Abstract:Karst bauxite is the most important source of bauxite in China, accounting for more than 90% of the total resources, mainly distributed in the North China Craton and the southwest margin of the South China Block. In recent years, as a kind of strategic scarce mineral resource, the prospecting prediction of bauxite has become extremely urgent. This paper systematically summarizes the results of karst bauxite prospecting prediction and explores the optimal combination of prospecting prediction methods, so as to summarize the prospecting experience. By combing the examples and methods of geology, geophysics, geochemistry, remote sensing and artificial intelligence of geological big data to review the research results of karst bauxite prospecting and prediction in China, it is considered that geology and geophysics are still the most major methods for Chinese karstic bauxite prospecting prediction at present. In addition, the limitation of geochemical and remote sensing methods in searching for paleo-karst bauxite and their causes are analyzed, and the far-reaching significance of intelligent prospecting with geological big data is pointed out in the future.

Abstract:The Gangdese metallogenic belt (GMB) in Tibet, located within the East Tethys metallogenic domain, is one of the most famous Pb, Zn, and other nonferrous metal areas in China. A notable discovery in recent years is the Pusangguo deposit, which is rich in cobalt and contains Cu–Pb–Zn ores. The ore bodies mainly occur within the contact zone between the magma and the Early Cretaceous Takena Formation strata, displaying a complex mineralization pattern. Within the Pushangguo deposit, sphalerite is one of the main sulfides in the quartz-sulfides mineralization stage. Notably, there are two distinct types of sphalerite: dark-brown type I sphalerite (SpI) and light-brown type II sphalerite (SpII). This paper employs electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) to analyze the trace elements present in sphalerites. The results show that sphalerite is generally rich in Co, with SpI exhibiting a higher Co content than SpII. Co mainly replaces Zn (Co2+→Zn2+) through isomorphism. Both SpI and SpII showcase enrichment of Fe, Mn, and Cd, as well as depletion of Ga, Ge, and In. The occurrence of Fe, Mn, Cd, and other elements is mainly in the form of isomorphism, while Cu, Ag, Pb, and As appear as mineral inclusions within sphalerite. Based on the observed correlation between different trace elements, it is proposed that there exist potential simple complex element substitution mechanisms. These mechanisms include Fe2++Mn2+→2Zn2+, (In3+, Sn3+)+(Cu+, Ag+)→2Zn2+, As3++Ag+→2Zn2+, and Pb2++2As3++□→4Zn2+ (where □ represents a lattice vacancy). Furthermore, the ratios of Fe, Mn, Ge, In/Ga, In/Ge, and Zn/Cd in sphalerite, along with the calculations based on the sphalerite GGIMPis geothermometer, indicate that sphalerite was formed in an environment of medium-high temperature (237~345℃), low oxygen fugacity, and low sulfur fugacity (logf(S2)=-13.4~-8.3).

Abstract:Topography is formed by the complex interactions between tectonics and erosional surface processes, which is primarily mediated by tectonic activity and bedrock erodibility. The rock uplift by tectonics can be negligible in the ancient orogens for its tiny tectonic activity, then it is possible to study the contribution of rock erodibility to the landscape evolution. However, most recent results show that topography is mainly controlled by tectonics in the active orogens, and the reports of lithological control on landscape evolution are not involved. As the controlling fault for the Hetao Basin, the Seerteng mountain-front fault had been active since the Holocene, which resulted the M 6.4 and M 5.9 history earthquake in the 1979 and 1934. Previous studies show that the center section (such as the Wujiahe site) has stronger activity than its west and east sections. However, the researches of geomorphic parameters are less than other faults in the northern margin of Hetao Basin (such as the Langshan fault, Wulashan fault and Daqingshan fault), which will hinder to understand its deformation dynamics. Using the 30 m DEM, we extracted the Hypsometric integral of 33 subbasins in the Seerteng Mountain and normalized channel steepness, longitudinal profile and the Knickpoint of the corresponding streams. The HI values are clustered between 0.44 and 0.66 with the highest value at the Wujiahe town, indicating that the evolution stage of the Seerteng Mountain is the “Middle” stage. The transient and steady rivers are all distributed along the fault, which reveal that the rivers in the Seerteng mountain-front are developed during the transient state and then evolved to the steady state. By comparing the knickpoint and lithology, we find that the knickpoints are under-controlled by tectonic uplift and/or lithology. The channel steepness (Ksn) has a character of spatial difference. The Ksn near the Wujiahe town is the highest, and it gradually decreases to the east and west part, then it increases to the west part at the River S8. By analyzing the rock lithology, precipitation and tectonic, the channel steepness (Ksn) is controlled by the lithology, and its spatial distribution is in accord with the fault activity (vertical slip rates and offsets). The landscape of the Seerteng Mountain is the results of the tectonic uplift and rock lithology.

Abstract:At the Permian Baliklik Formation in the northwest margin of the Tarim Basin, there developed massively thick reef limestone that bears oil and gas exploration significance. This paper makes macro and micro examinations of the reefs which cropped out at Kizilbulak Nangou in the northwest margin of the Tarim Basin. This set of reefs had bioclastic shoals as reef bases. The lower zone of the reef core is mainly composed of microbialite of various types formed by Cyanobacteria, with thrombolite and broken-up microclots as its most dominant structural components, followed by stromatolites. At this time, the hydraulic energy is low. In the upper zone of the reef core locally developed phylloid algal reefs, with a large quantity of marine benthic fauna among them. At this time, the reef body began to expose itself above the wave base, with a large number of brecciated limestone developed, and it was subjected to the transformation of atmospheric freshwater karstification. In addition to the platform margin zone, the synchronous restricted platform in the Keping area in the northwest Tarim Basin also developed small-scale intra-platform reef-shoal complexes, with microbial rock characteristics, indicating that the environmental conditions in the region during this period were generally favorable for reef building. The set of reef-shoal complexes in the Baliklik Formation formed in the late Atherian period of the Early Permian to the Sakmarian Age, contemporary with the early stage of large igneous provinces of Early Permian Tarim Basin. Therefore, it is speculated that the forming of this set of reef-shoal complexes was related to the "eutrophication" of the sea water in the residual basin of the South Tianshan Ocean; the “eutrophication” had been caused by the volcanic ash spurted out by volcanic activities at that time. As a result of the outbreak of algae, the δ13C value of the reef-shoal complexes in the Baliklik Formation shows a significant positive shift compared with that of the carbonate rocks in the Kangkelin Formation. However, the reef-shoal complexes of the Baliklik Formation was much transformed by cementation and other constructive types of diagenesis, unfavorable to the forming of reservoirs. In other words, the reef-shoal complexes of the Baliklik Formation in the region, despite their desirable facies belts, possess poor reservoir permeability; high permeability layers only developed where structural fractures occurred. Therefore, it can be theorized that reef-shoal reservoirs of the Early Permian Baliklik Formation in the northwest margin of the Tarim Basin are, generally speaking, not controlled by facies, and that fractured reservoirs were dominant. Thereupon, exploration of Permian reef-shoal oil and gas reservoirs in the northwest margin of the Tarim Basin should focus on the structural fractured members. In brief, this study is an attempt to provide some scientific basis for the prediction of high-quality reservoirs in the Baliklik Formation reefs of the Tarim Basin, and to promote further research into Permian microbial rocks in China and throughout the world.