Abstract Most of the sulfide nickel deposits in China occur on the margins of platforms and their outer mobile belts. The ore‐ bearing basic‐ ultrabasic rock bodies were formed in the Proterozoic and Variscan. The types of metallogenic rock bodies include ultrabasic‐ basic complexes related to volcanism in eugeosynclines and ultrabasic rock bodies, ultrabasic‐basic complexes and basic rock bodies related to deep fractures. On the basis of ore‐forming processes and modes, nickel sulfide deposits of China may be divided into two major types: in‐ situ magmatic liquid unmixing deposits and deep‐ seated magmatic liquid unmixing injection deposits. The latter may by subdivided into four types: single injection deposits, multiple injection deposits, and pulsatory injection depositis, and late injection deposits which may inject into either comagmatic rocks or other kinds of country rocks. Two metallogenic models for nickel sulfide deposits are proposed in this paper.
Abstract: The Zhou'an PGE‐Cu‐Ni deposit was recently discovered in the Qinling orogenic belt bound by the Yangtze and the North China Cratons. It is a blind deposit thoroughly covered by the Cenozoic alluvial sediments in the Nanyang Basin. As the first large PGE‐Cu‐Ni deposit discovered in the Qinling‐Dabie‐Sulu orogenic belt, its geological and geochemical characteristic, isotope age, genesis and tectonic setting are of wide concern in both scientific studies and ore exploration. In this contribution, we report the results obtained from a pioneering study. The Zhou'an ultramafic complex is ferruginous, with m/f = 4.79–5.08, and shows the nature of tholeiite series. It is rich in light rare earth elements, Rb, Th, U, La, Sm, Zr and Hf, and poor in heavy rare earth elements, Nd and Ta, suggesting an intraplate setting. It has high 87 Sr/ 86 Sr and low 143 Nd/ 144 Nd ratios. The ratios of Zr/Nb, La/Nb, Ba/Nb, Rb/Nb, Th/Nb, Th/La and Ba/La, suggest the magma originated from lithosphere mantle. The Fo values of olivine and Pd/Ir‐Ni/Cu diagram suggest primary magma was High Mg basalt. The laser ablation inductively coupled plasma atomic emission spectroscopy zircon U‐Pb age is 641.5 ± 3.7 Ma.
Noble gases are recognized as being exceptional tracers of volatile sources during mineralization He, Ne and Ar abundance and isotopic compositions from 23 silicate and sulfide separates in the Jinchuan Cu-Ni-PGE sulfide deposit, West China, have been investigated by melting extraction MM5400 mass spectrometer The results show that (3)He/(4)He ratios in silicate minerals (av 0 239Ra) are slightly lower than those in sulfide (av 0 456Ra), and decrease from olivine (av 0 291Ra), orthopyroxene (av 0 215Ra) to clinopyroxene (av 0 174Ra) (20)Ne/(22)Ne and (21)Ne/(22)Ne ratios are plotted Into the ranges between MORB line and continental crust line (3)He/(4)He and (40)Ar/(36)Ar of olivine (Olv) and orthopyroxene (Opx) deducted by radiogenic He and Ne are close to the He and Ar isotopic ranges of subcontinental lithosphere mantle (SCLM) He, Ne and Ar isotopic compositions suggested that SCLM, continental crust (CC) and air saturated water (ASW) three end-members were involved into ore-forming magma of the Jinchuan Cu-Ni-PGE sulfide deposit The segregation of immiscible sulfide liquid from magma took place at the early stage of magma evolution The primary ore forming magma had been formed by partial melting of SCLM, and undergone two stages of evolution It had been assimilated possibly with wall rock which resulted in the sulfur supersaturating in silicate magma and segregation of immiscible sulfide melt and formed a mixed component (MC) with SCLM and continental crust (CC) signatures The mixed component (MC) emplaced into upper chamber and mixed with a high proportion of deep circulatory ASW which induced sulfur supersaturating of ore-forming magma and in-situ formed the disseminated ore in upper magma chamber
Abstract: The Jinchuan deposit is hosted by the olivine‐rich ultramafic rock body, which is the third‐largest magmatic sulfide Ni–Cu deposit in the world currently being exploited. Seeking new relaying resources in the deep and the border of the deposit becomes more and more important. The ore body, ore and geochemistry characteristics of the concealed Cu‐rich ore body are researched. Through spatial analysis and comparison with the neighboring II1 main ore body, the mineralization rule of the concealed Cu‐rich ore body is summed up. It is also implied that Cu‐rich magma may exist between Ni‐rich magma and ore pulp during liquation differentiation in deep‐stage chambers, which derives from deep‐mantle Hi–MgO basalt magma. It is concluded that the type of ore body has features of both magmatic liquation and late reconstruction action. It has experienced three stages: deep liquation and pulsatory injection of the Cu‐ and PPGE‐rich magma, concentration of tectonic activation, and the later magma hydrothermal superimposition. In addition, the Pb and S isotopes indicate the magma of 16 concealed Cu‐rich ore body originates predominantly from mantle; however, it is interfused by minute crust material. Finally, it is inferred that the genesis of the Cu–Ni sulfide deposit is complex and diverse, and the prospect of seeking new deep ore bodies within similar deposits is promising, especially Cu‐rich ore bodies.
With the development of green energy, the demand for lithium resources has increased sharply, and salt lakes are an important source of lithium. In China, the Qinghai–Tibet Plateau has substantial lithium resources, and the Bangor Co Salt Lake is a typical Li-rich carbonate salt lake in northern Tibet. Research into the lithium source of the lake is of great significance for future sustainable industrial development. This article selects the Bangor Co Salt Lake recharge water system (river and cold spring water) and brine samples as the research objects, conducts hydrochemical composition and isotope testing of the water body, and determines the anions, cations, and B isotopes of the samples. This article uses the Piper three-line diagram, Gibbs diagram, and ion ratio relationship to study the hydrochemical characteristics and major ion sources of recharge water systems and salt lakes. The results indicate that the hydrochemical type has transitioned from the strong carbonate type to the moderate carbonate type from the recharge area to the lake area. The major source of ions in lakes is the weathering products of carbonate rocks, followed by evaporite and silicate solutes. The enrichment of lithium in salt lakes is mainly related to the contribution of rivers, followed by geothermal-related cold springs, and early sedimentary carbonate minerals may also make potential contributions. These findings provide a scientific basis for the mechanism of lithium enrichment, as well as for the further development and evaluation of lithium resources.
Chrome spinels occur in olivine-rich cumulates in the Jinchuan intrusion, host to one of the largest known accumulations of magmatic Ni-Cu in the world. The chemistry and mode of occurrence of these spinels is compared with those in two other similar but unmineralized mafic-ultramafic intrusions in the same belt.The Jinchuan intrusion contains Mg-poor chromites with widely varying TiO 2 contents, showing many features that are typical of chromites in normal tholeiitic layered intrusions. Wide compositional variance occurs on the scale of single thin sections, and is attributed to reaction between cumulus chromite and trapped intercumulus liquid. This process operated extensively, even on grains that were armored by cumulus olivine crystals. Different reaction paths correlate with the abundance of sulfides in the rock.The unmineralized intrusions show similar reaction trends, but are offset from the Jinchuan trends. Yejili spinels are generally higher in Al and Ga, while Zangbutai chromites are systematically higher in Fe (super 3+) . Jinchuan spinel-olivine pairs record equilibration temperatures well below the solidus, and are slightly but significantly lower than blocking temperatures recorded at Yejili.The Jinchuan ore zone contains low Cr, high Fe (super 3+) chromites that are unusual and distinctive. A plausible model for these unusual compositions is that these grains originated as normal aluminous spinels crystallizing from the parent silicate melt, and subsequently became enlarged and modified during crystallization of the sulfide melt. Ti-enriched chromites enclosed within sulfides record a prehistory of extensive reaction with trapped liquid.Sulfide-associated chromites from Jinchuan are strongly nickel depleted relative to expected Ni values for their Fe (super 3+) content when compared with the barren intrusions. This feature, combined with the distinctive chemistry of the sulfide-related spinels, may have applications in the use of heavy resistate minerals during exploration.Distinctively high Ti chromites are also a feature of intrusions associated with the Karoo flood basalts, suggesting that Jinchuan may have a similar affinity. However, TiO 2 enrichment in chromite can be a product of interaction with differentiated trapped liquid, as indicated by similar trends in lava lakes, layered intrusions, and at Sudbury, and therefore cannot be taken to prove unusually Ti-rich parent magmas.
Abstract Before intruding, primary magmas have undergone liquation and partial crystallization at depth; as a result the magmas are partitioned into barren magma, ore–bearing magma, ore–rich magma and ore magma, which then ascend and are injected into the present locations once or multiple times, thus forming ore deposits. The above–mentioned mineralizing process is known as deep–seated magmatic liquation–injection mineralization. The volume of the barren magma is generally much larger than those of the ore—bearing magma, ore—rich magma and ore magma. In the ascending process, most of the barren magma intrudes into different locations or outpours onto the ground surface, forming intrusions or lava flows. The rest barren magma, ore–bearing magma, ore–rich magma and ore magma may either multiple times inject into the same space in which rocks and ores are formed or separately inject into different spaces in which rocks and ores are formed. The intrusions containing such deep–seated magmatic liquation–injection deposits have a much smaller volume, greater ore potential and higher ore grade than that of in–situ magmatic liquation deposits. Consequently this mineralizing process results in the formation of large deposits in small intrusions.
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