Jeofizikkulubu | Geophysics

Jeofizikkulubu | Geophysics

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Dike distribution density: Method for quantitative mine targets prediction in the South Alatao Mountains area, NW China
The correlation between dike density and regional‐scale mineralization indicates a fundamental criterion for ore‐forming process. Here, a novel dike distribution density method is formulated for...
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Thermal and energetic processing of astrophysical ice analogues rich in SO2
Sulfur is an abundant element in the cosmos and it is thus an important contributor to astrochemistry in the interstellar medium and in the Solar...
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As climate stirs Arctic sea ice faster, pollution tags along
A warming climate is not just melting the Arctic’s sea ice; it is stirring the remaining ice faster, increasing the odds that ice-rafted pollution will...
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McDermott to Use Integrated Software Platform to Deliver Best in Industry EPCI Solutions for Project Lifecycle
McDermott is the first EPCI Company to implement an advanced data solution to improve schedule certainty for its customers. Cutting-edge platform, based on Dassault Systèmes’...
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Dike distribution density: Method for quantitative mine targets prediction in the South Alatao Mountains area, NW China
The correlation between dike density and regional‐scale mineralization indicates a fundamental criterion for ore‐forming process. Here, a novel dike distribution density method is formulated for...
Read More
Thermal and energetic processing of astrophysical ice analogues rich in SO2
Sulfur is an abundant element in the cosmos and it is thus an important contributor to astrochemistry in the interstellar medium and in the Solar...
Read More
As climate stirs Arctic sea ice faster, pollution tags along
A warming climate is not just melting the Arctic’s sea ice; it is stirring the remaining ice faster, increasing the odds that ice-rafted pollution will...
Read More
McDermott to Use Integrated Software Platform to Deliver Best in Industry EPCI Solutions for Project Lifecycle
McDermott is the first EPCI Company to implement an advanced data solution to improve schedule certainty for its customers. Cutting-edge platform, based on Dassault Systèmes’...
Read More
SEVEN DAYS
The week in science: 16–22 June 2017.
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Geochronology, geochemistry, and tectonic implications of Jishou Cretaceous diabase, western Xuefengshan tectonic zone in South China
From the east of the Xuefengshan tectonic zone (XTZ) to the Pacific coast of the South China Block, there exist widespread Mesozoic magmatic rocks, which...
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Late Triassic‐Early Jurassic abnormal thermal event constrained by zircon fission track dating and vitrinite reflectance in Xishan coalfield, Qinshui Basin, central North China
Xishan coalfield, Shanxi, is located in the northwest of the Qinshui Basin, central North China. It is notable for its varieties of coal rank ranging...
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ALMA Finds Methyl Isocyanate Around Infant Sun-like Stars
ALMA has observed stars like the Sun at a very early stage in their formation and found traces of methyl isocyanate -- a chemical building...
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Timing of formation of the Keketale Pb–Zn deposit, Xinjiang, Northwest China, Central Asian Orogenic Belt: Implications for the metallogeny of the South Altay Orogenic Belt

The Keketale is the largest Pb–Zn deposit in the volcano‐sedimentary Maizi Basin of the South Altay Orogenic Belt (AOB), Northwest China. The stratabound orebodies are hosted in a suite of meta‐sedimentary rocks intercalated with volcanic rocks of the Lower Devonian Kangbutiebao Formation. The massive and banded ores representing the main mineralization stage are relatively well‐preserved in the ore district. This paper reports systematic geochronological results including the zircon laser ablation–multiple collector–inductively coupled plasma–mass spectrometry (LA‐MC‐ICP‐MS) U–Pb analyses on two meta‐felsic volcanic rocks from the Kangbutiebao Formation and Rb–Sr isotope dating on seven sphalerite samples from the main mineralization stage, together with some sulphur isotopic data to constrain the mineralization age and the genesis of the deposit. Rb–Sr isotope dating yield an isochron age of 398.2 ± 3.3 Ma generally synchronous with the zircon (LA‐MC‐ICP‐MS) U–Pb analyses of a meta‐rhyolite and a meta‐dacite from the strata (410.5 ± 1.3 Ma and 394.8 ± 1.9 Ma, respectively). The δ34S values of seven pyrite samples in the main massive and banded ores vary from −12.4‰ to −6.2‰, indicating that the main ore‐forming sulphur of the deposit was derived from bacterial reduction of seawater sulphate. By integrating the field, chronological, and isotopic evidences, we conclude that the Keketale Pb–Zn deposit is a VMS‐type deposit. Combining our results with the isotopic geochronology in the South AOB, we argue that the South AOB has undergone three mineralization episodes: the syndepositional mineralization (412–387 Ma), the subvolcanic hydrothermal‐related mineralization (382–379 Ma), and the epigenetic mineralization that is genetically linked to regional metamorphism and deformation (260–204 Ma). The Keketale Pb–Zn deposit is a product of the Devonian seafloor hydrothermal exhalation system in the South AOB.

Discovery of Mesoproterozoic kimberlite from Dörbed Banner, Inner Mongolia and its tectonic significance

Porphyritic olivine kimberlitic breccia, discovered in the Dörbed Banner of Inner Mongolia, Western China, is referred to as Longtou Shan Kimberlite in our study. This kimberlite occurs as a pipe in the Halahuogete Formation of Bayan Obo Group. Zircon U–Pb ages of Longtou Shan Kimberlite reveals a Mesoproterozoic age of ~1,552 Ma, constraining the deposition age of Halahuogete Formation to the Mesoproterozoic. Compared with Mesoproterozoic kimberlite of the ancient landmass, it can be inferred that the North China Craton is a member of the Ur ancient continent of the Columbia supercontinent. Furthermore, according to the tectonic background of the Bayan Obo Group, we raise this possibility that “Bayan Obo Aulacogen” should be renamed the “Bayan Obo Continental Rift.”

Petrogenesis and tectonic setting of the Shiduolong skarn Pb–Zn deposit in the East Kunlun Orogenic Belt: Constraints from whole‐rock geochemical, zircon U–Pb and Hf isotope analyses

The Shiduolong Pb–Zn deposit, located in the East Kunlun Orogenic Belt, is a medium‐scale skarn deposit (0.4 Mt metal reserves with a grade of 1.46% Pb and 4.38% Zn). The mineralization occurs along the contact zone between Carboniferous marbles and Triassic quartz diorite and granodiorite. Zircon LA‐ICP‐MS dating indicates that the Shiduolong quartz diorite is coeval with the granodiorite (245 Ma). Whole‐rock geochemical analysis shows that both phases are high‐K calc‐alkaline metaluminous (A/CNK < 1) I‐type granites with similar rare earth (REE) element contents and (La/Yb)N values, indicating that they formed via crystal fractionation from a common parental magma. However, the granodiorite has higher SiO2 contents, lower total Fe2O3, TiO2, MgO, Sr, and Ba contents, and more negative Eu anomalies than the quartz diorites, suggesting that the granodiorite experienced stronger fractional crystallization during magmatic evolution. The zircon εHf(t) values of the quartz diorite range from −3.3 to 1.6. The two‐stage model ages (TDM2) vary from 1,175 to 1,487 Ma. Hf isotope data indicate that the magma of the quartz diorite was mainly derived from partial melting of Mesoproterozoic lower crustal materials with contributions from mantle‐derived magmas. Combined with the regional tectonic and magmatic activities, we propose that the Shiduolong Pb–Zn deposit might have formed during the hydrothermal event associated with the release of magmatic water from the granodiorite‐quartz diorite intrusions, which were generated by the subduction of the Paleo‐Tethys oceanic slab in the Early Triassic.

Fluid inclusion and isotope geochemistry of the Atebayue Sb deposit, South Tianshan Orogen, Kyrgyzstan

The Atebayue Sb deposit is hosted in the Silurian clastics in the South Tianshan Orogen in Kyrgyzstan. The Sb ores appear as veins/veinlets and disseminations, with stibnite being the main ore mineral. Gangue minerals comprise quartz, calcite, and clay minerals. The quartz at Atebayue only contains aqueous fluid inclusions with low homogenization temperature (215–336 °C) and salinity (3.4–6.9 wt.% NaCl equiv.), supporting an epizonogenic hydrothermal origin. The minimum trapping pressures estimated from the NaCl─H2O inclusions are 9–14 MPa, suggesting that the Sb mineralization mainly occurred at a depth of 0.9–1.4 km. Sulphur isotopes (δ34S = −0.4 to 6.2‰) suggest that the host rocks within the Silurian system to be a significant source of ore metals. The ores contain average 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of 18.112, 15.547, and 38.064, respectively, and 2‐stage model ages of 337–381 Ma, indicating the ores were likely sourced from the Paleozoic strata. Integrating the data obtained from the studies including ore geology, fluid inclusion, and S─Pb isotope geochemistry, we conclude that that the Atebayue Sb deposit is best classified as epizonogenic type formed by the Tarim–Kazakhstan continent–continent collision.

Early Carboniferous tectonic evolution of the northern Heihe–Nenjiang–Hegenshan suture zone, NE China: Constraints from the mylonitized Nenjiang rhyolites and the Moguqi gabbros

The Heihe–Nenjiang–Hegenshan suture zone has long been accepted as the major tectonic boundary between the Xing’an and Songliao blocks and extends through the Great Xing’an Range in NE China, but its location of the northern segment between the Moguqi and Nenjiang areas and its timing remain unclear. We address these issues by presenting zircon LA‐ICP‐MS U–Pb ages, Lu‐Hf isotopes, bulk‐rock major, and trace elemental data for mylonitized rhyolites collected from the Moergenhe Formation in the Nenjiang area and for gabbros of the Moguqi area, respectively. The mylonitized rhyolites, which display an arc‐related geochemical affinity with enrichment in Th and U, and depletion of Nb, Ta, and Ti, and gently right‐tilted rare earth element (REE) patterns (light REE [LREE]/heavy REE [HREE] =4.53–7.60), as well as the εHf (t) values (+6.4 to +11.8) of analyzed zircons, indicate an origin by partial melting of potentially young lower continental crust of a subducting slab. The zircon LA‐ICP‐MS U–Pb data show the formation age of the mylonitized rhyolites is 352.4 Ma. The analyzed gabbros with an emplacement age of 352.6 Ma have high concentrations of Th and U, slightly enriched LREE patterns and relative low LREE/HREE ratios (4.3 to 4.6). These features, together with their high positive εHf (t) values (+7.7 to +15.2), suggest that they were likely derived from the partial melting of a depleted mantle source that was metasomatized by subduction‐related fluids. Combined with the geochemical features of the coeval igneous rocks from the northern Great Xing’an Range, these results reveal that the existence of an early Carboniferous NE‐trending magmatic arc (ca. 350–330 Ma), extending along the west of the Heihe–Nenjiang–Hegenshan suture zone, gives more constraints on the amalgamation of the Xing’an and Songliao blocks along the Nenjiang–Moguqi areas and indicates that the amalgamation should have terminated by at least the end of the early Carboniferous.