The Kaolinite Crystallinity and Influence Factors of Coal-Measure Kaolinite Rock from Datong Coalfield, China

In order to ascertain the kaolinite crystallinity of Carboniferous Permian coal-measure kaolinite rocks, seven groups of fresh samples were collected from below the ground in the Xiaoyu mine, Datong coalfield. Microscopy, X-ray diffraction (XRD), differential thermal analysis (DTA), infrared (IR) spectroscopy and X-ray fluorescence (XRF) spectrometry methods were applied to the samples. The petrographic analysis results show that the kaolinite rocks are characterized as compact, phaneritic, clastic, sand-bearing, sandy and silty types; the kaolinite content in the Shanxi formation and upper Taiyuan formations was more than 95%, while it was 60–90% in the middle and lower Taiyuan formations. Based on the Hinckley index and the features of XRD, DTA and IR of kaolinites, crystallinity was classified as having three grades: ordered, slightly disordered and disordered. The kaolinites’ SiO2 /Al2O3 molar ratio was about 1.9–5.7, with a chemical index of alteration (CIA) of about 95.4–99.5. This research suggests that the kaolinite crystallinity correlates positively to its clay mineral content, purity and particle size, which are also related to the SiO2/Al2O3 molar ratio and CIA. The original sedimentary environment and weathering have a direct influence on kaolinite crystallinity, and the existence of organic matter is conducive to the stable existence of kaolinite. The study results have significance for the extraction and utilization of coal-measure kaolinite and the development of kaolinite crystallography and mineralogy.

The Role of New-Emerging Lands on Sources of Aeolian Sand Deposits Driven by Shrinking of the Urmia Salt Lake

Urmia Lake, the largest saline lake in Iran and the Middle East, is located in the northwest of Iran, has shrunk over the past decades. The reduced water level has increased the area of dry land around the lake allowing new environmental hazard such as sand dunes encroachment, particularly on the western side of the lake. There are five terrain types that could contribute sediment to the dunes, and it is the main aim of this research to identify the contributions to the dunes of each terrain type. Fifteen surface samples were collected from the five most erodible terrain types and eight samples were collected from the dunes both in downwind and upwind directions from the lake, and major element components were measured using X-ray fluorescence (XRF). According to the Besler classification, all samples are in the saline class. Also, the chemical index of alteration (CIA) values in all samples were less than 50, indicating weak weathering. Based on multivariate statistical analysis, suitable tracers were selected and were imported to the sourcing equations. Quantification of uncertainty and the creation of two new fingerprinting models for aeolian sediments based on both Bayesian and GLUE procedures were used. The highest proportion comes from the salty and puffy lands (44.2%) followed by salty polygon land (23.5%), clay-salty areas, puffy-flaky lands (7.01%), the terminus of the fine sandy alluvial fan (13.2%), and clay-salty abandoned lands (12.1%). It is concluded that if land managers use these results, they can more efficiently decrease the hazards posed by dune reactivation and migration though implementation of soil conservation on the affected lands around the dried lake.

Geochemical Maturity and Paleo-Weathering Indices of Sedimentary Succession in JV Field Greater Ughelli Depo-Belt Niger Delta Basin

This study evaluates the geochemical maturity and paleo weathering indices of X well JV-Field, Greater UghelliDepo belt Niger Delta Basin, using reflected light microscope and geochemical proxies. The data obtained identified three lithofacies units as Sand, Shale, and Shaly sand facies .The application of source area weathering using Chemical index of alteration (CIA) and Chemical index of weathering (CIW) values for the sampled intervals ranges from (48.6-94.9%) and (60.6-96.7%), and have median values of (83.2 and 90.3) % respectively which is an indication of high weathering at the source. The values are variable and it may be as a result of multiple provenances of the sediments which have variable proportions of source area weathering and related processes or may be due to low concentrations of the alkalis and alkaline earth elements. However, all the samples excluding one with depth (12430ft) show CIA and CIW values greater than 70% indicating high (intensive) weathering either at the source or during transportation before deposition .From the high alteration indices value recorded from the sampled intervals, it can be inferred that the sediments are geochemically and texturally mature.

Provenance and sedimentary environment of the Ek2 shale in the Cangdong Sag, the central Bohai Bay Basin, China

The second member of the Kongdian Formation (usually abbreviated as the E k2 shale) is one of the most significant exploring targets for shale oil at the Cangdong Sag of the central Bohai Bay Basin. It consists of siliceous shale, mixed shale, and calcareous shale. To better understand why organic matter accumulated in the E k2 shale, we have analyzed major and trace elemental compositions to reconstruct the provenance and sedimentary environment. Tectonic discriminatory diagrams suggest that the tectonic setting of the parental rocks for the E k2 shale belonged to the Continental Island Arc. The distribution patterns of trace elements and rare earth elements + yttrium (REEs + Y) are close to the intermediate igneous rock. The ratios of Al2O3/TiO2 ranging from 21.41 to 27.59 with a mean value of 23.93 also demonstrate a parental rock of the intermediate igneous rock. Siliceous and mixed shales indicate K2O/Al2O3 of 0.17–0.29, chemical index of weathering of 28.79–97.79, plagioclase index of alteration of 38.24–95.57, and chemical index of alteration of 40.29–80.23. These weathering proxies denote that the E k2 shale underwent a low weathering degree in an arid climate and a high weathering degree in a semiarid climate. The V/(V + Ni) ratios and pyrite framboids indicate an anoxic sedimentary condition. The δ18O values of carbonate minerals in the E k2 shale range from −9.8‰ to 0.7‰, and they are positively correlated to the δ13C values. The Sr/Ba ratios, δ18O, and chemical mineral associations indicate that siliceous and mixed shales were deposited in a fresh to brackish anoxic water column under a semiarid climate. Whereas calcareous shale was deposited in a saline to hypersaline anoxic water column under an arid climate.

Potassium-metasomatism in Anthracite: A Cluster of Geochemical Evidences

The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basin, as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim, India. The SiO2 content (48.05 to 65.09 wt% in the ash yield of the bituminous coal samples and 35.92 to 50.11 wt% in the ash yield of the anthracite samples) and the ratio of Al2O3/TiO2 (6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples) reveal the intermediate igneous source rock composition of the minerals. The ratio of the K2O/Al2O3 in the ash yield of the bituminous coal samples (0.03 to 0.09) may suggest the presence of kaolinite mixed with montmorillonite, while its range in the ash yield of the anthracite samples (0.16 to 0.27) may imply the presence of illite mixed with kaolinite. The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions. The plot of the bituminous coal samples in the A-CN-K diagram depicts the traditional weathering trend of parent rocks, but the anthracite samples plot near the illite field and are a bit offset from the weathering trend. This may imply the plausible influences of the potassium-metasomatism at post coalification stages. The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of the illite in the anthracite samples substantiating the effect of the epigenetic potassium-metasomatism. The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.

Provenance of sediments from Barra del Tordo and Tesoro beaches, Tamaulipas State, northwestern Gulf of Mexico

The mineralogy, bulk sediment geochemical composition, and U–Pb ages of detrital zircons retrieved from the Barra del Tordo (Tordo) and Tesoro beach sediments in the northwestern Gulf of Mexico were analyzed to determine their provenance. The beach sediments are mainly composed of quartz, ilmenite, magnetite, titanite, zircon, and anorthite. The weathering proxies such as the Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA), reveal a moderate-to-high intensity of weathering in the source area. The chondrite-normalized rare earth element (REE) patterns are similar to felsic igneous rocks, with large negative europium anomaly (Eu/Eu* = ~ 0.47–0.80 and ~ 0.57–0.67 in the Tordo and Tesoro beach sediments, respectively).Three major zircon U–Pb age groups are identified in the Tordo and Tesoro beach sediments, i.e., Proterozoic (~ 2039–595 Ma), Mesozoic (~ 244–70.3 Ma), and Cenozoic (~ 65.9–1.2 Ma). The differences of the zircon age spectrum between the Tordo and Tesoro beach sediments are not significant. The comparison of zircon U–Pb ages in this study with ages of potential source terranes suggests that the Mesozoic and Cenozoic zircons of the studied Tordo and Tesoro beach sediments were derived from the Eastern Alkaline Province (EAP) and Mesa Central Province (MCP). Similarly, the likely sources for the Proterozoic zircons were the Sierra Madre Oriental (SMOr) and Oaxaquia in the northwestern Gulf of Mexico. The results of this study further indicate that the sediments delivered to the beaches by rivers and redistributed by longshore currents were crucial in determining the sediment provenance.

Provenance Characterization and Palaeoenvironmental Analysis of the Meta-Sedimentary Rocks of Sonaghati Formation, Betul District, Madhya Pradesh Using Geochemical Approach

Betul belt, ENE-WSW trending, 135 km long, prominent litho-tectonic unit exposed in the central part of Central Indian Tectonic Zone (CITZ) is composed of meta-sedimentary & meta-volcanic rocks intruded by mafic-ultramafic and granitic suite of rocks, belonging to Palaeoproterozoic to Neoproterozoic age. This belt is traversed by several ENE-WSW trending, sub-vertical ductite shear zones. The meta-sedimentary rocks of Sonaghati Formation were geochemically characterized and their geochemical composition was interpreted for provenance characterization and paleo-environmental assessment. The weathering indices including Chemical index of Alteration, Chemical index of Weathering, Plagioclase Index of Alteration and Weathering Index of Parker indicate that theses meta-sedimentary rocks have witnessed the substantial amount of weathering at the source without any evidence of potash metasomatism. The Bivariate plots using the major and trace element composition show co-linear trends, which reflect that all these samples belong to co-genetic population and the visible compositional variation could be attributed to chemical, mineralogical and textural maturity. The Sonaghati metasedimentary rocks are enriched in REE with negative Eu anomaly. The LREE enrichment varies from 122 to 174 times and that of the HREE enrichment ranges from 12 to 31 times of Chondrite indicating highly varied protoliths. The provenance characterization was attempted using the large ion lithophile elements and high field strength elements. The results show that the precursor for these meta-sedimentary litho-units are mixed source with the major contributor being felsic to intermediate and minor contribution has come from the mafic end members. These meta-sedimentary rocks were deposited in the overall semi arid climate with a sequential transition, suggesting the variable climatic conditions ranging from semi-arid to arid. The Cu/Zn, V/Cr ratios, and presence of pyrites dissemination and stringers eventually indicate the prevalence of reducing environmental conditions during the deposition of these meta-sediments.