Abstract

Negative correlations between elements, molecules, or minerals can indicate a variety of geochemical processes, such as ion exchange, incongruent mineral precipitation/dissolution, and redox reactions. However, compositional data (those composed of relative parts) can also exhibit negative correlations simply due to displacement of one part by another, such as the addition of sodium chloride lowering the concentration of all ions other than sodium and chloride in a solution. Apart from this practical problem, the question is more general: how to address the relationships between components in data carrying relative information. For this purpose, the symmetric pivot coordinates were developed which allow for the identification of both positive and negative correlations between two parts in compositional data in terms of their relative dominance to the other parts. Accordingly, the symmetric pivot coordinate approach aggregates all of the logratios with those two parts of interest. This may not be desirable if data quality problems occur, because such parts would contribute the same weight to the coordinate as parts with good data quality. As a way out, the new method of weighted symmetric coordinates focusing on pairwise associations is proposed. In this approach, variables with large logratio variances are down-weighted to suppress their effect on the remaining variables, which is also demonstrated in a small simulation study. Finally, the weighted symmetric pivot coordinates are applied to chemistry data from a series of waste water samples from oil and gas wells produced from the lower Eagle Ford Group in the U.S. Gulf Coast Basin. In particular, strong negative correlations between ions are examined using this method to reveal processes which occur as a function of depth, including clay diagenesis, de-dolomitization, kerogen maturation, and sulfate and carbonate mineral saturation.

中文翻译：

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地球化学应用中组成数据的加权对称枢轴坐标

摘要

元素，分子或矿物之间的负相关可以指示各种地球化学过程，例如离子交换，矿物沉淀/溶解不一致以及氧化还原反应。但是，成分数据（由相对部分组成的数据）也可能仅由于一个部分被另一个部分置换而显示负相关，例如添加氯化钠会降低溶液中除钠和氯之外的所有离子的浓度。除了这个实际问题之外，这个问题更为笼统：如何处理携带相对信息的数据中组件之间的关系。以此目的，开发了对称的枢轴坐标，从而可以根据组成数据中两个部分相对于其他部分的相对优势来识别它们之间的正相关和负相关。因此，对称枢轴坐标方法将所有对数与感兴趣的这两个部分聚合在一起。如果发生数据质量问题，这可能是不希望的，因为这样的零件将为坐标提供与具有良好数据质量的零件相同的权重。作为一种解决方法，提出了一种以成对关联为重点的加权对称坐标的新方法。在这种方法中，对数对数方差较大的变量将进行权重降低，以抑制它们对其余变量的影响，这在小型模拟研究中也得到了证明。最后，加权的对称枢轴坐标被应用于来自美国墨西哥湾沿岸盆地下鹰福特集团生产的油气井的一系列废水样品的化学数据。特别是，使用此方法检查了离子之间的强负相关性，以揭示随深度而发生的过程，包括粘土成岩作用，脱白云石作用，干酪根成熟以及硫酸盐和碳酸盐矿物饱和度。