Weathering, recycling, hydraulic sorting and metamorphism/metasomatism implications of the NE Gondwana lower Cambrian-Lower Cretaceous siliciclastic succession of Jordan

Abstract

Whole rock major elements, detrital and authigenic light, heavy, and clay minerals, and neoformed zeolite minerals of the NE Gondwana lower Cambrian-Lower Cretaceous siliciclastic succession of Jordan were investigated to evaluate the factors controlling the chemical composition of the sandstone. The provenance source rocks, controlled by the tectonic setting at the time of deposition of the subarkosic arenites and the quartzarenites were the principal mineral- and chemical-governing factor, followed by an interplay of chemical weathering, recycling, hydraulic sorting, diagenesis, and very-low grade metamorphism/hydrothermal metasomatism. The sandstone provenance was mainly granitoids of the Arabian Shield formed during the Neoproterozoic Gondwana amalgamation, and minor Paleozoic and Mesozoic siliciclastic strata. High CIA and low WIP weathering index values indicate an intensive chemical weathering event that affected the provenance during the early Cambrian-Middle Ordovician, and gave rise to mature first-cycle quartzarenites. High CIA/WIP and SiO2/Al2O3 ratios indicate a pronounced recycling in the Early Cretaceous responsible for super mature second-poly-cycled quartzarenites. The subarkosic arenites were formed either under a thorough chemical weathering, coupled with a high rate of erosion and a rapid deposition in adjacent braidplains, or an arid, glacial climate devoid of chemical weathering. Hydraulic sorting caused enrichment of Al and K in the detrital clay minerals, Ti in the silt-sized Ti-bearing minerals and Si in the sand-sized quartz. The very low-grade metamorphism/hydrothermal metasomatism, recorded here for the first time, is indicated by illite crystallinity (IC = 0.36° 2θ), illite-sericite-muscovite transformation, zeolites-apatite-authigenesis, and alteration of monazite and titanite-ilmenite into thorite and leucoxene/hematite.