U–Pb zircon geochronology and geochemistry of Neoproterozoic volcanic rocks in the Tarim Block of northwest China: implications for the breakup of Rodinia supercontinent and Neoproterozoic glaciations

2005 ◽  
Vol 136 (2) ◽  
pp. 107-123 ◽  
Author(s):  
Bei Xu ◽  
Ping Jian ◽  
Haifei Zheng ◽  
Haibo Zou ◽  
Lifei Zhang ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Northwest China ◽  
Zircon Geochronology ◽  
Tarim Block ◽  
Rodinia Supercontinent ◽  
Neoproterozoic Glaciations

scholarly journals Lower Moscovian limestones of the Bogdashan Range (NW China) as an indicator of cessation of arc magmatism in the Junggar region

2019 ◽  
Vol 27 (1) ◽  
pp. 57-78
Author(s):  
D. V. Alexeiev ◽  
Yu. S. Biske ◽  
A. V. Djenchuraeva ◽  
B. Wang ◽  
O. L. Kossovaya ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Foreland Basin ◽  
Northwest China ◽  
Island Arc ◽  
Tien Shan ◽  
Lower Permian ◽  
Carbonate Sediments ◽  
Tropical Zone ◽  
Middle Carboniferous ◽  
Marine Facies

The field revision of the Carboniferous and Lower Permian stratigraphy of the northern Bogdashan (South Junggar, Northwest China) shows that the Lower to Middle Carboniferous island arc volcanic rocks, widely developed in this region, are overlapped everywhere by carbonate and terrigenous-carbonate sediments, containing occasional lava flows and overlain up the section by thick terrigenous series practically devoid of volcanic rocks. The deposition of limestone occurred at the stage of dying off of a volcanic arc, and the question of their age is of fundamental importance for dating this event. Carbonates are represented by facies of lagoons, shoals, and bioherms that formed on the leveled surface of the arc and on the slopes of the last active volcanoes. Bioherms are Waulsortian mounds and are mainly composed of algal limestones and carbonate mud. There are no framestones composed of corals and sponges (chaetetids) typical of the tropical zone. The facies of shallow crinoid-fusulinid limestones typical of the adjacent territories of the Southern Tien Shan and Tarim are poorly represented. Paleogeographically, the position of bioherms corresponds to the northern boundary of the realm of Pennsylvanian reefs. On the basis of foraminifers, brachiopods, and corals, the age of carbonates is early Moscovian (ca. 315–310 Ma). Cessation of island-arc volcanism, followed by the accumulation of limestone in Bogdashan, occurred sub-synchronously with formation of the West Junggar (Bayingou) suture and may reflect docking of the Bogdashan arc to the Yili active margin of the Kazakhstan continent. Further subsidence of Bogdashan and adjacent regions of the Junggar and Turfan basins, which was somewhat slower at the end of the Carboniferous and more intense in the Early and Middle Permian, may reflect the development of the foreland basin that formed along the northern flank of the Tien Shan orogen. Marine facies were locally preserved in this basin until the Artinskian (ca. 285 Ma), and later the Junggar and Turfan basins lost connection to the ocean and developed in continental environments.

scholarly journals Geology, Fluid Inclusions and Stable Isotopes of the Xialiugou Polymetallic Deposit in North Qilian, Northwest China: Constraints on its Metallogenesis

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 478
Author(s):  
Yongjun Shao ◽  
Huajie Tan ◽  
Guangxiong Peng ◽  
Jiandong Zhang ◽  
Jianzhou Chen ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Northwest China ◽  
Polymetallic Deposit ◽  
The North ◽  
Vms Deposits ◽  
Forming Temperature ◽  
North Qilian Orogenic Belt ◽  
North Qilian

The Xialiugou polymetallic deposit is located in the North Qilian Orogenic Belt, Northwest China, of which the main ore-bearing strata are the Middle Cambrian Heicigou Group. The mineralization is zoned with “black” orebodies (galena–sphalerite), which are stratigraphically above the “yellow” orebodies (pyrite–chalcopyrite–tennantite) at the lower zone, corresponding to the alteration assemblages of quartz–sericite in the ore-proximal zone and chlorite in the ore-distal zone. The Xialiugou mineralization can be divided into three stages: (1) Stage I (pyrite); (2) Stage II (chalcopyrite–tennantite–sphalerite); and (3) Stage III (galena–sphalerite). Fluid inclusions data indicate that the physicochemical conditions that lead to ore formation were the medium–low temperature (157–350 °C) and low salinity (0.17–6.87 wt % NaCleqv), and that the ore-forming temperature tended to decrease with the successive mineralization processes. Taking the H–O isotopic compositions (δDV-SMOW = −51.0‰ to −40.5‰, δ18OH2O = −0.4‰ to 8.6‰) into consideration, the ore-forming fluids were most likely derived from seawater with a small amount of magmatic- and meteoric-fluids input. In addition, the combined S (−3.70‰ to 0.10‰) and Pb isotopic (206Pb/204Pb = 18.357 to 18.422, 207Pb/204Pb = 15.615 to 15.687, 208Pb/204Pb = 38.056 to 38.248) data of pyrite indicate that the ore-bearing volcanic rocks may be an important source of ore-forming materials. Finally, we inferred that the Xialiugou deposit shares similarities with the most important volcanogenic massive sulfide (VMS) deposits (Baiyinchang ore field) in China and typical “black ore” type VMS deposits worldwide.

Reconciling zircon and monazite thermometry constrains H2O content in granitic melts

2020 ◽  
Author(s):  
Silvia Volante ◽  
William Collins ◽  
Chris Spencer ◽  
Eleanore Blereau ◽  
Amaury Pourteau ◽  
...  
Keyword(s):  
Water Content ◽  
Volcanic Rocks ◽  
Saturation Temperature ◽  
Granitic Rocks ◽  
Zircon Geochronology ◽  
Bulk Rock ◽  
Independent Evidence ◽  
Water Values ◽  
Host Rocks ◽  
Eastern Domain

<p>In this contribution, we compare and test the reliability of zircon and monazite thermometers and suggest a new and independent method to constrain the H<sub>2</sub>O content in granitic magmas from coeval zircon and monazite minerals. We combine multi-method single-mineral thermometry (bulk-rock zirconium saturation temperature (T<sub>zr</sub>), Ti-in-zircon (T<sub>(Ti-zr</sub><sub>)</sub>) and monazite saturation temperature (T<sub>mz</sub>)) with thermodynamic modelling to estimate water content and P–T conditions for strongly-peraluminous (S-type) granitoids in the Georgetown Inlier, NE Queensland. These granites were generated within ~30 km thick Proterozoic crust, and emplaced during regional extension associated with low-pressure high-temperature (LP–HT) metamorphism.</p><p>SHRIMP U–Pb monazite and zircon geochronology indicates synchronous crystallization ages of c. 1550 Ma for granitic rocks emplaced at different crustal levels—from the eastern deep crustal domain (P = 6–9 kbar), through the middle crustal domain (P = 4–6 kbar), to the western upper crustal domain (P = 0–3 kbar).</p><p>Bulk-rock T<sub>zr</sub> and T<sub>(Ti-zr</sub><sub>)</sub> yielded magma temperature estimates for the eastern domain of ~800°C and ~910–720°C, respectively. Magma temperatures in the central and western domains were ~730°C (T<sub>zr</sub>) and ~870–750°C (T<sub>(Ti-zr)</sub>) in the central domain, and ~810°C (T<sub>zr</sub>) and ~890–720°C (T<sub>(Ti-zr)</sub>) in the western domain, respectively. These temperature estimates were compared with P–T conditions recorded in the host rocks to determine if the magmas had equilibrated thermally with the crust. Similar temperatures were obtained for the middle and lower crust suggesting that the associated magmas thermally equilibrated at their respective depths, whereas the sub-volcanic rocks were, as expected, significantly hotter than the adjacent crust.</p><p>By plotting the results on a P–T–X<sub>H2O</sub> petrogenetic grid, and assuming adiabatic ascent through the crust, the sub-volcanic magmas appear to be drier (~3 wt% H<sub>2</sub>O) than the granitic magmas (~7 wt% H<sub>2</sub>O) which formed at greater depth. Monazite saturation temperatures (which depends on the water content, light–REE content and composition of the granitic melt), are in agreement with the zircon thermometers only if water values of ~3 wt% H<sub>2</sub>O and ~7 wt% H<sub>2</sub>O are assumed for the upper crustal magmas and deeper magmas, respectively. Moreover, melt compositions extracted from a modelled pseudosection of a sillimanite-bearing metapelite, which was interpreted to be the typical source rock for the surrounding granites (P=5 kbar and T=690°C–850°C), show comparable water content values.</p><p>The T<sub>mz</sub> results provide independent evidence for the H<sub>2</sub>O content in magmas, and we suggest that reconciling T<sub>zr</sub> with T<sub>mz</sub> is a new and independent way of constraining H<sub>2</sub>O content in granitic magmas.</p>

U-Pb zircon geochronology, geochemistry and kinetics of the Huaniushan A-type granite in Northwest China

2012 ◽  
Vol 31 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Jiang Zhu ◽  
Xinbiao Lü ◽  
Xiaofeng Cao ◽  
Yalong Mo ◽  
Chao Chen
Keyword(s):  
Northwest China ◽  
Zircon Geochronology ◽  
Type Granite ◽  
Kinetics Of
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