Search

There are 25 Li-rich geothermal fields (>15 mg/L) are displayed throughout nine geothermal zones in Tibet. The Kawu geothermal system is one of the representative high-enthalpy and Li-rich geothermal systems and is located in the Skaya dome, the Himalayas. Their boiling and hot and cold waters are Cl-HCO3-Na and HCO3-Ca types, respectively. The parent geothermal fluids are characterized by high Na, Cl, B, Si, As, Li, Rb+, Cs+ and F, and the Cl− concentration and enthalpy of the parent geothermal liquid are 515 mg/L and 1,485 J/g, respectively (corresponding to a temperature of 323.5°C). The stable oxygen and hydrogen isotopic compositions of geothermal fluids range from −19.7 to −23.4‰ and −155 to −181.2‰, indicating that the ratio of magmatic water mixed into geothermal fluid is between 11.7% and 19.5%. The lithium content in the geothermal system is high (13.04 to 20.8 ppm), but the δ7Li is relatively low (1.06 to 1.72‰). The high Cl, Li and B contents, constant Cl/Li and Cl/B ratios and low δ7Li indicate that they mainly originate from magmatic fluid, rather than from water rock reaction with the leucogranite and gneiss. While ascending from the reservoirs to the surface, the parent geothermal fluids gradually mixed with the meteoric waters infiltrated via brittle tensional small-scale faults, in turn forming four cooling processes upwelling patterns, i.e. conductive cooling, adiabatic cooling, mixing with cold water, and the combination of these processes. [ABSTRACT FROM AUTHOR]

The Cryogenian Period (717–635 Ma) experienced two low‐latitude "snowball Earth" glaciations, the Sturtian and the Marinoan of contrasting 57 and <16 Myr durations, respectively. A lack of reliable age controls on extensional tectonics and associated magmatic rocks during the Marinoan has hampered an understanding of the deglaciation. Furthermore, although deglaciation is generally assumed to have occurred once ongoing magmatism accumulated enough atmospheric CO2, as suggested by cap carbonates, specific geologic evidence linking volcanic events with deglaciation are lacking. Here, we present high‐precision zircon geochronology with chemical abrasion‐isotope‐dilution isotope ratio mass spectrometry that indicates an extensive and thick sequence of rift‐related magmatic rocks in South Qinling, Central China, erupted 2–6 Myr before the termination of the Marinoan. Climate modeling proposes a scenario explaining why the Marinoan was the shorter snowball and how volcanism may have driven the deglaciation. Plain Language Summary: Volcanic CO2 and dust emissions have been regarded as the major driver for Marinoan deglaciation. Most of CO2 outgassing is associated with seafloor spreading and subduction (arc magmatism), which are ongoing processes on geological timescales. To drastically increase CO2 emissions, there must have been many active rift zones during Marinoan glaciation. We provide age constraints on a previously little‐known major Marinoan rift‐related volcanic suite in South Qinling, which reveals volcanic activity lasting 4 Myr and ending 2 Myr before the termination of the Marinoan snowball Earth. Climate modeling provides constraints for the ice‐age duration deduced from the geological setting. Key Points: Volcanism is dated at 641–637 Ma using chemical abrasion‐isotope‐dilution isotope ratio mass spectrometry techniqueClimate modeling on the volcanism‐related CO2 emission is conductedEnhanced volcanic‐related dust and CO2 emission can shorten the Marinoan snowball Earth by 2–5 Myr [ABSTRACT FROM AUTHOR]

There has been considerable debate concerning the petrogenesis of Cenozoic highly felsic, strongly peraluminous, leucogranites within the Himalayan–Tibetan orogen, with two contrasting viewpoints regarding their origin, either as primary melts from parting melting or magmatic differentiation. This debate hampers our understanding of the tectono‐magmatic evolution and associated uplift and exhumation processes during Himalayan orogenesis. This study attempts to resolve this debate by means of an integrated petrographic, geochronological, and geochemical study on the Cenozoic Cuonadong leucogranites (including two‐mica granites, garnet‐bearing granites, and tourmaline‐bearing granites) in the eastern part of the south Himalayan–Tibetan orogen. One SHIRIMP zircon U–Pb dating of two‐mica granites and four LA–ICP–MS monazite U–Th–Pb dating of all three types of granites yield ages of ca. 21.9–19.7 Ma. Combined with previous published continuous U–Th–Pb zircon/monazite ages varying from 16.5 to 21.8 Ma, indicating that Cuonadong leucogranites have experienced continuously multiple episodes of intrusion and long‐term crystallization from ca.16 to 22 Ma, and lasted for ca. 6 Myrs. Major and trace element geochemistry combined with whole‐rock Sr–Nd isotope data suggest that the Cuonadong's three types of leucogranites are highly fractionated and garnet‐ and tourmaline‐bearing granites are more evolved. The Cuonadong leucogranite melts are mainly derived from metapelites within the High Himalayan Crystalline Sequence, and underwent fractional crystallization of biotite, monazite, and plagioclase during melt migration. This study indicates Cuonadong leucogranites are Cenozoic highly fractionated strongly peraluminous leucogranites, which, combined with previous intermittent documentations of fractionated leucogranites, point to an increasing maturation of the continental crust composition during continental orogenesis. [ABSTRACT FROM AUTHOR]

The article focuses on a research paper on the geological study of Chalapu Goldfield in South Tibet, China. Topics discussed include the nature and source of ore-forming fluids of the gold deposit, gold and sulphide mineralization and the analysis of fluid inclusions suggesting high carbon dioxide content.

The article focuses on a research paper discussing the geochemical characteristics of the Lower Jurassic Ritang formation in the North Himalayan Metallogenic Belt. It analyzes the ore-forming elements in the Zhaxikang animony-lead-zinc-silver (Sb-Pb-Zn-Ag) polymetallic ore-concentrated area in South Tibet, China. It also suggests that seafloor hydrothermal activity accounts for the enrichment of ore-forming elements in Ritang Formation.

Graphical abstract Highlights • Neoproterozoic sedimentary rocks in South China contain xenotime with SIMS Pb-Pb ages of ca. 400 Ma. • Ages and chemical and imaging analyses suggest these xenotime are hydrothermal in origin. • Xenotime and its rutile substrate were precipitated simultaneously from hydrothermal fluids. • Percolating hydrothermal fluids leached Fe and Ti from ilmenite and precipitated rutile and pyrite. Abstract This study has documented two kinds of xenotime overgrowths from the Cryogenian-Ediacaran sedimentary rocks in South China. The identical tetragonal dipyramidal structures prompted one type of xenotime to overgrow detrital zircon grains, whereas the other type coexists with rutile crystals. SIMS Pb-Pb, NanoSIMS, EPMA, and TEM imaging analyses suggest these xenotime overgrowths, together with their rutile substrate could be of hydrothermal origin; formed by means of percolating fluids leaching ilmenite and REE(Y) bearing silicate minerals. Iron, Ti, and REE(Y) ions leached in this way were combined with O, S, and P anions to precipitate rutile, xenotime, iron oxides, and pyrite in other pore spaces. Such fluid induced activities were probably induced by the ca. 460–390 Ma Wuyi-Yunkai Orogeny in South China. The most important finding is that the rutile-xenotime assemblage was precipitated almost simultaneously, rendering a dissolution-reprecipitation process impossible. Absence of dissolution margins on detrital zircons suggest detrital Fe-Ti oxides are more prone to be leached by fluids than zircon grains, probably because the latter has more stable chemical properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Jiru porphyry copper deposit was formed by two magmatic-hydrothermal events. [•] Early event was caused by 48.6Ma monzogranite formed in syncollision setting. [•] Late event resulted from 16Ma monzogranite porphyry in postcollisional setting. [ABSTRACT FROM AUTHOR]