Origin of Boron in the Gas Hure Salt Lake of Northwestern Qaidam Basin, China: Evidence from Hydrochemistry and Boron Isotopes

The Gas Hure Salt Lake(GHSL) in the northwestern Qaidam Basin, western China, is rich in boron(B) resources, but its B-resource origin is hardly known. Hydrochemical compositions and B isotope characteristics of different waters were collected around the GHSL, including the river water, stream water, spring water, salt-lake brine, intercrystalline brine, well water, drilling brine, and solar pond brine. The hydrochemical signatures suggest that silicates, carbonates and evaporates are the main B-bearing rocks during the water dynamic. The reservoir estimation of B resources shows that the Kulamulekesay River(KLMR) and the Atekan River(ATKR) contribute annually 18.3 tons and 22.84 tons of B, respectively, with a total amount of 11.72 × 10^(4) tons of B during the past 5.7 ka. In comparison with the known B reservoir(32.96 × 10^(4) tons) in the GHSL, a significant amount of B in the GHSL was probably recharged from deep fluids and sediments around the GHSL. The B concentration and B-enrichment degree are shaped by the evaporation process, which are highly elevated at the carnallite and bischofite stages.

Early Paleozoic Granite in the Talate Mining District, Chinese Altay, and its Geological Significance for the Altay Orogenic Belt

Zircon dating,geochemical and Nd-Sr isotopic analyses have been determined for samples from two granitic intrusions in the Talate mining district,Chinese Altay.Our data suggest that these intrusions were emplaced from 462.5 Ma to 457.8 Ma.These rocks have strong affinity to peralumious S-type granite and are characterized by prominent negative Eu anomalies(δEu=0.20–0.35),strong depletion in Ba,Sr,P,Ti,Nb,Ta and positive anomalies in Rb,Th,U,K,La,Nd,Zr,Hf.Nd-Sr isotopic compositions of the whole rock show negativeεNd(t)values(-1.21 to-0.08)and Mesoproterozoic Nd model ages(T2 DM=1.20–1.30 Ga).Their precursor magmas were likely derived from the partial dehydration melting of Mesoproterozoic mica-rich pelitic sources and mixed with minor mantle-derived components,under relatively low P(≤1 kbar)and high T(746–796℃)conditions.A ridge subduction model may account for the early Paleozoic geodynamic process with mantle-derived magmas caused by Ordovician ridge subduction and the opening of a slab window underplated and/or intraplated in the middle–upper crust,which triggered extensive partial melting of the shallow crust to generate diverse igneous rocks,and provided the heat for the crustal melting and juvenile materials for crustal growth.