Chemistry and mineralogy of ODP Leg 124 sediment samples

From X-ray mineralogical studies and chemical analyses of the whole rocks and the fine fractions (<2 µm) of ten to fifteen samples at each site of ODP Leg 124, two major sources were identified in the sedimentary components of the Celebes and Sulu basins: (1) a terrestrial and continental contribution; (2) a volcanic influx that gives way to well-defined volcanic units or to a dilute contamination, consisting of coarse-grained minerals (Plagioclase, pyroxene, olivine, spinel) or a smectitic-rich fraction produced by the alteration of volcanic glasses and ashes.
The continental signature increases the amount of quartz in the rocks and the phyllitic association is complex: micas, kaolinite, disordered interstratified clay-minerals. The chemical compositions of the bulk rocks and the fractions <2 µm are more potassic and aluminum-rich. The volcanic imprint depends on the grain-size and chemical properties of the components. Ca/Na contents highly variable compared to the K content of the bulk composition are due to the presence of coarse-grained volcanic Plagioclase. The fractions <2 µm are more magnesian than in the continental regime.
The diagenesis is revealed by the crystallization of zeolites, the fixation of magnesium into the smectites that depletes the pore fluids in this element. Smectitization of the disordered interstratified clay minerals enriches the alkalinity of the pore fluids. Some deep formations of the Sulu Basin are affected by a thermal event, but no thermal event was recognized in the Celebes Basin.

基于对大洋钻探计划（Ocean Drilling Program，ODP）第124航次各站位的10至15件全岩及细粒组分（粒径<2 µm）样品的X射线矿物学研究与化学分析，研究人员在西里伯斯海盆与苏禄海盆的沉积组分中识别出两大主要物源：(1) 陆源-大陆成因贡献；(2) 火山物质输入，其既可形成特征明确的火山岩单元，也可表现为以粗粒矿物（斜长石(Plagioclase)、辉石(pyroxene)、橄榄石(olivine)、尖晶石(spinel)）构成的轻度混染形式，或是由火山玻璃与火山灰蚀变形成的富蒙脱石(smectite)组分。
大陆成因特征会提升岩石中石英的含量，且页状黏土矿物组合较为复杂，包含云母、高岭石以及无序层间黏土矿物。全岩样品与粒径<2 µm组分的化学组成整体更富钾与铝。火山作用的影响程度取决于组分的粒径与化学性质。全岩组分中钙钠比值相较于钾含量波动幅度更大，这是由于粗粒火山斜长石的存在所致。粒径<2 µm的组分相较于大陆成因体系，其镁含量更高。
成岩作用表现为沸石的结晶作用，以及镁被固定进入蒙脱石中，从而导致孔隙流体中镁元素发生损耗。无序层间黏土矿物的蒙脱石化作用会提升孔隙流体的碱度。苏禄海盆的部分深部地层受热事件影响，而西里伯斯海盆中未发现此类热事件。