Integration of Petrology with Aqueous Geochemistry in a Recent Mixing Zone, Southeastern Barbados, West Indies

巴巴多斯岛晚更新世凸起的礁台为研究碳酸盐岩的早期近地表成岩作用提供了无与伦比的环境。在巴巴多斯东南部现代混合带的岩心样品中发现了白云石。该白云岩可能年龄较近，与现代水化学有关。我们将通过岩心钻探、岩性、地球化学和水文地球化学研究进一步调查该白云岩的产状。四个钻孔将在东南迎风海岸线的海崖上钻，在这个地区有大量的大气潜水排放物和潜在的厚混合带。巴巴多斯东南部为测试混合模型与海洋模型提供了理想的场所，可以直接对与碳酸盐沉积物和正在成岩作用的岩石接触的新鲜、混合和正常的海洋孔隙水进行采样。混合区模型尚未得到普遍接受。因此，重要的是记录白云岩和孔隙流体的产状和地球化学，以检验该模型的有效性。这将通过矿物学、岩石学、微量元素、稳定同位素、锶同位素、流体包裹体和绝对测年技术来完成。与R. K. Stoessell合作，将对钻孔孔隙水的温度、盐度、电导率、pH、Eh、碱度、溶解氧、溶解硫化氢、主要和次要元素和离子、饱和度指数和稳定同位素组成进行表征。鉴于巴巴多斯的地质/水文环境，导致白云化的流体/岩石相互作用必然局限于正常的海水或混合的大气/海洋模式。这种综合岩石学和水文地球化学方法代表了一种全面的努力，以回答有关早期白云化过程的神秘问题，并将直接测试这些可能模型的可行性。

Late Pleistocene raised reef terraces on the island of Barbados provide an unparalleled setting to investigate early, near-surface diagenesis in carbonate rocks. Dolomite has been encountered in core samples from within the modern mixing zone in southeastern Barbados. This dolomite may be Recent in age and related to the modern water chemistry. We well further investigate this dolomite occurrence with additional core-drilling, lithologic, geochemical, and hydrogeochemical studies. Four boreholes will be drilled atop sea-cliffs along the windward southeastern coastline, in an area where there is significant meteoric phreatic discharge and a potentially thick mixing zone. Southeastern Barbados provides the ideal site to test the mixing versus marine models and to directly sample fresh, mixed, and normal marine pore waters in contact with carbonate sediments and rocks actively undergoing diagenesis. The mixing zone model has not received universal acceptance. It is therefore important to document the occurrence and geochemistry of the dolomite and pore fluids in question to test the validity of the model. This will be accomplished through minerologic, petrographic, trace element, stable isotope, strontium isotope, fluid inclusion, and absolute dating techniques. In collaboration with R. K. Stoessell, pore waters from the boreholes will be characterized by temperature, salinity, conductivity, pH, Eh, alkalinity, dissolved oxygen, dissolved hydrogen sulfide, major and minor elements and ions, saturation indices and stable isotopic compositions. Given the geologic/hydrologic setting of Barbados, the fluid/rock interactions responsible for dolomitization must necessarily be confined to either a normal seawater or mixed meteoric/marine model. This integrated petrologic and hydrogeochemical approach represents a comprehensive effort to answer important questions regarding the enigmatic process of early dolomitization, and will directly test the viability of each of these possible models.