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Critical elements in coal and coal-bearing sequences (e.g., Li, Sc, V, Ga, Ge, Se, Y and rare earth elements, Zr, Nb, Au, Ag, platinum group elements, Re, and U) have attracted great attention because their concentrations in some cases may be comparable to those of conventional ore deposits. The enrichment of critical elements in coals, particularly those of Carboniferous-Permian and Cenozoic ages, have generally been attributed to within-plate (plume-related) volcanism and associated hydrothermal activity. However, Cretaceous coals are not commonly rich in critical elements, with the exception of some (e.g., Ge and U) in localised areas. This paper globally reviewed metalliferous coals from Siberia, the Russian Far East, Mongolia, South America, the United States and Mexico, Canada (Alberta and British Columbia), China, Africa, and Australasia (Victoria, Queensland, New South Wales, South Australia, Northern Territory, New Zealand, Nelson, West Coast, Canterbury, Otago, and Southland). The world-class Ge-U or Ge deposits in North China, Mongolia, and Siberia are the only commercially significant representatives of the Cretaceous metalliferous coals, which are related to bio-chemical reduction of oxidized meteoric, hydrothermal, or sea waters by organic matter of the peat bogs. The common Cretaceous coals worldwide are generally not rich in critical elements because intensive igneous activity led to extensive acidification of terrestrial and marine waters, which are responsible for the low coal metallogenesis during the Cretaceous period, especially the Early Cretaceous time. [ABSTRACT FROM AUTHOR]

A compliance-based excavation on Parramatta River (western Sydney) found evidence of a brief visitation by Aboriginal people during the terminal Pleistocene (c.14 ka), from which an exotic raw material–medium-grained porphyroblastic andalusite-cordierite hornfels–was recovered. This raw material is rare in the region, only found in the Megalong Valley situated some 75 km west of the site in Parramatta, and separated from the site by the Blue Mountains–a 40 km wide, 1 km high dissected sandstone upland. Historical observations and geological evidence suggest that the Coxs River, which runs through the upland, formed the probable connection between the two locales. The formation of the site at c.14 ka, along with our broader understanding of the region, suggests that the upland was only explored after the Last Glacial Maximum (LGM) and that the Great Dividing Range may have formed a significant barrier to early peopling of Sahul. Further, a delay between the end of the LGM and the exploration of the region implies populations were severely affected by the event and required considerable time to recover. The coincident timing of rapid sea-level rise from Meltwater Phase Pulse 1A and an increased supply of moisture associated with the Antarctic Climate Reversal at the time of many site initiations may have been factors in the upland and south west slopes visitation. Finally, the movement of the unusual hornfels artefact provides a coarse indication of the ranging territory for hunter-gatherers living in a temperate region (c. 8,000 km2) at this time. This is probably a lower estimate but begins to provide a quantitative value with which to begin to ratify the increasing divergence between archaeological and genomic studies in their definitions of mobility, sedentism and regional nomadism. [ABSTRACT FROM AUTHOR]

The clay mineralogy of pyroclastic Nb(Ta)-Zr(Hf)-REE-Ga mineralization in Late Permian coal-bearing strata from eastern Yunnan Province; southwest China was investigated in this study. Samples from XW and LK drill holes in this area were analyzed using XRD (X-ray diffraction) and SEM (scanning electronic microscope). Results show that clay minerals in the Nb-Zr-REE-Ga mineralized samples are composed of mixed layer illite/smectite (I/S); kaolinite and berthierine. I/S is the major component among the clay assemblages. The source volcanic ashes controlled the modes of occurrence of the clay minerals. Volcanic ash-originated kaolinite and berthierine occur as vermicular and angular particles, respectively. I/S is confined to the matrix and is derived from illitization of smectite which was derived from the original volcanic ashes. Other types of clay minerals including I/S and berthierine precipitated from hydrothermal solutions were found within plant cells; and coexisting with angular berthierine and vermicular kaolinite. Inferred from the fact that most of the I/S is R1 ordered with one case of the R3 I/S; the paleo-diagenetic temperature could be up to 180 °C but mostly 100-160 °C. The micro-crystalline quartz grains (<10 µm) closely associated with I/S were observed under SEM and were most likely the product of desiliconization during illitization of smectite. [ABSTRACT FROM AUTHOR]

Silicic, mafic and alkali intra-seam tonsteins have been known from SW China for a number of years. This paper reports on the geochemical compositions of coals and tonsteins from three seam sections of the Songzao Coalfield, SW China, and evaluates the geological factors responsible for the chemical characteristics of the coal seams, with emphasis on the influence from different types of volcanic ashes. The roof and floor samples of the Songzao coal seams mostly have high TiO2 contents, consistent with a high TiO2 content in the detrital sediment input from the source region, namely mafic basalts from the Kangdian Upland on the western margin of the coal basin. The coals from the Songzao Coalfield generally have high ash yields and are highly enriched in trace elements including Nb, Ta, Zr, Hf, rare earth elements (REE), Y, Hg and Se; some variation occurs among different seam sections due to input of geochemically different volcanic ash materials. The geochemistry of the Songzao coals has also been affected by the adjacent tonstein/K-bentonite bands. The relatively immobile elements that are enriched in the altered volcanic ashes also tend to be enriched in the adjacent coal plies, possibly due to leaching by groundwaters. The coals near the alkali tonstein bands in the Tonghua and Yuyang sections of the Songzao Coalfield are mostly high in Nb, Ta, Zr, Hf, Th, U, REE and Y. Coal samples overlying the mafic K-bentonite in the Tonghua section are high in V, Cr, Zn and Cu. The Datong coal, which has neither visible tonstein layers nor obvious volcanogenic minerals, has high TiO2, V, Cr, Ni, Cu and Zn concentrations in the intervals between the coal plies affected by mafic and alkaline volcanic ashes. This is consistent with the suggestion that a common source material was supplied to the coal basin, derived from the erosion of mafic basaltic rocks of the Kangdian Upland. Although the Songzao coal is generally a high-sulfur coal, most of the chalcophile trace elements show either poor or negative correlations with total iron sulfide contents. The absence of traditional pyrite-metal associations may reflect wide variations in the concentrations of these elements in individual pyrite/marcasite components, or simply poor retention of these elements in the pyrite/marcasite of the relevant coals. [ABSTRACT FROM AUTHOR]

Calcite-pyrrhotite-chalcopyrite veins are pervasively developed in a diorite intrusion (∼2.06 Ga), associated calc-silicate hybrid rock, and carbonate country rock in the direct vicinity of Marble Hall, Mpumalanga Province, South Africa. The diorite intrusion is probably sill-like in shape and related to a series of sills that formed a ∼500m thick package within the impure siliceous carbonate rocks of the Malmani Subgroup, Transvaal Supergroup. The intrusion comprises a hybrid rock at the base, followed upward by cumulate-layered diorite and a capping of diorite pegmatite. Fluid build-up due to crystal differentiation and fractionation of mainly amphibole and plagioclase gave rise to the development of H2S-bearing hydrous fluids that permeated and reacted with the dolomitic country rocks, thereby releasing CO2 into the fluids. Scavenging of aluminium, titanium, iron, calcium, sodium, potassium and zirconium (rare) from the early-formed minerals took place as the fluids channelled into contraction cracks and fissures. Early-formed magmatic and metamorphic (in diorite-related hybrid rocks) amphibole, andesine, magnetite and ilmenite were transformed into secondary assemblages containing actinolite-ferroactinolite, albite, chlorite, calcite, apatite, sphene, zircon (rare), pyrrhotite, chalcopyrite and pyrite. With increasing degree of alteration, magmatic-textured mesocratic diorite went to bleached diorite, allotriomorphic-textured diorite and finally to granoblastic albite-rich diorite. Final crystallisation of the fluids gave rise to aggregates of calcite, pyrrhotite, rare chalcopyrite and sphene. The existence at Marble Hall of coincident gravity and magnetic anomalies, nickeliferous ultrabasic rocks, the presence of sulphur (manifested by the calcite-pyrrhotite veins), and the apparent overprint of a high temperature metamorphic-metasomatic event, collectively enhance the area's prospectivity for base metal deposits. [ABSTRACT FROM AUTHOR]

This paper reports the mineralogy and geochemistry of the Late Permian C1 Coal from Bole and Laibin mines in eastern Yunnan, Southwestern China (C1 Coal in Laibin mine is composed of three layers termed B1, B2, and B3). The coals are characterized by medium-high ash yields and very low sulfur contents. Compared with average values of trace element concentrations in hard coals worldwide, the Bole and Laibin coals are enriched in V, Co, Cu, Zn, and Se, which were mainly derived from the sediment-source region of the Kangdian Upland. Major minerals in the coal samples and roof and floor strata include quartz, interstratified berthierine/chamosite (B/C), as well as kaolinite, mixed layer illite/smectite, calcite, pyrite, and anatase. Unlike a pure chamosite, the 7 Å peak of interstratified B/C is sharp and narrow, while the 14 Å peak is broad and weak, or absent in some coal samples. Interstratified B/C was largely precipitated from low-temperature Fe-rich and Mg-rich hydrothermal fluids or, in some cases, is an alteration product of kaolinite. Secondary phases of quartz, calcite, pyrite, kaolinite, chalcopyrite, gypsum, and REE-phosphates in the coal samples are the dominant authigenic minerals formed at syngenetic and early diagenetic stages. Four intra-seam partings in C1 Coal, B1, and B3 layers are identified as tonsteins derived from felsic volcanic ashes. These tonsteins consist mainly of cryptocrystalline kaolinite with graupen and vermicular textures, and minor amounts of high-temperature quartz, zircon, apatite, monazite, and anatase. The floor of the C1 Coal in the Bole mine is a tuffaceous claystone and consists of altered high-Ti basalt volcaniclastics, characterized by high concentrations of Zr, Nb, V, Co, Cu, and Zn, low Al2O3/TiO2 ratio (~4.62), high Ti/Y ratio (~900), enrichment of middle rare earth elements, and positive Eu anomalies. [ABSTRACT FROM AUTHOR]

In this study, the oxygen isotope (δ18O) composition of pink to red gem-quality rubies from Paranesti, Greece was investigated using in-situ secondary ionization mass spectrometry (SIMS) and laser-fluorination techniques. Paranesti rubies have a narrow range of δ18O values between ~0 and +1‰ and represent one of only a few cases worldwide where δ18O signatures can be used to distinguish them from other localities. SIMS analyses from this study and previous work by the authors suggests that the rubies formed under metamorphic/metasomatic conditions involving deeply penetrating meteoric waters along major crustal structures associated with the Nestos Shear Zone. SIMS analyses also revealed slight variations in δ18O composition for two outcrops located just ~500 m apart: PAR-1 with a mean value of 1.0‰ ± 0.42‰ and PAR-5 with a mean value of 0.14‰ ± 0.24‰. This work adds to the growing use of in-situ methods to determine the origin of gem-quality corundum and re-confirms its usefulness in geographic "fingerprinting". [ABSTRACT FROM AUTHOR]