Abstract
Zircons are abundant in the beach sediments. In this study, surface microtexture, mineralogy, bulk sediment geochemistry, trace element composition and U–Pb isotopic geochronology of detrital zircons collected from the Riachuelos and Palma Sola beach areas, southwestern Gulf of Mexico were performed to infer the sediment provenance and palaeoenvironment. The zircon microtexture was categorized as mechanically- and/or chemically-induced features. The weathering index values for the Riachuelos (~ 72–77) and Palma Sola (~ 71–74) beach sediments indicated moderate weathering of both of the two source areas. The major and trace element data of bulk sediments suggested passive margin settings for the two areas. The trace elemental ratios and chondrite-normalized rare earth element (REE) patterns of bulk sediments revealed that the sediments were likely sourced by felsic and intermediate igneous rocks. And the zircon Th/U ratios (mostly more than 0.2) and zircon REE patterns (with negative Eu and positive Ce anomalies) suggested a magmatic origin for both of the beach sediments from these two areas. Two distinct zircon age peaks respectively belonging to the Paleozoic and the Cenozoic were identified both in the Riachuelos and Palma Sola beach sediments. Zircon geochronology comparison research between the Riachuelos–Palma Sola beach sediments and potential source areas in SW Gulf of Mexico revealed that the source terrane supplied the Paleozoic zircons of this study was identified as the Mesa Central Province (MCP), and the Cenozoic zircons were transported from the nearby Eastern Alkaline Province (EAP). Moreover, although the Precambrian zircons were very few in the studied sediments, their geochronology and geochemistry results still could infer that they were contributed by the source terranes of Grenvillian igneous suites in the Oaxaca and the Chiapas Massif Complexes.
Highlights
Zircon is a common accessory mineral in clastic sediments, which retains U–Pb isotopic signatures during erosion, recycling, and transport; differences in zircon age populations in sediments are linked to the nature and age of source terranes (Ji et al 2019; Joy et al 2019; Liu et al 2019; Chaudhuri et al 2020)
4.1 Mineralogy of bulk sediments X-Ray diffraction analysis reveals that zircon, quartz, magnetite, and ilmenite are the major and chromite, geikielite, spinel, and labradorite are the minor minerals in the Riachuelos (Fig. 3a, b) and Palma Sola (Fig. 3c, d) beach sediments
4.2 Zircon CL images Zircons collected from the Riachuelos and Palma Sola beach sediments are mostly prismatic and showing oscillatory zoning with luminescent overgrowths, which supports for a magmatic origin (Fig. 5)
Summary
Zircon is a common accessory mineral in clastic sediments, which retains U–Pb isotopic signatures during erosion, recycling, and transport; differences in zircon age populations in sediments are linked to the nature and age of source terranes (Ji et al 2019; Joy et al 2019; Liu et al 2019; Chaudhuri et al 2020). Detrital zircon U–Pb age geochronology is reliable to infer provenance, as well as helpful to discriminate sediments derived from various source terranes and to understand their sediment-transport pathways (An et al 2016; Madhavaraju et al 2018; Wang et al 2018a). U–Pb ages of detrital zircons have been used widely in different studies to investigate sediment provenance, few studies recommended that the combination of zircon age data and trace element data is more reliable to better understand the depositional history of a complex depositional basin (Wang et al 2017; Li et al 2019). The mobile elements like K, Na, and Ca among major elements are useful to infer the weathering intensity and other palaeoenvironmental conditions of the source area (Barros dos Santos et al 2019)
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