40Ar-39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance

40Ar-39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the Tancheng Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent.

The geology, structure and mineralisation of the Oyu Tolgoi porphyry copper-gold-molybdenum deposits, Mongolia： A review

The Oyu Tolgoi cluster of seven porphyry Cu-Au-Mo deposits in southern Mongolia,define a narrow,linear,12 km long,almost continuously mineralised trend,which contains in excess of 42 Mt of Cu and1850 t of Au,and is among the largest high grade porphyry Cu-Au deposits in the world.These deposits lie within the Gurvansayhan island-arc terrane,a fault bounded segment of the broader Silurian to Carboniferous Kazakh-Mongol arc,located towards the southern margin of the Central Asian Orogenic Belt,a collage of magmatic arcs that were periodically active from the late Neoproterozoic to PermoTriassic,extending from the Urals Mountains to the Pacific Ocean.Mineralisation at Oyu Tolgoi is associated with multiple,overlapping,intrusions of late Devonian（～372 to 370 Ma） quartzmonzodiorite intruding Devonian（or older） juvenile,probably intra-oceanic arc-related,basaltic lavas and lesser volcaniclastic rocks,unconformably overlain by late Devonian（～370 Ma） basaltic to dacitic pyroclastic and volcano sedimentary rocks.These quartz-monzodiorite intrusions range from earlymineral porphyritic dykes,to larger,linear,syn-,late- and post-mineral dykes and stocks.Ore was deposited within syn-mineral quartz-monzodiorites,but is dominantly hosted by augite basalts and to a lesser degree by overlying dacitic pyroclastic rocks.Following ore deposition,an allochthonous plate of older Devonian（or pre-Devonian） rocks was overthrust and a post-ore biotite granodiorite intruded at～365 Ma.Mineralisation is characterised by varying,telescoped stages of intrusion and alteration.Early A-type quartz veined dykes were followed by Cu-Au mineralisation associated with potassic alteration,mainly K-feldspar in quartz-monzodiorite and biotite-magnetite in basaltic hosts.Downward reflux of cooled,late-magmatic hydrothermal fluid resulted in intense quartz-sericite retrograde alteration in the upper parts of the main syn-mineral intrusions,and an equivalent chlorite-muscovite/illite-hematite assemblage in basaltic host rocks.Uplift,facilitated by syn-mineral longitudinal faulting,brought sections of the porphyry deposit to shallower depths,to be overprinted and upgraded by late stage,shallower,advanced argillic alteration and high sulphidation mineralisation.Key controls on the location,size and grade of the deposit cluster include（i） a long-lived,narrow faulted corridor;（ii） multiple pulses of overlapping intrusion within the same structure;and（iii） enclosing reactive,mafic dominated wall rocks,focussing ore.

Geological and Geochemical Characteristics and Genesis of the Shaxi Porphyry Copper (Gold) Deposits, Anhui Province

The Shaxi porphyry copper (gold) deposits are a typical example of porphyry copper deposits associated with diorite in eastern China. Quartz diorite, which hosts the deposits, has a Rb-Sr isochron age of 127.9 ± 1.6 Ma. Geochemically, the rock is rich in alkalis (especially sodium), light rare earth elements (LREE) and large-ion lithophile elements (LILE), and has a relatively low initial strontium isotopic ratio (Isr=0.7058); thus it is the product of differentiation of crust-mantle mixing source magma. The model of alteration and mineralization zoning is similar to the Hollister (1974) diorite model. The ore fluids have a relatively high salinity and contain significant amounts of CO2, Ca2+, Na+ and ***CI?. The homogenization temperatures of fluid inclusions for the main mineralization stage range from 280 to 420°C, the δ18O values of the ore fluids vary from 3.51 to 5.52 %, the δD values are in the range between ?82.4 and ?59.8 %, the δ34S values of sulphides vary from ?0.3 to 2.49 %, and the δ13C values of CO2 in inclusions range between ?2.66 and ?6.53 %. Isotope data indicate that the hydrothermal ore fluids and ore substances of the Shaxi porphyry copper (gold) deposits were mainly derived from magmatic systems.

Integration of Deep-time Digital Data for Mapping Clusters of Porphyry Copper Mineral Deposits

1 Introduction PCDs are generated in continental arcs in response to plate converging processes(subduction and collision)(Hou et al.,2009;Richards,2013).It is generally accepted that the formation of PCDs is associated with igneous activities either originating from lower crust or upper mantle,with contributions of crusts during the evolution of continental lithosphere.

The formation of porphyry copper deposits

Copper is a moderately incompatible chalcophile element.Its behavior is strongly controlled by sulfides.The speciation of sulfur is controlled by oxygen fugacity.Therefore,porphyry Cu deposits are usually oxidized(with oxygen fugacities > AFMQ +2)(Mungall 2002;Sun et al.2015).The problem is that while most of the magmas at convergent margins are highly oxidized,porphyry Cu deposits are very rare,suggesting that high oxygen fugacity alone is not sufficient.Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly(Lee et al.2012;Wilkinson 2013).Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity(>AFMQ +2) may form magmas with initial Cu contents up to >500 ppm,favorable for porphyry mineralization.Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization.In contrast,remelting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits.Thick overriding continental crust reduces the "leakage" of hydrothermal fluids,thereby promoting porphyry mineralization.Nevertheless,it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2—4 km where porphyry deposits form.

Rule of Structural Factors in Formation of Porphyry Copper Deposits in South Western Part of Kerman Area, Iran

Kerman area is located in southern parts of central Iranian volcanic belt. The area under study is located in the southern part of this complex copper mineralization in the area, which is mainly porphyry type and is associated with extensive hydrothermal alteration. This area has a great potential as far as tertiary porphyry copper deposits are concerned. To the exploration of porphyry copper deposits in study area, we have analyzed the lineaments. The lineaments interpreted out from ETM + (band8) data is recognized as another method for locating porphyry type copper mineralization. There is a close correlation between photo lineament factor values and the known copper mineralization in the area. The relationship between 16 porphyry copper deposits with faults and fractures in the area is studied. Photo lineament factor assessments by using satellite photos indicate a strong relationship between a number of lineation intersection in each cell refer to an amount of average lineation in whole map (c/C ratio). In the study area, ratio of c/C even has more relationship refers to PF factor that has previously described in the papers.

Origin of the Oligocene Tuolangla porphyry-skarn Cu-W-Mo deposit in Lhasa terrane,southern Tibet

Although some porphyry-skarn deposits occur in post-collisional extensional settings,the post-collisional deposits remain poorly understood.Here the authors describe the igneous geology,and mineralization history of Tuolangla,a newly-discovered porphyry-skarn Cu-W-Mo deposit in southern Tibet that belongs to the post-collisional class.The deposit is associated with Lower Cretaceous Bima Formation.It was intruded by granodiorite porphyry intrusions at about 23.1 Ma.Field investigation indicated that mineralization is spatially and temporally associated with granodiorite porphyry.Molybdenite yielded a Re-Os weighted mean age of 23.5±0.3 Ma and is considered to represent the age of skarn mineralization at the deposit.Theδ^34S values of sulfides,concentrated in a range between 0.6‰to 3.4‰,show that the sulfur has a homogeneous source with characteristics of magmatic sulfur.The Pb isotopic compositions of sulfides indicate that ore-forming metal materials were derived from the mantle and ancient crust.The granodiorite porphyry displays high SiO2(68.78%–69.75%)and K2O(3.40%–3.56%)contents,and relatively lower Cr(2.4×10^-6–4.09×10^-6),Ni(2.79×10^-6–3.58×10^-6)contents,and positiveεHf(t)values(7.7–12.9)indicating that the mineralization porphyry was derived from the partial melting of juvenile lower crust.The Tuolangla deposit is located in the central part of Zedang terrane.This terrane was once considered an ancient terrane.This terrane is in tectonic contact with Cretaceous ophiolitic rocks to its south and Mesozoic continental margin arc volcanics and intrusions of the Gangdese batholith of the Lhasa terrane to its north.Thus,the authors proposed that the Oligocene porphyry skarn Cu-W-Mo mineralization is probably associated with the Zedang terrane.This finding may clarify why the Oligocene(about 23 Ma)deposits are found only in the Zedang area and why mineralization types of the Oligocene mineralization are considerably different from those of the Miocene(17–14 Ma)mineralization.

Geochemical Trace of Silicon Isotopes of Intrusions and Ore Veins Related to Alkali-rich Porphyry Deposits in Western Yunnan, China

Western Yunnan is the well-known polymetallic province in China. It is characterized by copper-gold mineralization related to Cenozoic alkali-rich porphyry. This paper analyzes the silicon isotope data obtained from four typical alkali-rich porphyry deposits based on the dynamic fractionation principle of silicon isotope. The study shows that the ore materials should originate mainly from alkali-rich magmas, together with silicon-rich mineralizing fluids. The process of mineralization was completed by auto-metasomatism, i.e. silicon-rich mineralizing fluids (including alkali-rich porphyry and wall-rock strata) replaced and altered the country rocks and contaminated with crustal rocks during the crystallization of alkali-rich magmas. Such a process is essentially the continuance of the metasomatism of mantle fluids in crust's mineralization. This provides important evidence of silicon isotopic geochemistry for better understanding the mineralization of the Cenozoic alkali-rich porphyry polymetallic deposits

Enrichment of Platinum-group Elements(PGE) and Re-Os Isotopic Tracing for Porphyry Copper(Gold) Deposits

Platinum-group elements （PGE） in PGE-rich porphyry copper （gold） deposits are mainly Pt and Pd, whereas the concentrations of other PGE （Ru, Rh, Os, Ir） are significantly low. Moreover, Pt and Pd mainly exist in sulfides in the forms of crystal lattice or tiny platinum-group mineral （PGM） inclusions. The present data show that there is a positive relationship between Pt and Pd concentrations and Cu （Au） in porphyry copper （gold） deposits. The comparison of chondrite-normalized PGE distribution patterns between the ore-bearing porphyry intrusions and ore-barren porphyry intrusions in arc setting, 187^Os/188^Os, 87^Sr/86^Sr and S isotopes for porphyry copper （gold） deposits shows that PGEs were mainly derived from the mantle, and fluids from subduction zones devoted trivial PGE to the magma. The porphyry copper （gold） deposits associated with subducted events are most probably enriched in PGE, whereas those related to crustal thickening, lithospheric delamination or underplating rarely concentrate PGE. The osmium isotopic compositions in porphyry copper （gold） deposits reveal that （187^Os/188^Os）i values are highly variable and not lower than those of primitive upper mantle （PUM） and mantle peridotite, however, osmium concentrations are commonly lower than mantle peridotite, suggesting that parental magmas of some porphyry intrusions had experienced crustal contamination during magma evolution. Experimental investigations have proved that PGE exist in the forms of Cl^- and HS^- complexes during transportation and migration of the oreforming fluids. This paper summarizes previous studies including crucial controlling factors and mechanisms for PGE enrichment, and points out that the mantle-derived magmas parental to porphyry intrusions are the prerequisite for PGE enrichment in porphyry copper （gold） deposits. Favorable physical and chemical conditions （including salinity, temperature, pressure, pH, and oxygen fugacity） in hydrothermal fluids crucially control the PGE enrichment, and sulfur concentrations of melts play important roles in this process as well.

Trace element compositions of pyrite and stibnite:implications for the genesis of antimony mineralization in the Yangla Cu skarn deposit,Northwestern Yunnan,China

The Yangla Cu skarn deposit is located in the central part of the Jinshajiang Suture Zone,southwest China,with a total reserve of 150 Mt Cu@1.03%.The newly discovered antimony orebodies at the depth of Yangla are strictly controlled by the stratum,structure,and lithology,which are lenticular and vein-like within the marble fracture zone,which can provide a window into multistage miner-alization and ore genesis at Yangla.Mineralization can be divided into three types,Cu–Pb–Zn(skarn)pyrite,galena,and sphalerite,Cu(porphyry)chalcopyrite and pyrite,and Sb(hydrothermal)stibnite and pyrite.The mineral assem-blages were stibnite+pyrite+calcite+quartz±minor scheelite in antimony ores.This study presents quantitative measurements of the trace element compositions of pyrite and stibnite from the Yangla antimony ores.Analysis of pyrite with electron probe microanalysis(EPMA)showed enrichment in Co,Ni,Sb,As,and Mo,and deficit in its S and Fe contents when compared to the stoichiometric con-centrations of S and Fe in pyrite.The Sb-related pyrite may belong to sedimentary-reworked genesis and may be modi-fied by hydrothermalfluids,thereby presenting a certain dif-ference(i.e.,crystal morphology,texture,and chemical com-position)compared to the skarn and porphyry Cu-related pyrite in the Yangla Cu skarn deposit.Analysis of stibnite with EPMA and inductively coupled plasma-mass spectrom-etry showed enrichment in As,Pb,Sn,Pb,Cu,and Zn,and presented much higher Sb contents and slightly lower S con-tents when compared to the stoichiometric concentrations of Sb and S in stibnite.Statistical analysis of the stibnite trace elements showed correlations for the elemental pairs Cu–Pb,As–Sb,and Sn–Pb,and the coupled substitution equations Sb^(3+)↔Cu^(+)+Pb^(2+),Sb^(3+)↔As^(3+),and Sn^(2+)↔Pb^(2+)may be the major factors governed the incorporating Cu,Pb,As and Sn within the stibnite.Moreover,this study preliminary shows that the antimony mineralization may belong to a car-bonate replacement hydrothermal genesis at Yangla.

Dynamics of Ore-Forming Processesof the Stratabound Skarn Copper Depositsof Tongling, Anhui Province

The skarn and ore bodies of the stratabound skarn copper deposits of Tongling, Anhui Province, are both controlled by definite stratigraphic horizons, and they are concordant with the strata. They occur as layers and layer-like bodies in permeable carbonate rocks of the Middle-Upper Carboniferous Huanglong and Chuanshan Formations which are underlain by impermeable shale or siliceous rocks of the Upper Devonian Wutong Formation. The authors study the dynamics of ore-forming processes of the ore deposits with the dynamic model of coupled transport and reaction, and the following results are obtained: The salinity gradient and flow rate of the ore-forming fluids can both promote the mixing and reaction of juvenile water and formation water, and the permeable strata are favourable sites for the intense transport-reaction of mixing and the formation of deposits. (2) As isothermal transport-reaction took place along the bedding of strata, the moving transport-reaction front formed at the contact between the ore-forming fluids and the rocks advanced slowly along the permeable strata, and then stratiform skarn and ore bodies concordant with the strata were formed. (3) The gradient transport-reaction taking place across the isotherms in the cross-bedding direction caused the mineralogical composition to alter gradually from magnesian skarn to sulphide ore bodies.

Geochemical Behaviors of REE and Other Trace Elements during the Formation of Strata-bound Skarns and Related Deposits:A Case Study of the Dongguashan Cu(Au)Deposit,Anhui Province,China

REE and other trace elements in the altered marbles, massive skarns and ores, as well as garnet and quartz were determined in order to examine the behaviors of trace elements during hydrothermal alteration. It is demonstrated that the high-field-strength (HFS) elements Zr, Hf, Th and Nb were immobile while other trace elements were mobile during the formation of skarns and related deposits. REE and ore-forming elements such as Cu and Ag in hydrothermally-altered marbles and skarns were provided primarily by hydrothermal fluids. In the direction transverse of the strata, the more deeply the marbles were altered, the higher the total REE abundance and the larger the negative Eu anomalies would be. The chondrite-normalized REE patterns of skarns are similar to those of the marbles, but the former are distinguished by much higher REE contents and more remarkable negative Eu anomalies. Those patterns were apparently not inherited from the marble protolith, but were controlled by garnets, which were determined by the hydrothermal solutions involved in the infiltration metasomatism. The hydrothermal fluids are characterized by having slightly right-hand dipping REE patterns, being enriched in LREE and having strongly negative Eu anomalies. The uptake of REE from hydrothermal fluids during the growth of garnet crystals resulted in the garnets having similar REE patterns to the hydrothermal fluids. Based on the spatial variation of REE in skarns and the structures of the hosting strata, we can get a better understanding of the transport path and pattern of the fluids involved in the formation of skarns and their related deposits. REE geochemistry investigation can help elucidate the genesis of skarns and skarn-related deposits.

Discrimination of Different Erosion Levels of Porphyry Cu Deposits using ASTER Image Processing in Eastern Iran:a Case Study in the Maherabad,Shadan,and Chah Shaljami Areas

The Lut block, eastern Iran, is one of the most extensive Cenozoic magmatic rocks, that show suitable targets for porphyry Cu-Au and high-sulfidation epithermal Au related to porphyry Cu-Au mineralization. In this study, Advanced Spaceborne Thermal Emission and Reflection Radiometer （ASTER） was used to identify different erosion levels of three porphyry Cu deposits, including Maherabad, Shadan, and Chah Shaljami, located in the Lut block volcanic-plutonic belt. Alteration minerals, including kaolinite, dickite, alunite, jarosite, epidote, chlorite, montmorillonite, muscovite, biotite, orthoclase, gypsum, and quartz, are selected to map different alteration zones and erosion levels. Distributions of end-members are mapped by using the SAM and MTMF in VNIR and SWIR of ASTER bands and the results are evaluated against the field studies. For some end-members, the results of SAM processing are more reliable compared to the MTMF because the latter looses field spectra. The use of angle threshold in the SAM, and MF-score and infeasibility value in the MTMF or low abundance of some end-members, and finally comparison of output images of spectral processing show good correlation with alteration maps. Differentiation and explanation of various erosion levels of porphyry Cu deposits are done successfully by using the ASTER sensor data.

PETROGENETIC AND METALLOGENETIC AGES FOR THE PORPHYRY COPPER DEPOSITS IN THE GANGDISE METALLOGENIC BELT IN SOUTHERN TIBET

Recent examination and assessment about the porphyry copper deposits in Gangdise metallogenic belt in southern Tibet have revealed that these porphyry copper deposits are highly prospective. Several methods have been used for the isotopic dating of the Qulong, Tinggong and Chongjiang porphyry copper deposits, which gives out a petrogenetic age of 17.58±0.74Ma (single-zircon dating of SHRIMP), a metallogenetic age of 15.99±0.32Ma (Re-Os isochron dating) and an alteration age ranging between 12.00Ma and 16.5Ma (K-Ar dating). The metallogenetic age is in general agreement with the alteration age. It can be seen that the petrogenetic and metallogenetic ages for the porphyry copper deposits in Gangdise metallogenic belt are noticeably later than the age for the collisional granitic intrusion in this belt. The authors contend that the porphyry copper deposits in the study area were formed in a post-collisional extensional tectonic setting, and are closely related to the delamination of the mountain roots of the orogenic belts and the uplifting of the Qinghai-Tibet Plateau.

Reduced magma generation and its implications for the Pulang giant porphyry Cu-polymetallic deposit in Northwest Yunnan,China

The Pulang giant porphyry Cu-Mo polymetallic deposit is located in the Zhongdian area in the center of the Sanjiang Tethys tectonic domain,which was formed by the westward subduction of the Garze-Litang oceanic slab beneath the Zhongza massif.Chalcopyrite-pyrrhotite-pyritemolybdenite occurs as disseminations,veins,veinlets,and stockworks distributed in the K-silicate alteration zone in the monzonite porphyry,which is superimposed by propylitization.The chemical compositions of biotite and amphibole analyzed by electron probe microanalysis(EPMA)indicate that the ore-forming magma and exsolved fluids experienced a continuous decrease in the oxygen fugacity(fO_(2)).Primary amphibolite and biotite(type I)crystallized at relatively high temperatures(744-827°C)and low fO_(2)(log fO_(2)=−12.26 to−11.91)during the magmatic stage.Hydrothermal fluids exsolved from the magma have a relatively lower temperature(621-711°C)and fO_(2)(log fO_(2)=−14.36 to−13.32)than the original magma.In addition,the presence of a high abundance of pyrrhotite and an insufficiency of primary magnetite and sulfate in the ore(i.e.,anhydrite and gypsum)indicate that the deposit may be a reduced porphyry deposit.Magma and fluid fO_(2)results,combined with previous research on magmatic fO_(2)at the Pulang deposit,indicate that the magma associated with the reduced Pulang ore assemblages was initially generated as a highly oxidized magma that was subsequently reduced by sedimentary rocks of the Tumugou Formation.

New insights into petrogenesis of Miocene magmatism associated with porphyry copper deposits of the Andean Pampean flat slab,Argentina

The Paramillos de Uspallata mining district located in the backarc region of the Pampean flat-slab segment(28°-33°S) features porphyry-type deposits genetically associated with Middle Miocene volcanics. This mineralizing magmatism comprising hydrothermally altered(sodic-calcic, potassic and phyllic alteration) subvolcanic and pyroclastic rocks of andesite-basaltic andesite and dacite-rhyolite composition with a typical arc signature, represents the eastward broadening of the Farellones arc by ~17 Ma. Its geochemistry also reveals a residual mineralogy of amphibole ± garnet with limited plagioclase fractionation resulting in an adakitic signal; however, according to the isotopic data collected in our study, the contributions of MASH(melting-assimilation-storage-homogenization) processes in the acquisition of this signal cannot be disregarded.Both the broadening of the Farellones arc and its residual mineralogy e typical of relatively deep magmatic chambers e are consistent with a slab shallowing and outcoming crustal thickening setting.This tectonic scenario could be interpreted as a result of an early effect of the Juan Fernandez Ridge collision that was further to the north by ~17 Ma. Our findings suggest that magmas were fertile for porphyry type deposits during the early stages of the slab shallowing.

In situ U-Pb dating and trace elements of magmatic rutile from Mujicun Cu-Mo deposit,North China Craton:Insights into porphyry mineralization

Porphyry Cu(Mo-Au)deposit is one of the most important types of copper deposit and usually formed under magmatic arc-related settings,whilst the Mujicun porphyry Cu-Mo deposit in North China Craton uncommonly generated within intra-continental settings.Although previous studies have focused on the age,origin and ore genesis of the Mujicun deposit,the ore-forming age,magma source and tectonic evolution remain controversial.Here,this study targeted rutile(TiO_(2))in the ore-hosting diorite porphyry from the Mujicun Cu-Mo deposit to conduct in situ U-Pb dating and trace element composition studies,with major views to determine the timing and magma evolution and to provide new insights into porphyry Cu-Mo metallogeny.Rutile trace element data show flat-like REE patterns characterized by relatively enrichment LREEs and depleted HREEs,which could be identified as magmatic rutile.Rutile U-Pb dating yields lower intercept ages of 139.3–138.4 Ma,interpreted as post magmatic cooling timing below about 500℃,which are consistent or slightly postdate with the published zircon U-Pb ages of diorite porphyry(144.1–141.7 Ma)and skarn(146.2 Ma;139.9 Ma)as well as the molybdenite Re-Os ages of molybdenum ores(144.8–140.0 Ma).Given that the overlap between the closure temperature of rutile U-Pb system and ore-forming temperature of the Mujicun deposit,this study suggests that the ore-forming ages of the Mujicun deposit can be constrained at 139.3–138.4 Ma,with temporal links to the late large-scale granitic magmatism at 138–126 Ma in the Taihang Orogen.Based on the Mg and Al contents in rutile,the magma of ore-hosting diorite porphyry was suggested to be derived from crust-mantle mixing components.In conjunction with previous studies in Taihang Orogen,this study proposes that the far-field effect and the rollback of the subducting Paleo-Pacific slab triggered lithospheric extension,asthenosphere upwelling,crust-mantle interaction and thermo-mechanical erosion,which jointly facilitated the formation of dioritic magmas during the Early Cretaceous.Subsequently,the dioritic magmas carrying crust-mantle mixing metallic materials were emplaced and precipitated at shallow positions along NNE-trending ore-controlling faults,eventually resulting in the formation of the Mujicun Cu-Mo deposit within an intracontinental extensional setting.

Petrogenesis and Physicochemical Conditions of Fertile Porphyry in Non-arc Porphyry Mineralization:A Case from Habo Porphyry Cu-Mo Deposits,SW China

The Habo deposit is a typical porphyry Cu-Mo deposit in the Ailaoshan–Red River metallogenic belt.Ore minerals in the Habo deposit typically occur as veins in the monzonite porphyry.Zircon U-Pb dating suggests that the monzonite porphyry formed at 35.07±0.38 Ma.The monzonite porphyry is characterized by high SiO_(2),Al_(2)O_(3),K_(2)O and Na_(2)O contents,with A/CNK ratios ranging from 0.97 to 1.02.All samples exhibit fractionated REE patterns,characterized by high(La/Yb)N ratios(9.4–13.6,average of 11.2).They show adakite-like geochemical features,high Sr concentrations(627–751 ppm,average of 700 ppm),low Y concentrations(15.13–16.86 ppm,average of 15.81 ppm)and high Sr/Y values(39.5–47.4,average of 44.3).These samples have high initial^(87)Sr/^(86)Sr ratios(0.7074–0.7076)and negativeεNd(t)values(-5.1 to-3.7),whereas the zirconεHf(t)values range from-2.2 to+0.4,suggesting that the monzonite porphyry was derived from the partial melting of a thickened juvenile lower crust.The oxygen fugacity,calculated on the basis of the chemical composition of the amphiboles,shows?NNO values ranging from+1.65 to+2.16(average of 1.94)and lg(fO_(2))ranging from-12.72 to-11.99(average of-12.25),indicating that the monzonite porphyry has high oxygen fugacity.Zircons have high Ce^(4+)/Ce^(3+)ratios(29.29–164.24,average of 84.92),with high?FMQ values ranging from+0.50 to+1.51(average of 0.87)and high lg(fO_(2))values ranging from-14.72 to-12.85(average of-14.07),which also indicates that the oxygen fugacity of the magma was high.The dissolved water content of the Habo monzonite porphyry is 9.5–11.5 wt%,according to the geochemical characteristics,zircon-saturation thermometry(692–794°C)and the mineral phases(amphibole,no plagioclase)in the deep magma chamber.Combined with previous studies,we propose that the high oxygen fugacity and high water content of magma played key roles in controlling the formation of the Habo and other Cu-Mo-Au deposits in the Ailaoshan–Red River metallogenic belt.

+-Evidence of Porphyry Deposits in the Ntem Complex: A Case Study from Structural and Hydrothermal Alteration Zones Mapping through Landsat-8 OLI, Aeromagnetic and Geological Data Integration in the Yaounde-Sangmelima Region (Southern Cameroon)

A semi-regional study was carried out in the Yaounde-Sangmelima area, a densely vegetated tropical region of southern Cameroon located in the Central Africa Fold Belt (CAFB)/Congo Craton (CC) transition zone. Towards structural lineaments and predictive hydrothermal porphyry deposits mapping, an integrated analysis of Landsat-8 OLI data, aeromagnetic, geological and mineral indices maps was performed. The Remote sensing using False colour composite images involving bands combinations and Crosta method (features oriented principal components analysis) enabled the mapping of the gneisses and schists domains without a clear differentiation between the Yaounde and Mbalmayo schists;despite the reflectance anomalies evidenced NW of Akonolinga, hydrothermal alterations in the study area failed to be detected. Besides, aeromagnetics depicted a moderately fractured northern zone (the CAFB) contrasting with a high densely fractured zone (the CC, known as Ntem complex). The Ntem complex displays signatures of a meta-igneous, an intrusive complex, greenstone relics south of Sangmelima and hydrothermal activity. Indeed, CET porphyry analysis tool detected many porphyry centres. In general, the study revealed many lineaments including contacts, fractures faults zones and strike-slips. The major aeromagnetics structures are SW-NE to WSW-ENE and WNW-ESE to NW-SE while those from Landsat-8 are NE-SW, WNW-ESE, NW-SE, WSW-ENE and NW-ESE to NNW-SSE. Together, these structures depict trans-compressions or trans-tensions corresponding to a broad NE-SW strike-slips channel that affect both the CAFB and the Ntem Complex, and they control the intrusions thus confirming a pervasive hydrothermal activity within the Ntem Complex. The proximity or coincidence of these porphyry centres with some mapped Iron-Gold affiliated mineral indices and porphyry granites indicate the possible occurrence of many hydrothermal ore deposits. These results show the high probability for the Ntem complex to host porphyry deposits so they may serve to boost mineral exploration in the Yaounde-Sangmelima region and in the entire southern Cameroon as well.

Magmatic Evolution and Mineralization of Porphyry Copper-Gold Deposits in the Duolong Ore Concentration Area, Tibet

The Bangong Lake-Nujiang River metallogenic belt is located between the Qiangtang Block and Lhasa Block, and the Duolong ore concentration area is located in the western section of the Bangong Lake-Nujiang River metallogenic belt. Till now, several large and super large copper-gold deposits, such as Duobuza, Bolong, Dibaonamugang, Naruo and Rongna deposits have been discovered in this area, mainly porphyry copper-gold ones.