Three-dimensional Modeling of Ore-forming Elements and Mineralization Prognosis for the Yechangping Mo Deposit,Henan Province,China

Three-dimensional geochemical modeling of ore-forming elements is crucial for predicting deep mineralization.This approach provides key information for the quantitative prediction of deep mineral localization,three-dimensional fine interpolation,analysis of spatial distribution patterns,and extraction of quantitative mineral-seeking markers.The Yechangping molybdenum(Mo)deposit is a significant and extensive porphyry-skarn deposit in the East Qinling-Dabie Mo polymetallic metallogenic belt at the southern margin of the North China Block.Abundant borehole data on oreforming elements underpin deep geochemical predictions.The methodology includes the following steps:(1)Threedimensional geological modeling of the deposit was established.(2)Correlation,cluster,and factor analyses post delineation of mineralization stages and determination of mineral generation sequence to identify(Cu,Pb,Zn,Ag)and(Mo,W,mfe)assemblages.(3)A three-dimensional geochemical block model was constructed for Mo,W,mfe,Cu,Zn,Pb,and Ag using the ordinary kriging method,and the variational function was developed.(4)Spatial distribution and enrichment characteristics analysis of ore-forming elements are performed to extract geological information,employing the variogram and w(Cu+Pb+Zn+Ag)/w(Mo+W)as predictive indicators.(5)Identifying the western,northwestern,and southwestern areas of the mine with limited mineralization potential,contrasted by the northeastern and southeastern areas favorable for mineral exploration.

Genesis and metallogenic characteristic of Dongnan Cu–Mo deposit associated granitoids:LA-ICP-MS zircon U–Pb dating and isotope constraint from Zijinshan ore field in southeastern China

The Dongnan Cu–Mo deposit,located in the southeast of the Zijinshan ore field(the largest porphyry–epithermal system in Southeast China),represents the complex magmatic and metallogenesis events in the region.The petrogenesis and metallogenesis of granitoids from the deposit are not determined,especially the interactions between ore-bearing(granodiorite porphyry)and barren samples(granodiorite and diorite).In the paper,the whole rock geochemical features shared a similar affinity to the middle-lower content and revealed that they derived from partial melting of the Cathaysian basement with the contribution of mantle materials,even represented that they generated in the plate subduction;LA-ICP-MS zircon U–Pb ages show that these granodiorites,granodioritic porphyry and diorite,were generated during 114–103 Ma.The ore-bearing samples mostly presented ε_(Hf)(t)of negative values(peak value is-4 to-3)with old two-stage Hf model ages(t_(DM)^(2))(peak value is 1.10–1.15 Ga),while the barren sample showed slightly negative ε_(Hf)(t)(peak value is-1 to 0)values with young t_(DM)^(2)(peak value is 1.00–1.05 Ga).The value of zircon Ce^(4+)/Ce^(3+)ratio mostly higher than 450 was first verified for the ore-bearing samples in the Dongnan Cu–Mo deposit,and the values of ore-bearing were found to be higher than those from the barren,which suggests that the ore-bearing formed in more oxidized parental magma with higher oxygen fugacity.Based on the geochemical characteristic of the element and isotope,we concluded that the Early Cretaceous multiphases magmatic activities,low melting temperature and low pressure of pluton,and high oxygen fugacity of zircon,were the favorable conditions for metallogenesis of Dongnan Cu–Mo deposit.

Re-Os geochronology of Cu and W-Mo deposits in the Balkhash metallogenic belt,Kazakhstan and its geological significance

The Central Asian metallogenic domain （CAMD） is a multi-core metallogenic system controlled by boundary strike-slip fault systems. The Balkhash metallogenic belt in Kazakhstan, in which occur many large and super-large porphyritic Cu--Mo deposits and some quartz vein- and greisen-type W-Mo deposits, is a well-known porphyritic Cu--Mo metallogenic belt in the CAMD. In this paper 11 molybdenite samples from the western segment of the Balkhash metallogenic belt are selected for Re--Os compositional analyses and Re--Os isotopic dating. Molybdenites from the Borly porphyry Cu deposit and the three quartz vein-greisen W--Mo deposits--East Kounrad, Akshatau and Zhanet--all have relatively high Re contents （2712--2772 μg/g for Borly and 2.267--31.50 μg/g for the other three W-Mo deposits）, and lower common Os contents （0.670-2.696 ng/g for Borly and 0.0051--0.056 ng/g for the other three）. The molybdenites from the Borly porphyry Cu--Mo deposit and the East Kounrad, Zhanet, and Akshatau quartz vein- and greisen-type W-Mo deposits give average model Re--Os ages of 315.9 Ma, 298.0 Ma, 295.0 Ma, and 289.3 Ma respectively. Meanwhile, molybde- nites from the East Kounrad, Zhanet, and Akshatan W-Mo deposits give a Re--Os isochron age of 297.9 Ma, with an MSWD value of 0.97. Re--Os dating of the molybdenites indicates that Cu-W-Mo metallogenesis in the western Balkhash metallogeuic belt occurred during Late Carboniferous to Early Permian （315.9--289.3 Ma）, while the porphyry Cu--Mo deposits formed at ~316 Ma, and the quartz vein-greisen W--Mo deposits formed at ~298 Ma. The Re--Os model and isochron ages thus suggest that Late Carboniferous porphyry granitoid and pegmatite magmatism took place during the late Hercy- nian movement. Compared to the Junggar-East Tianshan porphyry Cu metallogenic belt in northwestern China, the formation of the Cu-Mo metallogenesis in the Balkhash rnetallogenic belt occurred between that of the Tuwu-Yandong in East Tianshan and the Baogutu porphyry Cu deposits in West Junggar. Collectively, the large-scale Late Carboniferous porphyry Cu-Mo metallogenesis in the Central Asian metallogenic domain is related to Hercynian tectono-magmatic activities.

Geochemistry and Sr-Nd-Pb Isotopes of the Granites from the Hashitu Mo Deposit of Inner Mongolia, China： Constraints on Their Origin and Tectonic Setting

The Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite. Sr-Nd-Pb isotopes of the intrusions show that the porphyritic syenogranite has initial ^87Sr/^86Sr ratios of 0.70418-0.70952, ENd（t） values of 1.3 to 2.1 （t=143 Ma）, ^206Pb/^204Pb ratios of 19.191-19.573, ^207Tpb/^204pb ratios of 15.551-15.572, and ^208Pb/^204Pb ratios of 38.826-39.143. The monzogranite has initial 87Sr/86Sr ratios of 0.70293-0.71305, εNd（t） values of 1.1 to 2.0 （t=-147 Ma）, ^206Pb/^204pb ratios of 19.507-20.075, ^207Pb/^204Pb ratios of 15.564-15.596, and ^208Pb/^204Pb ratios of 39.012-39.599. The calculated Nd model ages （TDM） for monzogranite and porphyritic syenogranite range from 866 to 1121 Ma and 795 to 1020 Ma, respectively. The granitic rocks in the Hashitu area have the same isotope range as granites in the southern parts of the Great Hinggan Range. The isotope composition indicates that these granites are derived from the partial melting of a juvenile lower crust originating from a depleted mantle with minor contamination by ancient continental crust. The integrating our results with published data and the Late Mesozoic regional tectonic setting of the region suggest that the granites in the Hashitu area formed in an intra-continent extensional setting, and they are related to the thinning of the thickened lithosphere and upwelling of the asthenosphere.

Genesis of the Huoshenmiao Mo deposit in the Luanchuan ore district, China: Constraints from geochronology, ?uid inclusion, and H-O-Sisotopes

The Huoshenmiao δeposit is Mo skarn δeposit, located in the western part of the Luanchuan ore δistrict.Mineralization process can be δivided into a skarn and a quartz-sulfide episodes with six stages: prograde(I), retrograde(II), quartz-K-feldspar(III), quartz-molybdenite(IV), quartz-pyrite(V), and quartzcalcite(VI). A combined study of geochronology, fluid inclusion(FI), and stable isotopes was conducted to constrain the mineralization age, source of ore materials, as well as the origin and evolution of the ore-forming fluids. Molybdenite Ree Os δating indicates that the δeposit was formed in the Late Jurassic(~145 Ma). The δ^(34)S values of sulfides range from 3.0‰ to 7.1‰, implying that the ore materials in the δeposit are magmatic in origin. Three types and six subtypes of FIs are δistinguished, namely, aqueous two-phase(W_1-and W_2-type), δaughter mineral-bearing multiphase(S_1-and S_2-type), and CO_2-bearing three-phase(C_1-and C_2-type). In stages I and II, the W_1-type FIs δisplay homogenization temperatures(Th) from 496°C to >600°C, with salinities of 14.9-18.3 wt.% NaCl eqv. The FIs in stages III, IV and early stage V composed of coeval S-, C-and W-types, respectively homogenize at similar Th, suggesting the occurrence of boiling. The W1-type FIs in late stage V and stage VI, yield Th of 102-406°C and salinities of 0-4.7 wt.% NaCl eqv. The δD_(H_2O)and δ^(18) O(H_2O)values of the ore-forming fluids in quartz-sulfide episode vary from-112‰ to-76‰, and 11.0‰ to 1.0‰, respectively. All these above observations reveal that the early ore-forming fluids are magmatic in origin, and characterized by high temperature and moderate to high salinity, and gradually evolve to low temperature, low salinity meteoric water. The Huoshenmiao Mo δeposit is associated with the magmatism event induced by the protracted subduction of the Izanagi plate beneath the eastern China continent. The δecrease in temperature, salinity and f(O_2), as well as change of p H δue to boiling and fluid-rock interaction, are the main factors controlling Mo δeposition.

The Late Early Cretaceous Mo Mineralization in the South China Mo Province: Constraints from U–Pb and Re–Os Geochronology of the Lufeng Porphyry Mo Deposit

Compared to other Mo provinces,few studies focused on the South China Mo Province(SCMP),especially for Early Cretaceous Mo mineralization.The Lufeng porphyry Mo deposit in the SCMP is characterized by disseminated and veinlet-type mineralization in granite porphyry,gneiss,and rhyolite.In this study,six molybdenite samples yield a Re–Os isochron age of 108.0±1.8 Ma,which is consistent with the zircon U–Pb age of the granite porphyry(108.4±0.8 Ma).The coincidence of magmatic and hydrothermal activities indicates that Mo mineralization was associated with the intrusion of granite porphyry during the late Early Cretaceous.A compilation of U–Pb and Re–Os chronological data suggests that an extensive and intensive Mo mineralization event occurred in the SCMP during the late Early Cretaceous.The marked difference in molybdenite Re contents between Cu-bearing(85–536 ppm)and Cu-barren(1.3–59 ppm)Mo deposits of the late Early Cretaceous indicates that the ore-forming materials were derived from strong crust–mantle interactions.Together with regional petrological and geochemical data,this study suggests that late Early Cretaceous Mo mineralization in the SCMP occurred in an extensional setting associated with the roll-back of the Paleo-Pacific slab.

Helium and argon isotope geochemistry of the Tibetan Qulong porphyry Cu-Mo deposit,China

The Qulong porphyry Cu-Mo deposit,generated in the Miocene post-collisional extension environment of the Gangdese Copper(Molybdenum)Metallogenic Belt,is one of the largest porphyry Cu deposits in China.This study reports the noble gas isotopic compositions of volatiles released from fluid inclusion reserved in pyrite from the Qulong deposit.3He/4 He and 40Ar/36Ar ratios range from 0.54 to 1.015 Ra and 300-359,respectively.Concentrations of 4 He and 40Ar range from 1.77 to 2.62×10^(-8)cm^(3)STP and 1.7-34×10^(-8)cm^(3)STP,respectively.The isotopic composition of noble gases indicates that the ore-forming fluids of the Qulong Cu-Mo deposit were a mixture of fluid containing mantle component,which is exsolved from the porphyry magma,and crustal fluid characterized by atmospheric Ar and crustal radiogenic He.Theδ34S values of pyrite and molybdenite range from-0.52‰to 0.31‰,with an average of-0.12‰,indicating a magmatic origin.More mantle components were involved in the Cu-Mo deposit than in the Mo-Cu deposit in the Qulong-Jiama ore-district.

Petrogenesis of granite from Xiaofan Mo deposit, Dabie Orogen

The Mesozoic granitoids in the Dabie Orogen are of particular geological interest as indicators for Mesozoic lithospheric evolution because of their close association with porphyry Mo mineralization. Here, we present a study using petrogeochemistry data to constrain the petrogenesis of the Xiaofan granites in the Dabie Mo mineralization belt （DMB）, Henan Province, China. Field investigations show that the Xiaofan pluton mainly consists of porphyritic granite. The Xiaofan granites have high SiO2 contents of 74.29 wt%-76.07 wt% （average： 75.18 wt%）, A1203 contents of 11.66 wt%-12.83 wt% （average： 12.13 wt%）, and K20 contents of 5.37 wt%-7.90 wt% （average： 6.86 wt%） and low MgO （0.06 wt%-0.16 wt%）, TiO2 （0.09 wt%-0.10 wt%）, and P205 （0.047 wt%-0.103 wt%） contents. They are enriched in Rb, U, K and Hf but depleted in Ba, Nb, Ta, Sr and Ti. By geochemical and mineralogical features, we propose that the Xiaofan granites belong to A-type type granite and dominantly sourced from the crust. The granites from the Xiaofan Mo deposit may have formed in a post-collision extensional setting.

Fluid inclusion and H-O isotope study of the Jiguanshan porphyry Mo deposit,Xilamulun Metallogenic Belt:implications for characteristics and evolution of ore-forming fluids

We studied the fluid inclusions of the Jiguanshan Mo deposit in China,which is a large porphyry deposit located in the southern Xilamulun Metallogenic Belt.The irregular Mo ore body with various types of hydrothermal veinlets is hosted by Late Jurassic granite porphyry.Intense hydrothermal alterations in the deposit from the core to margin are silicification-potassium feldspar alteration,pyrite-quartz-sericite-fluorite alteration,and propylitic alteration.Based on the mineral assemblages and crosscutting relationships of ore veins,the ore-forming process were divided into three stages and two substages:quartz-pyrite veins(stage I)associated with potassic alteration;quartz-molybdenite-chalcopyrite-pyrite veins(substage Ⅱ-1)and quartz-molybdenite-fluorite veins(substage Ⅱ-2)associated with phyllic alteration;and fluorite-quartz-carbonate veins(stage Ⅲ)with carbonation.Five majorfluid inclusions(FIs)types were distinguished in the quartz associated with oxide and sulfide minerals,i.e.polyphase brine(Pb-type),opaque-bearing brine(Ob-type),solid halite(S-type),two-phase aqueous(A-type),and vapor(Vtype)inclusions.The FIs of stage I were composed of liquid-rich S-,A-,and V-type FIs with homogenization temperatures and salinities of 490 to 511℃ and 8.9 to 56.0 wt%NaCl equiv.,respectively.The FIs of substage Ⅱ-1 are composed of Pb-,Ob-,S-,A-,and V-type FIs with homogenization temperatures and salinities of 352 to 460℃ and 3.7 to 46.1 wt%NaCl equiv,respectively.The FIs of substage Ⅱ-2 are Ob-,S-,A-,and V-type FIs with homogenization temperatures and salinities of 234 to309°C and 3.7 to 39.2 wt%NaCl equiv,respectively.The FIs of stage Ⅲ are A-type FIs with homogenization temperatures and salinities of 136 to 172℃ and 1.1 to 8.9 wt%NaCl equiv,respectively.Fluid boiling,which resulted in the precipitation of sulfides,occurred in stages I andⅡ.The initial ore-forming fluids of the Jiguanshan deposit had high temperature,high salinity,and belonged to an F-rich NaCl±KCl-H2O system.The fluids gradually evolved to low temperature,low salinity,and belonged to a NaCl-H2O system.Studies of the hydrogen and oxygen isotope compositions of quartz(δ^18OH2O=-7.3 to 6.3%,δDH2O=-104.3 to-83.3%)show that the ore-formingfluids gradually evolved from magmatic water to meteoric water.

Discriminating characters of ore-forming intrusions in the super-large Chalukou porphyry Mo deposit,NE China

The Chalukou porphyry Mo deposit, located in the Great Hinggan Range, is the largest Mo deposit in northeast China, although the age and genesis of the associated magmatic intrusions remain debated.Here we report zircon U-Pb ages and trace elements, whole rock geochemistry and Sre Nd isotope data with a view to understand the relationship between the magmatism and molybdenum mineralization.Zircon U-Pb analysis yield an age of 475 Ma for rhyolite in the older strata, 168 Ma for the premineralization monzogranite, and 154 Ma for the syn-mineralization granite porphyry. The granite porphyry and quartz porphyry are considered as the ore-forming intrusions. These rocks are peraluminous, alkali-calcic, and belong to high-K to shoshonitic series with a strong depletion of Eu. They also display characteristics of I-type granites. The rocks exhibit wide variations of(87 Sr/86 Sr)iin the range of 0.705426 -0.707363, and ε_(Nd)(t) of -3.7 to 0.93. Zircon REE distribution patterns show characteristics between crust and the mantle, implying magma genesis through crust-mantle interaction. The Fe_2O_3/FeO values(average 1) for the whole rock and EuN/Eu*Nvalues(average 0.45), Ce^(4+)/Ce^(3+) values(average 301)for zircon grains from the granite porphyry are higher than those from other lithologies. These features suggest that the ore-forming intrusions(syn-mineralization porphyry) had higher oxygen fugacity conditions than those of the pre-mineralization and post-mineralization rocks. The Chalukou Mo deposit formed in relation to the southward subduction of the Mongol-Okhotsk Ocean. Our study suggests that the subduction-related setting, crust-mantle interaction, and the large-scale magmatic intrusion were favorable factors to generate the super-large Mo deposits in this area.

Fluorite REE characteristics of the Diyanqinamu Mo deposit,Inner Mongolia, China

The Diyanqinamu Mo deposit, a newly discovered porphyry deposit in the northern-central part of the Great Xing'an Range, Inner Mongolia, China, is characterized by widely distributed fluorite. It is important to note that almost all the fluorite that is paragenetic with molybdenite is purple. The Tb/Ca–Tb/La ratios of these purple fluorite samples show that they have a hydrothermal origin.The unidirectional solidification texture at the apex of the aplitic granite and the low F contents in the andesite suggest that most of F in fluorite was derived from granitic melts. These observations suggest that the fluorite was related to the magmatic-hydrothermal fluids. All the fluorite separates have consistent total REE contents with LREE-depleted, HREE-enriched, negative Eu anomaly,unapparent Ce anomaly and positive Y anomaly. These characteristics are significantly different than those of country granite, andesite and tuff whole-rock. The positive Y anomaly of the fluorite separates implies that the hydrothermal fluids migrated a long distance, as suggested by the fact that the fluorite-molybdenite veins were mostly hosted in andesite and tuff, far from the Mo ore-forming granites. The features of LREE-depleted and HREE-enriched fluorite are due to the REE-complex in the F-enriched fluids during migration. The stronger negative Eu anomaly of fluorite than those of country rocks suggests that the Eu anomaly of the original hydrothermal fluid was enhanced by the high temperature(generally above 200 or250 °C). The widespread magnetite in the studied deposit indicates that the magmatic-hydrothermal fluid was oxidized at early stage. On the other hand, the pyrite was also paragenetic, with the molybdenite and unapparent Ce anomaly implying that the hydrothermal fluid probably experienced oxygen fugacity decreasing during migration,which is important for Mo mineralization.

Mineral Chemistry of Scheelite as An Indicator of Multi-stage Fluid Evolution Associated with the Riviera W-REE-Mo Deposit South Africa

The Neoproterozoic Riviera W-REE-Mo deposit is one of the largest unmined tungsten resources in the world and is associated with pervasively altered A-type granites of the Neoproterozoic Cape Granite Suite Western Cape, South Africa. The present study investigated the mineral chemistry of scheelite, the principal ore mineral with the aim to record the variation of solid solution molybdenum for geometallurgical purposes and also as an indicator of changing redox conditions of the mineralizing hydrothermal fluids. Methodology included UV-fluorescence studies and micro-analyses by LA-ICP-MS. Results have shown that at least four phases of scheelite are hosted by the endoskarn zone, potassic alteration zone and various quartz-carbonate veins. This reflects hydrothermal fluid evolution from early stage reduced to late stage, vein associated and more oxidized. The molybdenum content of the dominant early phase scheelite is low and renders the deposit amenable to low penalty mineral recovery.

秘鲁Morococha斑岩-矽卡岩-浅成低温热液型矿床成矿地质特征与区域找矿方向

秘鲁中部Morococha地区位于中安第斯秘鲁中新世成矿带,是全球最具代表性的世界级斑岩-矽卡岩型和浅成低温热液型成矿系统之一。系统总结了该区斑岩型、矽卡岩型、浅成低温热液型等多种铜钼铅锌银多金属矿化成矿作用特征和最新的研究进展,结合区域岩浆-热液成矿作用过程,提出了下一步找矿方向。Morococha矿区位于秘鲁中部Yali穹隆北段,由中心部位的Toromocho斑岩型铜钼矿床及外围铅锌银金多金属矿脉组成。区内主要构造为北西向Morococha背斜,地层主要为二叠纪—三叠纪Mitu群火山碎屑岩、侏罗纪Pucara群碳酸盐岩、早白垩世Goyllarisquizga群海相碎屑岩和碳酸盐岩。矿区中新世岩浆活动主要为中中新世不含矿的闪长质侵入岩(14.3~14.1 Ma)和晚中新世与成矿有关的花岗闪长岩和长石斑岩岩株(9.4~7.7 Ma)。Morococha岩浆-热液系统(8.5~7.2 Ma)是其形成超大型斑岩型铜矿成矿的原因之一,铅锌银多金属矿化主要发生在斑岩型矿化之后约0.5 Ma,受区域构造控制。矿床在空间上显示出明显的金属分带特征,中心斑岩区域为富铜矿石,而远离斑岩区出现更多的富铅锌银矿石。秘鲁中部中新世成矿带分布着众多具有重要经济价值的脉状热液型铅锌银多金属矿床,总结近年来综合地质调查和研究成果,表明这些多金属矿床都属于斑岩-矽卡岩成矿系统的一部分,因此斑岩-矽卡岩型铜矿床及浅成低温热液型贵金属矿床是秘鲁中部重要的找矿方向。

右江盆地大际山U-(Mo)矿床围岩蚀变特征及微量元素迁移规律——对区域内U、Au成生关系的指示

位于扬子地块西南缘的右江盆地,是全球第二大的卡林型Au矿(共伴生有Sb、Hg、Tl异常/矿化)矿集区,有着滇黔桂“金三角”的美誉。值得注意的是,该区除发育Au(-Sb-Hg-Tl)矿床外,还产有大量赋矿岩性和控矿构造相似的U矿床(点),成矿特色鲜明。前人对该区Au矿开展了大量研究,而U矿研究较少,对U、Au的成生关系尚不清楚。基于此,文章选取右江盆地内典型的U矿床——大际山U-(Mo)矿床为研究对象,通过开展岩矿相学研究和地球化学分析,厘定了矿化的围岩蚀变为硫化、沥青质化、磷铝锶石化、硅化和伊利石化,揭示了矿化过程中Re、Tl、Mo、U、Cd、Ni、Co、As、Sb、MREE的相对富集。蚀变矿物组合及元素迁移规律约束大际山U-(Mo)矿床中成矿物质可能来源于牛蹄塘组,成矿流体应为还原性有机流体与地表-近地表酸性、氧化性流体的混合,矿质沉淀发生在低温、酸性、还原环境中。综合分析认为,右江盆地内U、Au分布特征及矿床成因具有明显差异,二者应是不同成矿事件的产物。

Geology,Geochemistry and Zircon U-Pb Geochronology of Porphyries in the Dabate Mo-Cu Deposit,Western Tianshan,China:Petrogenesis and Tectonic Implications

The Dabate Mo-Cu deposit is a medium-sized porphyry-type deposit in the Sailimu Lake region, western Tianshan, China. We present the geology, geochemistry and zircon U-Pb geochronology of granite porphyries from the Dabate district with the intent to constrain their tectonic setting and petrogenesis. Porphyries in the Dabate district include granite porphyry I（gray white color with large phenocrysts）, granite porphyry II（pink color with small phenocrysts） and quartz porphyry. Granite porphyry II is the Cu and Mo ore-bearing granitoid in the Dabate deposit. LA-ICPMS zircon U-Pb analyses indicate that granite porphyry II was emplaced at 284.2±1.8 Ma. Granite porphyry I and II have similar geochemical features and are both highly fractionated granites：（1） They have high SiO2 content（70.93–80.18 wt% and 72.14–72.64 wt%, respectively）, total alkali（7.58–8.95 wt% and 9.35–9.68 wt%, respectively）, mafic index（0.95–0.98 and 0.93–0.94, respectively） and felsic index（0.79–0.94 and 0.89–0.91, respectively）;（2） They are characterized by pronounced negative Eu anomaly, ＂seagullstyle＂ chondrite-normalized REE patterns and ＂tetrad effect＂ of REE;（3） They are rich in Rb, K, Th, Ta, Zr, Hf, Y and REE, but depleted in Sr, P, Ti and Nb. The magma of granite porphyries in Dabate can be interpreted to have been generated by partial melting of the upper crust due to mantle-derived magma underplating in a post-collisional extensional setting.

Rare Earth Element Behaviour in theWunugetushan Copper - Molybdenum Deposit,Inner Mongolia, and Its Implications

Considering porphyry and wall rocks as a whole system, the behaviour of rare earth elements (REE) in hydrothermal alteration and mineralization of the exceedingly large Wunugetushan porphyry Cu-Mo deposit of Inner Mongolia has been studied. It has been found for the first time that there exists complementary REE variation in hydrothermal alteration between porphyry and wall rocks, and Eu depletion has certain significance in indicating mineralization. Based on an analysis of the variation in REE contents of relevant minerals during the hydrothermal alteration, the ore-forming fluids are inferred to be depleted in ∑REE, comparatively enriched in ∑Y and strongly depleted in Eu. In the intermediate-strong alteration zones, porphyry and wall rock took part in hydrothermal metasomatism and alteration almost in equal ratio mass. Furthermore, studies of REE and hydrogen and oxygen isotopes and fluid inclusions confirm the existence of hydrothermal convection and the possibility of supplying part of ore materials by the wall rock and indicate that the application of REE geochemistry in mineral prospecting is promising.

Geochemical Characteristics and Significance of Major Elements, Trace Elements and REE in Mineralized Altered Rocks of Large-Scale Tsagaan Suvarga Cu-Mo Porphyry Deposit in Mongolia

The alteration types of the large-scale Tsagaan Suvarga Cu-Mo porphyry deposit mostly comprise stockwork silicification, argillization, quartz-sericite alteration, K-silicate alteration, and propylitization. The mineralized and altered zones from hydrothermal metallogenic center to the outside successively are Cu-bearing stockwork silicification zone, Cu-beating argillized zone, Cu-Mo-bearing quartz-sericite alteration zone, Cu-Mo-bearing K-silicate alteration zone, and pro- pylitization zone. The K-silicate alteration occurred in the early phase, quartz-sericite alteration in the medium phase, and argillization and carbonatization （calcite） in the later phase. Ore-bearing-altered rocks are significantly controlled by the structure and fissure zones of different scales, and NE- and NW-trending fissure zones could probably be the migration pathways of the porphyry hydrothermal system. Results in this study indicated that the less the concentrations of REE, LREE, and HREE and the more the extensive fractionation between LREE and HREE, the closer it is to the center circulatory hydrothermal ore-forming and the more extensive silicification. The exponential relationship between the fractionation of LREE and HREE and the intensity of silicification and K-silicate alteration was found in the Cu-Mo deposit studied. The negative Eu anomaly, normal Eu, positive Eu anomaly and obviously positive Eu anomaly are coincident with the enhancement of Na2O and K2O concentrations gradually, which indicated that Eu anomaly would be significantly controlled by the alkaline metasomatism of the circulatory hydrothermal ore-forming system. Therefore, such characteristics as the positive Eu anomaly, the obvious fractionation between LREE and HREE and their related special alteration lithofacies are suggested to be metallogenic prognostic and exploration indications for Tsagaan Suvarga-style porphyry Cu-Mo deposits in Mongolia and China.

Evidence from pseudomorphous β-quartz phenocryst for decompression of rock-forming and ore-forming processes in Shapinggou porphyry Mo deposit

The Shapinggou porphyry molybdenum(Mo) deposit, located in Jinzhai County, Anhui Province, China, is the largest in the Qinling-Dabie Mo Metallogenic Belt. The intrusive rocks in the Shapinggou Mo ore district formed in the Yanshanian can be divided into two stages based on zircon U-Pb dating and geochemical features. This study focuses on the late stage intrusions(quartz syenite and granite porphyry), which are closely genetically related to molybdenum mineralization. Petrographic observations identified two quartz polymorphs in the quartz syenite and granite porphyry, which were derived from the same magmatic sources and similar evolutionary processes. The quartzes were identified as a xenomorphic β-quartz within quartz syenite, while the quartz phenocrysts within the granite porphyry were pseudomorphous b-quartz, characterized by a hexagonal bipyramid crystallography. The pseudomorphous b-quartz phenocrysts within the granite porphyry were altered from b-quartz through phase transformation. These crystals retained b-quartz pseudomorph. Combined with titanium-inzircon thermometry, quartz phase diagrams, and granitic Q-Ab-Or-H_2O phase diagrams, it is suggested that the quartz syenite and granite porphyry were formed under similar magmatic origins, including similar depths and magmatic crystallization temperatures. However, the β-quartz within quartz syenite indicated that the crystallization pressure was greater than 0.7 GPa, while the original b-quartz within the granite porphyry was formed under pressures between 0.4 and 0.7 GPa. The groundmass of the granite porphyry which formed after the phenocryst indicated a crystallizing pressure below 0.05 GPa. This indicates that the granite porphyry was formed under repetitive and rapid decompression. The decompression was significant as it caused the exsolution of the ore-forming fluids, and boiling and material precipitation during the magmatic-fluid process. The volumetric difference during the phase transformation from b-quartz to β-quartz caused extensive fracturing on the granite porphyry body and the wall rocks. As the main ore-transmitting and ore-depositing structures, these fractures benefit the hydrothermal alteration and stockwork-disseminated mineralization of the porphyry deposit. It is considered that the pseudomorphous β-quartz phenocrysts of the porphyritic body are metallogenic indicators within the porphyry deposits. The pseudomorphous β-quartzes therefore provide evidence for the formation of the porphyry deposit within a decompression tectonic setting.

Geochronological Constraints on the Haftcheshmeh Porphyry Cu-Mo-Au Ore Deposit, Central Qaradagh Batholith, Arasbaran Metallogenic Belt, Northwest Iran

The Haftcheshmeh porphyry Cu-Mo-Au deposit in the Arasbaran metallogenic belt （AMB） of NW Iran contains more than 185 Mt of ore, with a grade ranging from 0.3% to 0.4%. It is hosted within a porphyritic diorite to granodiorite intruded into an older gabbro - diorite intrusion. 40Ar/39Ar analyses of primary magmatic hornblende from the granodiorite porphyry and gabbro - diorite show plateau ages of 26.41 ± 0.59 Ma, with an inverse isochron age of 25.9 ± 1.0 Ma and a plateau age of 27.47 ± 0.17 Ma, with an inverse isochron age of 27.48 ± 0.35 Ma for these two rock types, respectively. Comparing these new age data with those from the nearby Sungun （20.69 ± 0.35 Ma） and Kighal porphyry deposits defines a northwest-southeast Cu-Mo-Au mineralization zone extending for 20 km over the time span of-27 to 20 Ma. Geochemically, Haftcheshmeh rocks are calc-alkaline with high potassium affinities with tectonic setting in relation to volcanic arc setting. Large ion lithophile elements （LILE） such as Th, U and K show enrichment on a primitive mantle normalized diagram （specially Pb）, and are depleted in high field strength elements （HFSE） such as Ti and Nb, pointing to a mantle magma source contamination with crustal materials by subducted oceanic crust.

Porphyry Cu-Mo deposits in the eastern Xing’an-Mongolian Orogenic Belt: Mineralization ages and their geodynamic implications

东方 Xing “一 -- 蒙古(Xing-Meng ) Orogenic 带(XMOB ) 是斑岩铜(Cu ) 的重要区域之一在中国的铝(瞬间) 存款。然而，在矿化作用和他们的 geodynamic 意义的准确年龄的研究是很有限的。在这研究，从 Duobaoshan Cu 的 granodioritic 岩石扔， Daheishan 瞬间沉积物被选择做锆石虾 U-Pb 分析以便抑制他们的矿化作用年龄。Geochronological 数据显示矿化作用的二个事件发生在 Duobaoshan Cu 存款。与 Duobaoshan 斑岩 Cu 存款有关的 granodiorite 被形成在与 485 ± 8 妈的锆石 U-Pb 年龄早古生代，而与 Sankuanggou skarn 类型 Cu 存款有关的 granodiorites 是 emplaced 在里面，有锆石 U-Pb 的侏罗记 176 ± 3 和 177 ± 3 妈变老。在吉林省的 Daheishan 区域，与斑岩瞬间存款有关的 granodiorite 斑岩的炮兵阵地年龄在 178 ± 3 妈在 170 ± 3 妈，和 unmineralized monzogranite 被标明日期。因此， Cu 瞬间矿化作用的二个事件分别地在东方 XMOB 被开发，在 -485 妈和 -175 妈。基于地质的历史和 granitoids 的空间时间的分发在东北( NE )中国， Duobaoshan Cu 存款与 Xing 的碰撞有关，这被建议“and Erguna 堵住在早古生代，并且 Sankuanggou Cu 和 Daheishan 瞬间存款在侏罗记期间与Paleo和平的板的 subduction 有关。