Shouting Zhang

Mineral potential targeting and resource assessment based on 3D geological modeling in Luanchuan region, China

In this paper, we used 3D modeling and nonlinear methods (fractal, multifractal, and probabilistic neural networks (PNN)) for regional mineral potential mapping and quantitative assessment for porphyry and skarn-type Mo deposits and hydrothermal vein-type Pb-Zn-Ag deposits in the Luanchuan region, China. A 3D geological model was constructed from various geological maps, cross sections, boreholes, and gravity and magnetic data. Geological features associated with mineralization were extracted using the 3D geological model and metallogenic models of porphyry and skarn-type Mo and Pb-Zn-Ag deposits. The multifractal method, principal component analysis, and power spectrum-area method were used to separate regional variability from local variability in the geochemical data. A 2.5D forward modeling of gravity and magnetic data was carried out to define the geometry, depth, and physical properties of geological bodies at depth. 3D visualization of the results assisted in understanding the spatial relations between the deposits and the other geological bodies (e.g., igneous intrusions). The PNN method was applied to represent and integrate multiple anomalies for mineral potential modeling. The concentration-area fractal method was used to classify the PNN mineral potential model. Three levels (ground surface and two subsurface horizontal planes) of mineral potential models were evaluated for undiscovered Mo and Pb-Zn-Ag deposits. Validation of the results shows that 3D modeling was useful for not only accurately extracting geological features but also for predicting potential mineral targets and evaluating mineral resources. The mineral potential targets identified consist of eight Mo potential targets and 15 Pb-Zn-Ag potential targets. Based on grade-tonnage data from the known Mo and Pb-Zn-Ag deposits and the results of 3D modeling, estimated potential resources of each of these types of deposits are 10.8 and 153.1Mt (Pb+Zn is 152.9Mt and Ag is 0.92Mt), respectively.

Geochemistry, zircon U–Pb geochronology and Hf isotopes of Jurassic-Cretaceous granites in the Tengchong terrane, SW China: implications for the Mesozoic tectono-magmatic evolution of the Eastern Tethyan Tectonic Domain

ABSTRACT Recently identified Early Jurassic, Early Cretaceous, and Late Cretaceous granites of the Tengchong terrane, SW China, help to refine our understanding of the Mesozoic tectonic-magmatic evolutionary history of the region. We present new zircon U–Pb geochronological, Lu–Hf isotopic and geochemical data on these rocks. The zircon LA-ICP-MS U–Pb ages of the Mangzhangxiang, Laochangpo, and Guyong granites, and Guyong granodioritic microgranular enclaves are 185.6, 120.7, 72.9, and 72.7 Ma, respectively. Geochemical and Hf isotopic characteristics suggest the Mangzhangxiang and Laochangpo S-type granites were derived from partial melting of felsic crust and that the Guyong I-type granite and associated MMEs were generated through magma mixing/mingling. Mesozoic magmatism in the Tengchong terrane can be divided into three episodes: (1) the Triassic syn- and post-collisional magmatic event was related to the closure of the Palaeo-Tethyan Ocean, as represented by the Changning-Menglian suture zone; (2) the Jurassic to Early Cretaceous magmatism was related to the subduction of the Meso-Tethyan oceanic crust, as represented by the Myitkyina ophiolite belt; and (3) the Late Cretaceous magmatism was related to the subduction of the Neo-Tethyan oceanic crust, as represented by the Kalaymyo ophiolite belt. GRAPHICAL ABSTRACT

Petrogenesis of the late Mesozoic highly fractionated I-type granites in the Luanchuan district: implications for the tectono-magmatic evolution of eastern Qinling

Late Mesozoic granites are extensively distributed in the Luanchuan district of eastern Qinling and can be divided into two types: Late Jurassic to Early Cretaceous granites (ore-related plutons) and Late Cretaceous granites (Laojunshan batholith). This study presents new geochemical and zircon U-Pb-Hf isotopic data from the Shibaogou and Yuku plutons to provide robust constraints on the petrogenesis and tectonic significance of the late Mesozoic granites in the Luanchuan district. Zircon U-Pb dating results yielded weighted mean 206Pb/238U ages of 149.1 ± 0.8 Ma and 150.5 ± 0.8 Ma, which were interpreted as the crystallization ages of the Shibaogou and Yuku plutons, respectively. We propose that the late Mesozoic granites contain high concentrations of SiO2 and alkali elements (Na2O + K2O) and feature metaluminous to weakly peraluminous characteristics. Enrichment in light rare earth elements and large ion lithophile elements and depletion in high field strength elements are observed. Mineralogical and geochemical evidence reveal that the late Mesozoic granites are highly fractionated I-type granites with fractional crystallization of feldspar, plagioclase and accessory minerals (e.g., apatite and titanite or magnetite). Based on the Hf composition, we suggest that the parental magmas of the ore-related plutons were derived from remelting of the Taihua and Xiong’er groups with minor contributions of mantle-derived materials and that the Laojunshan batholith was generated by the hybridization of ancient crust- (Kuanping group) and mantle-derived components. Collectively, the above arguments indicates a tectonic transition from compression to post-collisional extension during the late Mesozoic, that was likely triggered by the continental collision of the North China Block and the Yangtze Block, which generated numerous contemporaneous granites and Mo-W-Pb-Zn-Ag-Au poly-metallic deposits.

Permo–Triassic granitoids of the Xing’an–Mongolia segment of the Central Asian Orogenic Belt, Northeast China: age, composition, and tectonic implications

ABSTRACT The Xing’an–Mongolia orogenic belt is located in the southeastern segment of the Central Asian Orogenic Belt. Its tectonic evolution, especially during the Late Palaeozoic to Early Mesozoic, remains controversial. Here, we report new zircon U–Pb dates, whole-rock geochemistry, and Hf isotopes of representative samples from four plutons in the Linxi area of Northeast China to provide new constraints on this issue. Zircon U–Pb dating indicates that the intrusions were emplaced in two stages: (1) Late Permian to Early Triassic (the Banshifangzi and Xinangou plutons (252 ± 3)–(246.3 ± 3.3) Ma); and (2) Late Triassic (the Baoshan and Hada plutons (220.8 ± 2.7)–(211.4 ± 2.6) Ma). Their positive εHf(t) values (6.6–14.1), coupled with their geochemical characteristics, suggest that the provenance of investigated granitoids were most likely to be dominated by juvenile crustal materials. Based on these new data and previous studies, we propose three stages of tectonic evolution during the Late Palaeozoic–Early Mesozoic in the XMOB: (1) Late Carboniferous–Early Permian (330–270 Ma): double-sided subduction of the Palaeo-Asian Ocean; (2) Middle Permian–Middle Triassic (270–237 Ma): the closure of the Palaeo-Asian Ocean and subsequent continent–continent collision between the North China Craton and the South Mongolia Terrane; and (3) Late Triassic (237–211 Ma): post-collisional extension. Graphical Abstract

3D-GIS Analysis for Mineral Resources Exploration in Luanchuan, China

Three-dimensional (3D) geological modeling is an important method for understanding geological structures and exploring for mineral deposits. This paper presents 3D visualization and spatial analysis methodology for molybdenum polymetallic resources exploration by integrating geological, geophysical, and geochemical data to identify high potential targets for mineralization at depth in Luanchuan district. The research results show prospective targets in Luanchuan district can be derived by three methods: ① Jurassic pluton can be applied to recognize prospective targets of skarn-Mo deposit on basis of metallogenic genesis and exploration model by 3D buffer analysis using 3D geological model of Luanchuan district, ② Geoscience data (geological, geophysical, and geochemical data) can be applied to integrate and identify all potential targets of granite porphyry-skarn deposits by non-linear mathematical modeling in 3D space, and ③ gravity and magnetic data inversion and fusion additional metallogenic knowledge can be used to identify concealed orebody at depth of large porphyry Mo deposit, and the bottom of the large Mo deposit generally has higher Mo grade and alteration belt which is associated with concealed ore-bearing Jurassic granite porphyry objects/veins. Therefore, 3D geological model of Luanchuan district using geoscience data and metallogenic genesis knowledge can be applied to delineate complex geological events including stratum, fault, structure, intrusive rocks, and alteration belt, and it can be used to identify prospective targets at depth in district-scale exploration.

The Evolution of Granitic Magmas and Implications for Mo Deposit Formation within the Luanchuan Metallogenic Belt, Eastern Qinling Orogen, Central China

Zircon U-Pb dating were carried out at the Laboratory Center for Physical Geology of China University of Geosciences, Beijing, China. Zircon U–Pb dating of lithologically distinct plutons has yielded ages of 153.2 ± 1.3, 154.1 ± 1.8, 151.5 ± 2.1, and 148.3 ± 1.0 Ma, with previously reported Re–Os ages of molybdenite from these granites being clustered around an age of ~146 Ma. Zircons of the mineralization-related granites have similar positive Ce anomalies, HREE distributions, and (Eu/Yb)N values. Lead isotope analyses were conducted at the Geochemistry Division of the National High Magnetic Field laboratory, Florida State University, USA. Highprecision MC–ICP–MS Pb isotope analyses of K-feldspar megacrysts from mineralization-related granites yielded Pb/Pb values of 17.3108–17.7514, Pb/Pb values of 15.4601–15.5233, and Pb/Pb values of 38.0454– 38.6341 (2s), suggesting that these granites were derived from the lower crust. In addition, Pb isotope analysis of pyrite that was coprecipitated with molybdenite, yielding 206Pb/204Pb values of 17.491–18.028, 207Pb/204Pb values of 15.476–15.546, and 208Pb/204Pb values of 38.279–38.534, suggesting that the metals within these deposits were derived from both the mantle and the lower crust.

Probabilistic neural networks and fractal method applied to mineral potential mapping in Luanchuan region, Henan Province, China

This paper presents an application of probabilistic neural networks (PNN) to integrated analysis multi-mineral anomalies caused by geological information (geology, geophysics, geochemistry, and remote sensing) and to map the 1∶25000 scale potential for Molybdenum polymetallic Pb-Zn-Ag mine targets with in Luanchuan region, Hennan Province. On the one hand, according to geological anomaly theory, the use of GIS technologies for the study area of geological anomaly information extraction, Mo ore-forming elements of the multi-fractal anomaly delineation, ETM+ remote sensing data, hydroxyl and iron staining alteration of information extraction, gravity and high magnetic anomaly deep geological body inversion; the other hand, the use of PNN method (via the probability density function (non-linear Gauss transform function) for complex non-linear classification), to carry out the study area to study geoanomaly associated with mineralization (variable) integrated analysis and metallogenic prediction. The results show that PNN method combined with fractal analysis can not only integrate the study area Pb-Zn-Ag-Mo polymetallic mines pluralistic, multi-scale and multi-types of geoanomaly associated with mineralization, but also carved out of the study area of molybdenum (tungsten), and Pb-Zn-Ag are two types of mineralization favorable target areas, and this work provides a scientific basis for the deployment of mineral exploration projects in the study area.