Sediment Source Regions Research Articles

Petrographic signature of the gravel fraction from late Quaternary glacigenic sediments in the Ross Sea (Antarctica): Implications for source terranes and Neogene glacial reconstructions

The Ross Embayment is a key region to study the dynamics of the ice sheets during colder and warmer than present climatic conditions, because both the East and West Antarctic Ice sheets shed into the Ross Sea. Numerical modeling and reconstructions of the paleo ice flows during the Last Glacial Maximum show variable contribution of East and West Antarctic Ice sheets based on a variety of proxies. In this study, we present the first petrographic and minero-chemical investigation of the gravel-sized fraction of Last Glacial Maximum subglacial-glacimarine sediments collected with piston cores in a W–E transect across the Ross Sea. The clast petrographic features are compared with outcropping geology to individuate the sediment source regions. The gravel content of the glacigenic diamictite was classified on the basis of petrographic and minero-chemical features, and three main petrofacies were identified. They reflect changes in the basement geology of the source regions, allowing the reconstruction of the paleo ice flow pattern and their comparison with scenarios built up with other datasets. Moreover, the comparison with the Oligocene to Pleistocene glacigenic sediments provided information about the changes of the gravel signature across the Ross Sea and the erosion history of the source regions during Cenozoic.

Tracing uplift and erosion in orogenic settings using quartz luminescence sensitivity: Insights from the Northern Andes uplift

The optically stimulated luminescence (OSL) sensitivity of the fast component in quartz has been increasingly used in provenance analysis of Quaternary sediments. Quartz OSL natural sensitization is thought to be mainly controlled by the formation conditions of the source bedrock and surface processes occurring mainly in sediment source areas. Thus, quartz OSL sensitivity can be linked to distinct sediment source regions, based on their tectonic setting and erosion conditions. In this way, changes in quartz OSL sensitivity within siliciclastic successions would track variations in sediment provenance. So far, few works evaluated how the OSL sensitivity of quartz sand grains varies in sedimentary successions that experienced long-term cycles of deep burial, exhumation, and erosion. Therefore, this work aims to characterize the sensitivity of the fast OSL component of quartz sand grains retrieved from the Cenozoic sedimentary rocks of the Northern Andes basins and assess its spatiotemporal changes. We found that quartz grains with the lowest OSL sensitivity are sourced by crystalline and volcanic rocks related to the Andean Continental Arc emplaced in the Colombian Central Cordillera, reflecting the onset of denudation in orogenic sources during the Paleocene. Subsequently, increasing trends in OSL sensitivity are related to the sedimentary recycling during the Andean orogeny, reaching maximum values as a result of the progressive unroofing of Cretaceous rocks in the Colombian Eastern Cordillera, originally sourced from the low-relief Amazon Craton. Changes in quartz OSL sensitivity measured in the Cenozoic sedimentary basin-fill sequences of the Northern Andes vary according to the shifts in sediment provenance related to the orogenic construction and sediment recycling of the Andean range.

Geochemical Record of Late Quaternary Paleodepositional Environment from Lacustrine Sediments of Soda Lake, Carrizo Plain, California

This study investigates the responses of the depositional environments of Soda Lake sediments to climatic shifts from the Last Glacial Maximum to the Holocene epoch based on the results of major and trace elements of the North Soda Lake (NSL) NSL1A core. The NSL1A core records the sedimentary evolution of the Soda Lake watershed since at least 25 cal ka BP. Element analyses provide evidence that Soda Lake sediments are mostly derived from marine sequences in the Southern Coast Ranges of California. Variation in proxies for paleoweathering, paleoclimate, paleosalinity, paleoproductivity, paleoredox, and water depth is utilized to reconstruct the evolution of the sedimentary environment. The Chemical Index of Alteration (CIA) values indicate low to moderate chemical weathering in the sediment source regions. Paleoredox proxies indicate that the NSL1A core formed in a mainly subreduction environment. The NSL1A core is divided into four zones based on the results of the proxies. Zone 4 (5.0–5.8 m) of the sediment core indicates stable hydroclimatic conditions with low and constant sand and silt content, suggesting a warm and relatively humid environment. Zone 3 (3.35–5.0 m) represents the early half of the Last Glacial Maximum interval and a high lake stand. The elevated sand content suggests postflood events due to the northerly migration of westerly storm tracks. Zone 2 (1.075–3.35 m) reveals nuanced changes, including decreasing salinity, slight increases in wetness, detrital trace metals, and paleoproductivity. These subtle shifts suggest a multifaceted environmental evolution: a trend toward wetter conditions alongside a prolonged shift from cooler to warmer periods. Zone 1 (0.15–1.075 m) spans the Lateglacial to Holocene transition as well as Early and Middle Holocene, marked by significant hydrologic and ecologic variability including rapid warming during the Bølling–Allerød and rapid cooling linked to the Younger Dryas.

Provenance of the Copi North heavy mineral sands deposit, Murray Basin, Australia, based on the geochronology and geochemistry of detrital zircon, rutile and monazite

The Murray Basin hosts one of the world’s largest strandplain systems and has enormous potential for heavy mineral sand resources of titanium, zircon and rare earth elements. Further discovery of heavy mineral sand deposits can be aided via improved understanding of the source and transport of detrital heavy minerals of the basin. In this study, the provenance of two heavy mineral sand units of the Copi North deposit (western NSW) was determined using U–Pb geochronology and geochemistry of detrital zircon, rutile and monazite. Results from the two units are similar, indicating they derive from the same sources. Approximately 42% of the zircon population is aged <470 Ma and is interpreted to have been derived from the Tasmanides. Older zircon populations, up to ca 2.5 Ga, were largely derived from the Adelaide Superbasin and Delamerian Orogen, or from metasedimentary rocks of the Lachlan Orogen. Over 90% of rutile U–Pb ages are between 570 and 450 Ma, correlating either to Delamerian metamorphism or to detrital rutile from the Darling Basin; both sources are supported by rutile geochemistry that is indicative of a metasedimentary source. Most monazites have U–Pb ages of ca 600 Ma, which is consistent with an ultimate source from the Mt Arrowsmith Volcanics and/or Antarctica. A minor proportion of the monazite was sourced from igneous rocks of the New England Orogen. Temporal changes in sediment source regions can be inferred when considering the detrital mineral record for Copi North with other mineral sand deposits of the basin. Older (>ca 6.7 Ma) deposits such as Copi North feature a significant proportion of post-350 Ma detritus, reflecting the important role of the ancestral Darling River in supplying sediment from the north at the earliest stages of Murray Basin development. Post-6.7 Ma deposits lack a major component of detritus for far northern sources, and instead consist of sediment derived dominantly from western (Adelaide Superbasin) and eastern (Lachlan Orogen) sources, the latter delivered via the Murray River.

Basin provenance and its control on mineralisation within the Early Devonian Cobar Basin, western Lachlan Orogen, eastern Australia

The Cobar Basin, in central New South Wales, is an Early Devonian extensional basin that formed in the western Lachlan Orogen. The basin was filled with shallow- to deep-water sequences of the Cobar Supergroup and hosts small to large polymetallic deposits. Detrital zircon geochronology and whole-rock geochemical data collected from the Amphitheatre Group of the Cobar Supergroup provide constraints on the history of basin fill and illustrate the dynamic interplay between basin provenance and mineralisation, corresponding to the evolving tectonic regime. Data reveal provenance dissimilarity between the southern and northern parts of the basin. In the south, units of the Amphitheatre Group received abundant detritus from ca 430–410 Ma magmatic rocks situated to the southwest and southeast of the basin. By contrast, the northern successions were predominately sourced from recycled Ordovician basement found to the northwest, north, northeast of the basin, along with contributions associated with the Macquarie Arc. This spatial provenance variation, however, is less significant in the younger formations: the northern and southern sequences both exhibit an increase in older recycled detritus upwards with time. This reflects a progressive modification of basin paleogeography, during the transition from rift phase to sag phase. The rift-phase basin geography is characterised by fault-restricted deposition with predominant sediments derived from local proximal sources. The subsequent sag-phase subsidence exhibits a uniform depositional system with more homogenised basin input. This provenance variation is coeval with the stratigraphically controlled mineralisation features within the Amphitheatre Group successions, implying a provenance influence on mineralisation. Data suggest the different sediment source regions have produced distinct detrital mineral compositions between the major mineral-hosting and mineral-barren formations. The enrichment of some detrital minerals in the mineral-hosting units, such as feldspar, muscovite, Ti-minerals (and carbonate), is suggested to be an important factor for mineralisation in the basin.

An integrated petrographical and geochemical study of the Tredian Formation in the Salt and Trans‐Indus Surghar ranges, North‐West Pakistan: Implications for palaeoclimate

AbstractThe Middle Triassic Tredian Formation is well exposed in the western region of the Salt Range. It is mostly composed of sandstone with minor alternations of shales and dolomite. This is the first integrated attempt using petrographical and geochemical features to reveal palaeoclimate during deposition of the Tredian Formation. This work sheds light on the petrographical and geochemical properties of the Tredian sandstone in order to date various layers and evaluate the palaeoclimate. The formation was sampled at two distinct stratigraphic layers for petrographic and geochemical analysis of major and trace elements. The sandstone of the Tredian Formation is sub‐feldspathic to feldspathic arenite with sub‐angular to rounded grains that are moderately to extensively sorted. The relative proportions of the quartz, feldspars and lithoclasts in the examined sandstone samples shows that the Tredian sediments originated from the interior of the craton during a transitional continental regime. Chemical index of alteration values of 59, chemical index of weathering values of 67, and plagioclase index of alteration values of 74.5 indicate a low to moderate degree of weathering in the Tredian sediment source region. Based on the silica content, SiO2/Al2O3 ratios (2.7–6.1; mean 4.1), and chemical maturity index, it is deduced that the Tredian Formation was deposited in chemically immature to sub‐mature and dry to semi‐arid conditions. Geochemical proxies indicate the acidic source of sediment and deposition on the passive margin of the Indian Plate. The trace element characteristics of the sediments, especially the Rb/Sr, Cu/Zn, Ni/Co, V/Cr and Sr/Ba ratios, indicate that the sediments originated from the first weathering cycle and support the notion that they were deposited in an oxidising continental environment. A semi‐arid to arid palaeoclimate predominated through the Middle Triassic at the north‐western passive continental margin of the Indian Plate in the south‐eastern Neo‐Tethys.

Linking source and sink: The timing of deposition of Paleogene syntectonic strata in Central Asia

Abstract Determining the age of siliciclastic continental sequences in the absence of comprehensive biostratigraphy or radiometric dating of geological markers (e.g., volcanic layers) is inherently challenging. This issue is well exemplified in the current debate on the age of Cenozoic terrestrial strata in Central Asia, where competing age models constrained by non-unique paleomagnetic correlations are interpreted to reflect the growth of the Tibetan Plateau and its impact on Central Asian climate change. Here we present a new approach to evaluate competing age models by comparing the onset of rapid basement exhumation constrained by low-temperature thermochronology in the sediment source region with the initiation of growth strata in the adjacent sedimentary sink. We first validate this method in regions with well-constrained age models and subsequently apply this approach to the Tarim and Qaidam Basins in the northern Tibetan Plateau. The results of this analysis show that syntectonic sedimentation had already initiated during the Paleocene–Eocene and was followed by intensified Oligocene–Miocene mountain building along the northern margin of the plateau. Based on this refined Paleogene tectonic history, we further arrive at a temporal correlation between Paleogene tectonism in Northern Tibet and the retreat of the Proto-Paratethys Sea, a major water body that extended across Eurasia and was closely associated with climatic and biodiversity changes. We thus highlight the previously underestimated role tectonics in Northern Tibet had in the evolution and demise of the Proto-Paratethys Sea during the Paleogene.

Geochemical and mineralogical evidence for the formation of siderite in Late Permian coal-bearing strata from western Guizhou, SW China

This paper presents the results of the geochemical and mineralogical investigation of siderite in the Late Permian coal-bearing strata from western Guizhou, SW China. Siderite occurs as fine-grained ooids, as recrystallized stellate-like forms, as ellipsoidal, rhombohedral, and oolitic aggregates, indicating their authigenic origin. In contrast, pore filling and veinlet siderite are of epigenetic origin. The low sulfur contents, absence of pyrite, and Sr/Ba ratios indicate that the siderite was deposited in a freshwater (non-marine) environment. The V/(V + Ni) values of studied samples, ranging from 0.68 to 0.86, indicate that the siderite developed under anoxic conditions. The presence of authigenic kaolinite and epigenetic siderite in the same samplesuggests that the chemical conditions changed from acidic to alkaline conditions during early diagenesis.Iron in the siderite was not only derived from silicate weathering of high-Ti basalts in the sediment source regions followed by transport as ions by ground and surface waters, but was also generated from in situ alteration of the Fe-bearing minerals within the peat itself. In addition, ascending hydrothermal solutions would also contribute some Fe, with the Fe probably sourced from the leaching of the basaltic basement. The presence of siderite-rich layers indicates enhanced chemical weathering rates in the sediment source regions. The δ13CPDB, δ18OPDB, and δ18OSMOW values of siderite in claystones and mudstones vary within the ranges of −7.7 to 5.8‰, −12.1 to −6.6‰, and 18.4 to 24.1‰, respectively, indicating that carbon and oxygen primarily originated from marine carbonate, dehydroxylation of organic matter, carbonate dissolution, and hydrothermal fluids. The released CO2 invoked the alteration of reactive silicate minerals in the sediments, and ultimately the formation of siderite. Circulating pore fluids dissolving iron, which is derived from the silicate weathering of high-Ti basalts in the sediment source regions and from in situ alteration of the Fe-bearing minerals within the peat, would transport some iron from the overlying peat into the underlying sediments, and the flow of fluids would be diminished or stopped at the base of the peat due to the mechanical barrier of the impervious claystone or mudstone layers. The ferrous iron was precipitated due to the alkaline environment conditions of the peat, by reaction with HCO3− dissolved in the waters to form siderite.

Mineralogy and enrichment of critical elements (Li and Nb-Ta-Zr-Hf-Ga) in the Pennsylvanian coals from the Antaibao Surface Mine, Shanxi Province, China: derivation of pyroclastics and sediment-source regions

As a critical element, lithium plays an important role in a wide range of modern industries and in particular, battery storage and new energy technologies. Lithium in coal has attracted much attention in recent years because some coals are highly enriched in this element and consequently their corresponding coal combustion products may provide anm alternative source for this element. Previous studies showed that highly enriched Li in coals is generally associated with chlorite group minerals and in most cases attributed to the action of hydrothermal solutions. This paper provides mineralogical and geochemical data on the No. 9 Coal, the major minable coal from the Antaibao Surface Mine, Ningwu Coalfield, Shanxi Province, northern China, and focuses on the modes of occurrence and source of Li in this coal. The No. 9 Coal is a medium ash, medium sulfur, high volatile bituminous coal. The mineralogy of the No. 9 Coal is dominated by kaolinite, calcite, and pyrite, with minor amounts of anatase, rutile, goyazite, quartz, illite, boehmite, and bassanite, and traces of orthoclase, zircon and galena. The studied coal samples are characterized by high contents of Al2O3 (39.80% on average) in comparison with average Chinese coals, and high concentrations of Li, Ga, Se, Zr, Nb, Ta and Th compared with world hard coals. In addition to Li and Al, the critical elements Nb, Ta, Zr, Hf, and Ga in this coal also have a potential economic significance. The geochemical indicators (high Al2O3/TiO2, low Nb/Yb ratios and the specific rare earth element distribution patterns) and the mineral compositions (e.g., very low content of boehmite) indicate that the mineral matter in most coal benches and host rocks is dominantly derived from the Precambrian calc-alkaline granites of the Yinshan and northern Trans North China Orogens, and possibly from the bauxite of the Benxi Formation. Additionally, the geochemical and mineralogical characteristics of the intra-seam partings and some coal benches (quartz-free, kaolinite-dominated mineralogy, high Al2O3/TiO2 and Nb/Yb values) indicate that they were derived from an alkaline intermediate-felsic volcanic source. The highly enriched Li in the studied samples mainly occurs in kaolinite and is attributed to the input of material from sediment-source regions, rather than hydrothermal fluids. In addition, interaction of terrestrial and marine waters may have promoted the Li enrichment process in the partings.

A 10Be-based paleo-erosion record for the Qilian Shan (NE Tibet) over the past 4.2 Ma from a drillcore in the Hexi Corridor

Knowledge of erosion rates through time is of great importance to understand the effects of tectonics and climate on the topographic evolution of mountain belts. In this study, we present a 10Be-based paleo-erosion record for the northern Qilian Shan (NE Tibet) during the last 4.2 Ma. This new record is based on samples from a magnetostratigraphically dated drillcore from the foreland of the northern Qilian Shan (i.e., the Hexi Corridor). The 10Be-based paleo-erosion rates obtained from the drillcore lie between ~40 and ~150 m/Ma, with the exception of two transient peaks at ~3.4 Ma (~330 m/Ma) and ~2.0 Ma (~220 m/Ma). These high values may result from transitions to a generally cooler climate with more pronounced changes between glacial and interglacial periods. Apart from these peak values, erosion rates during the period from 4.2 to 2.8 Ma are rather low (~40 to ~70 m/Ma; mean: 50 m/Ma), whereas erosion rates over the last ~1.5 Ma are higher, ranging from ~80 to ~150 m/Ma (mean: ~112 m/Ma). We attribute the slower erosion between 4.2 and 2.8 Ma to a warmer climate, with more rainfall than today, and a lower relief in the sediment-source region. These factors led to a stabilization of hillslopes and caused erosion rates to be low. Subsequently, progressive cooling, aridification, and enhanced glacial and periglacial processes reduced the vegetation cover and increased hillslope erosion. In addition, ongoing rock uplift and concomitant river incision in the Qilian Shan may have increased the local relief. These factors explain the higher erosion rates in the past ~1.5 Ma. Available evidence on tectonic boundary conditions, drainage evolution, sedimentary environment, and paleo-climate conditions suggest that the geomorphology of the northern Qilian Shan has not significantly changed over that period.

Occurrence and origin of Cu, as and Se in a magmatic affected anthracite from the Yunjialing coal Mine, Handan Coalfield, northern China

This study investigated the elevated concentrations and modes of occurrence of trace elements such as Cu, As, and Se and sulfide minerals in the Pennsylvanian No. 9 coal seam from the Yunjialing Mine, the Handan Coalfield, north China. The techniques used for the investigation included electron probe micro-analysis, X-ray spectrometry, X-ray powder diffraction, atomic fluorescence spectrometry, and inductively-coupled plasma mass spectrometry. The coal in Yunjialing Mine is anthracite and is characterized by a high total sulfur content (0.61%–7.12%, dry basis). Minerals identified in the Yunjialing coal mainly include illite, quartz, calcite, and kaolinite and trace amounts of anatase, chalcopyrite, chalcocite, and chamosite. Furthermore, the studied coal samples are enriched in Cu content (431 μg/g on average, whole coal basis, the same below), with up to 1,095 μg/g in an individual coal ply. Moreover, the coals are slightly enriched in As (20.9 μg/g on average) and Se (4.27 μg/g on average).In this study, high proportions of albite and illite and almost all the quartz were derived from the sediment source region in the north of the basin. The high contents of sulfur and pyrite in the coal seam indicate the occurrence of seawater transgression during peat accumulation. However, the highly elevated concentrations of elements (especially S, Cu, and Ca) are found only in the upper part of the coal seam, along with ring-banded sulfide minerals (e.g., chalcopyrite and chalcocite), cleat- or fracture-filling calcite, and cavity-filling chamosite. These minerals were probably precipitated from the Ca-S-Fe-Mg-Cu-rich hydrothermal fluids generated by the igneous intrusions.

Mineral matter in the Pennsylvanian coal from the Yangquan Mining District, northeastern Qinshui Basin, China: Enrichment of critical elements and a Se-Mo-Pb-Hg assemblage

The Qinshui Basin, the largest reservoir of commercial coalbed methane in China, has attracted much attention and several studies have focused on the mineralogy and element geochemistry of coals in this basin. However, the sources of minerals and elements, particularly those of high-ash coals in the northeastern basin were yet unidentified. This study investigated mineralogy and geochemistry of the Pennsylvanian No. 8 Coal (including the roof strata and partings) from the Xinjing mine, northeastern Qinshui Basin, Shanxi Province, China. The Xinjing Coal is a low-ash, medium‑sulfur semi-anthracite. The minerals in the studied coals are mainly represented by kaolinite, illite, calcite, ankerite, siderite, dolomite, and pyrite. The Xinjing Coal is characterized by enriched Li, Zr, and Hg, and slightly enriched F, Ga, Ge, Se, Sr, Mo, Hf, and Pb. The diagrams of Al2O3-TiO2, Zr/TiO2-Nb/Y, as well as the REY (rare earth elements and Y) distribution patterns show that the sediment source region of the studied deposit is represented by the old granitoides, sedimentary rocks and bauxites of the Yinshan Upland located to the north of Qinshui Basin.In this study, three geological factors (sediment source regions, injections of hydrothermal fluids, and seawater) are identified as the dominant influences on geochemical and mineralogical compositions. Elevated concentrations of critical elements such as Li and Ga are dominantly derived from the sediment source region. Authigenic minerals including sulfides, quartz, carbonates, phosphates, and clausthalite, as well as the significant variations of Se-Mo-Pb-Hg assemblage across the coal seam, indicate that the Xinjing coal probably has been subjected to a multi-stage hydrothermal activities. Relatively high total sulfur contents (2.3% on average), framboidal pyrite, Sr/Ba (3.3) and Th/U values (2.2) suggest that seawater is another important geological factor affecting the Xinjing coal.

Improved Provenance Constraints for Nanaimo Group Sediments, British Columbia, Canada, Through Zircon LA‐ICP‐MS Depth‐Profiling

AbstractDetrital zircon from Late Cretaceous rocks of the Insular Superterrane have become an important constraint on Cordilleran paleogeography. These interpretations are largely based on the occurrence of a unique detrital zircon facies characterized by a broad Paleoproterozoic (mode 1.70 Ga) and narrow Mesoproterozoic mode (1.38 Ga) in Cordilleran sedimentary rocks. However, uncertainty about the provenance of this facies and the broad geographic distribution of rocks in which it is found limits its usefulness in constraining paleogeography. Detrital rims found on Mesozoic, Proterozoic, and Archean‐aged zircon cores from the Late Cretaceous Nanaimo Group of Western British Columbia, Canada provide constraints into its provenance. Depth‐profiling of a large population of grains (N = 16; n = 3,000), combined with observations regarding zircon external morphology, internal growth textures, U/Th ratios, and U concentrations, indicate high‐grade metamorphism occurred in the sediment source area between 99 Ma and 72 Ma. Rapid cooling of the metamorphic source area at rates of 35 to over 100°C/m.y. between 84 and 63 Ma was required to supply these metamorphic zircon to the basin. The geological history of the sediment source region defined by the rim populations (age of metamorphism and exhumation rate) is inconsistent with previously proposed sediment source areas for the Nanaimo Group in southern (Mojave region) or northern Laurentia (Lehmi Subbasin). We hypothesize that the sediment source area was the adjacent Coast Mountains Batholith and a metasedimentary rock, similar to the Pelona‐Orocopia‐Rand‐type schists, that was exhumed during the Late Cretaceous.

Critical element (Nb-Ta-Zr-Hf-REE-Ga-Th-U) mineralization in Late Triassic coals from the Gaosheng Mine, Sichuan Basin, southwestern China: Coupled effects of products of sediment-source-region erosion and acidic water infiltration

The Nb-Ta-Zr-Hf-REY-Ga mineralization in the Late Permian coals in southwestern China has been well investigated by several studies and has generally been attributed to alkaline pyroclastics coupled with input from hydrothermal fluids. The Late Triassic is one of the important coal-forming periods but the critical element mineralization in coals of this geological age has not been well documented. In this paper, the mechanism of Nb-Ta-Zr-Hf-REE-Ga-Th-U mineralization in the K5 coal seam of the Upper Triassic Xujiahe Formation from the Gaosheng Mine, Sichuan Basin, southwestern China, was investigated. The K5 coal is a high-ash, low-sulfur, and low-volatile bituminous coal. The minerals in this coal include illite, kaolinite, quartz, and, to a lesser extent, anatase, calcite, chamosite, bassanite, and pyrite, along with traces of ankerite, rutile, and zircon. Compared with the averages of common world hard coals, the studied coals are enriched in critical elements including Zr (247 ppm), Hf (5.56 ppm), Nb (23 ppm), Ta (1.55 ppm), rare earth elements and yttrium (REY, 168 ppm), Ga (18.3 ppm), Th (14.1 ppm), and U (6.18 ppm) (all on a whole coal basis). The Al2O3/TiO2 ratios, Eu anomalies, and the relationships of Al2O3/TiO2 vs. Zr/TiO2 and Nb/Yb suggest that the sediment-source rocks of the Gaosheng coals were Neoproterozoic and Early-Middle Triassic felsic-intermediate igneous rocks from the southeastern Qinling and Longmenshan Orogens, along with the Hannan and Micangshan-Dabashan Uplifts. Other probable sources are contemporaneous felsic-intermediate pyroclastics from the Late Triassic volcanic areas around the Sichuan Basin (i.e., East Kunlun Orogen, West Qinling Orogen, and East Tibetan Plateau). The relationships of Al2O3/TiO2 vs. Zr/Al2O3, Al2O3/TiO2 vs. Nb/Al2O3, Ga/Al2O3, and Al2O3/TiO2 vs. LREY/Al2O3 further indicate that the elevated concentrations of Nb(Ta)-Zr(Hf)-REY-Ga in the Gaosheng coal are probably sourced from both the erosion of sediment-source regions and contemporaneous pyroclastics. The illite-kaolinite aggregates with a vermicular texture and authigenic illite, quartz, anatase, pyrite, calcite, ankerite, barite, and REE-rich minerals, REY distribution patterns, as well as elemental variation trends of the coal seam, collectively indicate that the studied coals were likely influenced by multiple-stage infiltration of various solutions. These solutions leached the fresh pyroclastics and products of erosion derived from granites in the sediment-source regions, leading to redistribution of the critical elements (e.g., Zr, Nb, and HREY) between the roof, floor, and parting mudstones and the coal benches. The concentrations of (Nb,Ta)2O5, (Zr,Hf)2O5, and Ga in the coals are 107, 1093, and 57.6 ppm, respectively, close to or higher than the marginal grade of conventional ore deposits for these elements, and thus the Gaosheng coals have potential as raw materials for the recovery of the critical metals Nb, Ta, Zr, Hf, and Ga.

Denudation of the Cordillera and intraplate belt in central Patagonia inferred by detrital multi-dating of foreland basin deposits

The evolution of central Patagonia is associated with episodic shortening and extension that have greatly affected the topography of the Cordillera and intraplate belt. The San Jorge Basin is a site of sediment accumulation in the foreland that is surrounded by igneous and broken foreland relief. The latter originated from episodic deformation and reactivation of inherited structures associated with a period of slab shallowing that allowed the far-field transmission of Andean stresses to the foreland. Thus, due to of its location, the San Jorge Basin provides an exceptional opportunity to study the denudation of both Cordilleran and intraplate topography during the Cenozoic, particularly during the late Eocene–early Miocene interval of mild deformation. In this study, we use a single-grain geochronological approach combining apatite fission tracks and UPb dating on apatite, along with maximum deposition ages obtained from UPb zircon dating for Neogene foreland basin deposits, to distinguish between two distinctive sediment source regions in central Patagonia during the Cenozoic, despite the persistent volcanic signal. A compilation of previously published cooling ages combined with our new data define: (i) a dominant local source from the northern broken foreland from the late Eocene until the early Miocene; and (ii) a widespread source in the Cordillera during the Miocene based on a very uniform thermochronological signal observed throughout the entire foreland. Therefore, this study provides new insights into the variation in sediment sourcing in the central Patagonian foreland. This variation is primarily controlled by the decrease of post-orogenic erosional processes during a period of relative tectonic quiescence following the highly active Early Cretaceous–middle Eocene time interval.

Latest Cretaceous and Paleocene biostratigraphy and paleogeography of northern Zealandia, IODP Site U1509, New Caledonia Trough, southwest Pacific

ABSTRACT IODP Site U1509 (Expedition 371), New Caledonia Trough, provides a rare latest Cretaceous–Paleocene record from offshore northern Zealandia. We present new palynomorph and benthic foraminiferal assemblage data that show a transition from a latest Cretaceous vegetated sediment source region to a fully oceanic environment in the Paleocene. Latest Cretaceous (c. 68–66 Ma) non-calcareous claystone was deposited in upper bathyal paleodepths, with abundant plant microfossils that were likely transported in a northwest direction through the Aotea Basin region. A 2–3 Myr unconformity is identified at the Cretaceous/Paleogene boundary. Middle early–late Paleocene (c. 63.5–56 Ma) calcareous claystone shows evidence of deepening, deposited in middle bathyal or deeper paleodepths, and terrestrial input is minor. This latest Cretaceous to Paleocene deepening trend is consistent with inferred evolution of the Aotea and Northland basins further to the east, and other sparse northern Zealandia records, which show a common pattern of post-rift transgression consistent with long-term subsidence. Site U1509 allows for biogeographic extension and modification of the New Zealand Paleocene dinoflagellate zonation, description of a new dinoflagellate and pollen species, better inference of regional paleogeography, and may provide insights into the onset of western Pacific subduction initiation.

Granite-bauxite provenance of abnormally enriched boehmite and critical elements (Nb, Ta, Zr, Hf and Ga) in coals from the Eastern Surface Mine, Ningwu Coalfield, Shanxi Province, China

Critical elements in coal have attracted much attention in recent years as some coals and coal combustion products may provide an alternative source of these. This paper provides mineralogical and geochemical data on the No. 4 coal seam, the major minable coal from the Eastern Surface Mine, Ningwu Coalfield, Shanxi Province, northern China. It also discusses the provenance of mineral matter, the origin of aluminum minerals (boehmite), carbonates (calcite and ankerite) and phosphates (goyazite) and the potential economic significance of critical elements (e.g., Al, Nb, Ta, Zr, Hf, and Ga). Mineralogically, the studied coal samples are characterized by high kaolinite (64.7% on average, low-temperature ash basis) and boehmite (24.1%) contents, followed by carbonates (calcite, ankerite, siderite, and dolomite), titanium oxides (anatase and rutile), goyazite, quartz, and apatite. In comparison with average values for Chinese coals, the studied coal samples are characterized by high Al2O3 contents (mean 11.82% on a whole-coal basis and mean 49.49% on an ash basis). Compared with world hard coals, the No. 4 Coal is enriched in Ga, Se, Zr, Nb, La, Ce, Hf, Ta and Pb. In addition to Al, critical elements including Nb, Ta, Zr, Hf, and Ga in this coal have an economic significance. The Al2O3/TiO2 vs. Nb/TiO2, Al2O3/TiO2 vs. Zr/TiO2, Zr vs. Nb, Hf vs. Ta, and REY distribution patterns (REY, rare earth elements plus Y), indicate that the provenance of mineral matter (e.g., boehmite and critical elements Nb, Ta, Zr, Hf and Ga) in the No. 4 Coal is a number of sediment-source regions including the Neoarchean granites of the Yinshan Oldland, and the Paleoproterozoic granites and Benxi Formation bauxites (Late Carboniferous, to the northeast of the coal basin) of the northern Trans North China Orogen. Carbonate minerals (calcite and ankerite) are of epigenetic origin while the phosphate mineral (goyazite) was syngenetically deposited in the peat swamp during a period of a low water table.

Mineralogical and geochemical characteristics of tonsteins from the Middle Jurassic Yan'an Formation, Ordos Basin, North China

Although the Jurassic features a considerable accumulation of coal worldwide, only a few tonsteins within coal seams in this coal-forming period have been investigated. This paper presents the detailed mineralogical and geochemical compositions of six tonstein layers from the Middle Jurassic Yan'an Formation, Ordos Basin, North China. Based on the typical evidence of the distinct field characteristics occurring as paler thin beds with lateral continuity; conchoidal and flint-like fracture planes; sharp contacts with adjacent coals; and the mineralogical compositions, such as vermicular kaolinite, angular quartz, and euhedral zircon crystals with a single UPb age peak, the intra-seam clay beds of the Yan'an Formation were determined to have been mainly derived from a significant pyroclastic source. However, rounded quartz, muscovite, and detrital zircon grains in the tonsteins reflect minor contribution of terrigenous debris from sediment source regions. Moreover, a line of geochemical features including low TiO2/Al2O3 values, Al2O3/TiO2-Nb/Yb, and Al2O3/TiO2-Zr/TiO2 diagrams; low REY concentrations with high fractionation between light REE and heavy REY (REY, rare earth elements and Y; REE, rare earth elements); and pronounced negative Eu anomalies, suggest that the tonsteins have a felsic (rhyolitic) magma origin. A systematic geochemical analysis of enclosing coals of the tonsteins was also conducted to determine the leaching behavior of the trace elements from the tonsteins into the enclosing coals. The results show that Th, U, Nb, Ta, Zr, and Hf tend to be enriched in the overlying and underlying coals and have an enrichment width of up to 30 cm. Similarly, the elevated concentrations of Zn, Rb, Cs, Pb, La, Ce, Pr, and Nd only occur in a relatively narrow zone above and below the tonsteins. The width of the enrichment in the enclosing coals may be mainly related to the properties of the tonsteins, e.g., thickness and original volcanogenic material, the characters of elements including mobility and concentration, and the nature of coals, such as coal rank.

Petrology and geochemistry of Devonian cutinitic liptobioliths from northwestern China

Devonian cutinitic liptobioliths from northwestern China are notable for their distinct papery, sheet-like texture and unusually high cutinite content (>60%). They are bituminous coals with an exceptionally high yield of volatile matter and hydrogen content. Their measured random values of vitrinite reflectance range from 0.60% to 0.68%. Cutinitic liptobioliths are mainly composed of ribbon-like cutinites and collotelinites, usually showing alternations under the microscope. The cutinites are thick-walled types, with a width of 50–300 μm. The ribbon-like collotelinites are sandwiched by cutinites, representing a section through a ribbon-like stem. Fissures or cleats, caused by shrinkage, can be observed in collotelinites. Other macerals, particularly inertinite, are only present in small amounts. Lycopsids are suggested to be the dominant coal-forming plants based on spore and plant fossil research. The coal petrological characteristics and redox-sensitive trace element ratios indicate an anoxic peat depositional environment with still water or a weak current, different from the favorable conditions for massive cutinite accumulation. The formation of cutinitic liptobioliths was attributed to the unique structure and composition of Devonian land plants rather than the peat depositional conditions. During the Middle Devonian, well-developed cuticles and undeveloped woody tissues in early land plants may have resulted in the deposition of cutinitic liptobioliths. This is consistent with the fact that nearly all such coal deposits occur in the Middle Devonian.Low boron and sulfur contents in the coals support a freshwater depositional condition, which is different from that of the Luquan Devonian cutinitic liptobiolith from southwestern China. The dominant sediment-source regions for the studied cutinitic liptobiolith and its host rocks are the Xiemisitai-Shaerbuerti Mountains, as indicated by their elemental compositions. However, widespread hydrothermal solutions resulted in the enrichment of Nb, Ta，Zr, and Hf elements and heavy rare earth elements (HREEs) in the liptobioliths and their host rocks.

Evolution of the Late Cretaceous Nanaimo Basin, British Columbia, Canada: Definitive provenance links to northern latitudes

AbstractAccurate reconstruction of the Late Cretaceous paleogeography and tectonic evolution of the western North American Cordilleran margin is required to resolve the long-standing debate over proposed large-scale, orogen-parallel terrane translation. The Nanaimo Basin (British Columbia, Canada) contains a high-fidelity record of orogenic exhumation and basin subsidence in the southwestern Canadian Cordillera that constrains the tectonic evolution of the region. Integration of detrital zircon U-Pb geochronology, conglomerate clast U-Pb geochronology, detrital muscovite 40Ar/39Ar thermochronology, and Lu-Hf isotopic analysis of detrital zircon defines a multidisciplinary provenance signature that provides a definitive linkage with sediment source regions north of the Sierra Nevada arc system (western United States).Analysis of spatial and temporal provenance variations within Nanaimo Group strata documents a bimodal sediment supply with a local source derived from the adjacent magmatic arc in the southern Coast Mountains batholith and an extra-regional source from the Mesoproterozoic Belt Supergroup and the Late Cretaceous Atlanta lobe of the Idaho batholith. Particularly robust linkages include: (1) juvenile (εHf &amp;gt;+10) Late Cretaceous zircon derived from the southern Coast Mountains batholith; (2) a bimodal Proterozoic detrital zircon signature consistent with derivation from Belt Supergroup (1700–1720 Ma) and ca. 1380 Ma plutonic rocks intruding the Lemhi subbasin of central Idaho (northwestern United States); (3) quartzite clasts that are statistical matches for Mesoproterozoic and Cambrian strata in Montana and Idaho (northwestern United States) and southern British Columbia; and (4) syndepositional evolved (εHf &amp;gt;−10) Late Cretaceous zircon and muscovite derived from the Atlanta lobe of the Idaho batholith. These provenance constraints support a tectonic restoration of the Nanaimo Basin, the southern Coast Mountains batholith, and Wrangellia to a position outboard of the Idaho batholith in Late Cretaceous time, consistent with proposed minimal- fault- offset models (&amp;lt;~1000 km).