Th, P, and Hf were immobile and Cu, Cr, and Zn were mobile during alteration processes. However, Torres-Alvarado et al. (2007) recently studied the effect of hydrothermal alteration on the chemistry of volcanic rocks from the Los Azufres geothermal field, Mexico, and found that most major elements and a few trace elements, including high field strength elements such as Zr, Ti, and P, were mobilized during hydrothermal alteration. They cautioned against the use of these elements for petrogenetic studies of igneous and metamorphic rocks. Although provenance studies are common (Hossain et al., 2010(Hossain et al., , 2014Armstrong-Altrin and Natalhy-Pineda, 2013), studies focused on the geochemical variation in sediments with respect to grain size are meagre (e.g., Ohta, 2008;Effoudou-Priso, 2014).The study areas of the San Nicolás (SN) and San Carlos (SC) beaches are located along the Gulf of California.

The petrographic and geochemical compositions of the Lower Miocene Moghra siliciclastic sediments in the Qattara Depression, north Western Desert, were investigated to infer their provenance, tectonic setting, palaeoweathering conditions, and diagenetic history. The Moghra Formation (~200 m thick) is dominated by sandstones intercalated with mudstone and carbonates. X‐ray diffraction analysis revealed that smectite, kaolinite, and illite are the dominant clay minerals found in mudstones. The sandstones are mainly subarkose, sublitharenite, and quartzarenite types with an average modal composition of Q89F6L5. The sandstones possess various diagenetic overprints including mechanical infiltration of clay, compaction, cementation, dissolution, and replacement. Major and trace element concentrations suggested that the parent rocks are intermediate to felsic in composition derived from the Neoproterozoic Arabian Nubian Shield. The weathering indices such as the chemical index of alteration and the plagioclase index of alteration implied that the intensity of chemical weathering in the source area was moderate under semi‐arid climatic conditions. On the other hand, the index of chemical variability indicates a low compositional maturity. The tectonic discrimination diagrams demonstrated a collision setting for the Arabian Nubian Shield, which represents the main supplier of sediments to the study area. Statistical parameters, sedimentary structures, and ichnofossil contents suggested that the Moghra sediments were deposited in a tidally‐influenced fluvial environment.

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Texture, mineralogy, geochemistry, and 14 C ages of two deep-sea sediment cores (GM6 and GM7) recovered in the southwestern Gulf of Mexico were investigated to infer their provenance and depositional condition. The sediments are enriched in fine-grained silt and clay and poor in sand content. Mineralogically, the sediments consist of quartz, calcite, smectite, and kaolinite. Based on the 14 C data, the age of the GM6 and GM7 sediment cores were calculated as 23,615 cal yrs. BP and 19,007 cal yrs. BP, respectively. The weathering indices such as chemical index of alteration (CIA), chemical index of weathering (CIW), and plagioclase index of alteration (PIA) in GM6 (56-69, 60-74, and 61-73, respectively) and GM7 (54-69, 57-76, and 55-74, respectively) cores revealed a moderate-to-high intensity of weathering. The rare earth element (REE) patterns suggested that the sediments were derived mostly by the weathering of intermediate rocks, exposed along the coastal regions of the Gulf of Mexico. The trace elemental ratios like V/Cr (<2), Ni/Co (<2), and Cu/Zn (<1), authigenic uranium content (<1), and Ce anomaly (Ce/Ce * ≤ 1) suggested that the sediments were deposited under an oxic condition, which was also revealed by the benthic foraminiferal assemblages throughout the GM6 and GM7 sediment cores.