The recently discovered middle-sized Bojitian Carlin-type Au deposit is located in southwestern Guizhou Province, China, near the well-known Shuiyindong super-large-sized deposit. To improve the understanding on this deposit, here we investigate the minerals that host Au and the occurrence of Au in the deposit, using a combination of microscopic work and electron probe microanalysis (EPMA). Based on the results, the formation of the deposit was addressed. Results indicate that the dominant minerals that host Au include arsenian pyrite and arsenopyrite. Au in the cores of zoned pyrite exists mainly as natural nanoscale Au (Au 0 ), while Au in the rims exists mainly as solid solution Au (Au + ), but it likely also exists in the rims as natural nanoscale Au. The framboidal, coarse-grained, and banded pyrite types contain both natural nanoscale Au 0 and solid solution Au + . The arsenopyrite is of hydrothermal origin, and Au within the arsenopyrite exists as gold solution Au + . The Bojitian deposit was formed from As-bearing, H 2 S-rich, low-to-medium-temperature fluids that migrated along faults and other channels. Au that was already present in the strata or source beds migrated with the fluids in the form of Au(HS) − and ore-forming fluids were then formed in the reducing environment. The ore-forming fluids interacted with Fe-rich carbonates to form an abundance of Au-hosting arsenian sulfides.
Early Palaeozoic evolution of the Kazakhstan orocline in the Central Asian Orogenic Belt (CAOB) is key to reconstructing the Palaeozoic tectonic framework in Central Asia. This study presents field mapping, geochemistry, and geochronological data from the Wulasitai area of northern West Junggar to constrain the subduction polarity and major tectonic events in the Chingiz arc of the Kazakhstan orocline during the Early Palaeozoic. The mapping area outcrops imbricated coherent turbidite slices and mélanges that consist of chert, limestone, silt, sandstone, and conglomerate blocks in mudstone matrix, representing an OPS (Ocean Plate Stratigraphy) mélange in an accretionary complex. Existing fossil ages from these blocks range from the Ordovician to Silurian, while our new detrital zircon U-Pb samples from the turbiditic matrix yield maximum depositional ages (MDTs) from 428 ± 2 Ma to 450 ± 1 Ma. Detrital zircon ages of ~510 to 430 Ma in the mélange suggest the Chingiz arc to the south of the study area as a major sediment source, providing an indirect constraint on the polarity of subduction. We suggest that the northern part of the Chingiz arc may be underlain by southward subduction, with the accretionary complex located on the Wulasitai area of the northern West Junggar. The Wulasitai mélange is overlain depostionally by volcanic rocks carrying depleted HFSE and enriched LILE, LREE. The andesite and tuff are dated to 415 ± 5 Ma, 414 ± 3 Ma, and 402 ± 6 Ma, which we interpret as reflecting the development of the volcanic arc onto the previous subduction complex. This model implies the generation of the arc (accretion arc) as the slab rolling back and trench retreating, which may play an important role in the evolutionary history of CAOB.
Early Palaeozoic evolution of the Kazakhstan orocline in the Central Asian Orogenic Belt (CAOB) is key to reconstructing the Palaeozoic tectonic framework in Central Asia. This study presents field mapping, geochemistry, and geochronological data from the Wulasitai area of northern West Junggar to constrain the subduction polarity and major tectonic events in the Chingiz arc of the Kazakhstan orocline during the Early Palaeozoic. The mapping area outcrops imbricated coherent turbidite slices and mélanges that consist of chert, limestone, silt, sandstone, and conglomerate blocks in mudstone matrix, representing an OPS (Ocean Plate Stratigraphy) mélange in an accretionary complex. Existing fossil ages from these blocks range from the Ordovician to Silurian, while our new detrital zircon U-Pb samples from the turbiditic matrix yield maximum depositional ages (MDTs) from 428 ± 2 Ma to 450 ± 1 Ma. Detrital zircon ages of ~510 to 430 Ma in the mélange suggest the Chingiz arc to the south of the study area as a major sediment source, providing an indirect constraint on the polarity of subduction. We suggest that the northern part of the Chingiz arc may be underlain by southward subduction, with the accretionary complex located on the Wulasitai area of the northern West Junggar. The Wulasitai mélange is overlain depostionally by volcanic rocks carrying depleted HFSE and enriched LILE, LREE. The andesite and tuff are dated to 415 ± 5 Ma, 414 ± 3 Ma, and 402 ± 6 Ma, which we interpret as reflecting the development of the volcanic arc onto the previous subduction complex. This model implies the generation of the arc (accretion arc) as the slab rolling back and trench retreating, which may play an important role in the evolutionary history of CAOB.
A large-scale strong convection which is occurred in Jiangsu Province on August 6 2015 is diagnosed and analyzed from various angles using reanalysis data, surface observation data and the new generation radar data. The main conclusions are the followings: the ground squall line is the direct impact system of this strong convection. The upper air is dry and cold and the low level is warm and humid. During this convection, the wind direction is suddenly changed, wind speed is shot up, the pressure is upwelling, the temperature is dropped sharply, and the relative humidity rises sharply. The atmosphere energy is accumulated in the ground, there is an energy front area between the middle level and lower level, the strong vertical rising speed, the low-level convergence and high-level divergence of water vapor flux are the favorable factors for heavy precipitation. The radar echo shows that there is a clear gust front on the right side of the thunderstorm in Liuhe area, simultaneously, and there is a distinct weak narrow-band in the left front of the echo, corresponding to the outflow boundary of the rear side of the thunderstorm. In addition, the center of the radar echo is observed decline rapidly in the vertical direction. The above characteristics have a good indication of the prediction of severe winds.
Based on the data of volatile organic compounds (VOCs) collected from July to October, 2014 in the centre of Kunming, characteristic of their variability and source identification by principal component analysis (PCA) were analyzed. In summer, 40.60% of the total VOC concentrations were attributed to biogenic emissions and industrial process, 19.33% to vehicle emissions, 19.19% to solvent usage, 10.02% to fuel evaporation(including LPG/NG leakage and gasoline evaporation), and 8.34% to industrial production. In autumn, 39.73% of the total VOC concentrations were attributed to industrial production, 27.67% to solvent usage, 21.26% to vehicle emissions, 8.12% to fuel evaporation.
ABSTRACTLate Palaeozoic evolution of the Chinese Altai-East Junggar orogenic collage is vital for a better understanding of the accretionary evolution in the southern Altaids. This paper reports new geochronological, geochemical, and isotopic data for the magmatic rocks collected from the northern part of the Dulate arc. The ~304.6 Ma tonalite samples present typical adakitic features of high Sr (396–714 ppm), low Y (1.42–2.60 ppm), Yb (0.11–0.24 ppm), and high Sr/Y (177.25–440.23) ratios. Combining high Mg# (55.35–57.21) and depleted isotopic composition (εHf(t): +9.89 to +13.37 and εNd(t): +5.36 to +6.06), we suggest that they were derived from the partial melting of a subducted oceanic slab. The ~299.4 Ma monzogranite samples have high A/CNK values (1.08 to 1.25), CIPW normative corundum contents (1.28–3.25 wt.%), and positive εHf(t) (+5.14 to +8.63) and εNd(t) (+1.08) values, which are similar to S-type granite that may be generated by the melting of greywackes. The monzogranite (~286.9 Ma) and rhyolitic porphyry (~283.9 Ma) are high-K calc-alkaline and similar to the highly fractionated I-type granites with depleted isotopic features (εHf(t): +11.68 to +14.99 and +0.75 to +7.18, εNd(t): +5.91 and +6.18). The monzogranite and rhyolitic porphyry could have been derived from a depleted mantle source, but the rhyolitic porphyry probably suffered partial assimilation of the overlying crust materials. Combining regional rock associations of mafic-ultramafic complexes, adakitic rocks, high-Mg diorites, and A-type granites with close spatial-temporal relationship, we conclude that a mid-oceanic ridge of the Ob-Zaisan Ocean subducted southward beneath the Dulate arc during the latest Carboniferous to Permian. With the opening of the slab window, the upwelling asthenosphere provided high heat flux and triggered various magmatism in the upper plate. We propose that ridge subduction is one of the most effective mechanisms of continental growth in the southern Altaids.KEYWORDS: East JunggarOb-Zaisan Oceanadakitic rocksridge subductionslab window AcknowledgementWe are very grateful to Editor Robert J. Stern and two anonymous reviewers for the constructive revision advice about this paper. We thank Yichao Chen, Rubin Yan and Dzhovid Yogibekov for field work assistance. This work was jointly supported by the National Natural Science Foundation of China (41888101, 41822204), the Third Xinjiang Scientific Expedition Program (2022xjkk1301), the Science and Technology Major Project of Xinjiang Uygur Autonomous Region, China (2021A03001-1&4, 2022A03010-1), One Hundred Talent Program of the Chinese Academy of Sciences (E2250403), and Youth Innovation Promotion Association Chinese Academy of sciences (2022446). This is a contribution to IGCP 662.Disclosure statementNo potential conflict of interest was reported by the author(s).Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2246072Additional informationFundingThis study was financially supported by the National Natural Science Foundation of China (41888101, 41822204), the Third Xinjiang Scientific Expedition Program (2022×jkk1301), the Science and Technology Major Project of Xinjiang Uygur Autonomous Region, China (2021A03001-1&4, 2022A03010-1), One Hundred Talent Program of the Chinese Academy of Sciences (E2250403), and Youth Innovation Promotion Association Chinese Academy of sciences (2022446). This is a contribution to IGCP 662.
Indentify dangerous houses in rural areas isn't very efficient, considering the large workload to visit the rural area, patchy and untimely manual document's registration management. This study first uses UAV oblique photography technology to quickly obtain high-resolution aerial photographic images of villages and reconstruct three-dimensional reality models. Then, based on the YOLOv5 algorithm, the features of dangerous houses in aerial photography images are automatically detected, and the features of dangerous houses are mapped to the real 3D model to accurately locate the dangerous buildings. Finally, a digital management platform for rural dangerous houses is developed to support rural managers in identifying, measuring and tracking dangerous houses. The application results in a village along the coast of southern Fujian province showed that the accuracy rate of the final dangerous house screening rate of this method was 92%, and the coverage rate was 95%, which could greatly improve the efficiency, accuracy and coverage of dangerous house screening and reduce the workload of manual screening; and improve management efficiency through platform-based and visual methods.
The Palaeozoic tectonic evolution of the Western Kunlun Orogen plays an important role in deciphering the Tethyan tectonic evolution. This study provides new geochronology, geochemistry and Lu–Hf isotopic data of igneous rocks from the Omixia Complex in the eastern section of the northern Western Kunlun, as well as detrital zircon ages from turbidites and meta‐sediments north of it. From the Omixia Complex, the determined ages of five ultramafic–mafic rock samples are approximately 470, 456, 429, 401 and 382 Ma. Two samples of acidic rocks from the same complex yielded ages of approximately 438 and 378 Ma. One pegmatitic plagiogranite sample exhibits feature of accretionary arc granites, while other samples show geochemical characteristics of island arc tholeiite and E‐MORB. Additionally, four turbidite matrix and two limestone samples, with a major peak around ca. 480–500 Ma, have the youngest zircon ages ranging from ca. 481 to 387 Ma, paralleling the age range of igneous rocks in the ophiolitic mélange. The ε Hf ( t ) values of these samples reveal a broad spectrum of crustal and mantle processes. The youngest zircon ages of five meta‐sedimentary rock samples north of the Omixia Complex range from ca. 581 to 535 Ma, with peak ages concentrated around ca. 0.9–1.0 Ga. Their provenance characteristics differ from the turbidite matrix in the southern Omixia Complex and from the meta‐sediments in the northern Tiklik terrane with peak ages of ca. 0.8 Ga. A younger limestone sample yielded youngest zircon age of ca. 294 Ma, which is unconformably overlain the Omixia Complex and surrounding older rocks. Based on these new results, combined with previous data, we propose a new tectonic model for the eastern section of the northern Western Kunlun Orogen, suggesting a continuous evolution process of multi‐terrane subduction–accretion collage from the Early Ordovician to the Middle Devonian in the Paleo‐Tethys Ocean, which evolved into an Andean‐type active margin in the Early Permian, contributing to the substantial continental growth of the southern Tarim Craton.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)