排序方式： 共有7条查询结果，搜索用时 15 毫秒
1
1.
Bi Xianwu Hu Ruizhong J. J. Hanley J. E. Mungall Peng Jiantang Shang Linbo Wu Kaixing Suang Yan Li Hongli Hu Xiaoyan 《Mineralogy and Petrology》2009,96(1-2):43-58
The Oligocene Yao’an syenite porphyry, associated with gold mineralisation, and the Machangqing alkali granite porphyry–monzonite porphyry, associated with Cu mineralisation, belong to the Red River–Jinshajiang alkaline igneous belt that formed in a continental setting in southwestern China. A study of the mineral chemistry of major silicate minerals in these two mineralised intrusions provides insights into their overall crystallisation conditions. The temperature and pressure conditions, derived from amphibole–plagioclase and perthite–plagioclase geothermometry and Al-in-amphibole barometry, suggest that the Yao’an intrusion crystallised at around 820?±?50°C and 0.9–1.3 kbar, whereas the Machangqing intrusion crystallised at around 730?±?50°C and 2.2–2.8 kbar. The higher temperature and lower pressure of crystallisation for the Yao’an intrusion relative to the Machangqing intrusion indicates that it was emplaced at a shallower crustal level. Based on biotite composition, the two intrusions formed under imposed oxygen fugacities above the Ni–NiO buffer (NNO), and the Yao’an intrusion crystallised under more oxidising conditions than the Machangqing intrusion. The results show that the intrusions associated with Cu–Au mineralisation in the Red River–Jinshajiang alkaline igneous belt were emplaced at a relatively high fO2, which, together with the weakly fractionated magma, favoured Au enrichment relative to Cu in the belt. 相似文献
2.
James E. Mungall David R.A. Andrews Paul J. Sylvester 《Geochimica et cosmochimica acta》2005,69(17):4349-4360
We have performed six experiments in which we equilibrated monosulfide solid solution (mss) with sulfide melt in evacuated silica capsules containing solid buffers to fix oxygen and sulfur fugacity, at temperatures of 950°C, 1000°C and 1050°C at bulk concentrations of ∼50 ppm for each of the PGE and Au, 5% Ni, and 7% Cu. Concentrations of O, S, Fe, Ni and Cu were determined by electron microprobe, whereas precious metal concentrations were determined by laser-ablation inductively-coupled mass spectrometry. Partition coefficients of all elements studied show minimal dependences on oxygen fugacity from the IW to the QFM buffers when sulfur fugacity is fixed at the Pt-PtS buffer. Cu, Pt, Pd and Au are strongly incompatible and Ru remains moderately to strongly compatible under all conditions studied. At all oxygen fugacities, at the Pt-PtS sulfur buffer, Ir and Rh remain highly compatible in mss. In the single run at both low oxygen and low sulfur fugacity Ir and Rh were found to be strongly incompatible in mss. At QFM and Pt-PtS the partition coefficient for Ni shows weak temperature dependence, ranging from 0.66 at 1050°C to 0.94 at 950°C. At lower oxygen and sulfur fugacity Ni showed much more incompatible behavior. Comparison with the compositions of sulfide ores from the Lindsley deposit of Sudbury suggests that the sulfide magma evolved under conditions close to the QFM and Pt-PtS buffers. The compatible behavior observed for Ni, Ir and Rh at Lindsley and most other magmatic sulfide deposits hosted by mafic rocks requires equilibration of mss and sulfide liquid at moderately high sulfur fugacity and low temperatures near to the solidus of the sulfide magma. We argue that this constraint requires that the sulfide magma must have evolved by equilibrium crystallization, rather than fractional segregation of mss as is commonly supposed. 相似文献
3.
The Proterozoic Expo Intrusive Suite comprises a series of maficto ultramafic intrusions crosscutting the Povungnituk Groupof the Cape Smith Fold Belt in New Quebec. The intrusions aremainly in the form of blade-shaped dikes that penetrate a sediment-richhorizon in the middle of the Beauparlant Formation and terminatedownward against massive basalts of the lower Beauparlant Formation.Significant accumulations of magmatic sulfide occur at the basalterminations of the dikes. At stratigraphic levels above theBeauparlant Formation the intrusions appear as broad dikes orsills within the Nuvilik Formation, below the mineralized lavaflows and subvolcanic intrusions of the Raglan Formation. TheExpo Intrusive Suite and the mineralized bodies of the RaglanFormation are probably coeval and comagmatic with the overlyingChukotat Group. Post-emplacement folding has exposed the ExpoIntrusive Suite over about 5 km of structural relief, revealingthe basal sulfide concentrations where dike segments terminateon the flanks of anticlines. The parent magma as preserved inchilled margins and narrow dikes was a picrite containing 17wt % MgO (i.e. komatiitic basalt) and slightly depleted in Th,U and Nb relative to middle and heavy rare earth elements. Thecompositions of ultramafic cumulate rocks within the intrusionsare strongly enriched in Th, U and Nb relative to heavy rareearth elements, reflecting assimilation of the enclosing basaltsand metasediments. Modeling of the assimilation process suggeststhat the picritic magma was capable of assimilating masses ofbasalt or sediment up to 50% of the original mass of magma.Assimilation of 10% of a mixture of basalt and sediment causedthe magma to become sulfide-saturated, and was accompanied bythe crystallization of masses of ultramafic cumulates approximatelyequal to the mass of rock assimilated. The presence of dikeswhose chilled margins resemble uncontaminated primary magmasbut that contain abundant cumulates recording wholesale assimilationof host-rocks indicates that the process of assimilation andfractional crystallization required to produce continental tholeiitesfrom picritic parent magmas may not require the presence oflong-lived magma chambers, but can occur during transport alongdikes and reaction with wall-rocks. KEY WORDS: komatiite; Expo Intrusive Suite; assimilation; fractional crystallization; sulfide mineralization 相似文献
4.
与铜、金矿化有关的富碱侵入岩矿物化学研究 总被引：1，自引：0，他引：1
以哀牢山—金沙江富碱侵入岩带内与金矿化有关的姚安正长斑岩和与铜矿化有关的马厂箐花岗斑岩为研究对象,开展了系统的矿物化学研究。结果表明,姚安岩体形成的温压条件为(818±50)℃和0.9×108~1.3×108Pa,马厂箐岩体形成的温压条件为(729±50)℃和2.2×108~2.8×108Pa,两岩体的氧逸度均高于地幔石英-橄榄岩-磁铁矿出溶线,相对于马厂箐岩体而言,姚安岩体结晶时的氧逸度更高。两岩体矿化作用的差异与岩浆的分异程度有密切的关系。相对于铜矿化而言,氧逸度较高的岩浆有利于金矿化。 相似文献
5.
J. J. Hanley J. E. Mungall T. Pettke E. T. C. Spooner C. J. Bray 《Mineralium Deposita》2005,40(3):237-256
We report methane-dominant hydrocarbon (fluid) inclusions (CH4±C2H6–C2H2, C3H8) coexisting with primary brine inclusions and secondary halide melt (solid NaCl) inclusions in Au–Pt-rich quartz-sulfide-epidote
alteration veins associated with the footwall-style Cu–PGE (platinum-group element)–Au deposits at the Fraser Mine (North
Range of the Sudbury Igneous Complex). Evidence for coentrapment of immiscible hydrocarbon–brine, and hydrocarbon–halide melt
mixtures is demonstrated. A primary CH4–brine assemblage was trapped during quartz growth at relatively low T (min. T
trapping∼145–315°C) and P (max. P
trapping∼500 bar), prior to the crystallization of sulfide minerals in the veins. Secondary inclusions contain solid halite and a
mixture of CH4, C2H6–C2H2 and C3H8 and were trapped at a minimum T of ∼710°C. The halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally
postdate (by replacement) early alteration quartz hosting the primary, lower T brine–CH4 assemblage. Laser ablation ICP-MS analyses show that the brine, hydrocarbon and halide melt inclusions contain significant
concentrations of Cu (0.1–1 wt% range), Au, Bi, Ag and Pt (all 0.1–10 ppm range). Cu:Pt and Cu:Au ratios in the inclusions
are significantly (up to 4 log units) lower than in the host alteration veins and adjacent massive sulfide ore veins, suggesting
either (1) early Cu loss from the volatiles by chalcopyrite precipitation or (2) enhanced Au and Pt solubilities relative
to Cu at the temperatures of entrapment. Concentration ratios between coexisting brine and CH4 inclusions
are lower for Cu, Au, Bi and Ag than for other elements (Na, Ca, Fe, Mn, Zn, Pb) indicating that during interaction with
the brine, the hydrocarbon phase was enriched in ore metals. The high concentrations of ore metals in hydrocarbon, brine and
halide melt phases confirm that both aqueous and non-aqueous volatiles were carriers of precious metals in the Sudbury environment
over a wide range of temperatures. Volatile evolution and magmatic sulfide differentiation were clearly part of a single,
continuous process in the Sudbury footwall. The exsolution of H2O-poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of
PGE and Au in the footwall ore systems. The study reports the first measurements of precious metal concentrations in fluid
inclusions from a magmatic Ni–Cu–PGE environment (the Sudbury district).
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
6.
Petrogenetic modeling of the Recent lava succession of Santa Barbara and Pico Alto volcanoes and associated basaltic lavas
indicates that there are two discrete lava series present, one erupted from the axial rift linking the two central volcanoes
and one associated with monogenetic cones scattered around the flanks of Santa Barbara. The felsic lavas of both volcanoes
are peralkaline and appear to be derived from associated basalts by fractional crystallization of an assemblage including
essential amphibole. Trace element abundances in the felsic lavas, particularly those of Sr and REE, cannot be reconciled
with an origin through partial melting of basaltic material at the base of the volcanic pile. The difference between the comenditic
and pantelleritic differentiation trends of Santa Barbara and Pico Alto is attributed primarily to FO2 control of the crystallizing assemblage, probably related to thermal dissociation of magmatic water in the Santa Barbara
magma chamber. This effect may be augmented by minor differences in parent basaltic compositions, the Pico Alto pantellerites
being derived from the rift basalts whereas the Santa Barbara comendites are derived from the off-rift basalts. A compositional
gap between 54 and 64% silica content in the lavas is not present if the suite is extended to include co-magmatic hypabyssal
xenoliths, leading to the inference that the gap in this and other bimodal suites results solely from a relative inability
of magma of intermediate composition to erupt. 相似文献
7.
Jim Mungall 《中国科学D辑(英文版)》2005,48(6):834-839
There are a lot of mafic and ultra-mafic bodies in the earth,but only a few of them include Cu-Ni-PGE deposits.Of interest has been the formation of such deposits as Cu-Ni-PGE sulfide;especially the separa-tion of sulfide liquid from silicate melts.A lot of re-searcher[1—11]have investigated into the tectonic back-ground of Cu-Ni-PGE deposits,the mechanism of the origin and evolution of magma,and the metal element partition coefficient in sulfide liquid and silicate magma.However,the da… 相似文献
1