Combined Zircon, Molybdenite, and Cassiterite Geochronology and Cassiterite Geochemistry of the Kuntabin Tin-Tungsten Deposit in Myanmar

2020 ◽  
Vol 115 (3) ◽  
pp. 603-625 ◽  
Author(s):  
Wei Mao ◽  
Hong Zhong ◽  
Jiehua Yang ◽  
Yanwen Tang ◽  
Liang Liu ◽  
...  

Abstract The Kuntabin Sn-W deposit, located in southern Myanmar, is characterized by abundant greisen-type and quartz vein-type cassiterite and wolframite mineralization. We have conducted multiple geochronological methods and isotope and trace element analyses to reveal the age and evolution of the Kuntabin magmatichydrothermal system. Zircon U-Pb dating of the two-mica granite yielded a weighted mean 206Pb/238U age of 90.1 ± 0.7 Ma. Cassiterite U-Pb dating provided a lower intercept age of 88.1 ± 1.9 Ma in the Tera-Wasserburg U-Pb concordia diagram. Molybdenite Re-Os dating returned a weighted mean model age of 87.7 ± 0.5 Ma and an isochron age of 88.7 ± 2.7 Ma. These ages indicate a genetic relationship between granite and Sn-W mineralization in the Kuntabin deposit and record the earliest magmatism and Sn-W mineralization in the Sibumasu and Tengchong terranes related to subduction of the Neo-Tethys oceanic slab. Three generations of cassiterite have been identified with distinctive cathodoluminescence textures and trace element patterns, indicating the episodic input of ore-forming fluids and distinctive changes in the physical-chemical conditions of the Kuntabin magmatichydrothermal system. Sudden changes of fluid pressure, temperature, pH, etc., may have facilitated the deposition of Sn and W. Rhenium contents of molybdenite from the Kuntabin deposit and many other Sn-W deposits in Myanmar are characteristically low compared to porphyry Cu-Mo-(Au) deposits worldwide. In combination with zircon Hf isotope signatures, we infer that granites associated with Sn-W deposits in Myanmar were predominantly derived by melting of ancient continental crust and contain minimal mantle contribution. Subduction of the Neo-Tethys oceanic slab from west of the West Burma terrane reached beneath the Sibumasu terrane and led to magmatism and Sn-W mineralization at ~90 Ma when the Kuntabin deposit was formed. The Paleoproterozoic Sibumasu crust was activated during the subduction-related magmatism to form predominantly crust derived melts. After a high degree of fractional crystallization and fluid exsolution, physical-chemical changes of the hydrothermal fluid resulted in Sn and W precipitation to form the Kuntabin Sn-W deposit.

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 725
Author(s):  
Ludmila B. Damdinova ◽  
Bulat B. Damdinov

This article discusses the peculiarities of mineral composition and a fluid inclusions (FIs further in the text) study of the Kholtoson W and Inkur W deposits located within the Dzhida W-Mo ore field (Southwestern Transbaikalia, Russia). The Mo mineralization spatially coincides with the apical part of the Pervomaisky stock (Pervomaisky deposit), and the W mineralization forms numerous quartz veins in the western part of the ore field (Kholtoson vein deposit) and the stockwork in the central part (Inkur stockwork deposit). The ore mineral composition is similar at both deposits. Quartz is the main gangue mineral; there are also present muscovite, K-feldspar, and carbonates. The main ore mineral of both deposits is hubnerite. In addition to hubnerite, at both deposits, more than 20 mineral species were identified; they include sulfides (pyrite, chalcopyrite, galena, sphalerite, bornite, etc.), sulfosalts (tetrahedrite, aikinite, stannite, etc.), oxides (scheelite, cassiterite), and tellurides (hessite). The results of mineralogical and fluid inclusions studies allowed us to conclude that the Inkur W and the Kholtoson W deposits were formed by the same hydrothermal fluids, related to the same ore-forming system. For both deposits, the fluid inclusion homogenization temperatures varied within the range ~195–344 °C. The presence of cogenetic liquid- and vapor-dominated inclusions in the quartz from the ores of the Kholtoson deposit allowed us to estimate the true temperature range of mineral formation as 413–350 °C. Ore deposition occurred under similar physical-chemical conditions, differing only in pressures of mineral formation. The main factors of hubnerite deposition from hydrothermal fluids were decreases in temperature.


2021 ◽  
Vol 43 (4) ◽  
pp. 50-55
Author(s):  
L.V. SHUMLYANSKYY ◽  
V. KAMENETSKY ◽  
B.V. BORODYNYA

Results of a study of U-Pb and Hf isotope systematics and trace element concentrations in five zircon crystals separated from the Devonian Petrivske kimberlite are reported in the paper. Four zircons have yielded Paleoproterozoic and Archean ages, while one zircon grain gave a Devonian age of 383.6±4.4 Ma (weighted mean 206Pb/238U age). The Precambrian zircons have been derived from terrigenous rocks of the Mykolaivka Suite that is cut by kimberlite, or directly from the Precambrian rock complexes that constitute continental crust in the East Azov. The Devonian zircon crystal has the U-Pb age that corresponds to the age of kimberlite emplacement. It is 14 m.y. younger than zircon megacrysts found in the Novolaspa kimberlite pipe in the same area. In addition, Petrivske zircon is richer in trace elements than its counterparts from the Novolaspa pipe. Petrivske and Novolaspa zircons crystallized from two different proto-kimberlite melts, whereas the process of kimberlite formation was very complex and possibly included several episodes of formation of proto-kimberlite melts, separated by extended (over 10 M.y.) periods of time.


2017 ◽  
Vol 2 (1) ◽  
Author(s):  
Anna P. Rodrigues ◽  
Elena Moltchanova ◽  
David A. Norton ◽  
Matthew Turnbull

AbstractBiotic factors such as the presence of invasive animal and/or plant species are well known as major causes of ecological degradation and as limiting either natural or assisted (human-induced) ecological restoration. However, abiotic aspects of the landscape, such as water availability and soil physical/chemical conditions can also potentially limit restoration and should be considered. Dryland ecosystems are amongst the world’s most threatened and least protected. New Zealand’s drylands have been drastically changed, initially through burning, agricultural and grazing practices and the impacts of introduced herbivores and plants. This research aimed at identifying some of the key environmental factors preventing the reestablishment of native woody species in a New Zealand dryland ecosystem. The experiments involved a combination of shading, irrigation and grazing exclusion. The results showed that supplemental water was not beneficial for the survival and growth of the native seedlings, unless combined with shade. Fencing proved important for establishment, even though the species used are regarded in the literature as unpalatable to herbivores. The results indicated that the presence of shade was fundamental for the establishment and growth of the native seedlings likely due to improvements in the microclimate, soil aeration, and water availability to seedlings.


2018 ◽  
Vol 18 (2) ◽  
Author(s):  
Muhammad Junaidi ◽  
Nurliah Nurliah ◽  
Fariq Azhar

ABSTRAKMengingat peranan zooplankton dalam ekosistem perairan sangat penting, maka dilakukan penelitian dengan tujuan untuk menganalisis struktur komunitas zooplankton yang meliputi jenis, kelimpahan, dan indek ekologi, dan  kaitan  distribusi zooplankton dan kualitas perairan di Perairan Kabupaten Lombok Utara. Pengumpulan data dirancang dengan sistem informasi geografis (SIG) pada 23 stasiun pengamatan yang ditentukan dengan teknik acak sederhana.  Hasil penelitian menunjukkan bahwa jenis dan kelimpahan zooplankton yang ditemukan di Perairan Kabupaten Lombok Utara cukup bervariasi dengan jumlah genus  sebanyak 9 yang terbagi  dari  5 kelas.  Berdasarkan perhitungan indeks ekologi menunjukkan bahwa struktur  komunitas zooplankton dalam kategori perairan yang kurang stabil. Kelimpahan dan indeks ekologi zooplankton  dipengaruhi oleh kondisi lingkungan (fisik-kimia) perairan antara lain  kecerahan, pH dan oksigen terlarut. Kata kunci : zooplankton,  struktur komunitas, kualitas perairan, kelimpahanABSTRACTConsidering that the role of zooplankton in aquatic ecosystems is very  important, research is carried out with the aim of analyzing zooplankton community structure which includes the type, abundance, and ecological index, and the relation of zooplankton distribution and water quality in North Lombok Regency Waters. Data collection was designed with a geographical information system (GIS) on 23 observation stations that were determined by simple random techniques. he results of this study indicate that the type and abundance of zooplankton found in the waters of North Lombok Regency are quite varied with the number of genus as many as 9 which are divided into 5 classes. Based on the calculation of the ecological index shows that the zooplankton community structure is in the category of less stable waters. The abundance and ecological index of zooplankton is influenced by the environmental (physical-chemical) conditions of the waters including brightness, pH and dissolved oxygen. Keywords: zooplankton, community structure, water quality, abundance 


Author(s):  
Gustavo Ramírez T.

Physical-chemical conditions have been studied in the Bay of Santa Marta, Colombian Caribbean, from August 1980 to July 1981. The results obtained at nine stations indicate that the surface water is rather homogeneous and of mainly oceanic character. In the period from december to april water temperatures were lowest (<25®C), salinity highest (>36°/oo) and undersaturation with oxigen occured (<91%) these factors together with pH, alcalinity and the variation of water column stability are indicating an upwelling phenomenon in this period and allow the stablishment of an approximated model for the annual cycle the bay.


2010 ◽  
Vol 1 (1) ◽  
pp. 55-66 ◽  
Author(s):  
A. Gross-Wittke ◽  
G. Gunkel ◽  
A. Hoffmann

In the city of Berlin, artificial groundwater recharge techniques, such as bank filtration and infiltration ponds, are an important source for drinking water production. Climate change with increasing surface water temperatures can influence the water purification processes during bank filtration mainly due the intensification of metabolic processes leading to a decrease of oxygen and an increase of anaerobic conditions. In Lake Tegel a significant increase of water temperature in the epilimnion of 2.4°C within the last 30 years was recorded. For a better understanding of induced bank filtration at Lake Tegel, redox processes and physical-chemical conditions within the surface sediment layers (0–26 cm depth) at the littoral infiltration zone were investigated. The influence of temperature in the range of 0–25°C on microbial catalysis of redox processes, such as reduction of nitrate and sulphate, was examined during the period March 2004–June 2005. High water temperatures (16–25°C) were accompanied by negative redox potentials (EH=−47 mV) and decreasing Ninorg concentrations, while the amount of ammonia, Mn2 +  and Fe2 +  was rising. This indicates redox processes such as denitrification, Mn4 +  reduction, nitrate respiration and ammonification, as well as Fe3 +  reduction. The reduction of sulphate, however, has not yet become significant at Lake Tegel, but with increasing water temperature, sulphate reduction must be expected.


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