Adakite-like granitoids of Songkultau: A relic of juvenile Cambrian arc in Kyrgyz Tien Shan

The early Paleozoic Terskey Suture zone, located in the southern part of the Northern Tien Shan domain in Kyrgyzstan, comprises tectonic slivers of dismembered ophiolites and associated primitive volcanics and deep-marine sediments. In the Lake Songkul area, early-middle Cambrian pillow basalts are crosscut by the Songkultau intrusion of coarse-grained gneissose quartz diorites and tonalites with geochemical characteristics typical for high-SiO2 adakites (SiO2 ​> ​56 ​wt.%, Al2O3 ​> ​15 ​wt.%, Na2O ​> ​3.5 ​wt.% and high Sr/Y and La/Yb ratios). The Songkultau granitoids have positive initial εNd (+3.8 to +6.4) and εHf (+12.3 to +13.5) values indicating derivation from sources with MORB-like isotopic signature. Volcanic formations, surrounding the Songkultau intrusion, have geochemical affinities varying from ocean floor to island arc series. This rock assemblage is interpreted as a relic of an early-middle Cambrian primitive arc where the adakite-like granitoids were derived from partial melting of young and hot subducted oceanic crust. An age of 505 ​Ma, obtained for the Songkultau intrusion, shows that hot subduction under the Northern Tien Shan continued until middle Cambrian. The primitive arc complexes were obducted onto the Northern Tien Shan domain, where the Andean type continental magmatic arc developed in Cambrian and Ordovician. Formation of the Andean type arc was accompanied by uplift, erosion and deposition of coarse clastic sediments. A depositional age of ca. 470 Ma, obtained for the gravellites in the Lake Songkul area, is in agreement with the timing of deposition for lower Ordovician conglomerates elsewhere in the Northern Tien Shan, and corresponds to the main phase of the Andean type magmatism. The Songkultau adakites in association with surrounding ocean floor and island arc formations constitute a relic of a primitive Cambrian arc and represent a juvenile domain of substantial size identified so far within the predominantly crustal-derived terranes of Tien Shan. On a regional scale this primitive arc can be compared with juvenile Cambrian arcs of Kazakhstan, Gorny Altai and Mongolia.©2020 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Mineralogical study of the Gonçalo Li-pegmatite deposit, Portugal

Beside the Scandinavian countries and Serbia, Portugal is among the European countries with the most significant lithium resources. The Li-rich occurrences in Portugal are mainly associated with aplite-pegmatite dykes and sills intruded in granitic and metasedimentary rocks of the Central Iberian and Galicia – Trás-os-Montes geotectonic zones (Carvalho & Farinha, 2004). The Gonçalo Li-pegmatites in the Guarda district (currently only used as decorative stone) have significant economic importance. Among other deposits, Gonçalo is a reference site in the focus of the EU FAME project (www.fame-project.eu) that aims to unlock the development potential of the most promising European Sn-W-Li ore types. Results of optical microscopy, QEMSCAN©, Raman and electron-probe microanalysis of the Gonçalo Li-pegmatite deposit have been employed to determine the mineralogical variability of the pegmatites with the aim to determine the deportment of lithium and potential rare-metal by-products and to guide enhanced mineral processing technologies.Available to download freely and reproduced here with permission of the publisher. The attached file is the published pdf

Cooling and exhumation of the Late Paleozoic Tulasu epithermal gold system, Western Tianshan, NW China: implications for preservation of Pre-Mesozoic epithermal deposits

Epithermal gold deposits are rarely well preserved in pre-Mesozoic terranes because their low-temperature mineralization in shallow crust levels, and easily destroyed by subsequent erosion or depleted by tectonic events. However, several significant late Paleozoic epithermal gold deposits have been found in the Tulasu volcanic basin in NW China, forming one of the largest gold districts in the western Tianshan orogen. Here, we report new 40Ar/39Ar age from a monzonite porphyry enclave hosted in andesite and apatite fission track (AFT) data for 10 volcanic rocks from the Tulasu basin. These data, combined with the previous dataset, are used to perform inverse thermal modelling to quantify the district's cooling and exhumation history. Our modelling indicates a phase of burial reheating during late Paleozoic sedimentation following the mineralization, and subsequent a rapid exhumation in the Jurassic to Early Cretaceous (∼196–128 Ma), and a slow exhumation until to present. The Mesozoic exhumation is likely related to the far-field effects of the Cimmerian orogeny along the southern Eurasian margin. Therefore, we suggest that the quick burial by thick sediments and the slow protracted exhumation after mineralization were crucial for the preservation of the Paleozoic epithermal gold system at Tulasu.© 2020 The Author(s). Published by The Geological Society of London. All rights reserved. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics The attached file is the final accepted manuscript

Geochemical and isotope studies of element dispersal in the environment during mining and ore processing

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Geochemical and isotope studies of element dispersal in the environment during mining and ore processing

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

National-cultural identity and development of cultural identity of the population of Stavropol Territory

The article considers the results of the research of the national and cultural identity of the population of the Stavropol Territory. The analysis of representations of inhabitants of the territory of the South of Russia about their national identity and the role of cultural attributes defining this identification has been carried out. The factors influencing the development of cultural identity of the population have been studied

MINERALOGICAL AND GEOCHEMICAL FEATURES OF SATPAEV Ti-Zr PLACER DEPOSIT, EAST KAZAKHSTAN

The data of mineralogical and geochemical studies of Ti-Zr mineral sands and heavy fraction of the mineral concentrate of Placer No. 1 of the Satpaev deposit (East Kazakhstan) are obtained. The mineralogical composition of the mineral sands: quartz, albite, ilmenite, and feldspar; micro-sized crystals of barite, zircon, monazite, a mineral of pyrochlore composition, were identified by electron microprobe. Crystal morphology of ore minerals: ilmenite and zircon and chemical composition of ilmenite were determined. The development of leucoxenization in microcracks and edges of ilmenite crystals have also been revealed. Geochemical features of productive horizons include the apparent enrichment of light rare-earth elements (LREE) in comparison with heavy rare-earth elements (HREE), and pronounced negative Eu anomaly that indicate high degree of fractionation of source rocks. Granitoids of the Preobrazhensk intrusion are the likely source of the Satpaev placer deposit. Results of petrological and geochemical research indicate that localization of ore minerals took place during chemical weathering, which enabled release of ore minerals of titanium and zirconium with their further redeposition in local continental coastal settings in warm and humid climate.This is an open access article, available to all readers online. The attached file is the published version of the article

PREDICTIVE ESTIMATE OF Ti-Zr PLACER DEPOSITS IN MESOZOIC AND CENOZOIC SEDIMENTS AT NW MARGINS OF THE ZAYSAN BASIN, EAST KAZAKHSTAN

During the research of orographic, geological and geomorphological characteristics of the Zaysan basin area aiming to identify targeting factors of Ti-Zr alluvial deposits it has been established that the following special favourable conditions are required for their formation: neighbouring occurrence of magmatic rocks with Ti-Zr credit; well-formed deep chemical weathering crust, which has facilitated the release of ore minerals; alluvial, proluvial limnic hydrodynamic conditions for transportation, segregation and concentration of Ti and Zr minerals; availability of local structural particular qualities (tectonic layers, basins), which have prevented the deposits from washing out during transgression and regression of the Zaysan paleo-lake. It has been established that well-known Ti-Zr deposits in the north-west margin areas of the Zaysan basin are geomorphologically located in gentle slope, non-segmented plains of subaerial denudation of 400–700m altitude, within the littoral zone of the Zaysan paleolake. The orographic representation of modern relief of the region have been established, stratigraphic positions of Mesozoic and Cenozoic placer deposits were determined, and an area for prospecting of new Ti-Zr deposits was identified.© National Academy of Sciences of the Republic of Kazakhstan, 2019. This is an open access journal. The attached file is the published pdf

The Muruntau gold deposit (Uzbekistan) – A unique ancient hydrothermal system in the southern Tien Shan

The Muruntau gold deposit in the Central Kyzylkum, Uzbekistan is one of the largest single gold deposits worldwide. Data available from the literature are reviewed with the aim to (1) integrate the present knowledge on this unique deposit from Russian and English literature; (2) show the considerable progress made in the understanding of the genesis of the Muruntau deposit during the last decades; and (3) point to problems still open for future research. Deposit formation occurred through a multi-stage process involving sedimentation, regional metamorphism including thrusting, magmatism with formation of hornfels aureoles and several stages of hydrothermal activity. According to recent knowledge, synsedimentary or pure metamorphic formation of gold mineralization seems unlikely. The role of granite magmatism occurring roughly within the same time interval as the main hydrothermal gold precipitation remains uncertain. There are no signs of interaction of matter between the magma(s) and the hydrothermal system(s). On the other hand, there was an intense, high-temperature (above 400 °C) fluid – wall rock interaction resulting in the formation of gold-bearing, cone-like stockworks with veins, veinlets and gold-bearing metasomatites. Several chemical and isotope indicators hint at an involvement of lower-crustal or mantle-related sources as well as of surface waters in ore formation. Deposit formation through brecciation involving explosion, hydrothermal or tectonic breccias might explain these data. Further investigations on breccia formation as well as on the exact timing of relevant sedimentary, metamorphic, magmatic and hydrothermal events are recommended