SGER: Exploring Intracrystalline Boron Isotope Variations

威廉斯EAR-0108852硼替代了粘土矿物中的铝，具有较大的同位素分馏。伊利石/蒙皂石(I/S)粘土比其他粘土类型含有更多的硼，也是沉积盆地中最常见的粘土。我们想验证这样一种假设，即这些粘土的硼含量和同位素比率代表了这些粘土在埋藏到生烃深度期间生长的古流体的温度和成分的有价值的监视器。对沉积物中B的研究主要集中在吸附B的行为及其随温度和pH的变化。然而，当温度超过100摄氏度时，吸附的B的分配系数接近0。因此，在成岩条件下，了解B在粘土矿物晶格中置换过程中的分馏是非常重要的。在R1有序化过程中，由于层电荷导致蒙脱石部分坍塌形成伊利石，I/S中的层间B大量增加。使用甘露醇洗涤，然后碱性阳离子饱和，我们能够分离吸附的，中间层和四面体的层-B。来自不同结晶点的每个种群具有不同的B同位素比率。利用这一技术，我们将研究B在低温条件下作为单矿物地质温度计的潜力。

WilliamsEAR-0108852Boron substitutes for Al in clay minerals with a relatively large isotope fractionation. Illite/smectite (I/S) clays incorporate more boron than other clay types and they are also most common in sedimentary basins. We want to test the hypothesis that the boron contents and isotopic ratios of these clays represent valuable monitors of the temperature and composition of the paleofluids from which they grew during burial to depths of hydrocarbon generation. Research on B in sediments has primarily focussed on the behavior of adsorbed-B and its variations as a function of T and pH. As temperatures exceed 100 degrees C, however, the distribution coefficient for adsorbed-B approaches 0. Therefore, under diagenetic conditions it is more important to understand the fractionation of B during substitution in the clay mineral lattice. There is a large increase in the amount of interlayer-B in I/S during R1 ordering, when the layer charges cause partial collapse of smectite to form illite. Using a mannitol wash, followed by alkali cation saturation we were able to separate adsorbed, interlayer, and tetrahedral layer-B. Each population from different crystallographic sites had a different B-isotope ratio. Using this technique we will study the potential of B as a single-mineral geothermometer under low temperature conditions.