The first peak ground motion attenuation relationships for North of Vietnam

The first attenuation relationships of peak ground acceleration (PGA) and peak ground velocity (PGV) for northern Vietnam are obtained in this study. Ground motion data are collected by a portable broadband seismic network in northern Vietnam as a part of cooperation between the Institute of Geophysics, Vietnamese Academy of Science and Technology, Vietnam and Institute of Earth Sciences, Academia Sinica, Taiwan. The database comprises a total of 330 amplitude records by 14 broadband stations from 53 shallow earthquakes, which were occurred in and around northern Vietnam in the period between 01/2006 and 12/2009. These earthquakes are of local magnitudes between 1.6 and 4.6, focal depths less than 30 km, and epicentral distances less than 500 km. The new attenuation relationships for PGA and PGV are:

log₁₀(PGA)=-0.987+0.7521M_L-log₁₀(R)-0.00475R,     

Magnetic and structural study of the Eaux-Chaudes intrusion: understanding the Variscan deformation in the Western Axial Zone (Pyrenees)

The present study provides new magnetic and microstructural data for the Eaux-Chaudes granodioritic massif (Western Axial Zone, Pyrenees) and contributes to the understanding of its geometry, internal structure and emplacement mechanism. Moreover, the geological cross-sections and field data allow to reconstruct the evolution of the whole area from Variscan to Alpine times and to integrate the emplacement of the igneous body in the context of the Variscan orogeny. The Eaux-Chaudes pluton (301?±?9?Ma) is mainly composed by granodiorite, describing a normal compositional zoning and an approximately concentric arrangement that is consistent with the zonation of the low-field magnetic susceptibility. Magnetic foliation is subhorizontal in the inner part of the intrusion and becomes parallel to the petrographical contacts along pluton margins, roughly describing the geometry of the intrusion. Magnetic lineations are dominantly subhorizontal, with E–W to ENE–WSW directional maximum. The general parallelism between Variscan structures of the host rock and the geometry and magmatic fabric of the intrusion reveals a late syn-Variscan emplacement. The tectonic regime registered during magma emplacement is in agreement with an N–S shortening and an E–W stretching direction, consistent with the transpressive regime deduced for other Pyrenean intrusions. Alpine overprint produced a slight tilting in the southern part of the intrusion, but it can be considered that the original Variscan structure is basically unchanged.     

Experimental and petrological constraints on local-scale interaction of biotite-amphibole gneiss with H2O-CO2-（K, Na）Cl fluids at middle-crustal conditions： Example from the Limpopo Complex, South Africa

Reaction textures and fluid inclusions in the～2.0 Ga pyroxene-bearing dehydration zones within the Sand River biotite-hornblende orthogneisses（Central Zone of the Limpopo Complex） suggest that the formation of these zones is a result of close interplay between dehydration process along ductile shear zones triggered by H₂O-CO₂-salt fluids at 750—800℃and 5.5—6.2 kbar.partial melting,and later exsolution of residual brine and H₂O-CO₂ fluids during melt crystallization at 650—700℃.These processes caused local variations of water and alkali activity in the fluids,resulting in various mineral assemblages within the dehydration zone.The petrological observations are substantiated by experiments on the interaction of the Sand River gneiss with the H₂O-CO-2-（K,Na）Cl fluids at 750 and 800℃and 5.5 kbar.It follows that the interaction of biotite-amphibole gneiss with H₂O-CO₂-（K.Na）Cl fluids is accompanied by partial melting at 750—800℃.Orthopyroxene-bearing assemblages are characteristic for temperature 800℃and are stable in equilibrium with fluids with low salt concentrations,while salt-rich fluids produce clinopyroxene-bearing assemblages.These observations arc in good agreement with the petrological data on the dehydration zones within the Sand River orthoeneisses.     

Geology and vein tin mineralization in the Dadoushan deposit,Gejiu district,SW China

Vein-type tin mineralization in the Dadoushan deposit, Laochang ore field, Gejiu district, SW China, is predominantly hosted in Triassic carbonate rocks (Gejiu Formation) over cupolas of the unexposed Laochang equigranular granite intrusion. The most common vein mineral is tourmaline, accompanied by skarn minerals (garnet, diopside, epidote, phlogopite) and beryl. The main ore mineral is cassiterite, accompanied by minor chalcopyrite, pyrrhotite, and pyrite, as well as scheelite. The tin ore grade varies with depth, with the highest grades (~1.2 % Sn) prevalent in the lower part of the vein zone. Muscovite ⁴⁰Ar–³⁹Ar dating yielded a plateau age of 82.7 ± 0.7 Ma which defines the age of the vein-type mineralization. Measured sulfur isotope compositions (δ ³⁴S = −4.1 to 3.9 ‰) of the sulfides (arsenopyrite, chalcopyrite, pyrite, and pyrrhotite) indicate that the sulfur in veins is mainly derived from a magmatic source. The sulfur isotope values of the ores are consistent with those from the underlying granite (Laochang equigranular granite, −3.7 to 0.1 ‰) but are different from the carbonate wall rocks of the Gejiu Formation (7.1 to 11.1 ‰). The calculated and measured oxygen and hydrogen isotope compositions of the ore-forming fluids (δ ¹⁸O_H2O = −2.4 to 5.5 ‰, δD = −86 to −77 ‰) suggest an initially magmatic fluid which gradually evolved towards meteoric water during tin mineralization.     

Fluid evolution of the Hub Stock, Horní Slavkov–Krásno Sn–W ore district, Bohemian Massif, Czech Republic

The Horní Slavkov–Krásno Sn–W ore district is hosted by strongly altered Variscan topaz–albite granite (Krudum granite body) on the northwestern margin of the Bohemian Massif. We studied the fluid inclusions on greisens, ore pockets, and ore veins from the Hub Stock, an apical expression of the Krudum granite. Fluid inclusions record almost continuously the post-magmatic cooling history of the granite body from ～500 to <50°C. Rarely observed highest-temperature (～500°C) highest-salinity (～30?wt.% NaCl eq.) fluid inclusions are probably the result of secondary boiling of fluids exsolved from the crystallizing magma during pressure release which followed hydraulic brecciation of the gneissic mantle above the granite cupola. The greisenization was related to near-critical low-salinity (0–7?wt.% NaCl eq.) aqueous fluids with low amount of CO₂, CH₄, and N₂ (≤10?mol% in total) at temperatures of ～350–400°C and pressures of 300–530 bar. Crush-leach data display highly variable and negatively correlated I/Cl and Br/Cl values which are incompatible with both orthomagmatic and/or metamorphic origin of the fluid phase, but can be explained by infiltration of surficial and/or sedimentary fluids. Low fluid salinity indicates a substantial portion of meteoric waters in the fluid mixture that is in accordance with previous stable isotope data. The post-greisenization fluid activity associated with vein formation and argillitization is characterized by decreasing temperature (<350 to <50°C), decreasing pressure (down to ～50–100 bar), and mostly also decreasing salinity.     

Fluid inclusion study of the Wunugetu Cu–Mo deposit,Inner Mongolia,China

Hydrothermal alteration and mineralization at the Wunugetu porphyry Cu–Mo deposit, China, include four stages, i.e., the early stage characterized by quartz, K-feldspar and minor mineralization, followed by a molybdenum mineralization stage associated with potassic alteration, copper mineralization associated with sericitization, and the last Pb–Zn mineralization stage associated with carbonation. Hydrothermal quartz contains three types of fluid inclusions, namely aqueous (W-type), daughter mineral-bearing (S-type) and CO₂-rich (C-type) inclusion, with the latter two types absent in the late stage. Fluid inclusions in the early stage display homogenization temperatures above 510°C, with salinities up to 75.8 wt.% NaCl equivalent. The presence of S-type inclusions containing anhydrite and hematite daughter minerals and C-type inclusions indicates an oxidizing, CO₂-bearing environment. Fluid inclusions in the Mo- and Cu-mineralization stages yield homogenization temperatures of 342–508°C and 241–336°C, and salinities of 8.6–49.4 and 6.3–35.7 wt.% NaCl equivalent, respectively. The presence of chalcopyrite instead of hematite and anhydrite daughter minerals in S-type inclusions indicates a decreasing of oxygen fugacity. In the late stage, fluid inclusions yield homogenization temperatures of 115–234°C and salinities lower than 12.4 wt.% NaCl equivalent. It is concluded that the early stage fluids were CO₂ bearing, magmatic in origin, and characterized by high temperature, high salinity, and high oxygen fugacity. Phase separation occurred during the Mo- and Cu-mineralization stages, resulting in CO₂ release, oxygen fugacity decrease and rapid precipitation of sulfides. The late-stage fluids were meteoric in origin and characterized by low temperature, low salinity, and CO₂ poor.     

Metallophilic fungi research: an alternative for its use in the bioremediation of hexavalent chromium

Contamination by hexavalent chromium has had a large impact on modern society and human health. This problem is a consequence of its great industrial applicability to several products and processes. Short-term exposure to hexavalent chromium can cause irritation, ulceration in skin and stomach and in addition to cancer, dermatitis, and damage to liver, renal circulation and nervous tissues, with even death being observed in response to long-term exposures. Many techniques have been used for the remediation of this pollutant, including physical and chemical approaches and, in more recent years, biological methods. Filamentous fungi isolated from contaminated sites exhibit a significant tolerance to heavy metal; hence, they are an important source of microbiota capable of eliminating hexavalent chromium from the environment. However, these microorganisms can do so in different ways, including biosorption, bioreduction, and bioaccumulation, among others. In this review, we explore several of the most documented mechanisms that have been described for fungi/hexavalent chromium interactions and their potential use in bioremediation.     

Discussion: “Xenoliths in ultrapotassic volcanic rocks in the Lhasa block: direct evidence for crust–mantle mixing and metamorphism in the deep crust” by Wang et al. 2016 (Contributions to Mineralogy and Petrology) 171:62

Wang et al. (Contrib Mineral Petrol 171:62, 2016a) present data on composition of xenolith from Southern Tibet and conclude that ulrapotassic melts from the region formed by melting mantle, and complex interaction with a crustal component. In this discussion we demonstrate that numerous observations presented by Wang et al. (2016a) can be explained by partial melting of crust followed by interaction between that melt and the mantle. We show that this model can explain the variability of magmas in such suits without evoking occurrence of coincidental, unrelated events. Moreover we demonstrate that our model of a crustal origin of the proto-shoshonite melts is now supported by independent lines of evidence such as geochemistry of restites after high- and ultrahigh- pressure melting and melt inclusion studies.