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Provenance and Sedimentary Context of Clay Mineralogy in an Evolving Forearc Basin, Upper Cretaceous-Paleogene and Eocene Mudstones, San Joaquin Valley, California
Minerals ( IF 2.5 ) Pub Date : 2021-01-13 , DOI: 10.3390/min11010071
Andrew Hurst , Michael Wilson , Antonio Grippa , Lyudmyla Wilson , Giuseppe Palladino , Claudia Belviso , Francesco Cavalcante

Mudstone samples from the Moreno (Upper Cretaceous-Paleocene) and Kreyenhagen (Eocene) formations are analysed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) to determine their mineralogy. Smectite (Reichweite R0) is the predominant phyllosilicate present, 48% to 71.7% bulk rock mineralogy (excluding carbonate cemented and highly bio siliceous samples) and 70% to 98% of the <2 μm clay fraction. Opal CT and less so cristobalite concentrations cause the main deviations from smectite dominance. Opal A is common only in the Upper Kreyenhagen. In the <2 μm fraction, the Moreno Fm is significantly more smectite-rich than the Kreyenhagen Fm. Smectite in the Moreno Fm was derived from the alteration of volcaniclastic debris from contemporaneous rhyolitic-dacitic magmatic arc volcanism. No tuff is preserved. Smectite in the Kreyenhagen Fm was derived from intense sub-tropical weathering of granitoid-dioritic terrane during the hypothermal period in the early to mid-Eocene; the derivation from local volcanism is unlikely. All samples had chemical indices of alteration (CIA) indicative of intense weathering of source terrane. Ferriferous enrichment and the occurrence of locally common kaolinite are contributory evidence for the intensity of weathering. Low concentration (max. 7.5%) of clinoptilolite in the Lower Kreyenhagen is possibly indicative of more open marine conditions than in the Upper Kreyenhagen. There is no evidence of volumetrically significant silicate diagenesis. The main diagenetic mineralisation is restricted to low-temperature silica phase transitions.

中文翻译:

加利福尼亚圣华金河谷上白垩纪-上古生界和始新世泥岩演化的前陆盆地粘土矿物的物源和沉积背景

使用X射线衍射(XRD)和X射线荧光(XRF)分析了莫雷诺(上白垩纪-古新世)和克雷雅哈根(始新世)地层的泥岩样品,以确定其矿物学。绿土(Reichweite R0)是主要的页硅酸盐,块状岩石矿物学含量为48%至71.7%(不包括碳酸盐胶结物和高度生物硅质样品),而粘土含量<2μm的含量为70%至98%。蛋白石CT和更少的方石英浓度会导致与绿土优势度的主要偏差。蛋白石A仅在上克雷恩哈根(Kreyenhagen)常见。在小于2μm的馏分中,莫雷诺Fm比Kreyenhagen Fm富得多。莫雷诺火山岩中的蒙脱石是由同时期的流纹—胶泥岩浆弧火山作用引起的火山碎屑蚀变形成的。没有保存凝灰岩。Kreyenhagen Fm中的蒙脱石来源于始新世中期至中新世低温期间强烈的亚热带花岗岩-闪长岩地层风化。从本地火山活动中衍生的可能性不大。所有样品的化学变化指数(CIA)均表明源地强烈风化。铁的富集和局部常见的高岭石的出现是风化强度的有力证据。克雷恩哈根下游的斜发沸石浓度低(最高7.5%)可能表明比克雷恩哈根上游的海洋环境更为开放。没有证据表明硅酸盐的成岩作用明显。主要的成岩成矿作用仅限于低温二氧化硅相变。
更新日期:2021-01-13
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