mafic/ultramafic rocks in the Yinshan (Daqingshan-Wulashan) Block, northern Ordos Basin. The Cr-rich aquifer in K1h was developed due to a moderate chemical index of alteration (CIA) (mean, 56.7) under relatively warm and humid paleoclimate, as evidenced by high CIA-temperature (CIA-Temp) (mean, 6.79 °C) and paleoclimatic index values (mean, 0.40). Fe-Mn redox cycling in the oxic to suboxic environments contributed to aquifer Cr accumulation. Using path analysis, we identified that paleoclimate created favorable weathering conditions and enrichment of Fe contributed to the formation of high-Cr aquifers. The study reveals the formation of positive Cr anomalies in non-ultramafic aquifers, which is the potential source of groundwater Cr, and highlights the effects of depositional factors on Cr accumulation during aquifer deposition or early diagenesis. It can provide new insights into the natural processes of high-Cr sediments occurring in non-ultramafic aquifers.
摘要：
Cr（VI）是一种致癌物，具有经证实的诱变和遗传毒性作用。沉积环境的影响(例如，古气候,古气候，和古氧化还原条件）对非超镁铁质含水层固体中Cr富集的影响尚不清楚。在这项研究中,我们介绍了靖边典型的高Cr地下水非超镁铁质含水层钻孔的沉积特征，鄂尔多斯盆地中部，中国。K1h砂岩含水层中铬富集，特别是在400-500米的深度，具有最高的传质系数(τAl，Cr)高达92.13%和τAl，Fe高达33.5%。含水层Cr的来源主要是中间和长英质火成岩，具有镁铁质岩石混合物。这种镁铁质来源是从阴山（大青山-乌拉山）区块的富Cr花岗闪长岩和镁铁质/超镁铁质岩石中推断出来的，鄂尔多斯盆地北部。K1h中的富Cr含水层是由于适度的化学蚀变指数（CIA）而开发的（平均，56.7)在相对温暖潮湿的古气候下，如高CIA-温度(CIA-Temp)(平均值，6.79°C)和古气候指数值(平均值，0.40)。含氧到低氧环境中的Fe-Mn氧化还原循环有助于含水层Cr的积累。使用路径分析，我们发现古气候创造了有利的风化条件，Fe的富集有助于高Cr含水层的形成。该研究揭示了非超镁铁质含水层中Cr正异常的形成，这是地下水Cr的潜在来源，并强调了含水层沉积或早期成岩过程中沉积因素对Cr积累的影响。它可以为非超镁铁质含水层中发生的高Cr沉积物的自然过程提供新的见解。
