Synergy of Remote Sensing Data for Exploring Hydrothermal Mineral Resources Using GIS-Based Fuzzy Logic Approach

The Arabian Nubian Shield (ANS) contains a variety of gold deposits in the form of veins and veinlets formed by hydrothermal fluids. Characterizing potential areas of hydrothermal alteration zones therefore provides a significant tool for prospecting for hydrothermal gold deposits. In this study, we develop a model of exploration for hydrothermal mineral resources in an area located in the ANS, Egypt, using multiple criteria derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Landsat-Operational Land Imager (OLI), and Sentinel-2 data and field work through GIS-based fuzzy logic approach. The hydrothermal alteration zones (HAZs) map extracted from combining mineral indices, spectral bands, and ratios is consistent with observed argillic alteration zones around the mineralized veins. Combining HAZs and lineament density led to identification of six zones based on their mineralization potential, and provides a tool for successful reconnaissance prospecting for future hydrothermal mineral deposits. The detected zones are labeled as excellent, very high, high, moderate, low, and very low, based on their potential for Au production, and the predictive excellent and very high zones cover about 1.6% of the study area. This model also shows that target prospective zones are quartz veins controlled by NNW-SSE trending fracture/fault zones all crosscutting Precambrian rocks of the ANS. Field observations and petrographic and X-ray diffraction analyses were performed to validate the mineral prospective map and revealed that quartz veins consist of gold–sulfide mineralization (e.g., gold, pyrite, chalcopyrite, and sphalerite). Consistency between the high potential hydrothermal alterations zones (HAZs) and the location of gold mineralization is achieved.

Hydrothermal mineral assemblages of calcite and dolomite–analcime–pyrite in Permian lacustrine Lucaogou mudstones, eastern Junggar Basin, Northwest China

The eastern Junggar Basin, controlled by continental extension (rift), was deposited by lacustrine dominated sediments during middle Permian Lucaogou period. An unusual porphyritic-like texture was observed in Lucaogou/Pingdiquan dark fine-grained organic-rich sediments in two sub-tectonic units in the basin. The “phenocrysts” are composed of two types of mineral assemblages. The first is a coarse euhedral calcite assemblage in the Jimusar Sag, and the second consists of dolomite, analcime, and pyrite in the Shishugou Sag. The lithological and mineralogical features indicate a hydrothermal origin for these phenocryst-like minerals. The chondrite-normalized rare earth element patterns show flat or positive Ce anomalies and negative Eu anomalies, which reflect a suboxic to anoxic, off-axis site from the center of the fault system, where the temperature of the hydrothermal fluid might be less than 250 °C. The high ratios of BaN/LaN at 1.6–65.5, strongly positive Sr anomalies at Sr/Sr* = 5.54–39.9, and relatively low 87Sr/86Sr isotopes at 0.705002–0.705776 in the coarse calcite suggest an origin of mixed sources of lake water, underlying biogenetic sediments, and deep magmatic water. However, the low 87Sr/ 86Sr ratios of 0.705321–0.705968 in the dolomite and δ34SV-CDT of 10.8‰–12.3‰ in the pyrite indicate that water–underlying-rock interaction and the abiotic thermochemical sulfate reduction of lake water or organic matter might have participated together resulting in the precipitation of the dolomite–analcime–pyrite assemblages in the Shishugou Sag.

Coupled U–Pb Geochronology of Monazite and Zircon for the Bozhushan Batholith, Southeast Yunnan Province, China: Implications for Regional Metallogeny

Constraining the duration of magmatism is of vital importance to the understanding of the magmatic-hydrothermal mineral system. The Bozhushan batholith, located in the middle section of the southeastern Yunnan ore district, mainly consists of biotite monzogranite and monzogranite. Many Sn–W–polymetallic deposits are developed around the Bozhushan batholith, but their temporal and genetic relationships remain controversial. LA-ICP-MS U–Pb zircon and monazite dating were respectively conducted on the same two samples, yielding weighted mean 206Pb/238U zircon ages of 85.1 ± 0.7 and 85.6 ± 0.9 Ma, and weighted mean 206Pb/238U monazite ages of 87.1 ± 0.9 and 88.1 ± 1.1 Ma. The crystallization ages of S-type granites obtained from the zircon U–Th–Pb system and monazite U–Th–Pb system are consistent within the analytical errors. After combining the new ages obtained in this study with recently published U–Pb zircon and cassiterite ages from the giant Baniuchang Ag–Sn–Pb–Zn deposit in the north, and U–Pb zircon and Re-Os molybdenite ages from the large Guanfang W deposit in the south, a temporal framework of magmatism-mineralization in the Bozhushan region has been established. The duration of magmatic activity at Bozhushan is about 7 Ma, with W mineralization occurring at ca. 92 Ma and Sn mineralization at 88–87 Ma.

Heavy metals in oils and formation of bitumen-hydrothermal associations in the rocks of the Dnieper-Donetsk paleorift

Formulation of the problem of the article. The problem of common finding of hydrocarbons and heavy metals in the geological space is very interesting from the point of view of theoretical and practical meaning. It was discussed in many works of domestic and foreign scientists from different positions, stipulated by the absence of ambiguity in the explanation of this fact. It is important that heavy metals are present not only in oils, but also in bitumen of bituminous-hydrothermal mineral associations of ore fields in the region. The main aim of the article is to research the genetic, spatial and temporal correlation of heavy metals and hydrocarbons. Research Methods. The processes adducting to the accumulation of heavy metals in oils and the formation of bituminous-hydrothermal associations in rocks have been researched. In particular, the definition of heavy metals in oils from various deposits of the Dnieper-Donetsk basin was performed using the X-ray fluorescence method and the definition of the isotopic composition of carbon of solid bitumen - by mass spectrometric methods. Results. The processes adducting to the accumulation of heavy metals in oils and the formation of bituminous-hydrothermal associations in rocks have been researched. These processes are associated with ascending heat and mass transfer, which adduct to the unloading of fluid streams, which contained a variety of chemical elements, including compounds of carbon dioxide, methane, mercury vapor, and complexes of heavy metal. Spatially, that process coincides with the anticlannel structures which accompany the zones of deep faults. It has been found that the concentrations of heavy metals in oils are associated with the peculiarities of deposits formation within different geological structures. Physical-chemical conditions for the formation of hydrocarbon-hydrothermal fluid systems, which involve both biogenic and abiogenic (synthesized) hydrocarbons, were determined. The established geochemical regularity of increasing concentrations of heavy metals with the depth of oil occurrence is associated with high contents of sulfur compounds in the form of hydrothermal sulfide minerals, which are actively hydrolyzed at high temperatures and lead to leaching of metals and their entry into fluid`s systems where stable sulfur complexes are formed. Scientific novelty and practical importance. The formation of hydrocarbon-heavy metal systems within the Dnieper-Donetsk basin occurs with the participation of synthesized and organic hydrocarbons, as well as mantle exhalates and hydrothermal vent. The result is cooling of these systems. Hydrocarbon fractions (oil) are enriched with heavy metals, and hydrothermal vents are enriched with bitumen-forming naphthides. The practical importance of this research is increase in the efficiency of forecasting and prospecting of hydrocarbon deposits at the expense of theoretical modeling of the bituminous-hydrothermal mineral associations formation in ore fields.