Elemental and Sr-Nd isotopic geochemistry of Cretaceous to Early Paleogene granites and volcanic rocks in the Sikhote-Alin Orogenic Belt (Russian Far East): implications for the regional tectonic evolution

2017 ◽  
Vol 146 ◽  
pp. 383-401 ◽  
Author(s):  
Pan Zhao ◽  
Bor-ming Jahn ◽  
Bei Xu
Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 103
Author(s):  
Nikolai Berdnikov ◽  
Victor Nevstruev ◽  
Pavel Kepezhinskas ◽  
Ivan Astapov ◽  
Natalia Konovalova

While gold partitioning into hydrothermal fluids responsible for the formation of porphyry and epithermal deposits is currently well understood, its behavior during the differentiation of metal-rich silicate melts is still subject of an intense scientific debate. Typically, gold is scavenged into sulfides during crustal fractionation of sulfur-rich mafic to intermediate magmas and development of native forms and alloys of this important precious metal in igneous rocks and associated ores are still poorly documented. We present new data on gold (Cu-Ag-Au, Ni-Cu-Zn-Ag-Au, Ti-Cu-Ag-Au, Ag-Au) alloys from iron oxide deposits in the Lesser Khingan Range (LKR) of the Russian Far East. Gold alloy particles are from 10 to 100 µm in size and irregular to spherical in shape. Gold spherules were formed through silicate-metal liquid immiscibility and then injected into fissures surrounding the ascending melt column, or emplaced through a volcanic eruption. Presence of globular (occasionally with meniscus-like textures) Cu-O micro-inclusions in Cu-Ag-Au spherules confirms their crystallization from a metal melt via extremely fast cooling. Irregularly shaped Cu-Ag-Au particles were formed through hydrothermal alteration of gold-bearing volcanic rocks and ores. Association of primarily liquid Cu-Ag-Au spherules with iron-oxide mineralization in the LKR indicates possible involvement of silicate-metallic immiscibility and explosive volcanism in the formation of the Andean-type iron oxide gold-copper (IOCG) and related copper-gold porphyry deposits in the deeper parts of sub-volcanic epithermal systems. Thus, formation of gold alloys in deep roots of arc volcanoes may serve as a precursor and an exploration guide for high-grade epithermal gold mineralization at shallow structural levels of hydrothermal-volcanic environments in subduction zones.


2015 ◽  
Vol 9 (6) ◽  
pp. 411-427 ◽  
Author(s):  
V. G. Gonevchuk ◽  
A. I. Khanchuk ◽  
G. A. Gonevchuk ◽  
V. A. Lebedev

2017 ◽  
Vol 47 ◽  
pp. 358-371 ◽  
Author(s):  
Yurii A. Martynov ◽  
Alexander I. Khanchuk ◽  
Andrei V. Grebennikov ◽  
Alexander A. Chashchin ◽  
Vladimir K. Popov

Author(s):  
L. А. Fedina ◽  
◽  
О. L. Burundukova ◽  

Wild ginseng Panax ginseng C. A. Mey. (Araliaceae) is a rare medicinal plant. The aim of this work is to assess the state of ginseng cenopopulations in the Ussuriysky State Nature Reserve, and to search of indicator species of its optimal habitats. The reserve is located on the southern spurs of the Sikhote-Alin ridge in the basins of the Artyomovka and Komarovka rivers. In the course of route studies in the period from 2012 to 2019, phenological observations, description of habitats, determination of the age status and morphometry of 77 plants found in 8 types of forest were carried out. A large part of the finds belong to the cedar forests hornbeam – 44.4 %. Analysis of the species composition of the immediate environment of the relic, performed on 36-meter sites, revealed 41 species of vascular plants. Based on the generalized analysis of author's and literature data, a list of 7 species–indicators of optimal habitats for ginseng reintroduction was selected: Oxalis acetosella, Phryma asiatica, Hylomecon vernalis, Thalictrum filamentosum, Maianthemum bifolium, Galium davuricum, Carex ussuriensis. The number and composition of associated species varies depending on the type of forest. Long-term observations carried out in the reserve have revealed significant changes in the phenology of P. ginseng. In recent years, there has been a shift in the beginning of the growing season, flowering and ripening of fruits to earlier dates. Modern findings of ginseng in atypical habitats are described, indicating a broader ecological amplitude of its growth than was indicated by the first researchers. The age composition of the population is normal, but incomplete, there are no senile, very few mature generative plants, the rise falls on the group of medium-generative plants. In order to construct a vitality spectrum, plants from the most numerous age group in the generative middle-aged state g2 (n = 22) are ranked according to stem height into three vitality classes: higher (> 55 cm), medium (35-55 cm) and lower (< 35 cm). Frequency distribution analysis revealed predominance plants of the higher and middle classes of vitality. The vital spectrum indicates the equilibrium state of the population. Good fruiting and renewal of ginseng indicates the preservation of the species in the protected area, and the compliance of modern conditions of natural habitats to its ecological optimum.


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