Compositional Data Analysis (CoDA) of Clinopyroxene From Abyssal Peridotites
Compositional Data Analysis (CoDA) of Clinopyroxene From Abyssal Peridotites
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深渊橄榄岩中单斜辉石的成分数据分析 (CoDA)
DOI：
10.1029/2022gc010472
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Morishita T.
中科院分区：
文献类型：
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作者：
Nishio I.;Itano K.;Waterton P.;Tamura A.;Szilas K.;Morishita T.
为了更好地理解深海橄榄岩中单斜辉石的组成系统，我们利用对数比变换、主成分分析（PCA）和k均值聚类分析了一个大型深海橄榄岩单斜辉石组成数据库。我们将联合收割机的分析与开放系统熔融模型相结合，以研究成分变化的潜在来源。主成分分析表明，84%的单斜辉石组成的变化可以只用二维信息来表示。我们使用k-均值聚类将单斜辉石组合物分为四个簇。代表85%的数据的集群1-3，显示LREE/HREE的渐进式亏损，并与单斜辉石中Na 2 O的减少和尖晶石中Cr#的普遍增加有关。我们解释橄榄岩与单斜辉石组合物从集群1-3代表残留物的部分熔融提取。熔体萃取的程度从簇1增加到簇3，并且对组成变化施加主要控制。在尖晶石场熔融之前石榴石场熔融的存在或不存在以及部分熔融期间保留的熔融分数对单斜辉石组合物施加次级控制。第4组单斜辉石，代表在其寄主橄榄岩中表现出较低的LREE/HREE分馏，低-HREE丰度，高Sr和亏损特征。单斜辉石组合物在集群4不能单独熔融亏损建模。相反，它们只在我们的模型中重建，其中熔体-岩石相互作用，表明具有4簇单斜辉石的橄榄岩经历了这两个过程。在大多数脊中观察到第1-4类，反映了每个脊的成分不均匀性。这种变化反映了部分熔融程度、石榴石场熔融量、保留熔体分数和熔体-岩石相互作用的变化。
We analyze a large database of abyssal peridotite clinopyroxene compositions using log‐ratio transformation, principal component analysis (PCA) andk‐means clustering, to better understand clinopyroxene compositional systematics in abyssal peridotites. We combine this analysis with open‐system melting models to investigate the potential sources of compositional variation. PCA shows that 84% of the variation in clinopyroxene compositions can be represented using only 2‐dimensional information. We usek‐means clustering to classify clinopyroxene compositions into four clusters. Clusters 1–3, representing 85% of the data, show progressive depletions in LREE/HREE, and are associated with decreases in Na2O in clinopyroxene, and general increases in Cr# of spinel. We interpret peridotites with clinopyroxene compositions from clusters 1–3 to represent residues of partial melt extraction. The degree of melt extraction increases from cluster 1 to 3, and exerts a primary control on compositional variations. The presence or absence of garnet‐field melting prior to spinel‐field melting and the retained melt fraction during partial melting exert secondary controls on clinopyroxene compositions. Cluster 4 clinopyroxenes, representing show less fractionated LREE/HREE with low‐HREE abundances, elevated Sr, and depleted signatures in their host peridotites. Clinopyroxene compositions in cluster 4 cannot be modeled by melt depletion alone. Instead, they are only reconstructed in our models where melt‐rock interaction, suggesting that peridotites with cluster 4 clinopyroxenes have experienced both of these processes. Clusters 1–4 are observed in most ridges, reflecting compositional heterogeneity on each ridge. This variability reflects variations in the degree of partial melting, amount of garnet‐field melting, retained melt fractions, and melt‐rock interaction.