Geological, Alteration and Mineralization Characteristics of Ali Javad Porphyry Cu-Au Deposit, Arasbaran Zone, NW Iran

Ali Javad porphyry Cu-Au deposit is located 20 Km north of Ahar city in Arasbaran metallogenic zone which is considered as a part of Alp-Himalayan mineralization belt. Magmatism in this area began in Late Cretaceous, followed by extensive magmatism in Cenozoic and Quaternary periods. Porphyry type mineralization developed in Ali Javad quartz monzonitic porphyry stock and Eocene pyroclastic and volcanic country rocks. Ali Javad porphyry intrusion has shoshonitic nature and shows characteristics of volcanic arc granitoids that it is have been emplaced in a post-collision tectonic setting. Alteration zones at the deposit demonstrated zoning which is comparable with Lowel-Guilbert model proposed for quartz-monzonite type porphyry copper deposits. Phyllic, argillic, silicic and propylitic alteration zones were observed at the surface while potassic alteration zone could be observed at depth in drill core samples. Mineralization was recognized both as supergene and hypogene, the latter was as veins, veinlets and disseminations. Dominant hypogene minerals were chalcopyrite, bornite, molybdenite, pyrite and magnetite while chalcocite, covellite and limonite were dominant supergene minerals. Four mineralization zones were observed in the deposit as leached, transitional, supergene and hypogene zones. Average grades were 0.75% for copper and 1.86 ppm for gold with 81.5 Mt proved reserve for copper and 37.8 Mt for gold.

^(40)Ar/^(39)Ar Dating of the Shaxi Porphyry Cu-Au Deposit in the Southern Tan-Lu Fault Zone, Anhui Province

Four samples of plagioclase and biotite from the Shaxi porphyry in the lower part of the Yangtze metallogenic belt were analyzed for age determination with the ^40 Ar/^39Ar method. The results yield reproducible ages of 126 Ma to 135 Ma with a high level of confidence according to the agreement between isochron and plateau ages. The four Ar-Ar ages are relatively consistent within the analytical error. These ages are also consistent with, but more precise than, previous K-Ar and Rb-Sr ages and thus provide better constraints on the time of porphyry formation and associated Cu-Au mineralization along the middle to lower part of the Yangtze metallogenic belt. The ages of 126 to 135 Ma are interpreted to represent the intrusive time of the Shaxi porphyry, so that the Cu-Au mineralization should have occurred later due to the post-magmatic hydrothermal event.

Texture and Geochemistry of Multi-stage Hydrothermal Scheelite in the Mamupu Cu-Au-Mo(-W)Deposit,Eastern Tibet:Implications for Tungsten Mineralization in the Yulong Belt

Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt(YPCB),Tibet.This study reports the results of cathodoluminescence,trace element and Sr isotope analyses of Mamupu scheelite samples,undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore-forming fluids.Three different types of scheelite are identified in the Mamupu deposit:scheelite A(Sch A)mainly occurs in breccias during the prograde stage,scheelite B(Sch B)forms in the chlorite-epidote alteration zone in the retrograde stage,while scheelite C(Sch C)occurs in distal quartz sulfide veins.The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage.Compared with ore-related porphyries,Sch A has a similar REE pattern,but with higher ΣREE,more depleted HREE and slightly lower(^(87)Sr/^(86)Sr)i ratios.These features suggest that Sch A is genetically related to ore-related porphyries,but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition.Sch B shows dark(Sch B-I)and light(Sch B-II)domains under CL imaging.From Sch B-I to Sch B-II,LREEs are gradually depleted,with MREEs being gradually enriched.Sch C has the highest LREE/HREE ratio,which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE-rich minerals,such as diopside and garnet,in the early prograde stage.The Mo content in Sch B and Sch C gradually decreased,indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later,the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity.The extensive interaction of magmatic-hydrothermal fluids and carbonate provides the necessary Ca^(2+)for the precipitation of scheelite in the Mamupu deposit.

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.

Geology and mineralization of the Duobaoshan supergiant porphyry Cu-Au-Mo-Ag deposit(2.36 Mt)in Heilongjiang Province,China:A review

The reserves of the Duobaoshan porphyry Cu-Au-Mo-Ag deposit(also referred to as the Duobaoshan porphyry Cu deposit)ranks first among the copper deposits in China and 33rd among the porphyry copper deposits in the world.It has proven resources of copper(Cu),molybdenum(Mo),gold(Au),and silver(Ag)of 2.28×10^(6)t,80×10^(3)t,73 t,and 1046 t,respectively.The major characteristics of the Duobaoshan porphyry Cu deposit are as follows.It is located in a zone sandwiched by the Siberian,North China,and paleo-Pacific plates in an island arc tectonic setting and was formed by the Paleozoic mineralization and the Mesozoic mineralization induced by superposition and transformation.The metallogenic porphyries are the Middle Hercynian granodiorite porphyries.The alterations of surrounding rocks are distributed in a ring form.With silicified porphyries at the center,the alteration zones of K-feldspar,biotite,sericite,and propylite occur from inside to outside.This deposit is composed of 215 ore bodies(including 14 major ore bodies)in four mineralized zones.Ore body No.X in the No.3 mineralized zone has the largest resource reserves,accounting for more than 78%of the total reserves of the deposit.Major ore components include Cu,Mo,Au,Ag,Se,and Ga,which have an average content of 0.46%,0.015%,0.16 g/t,1.22 g/t,0.0003%,and 0.001%-0.003%,respectively.The ore minerals of this deposit primarily include pyrite,chalcopyrite,bornite,and molybdenite,followed by magnetite,hematite,rutile,gelenite,and sphalerite.The ore-forming fluids of this deposit were magmatic water in the early metallogenic stage and then the mixture of meteoric water and magmatic water at the late metallogenic stage.The ore-forming fluids experienced three stages.The ore-forming fluids of stageⅠhad a hydrochemical type of H_(2)O-CO_(2)-Na Cl,an ore-forming temperature of 375-650℃,and ore-forming pressure of 110-160 MPa.The ore-forming fluids of stageⅡhad a hydrochemical type of H_(2)O-CO_(2)-Na Cl,an ore-forming temperature of 310-350℃,and ore-forming pressure of 58-80 MPa.The ore-forming fluids of stageⅢhad a hydrochemical type of Na Cl-H_(2)O,an ore-forming temperature of 210-290℃,and ore-forming pressure of 5-12 MPa.The CuAu-Mo-Ag mineralization mainly occurred at stagesⅠandⅡ,with the ore-forming materials having a mixed crust-mantle source.The Duobaoshan porphyry Cu deposit was formed in the initial subduction environment of the Paleo-Asian Ocean Plate during the Early Ordovician.Then,due to the closure of the Mongol-Okhotsk Ocean and the subduction and compression of the Paleo-Pacific Ocean,a composite orogenic metallogenic model of the deposit was formed.In other words,it is a porphyry-epithermal copper-gold polymetallic mineralization system of composite orogeny consisting of Paleozoic island arcs and Mesozoic orogeny and extension.

Application of tensor CSAMT with high-power orthogonal signal sources in Jiama porphyry copper deposit,South Tibet

The Jiama porphyry copper deposit in Tibet is one of the proven supergiant copper deposits in the Qinghai-Tibet Plateau at present,with the reserves of geological resources equivalent to nearly 20×10^(6) t.However,it features wavy and steep terrain,leading to extremely difficult field operation and heavy interference.This study attempts to determine the effects of the tensor controlled-source audiomagnetotellurics(CSAMT)with high-power orthogonal signal sources(also referred to as the high-power tensor CSAMT)when it is applied to the deep geophysical exploration in plateaus with complex terrain and mining areas with strong interference.The test results show that the high current provided by the highpower tensor CSAMT not only greatly improved the signal-to-noise ratio but also guaranteed that effective signals were received in the case of a long transmitter-receiver distance.Meanwhile,the tensor data better described the anisotropy of deep geologic bodies.In addition,the tests also show that when the transmitting current reaches 60 A,it is still guaranteed that strong enough signals can be received in the case of the transmitter-receiver distance of about 25 km,sounding curves show no near field effect,and effective exploration depth can reach 3 km.The 2D inversion results are roughly consistent with drilling results,indicating that the high-power tensor CSAMT can be used to achieve nearly actual characteristics of underground electrical structures.Therefore,this method has great potential for application in deep geophysical exploration in plateaus and mining areas with complex terrain and strong interference,respectively.This study not only serves as important guidance on the prospecting in the Qinghai-Tibet Plateau but also can be used as positive references for deep mineral exploration in other areas.

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.

Geology, geochronology, and exploration of the Jiama giant porphyry copper deposit (11 Mt), Tibet, China: A review

Jiama,with more than 11 Mt of copper metal,is the largest porphyry-skarn copper system in the Gangdese metallogenic belt,Tibet,China,creating ideal conditions for deciphering the origin of porphyry ores in a collision setting.Despite massive studies of the geology,chronology,petrogenesis,and ore-related fluids and their sources in Jiama,there is a lack of systematic summaries and reviews of this system.In contrast to traditional porphyry copper systems in a subduction setting,recent studies and exploration suggest that the Jiama deposit includes porphyry-type Mo-Cu,skarn-type Cu polymetallic,vein-type Au and manto orebodies.This paper reviews the latest studies on the geology,chronology,petrogenesis,fluid inclusions,and isotopic geochemistry(hydrogen,oxygen,sulfur,and lead)of the Jiama deposit.Accordingly,a multi-center complex mineralization model was constructed,indicating that multi-phase intrusions from the same magma reservoir can form multiple hydrothermal centers.These centers are mutually independent and form various orebodies or are superimposed on each other and form thick,high-grade orebodies.Finally,a new comprehensive exploration model was established for the Jiama porphyry copper system.Both models established in this study help to refine the theories on continental-collision metallogeny and porphyry copper systems.

Textural and compositional variation of mica from the Dexing porphyry Cu deposit:constraints on the behavior of halogens in porphyry systems

The Dexing porphyry deposit is the largest porphyry Cu–Mo–Au deposit in South China.Biotite composition can record the physicochemical conditions and evolution history of magmatic-hydrothermal system.Biotite from the Dexing porphyry deposit could be divided to three types:primary magmatic biotite(Bi-M),hydrothermal altered magmatic biotite(Bi-A)and hydrothermal biotite(Bi-H).The temperature of Bi-M and Bi-H range from 719 to 767℃ and 690 to 727℃,respectively.Both magmatic and hydrothermal biotite have high Fe^(3+)/Fe^(2+)ratios(from 0.18 to 0.24)and XMgvalues(from 0.57 to 0.66),indicating a high oxygen fugacity.BiM has F lower than Bi-A and Bi-H(up to 0.26 wt%),but has Cl(Cl=0.18–0.30 wt%)similar to Bi-A and Bi-H(Cl=0.21–0.35 wt%),suggesting that high Cl/F ratios of early hydrothermal fluid may result from the exsolution from high Cl magma.From potassic alteration zone to phyllic and propylitic alteration zones,Cl decreases with increasing Cu,whereas F increases roughly.Therefore,Cl mostly originate from magma,but enrichment of F possibly results from reaction of fluids and Neoproterozoic strata.Negative correlation between Cl and Cu indicates that Cl might act as an important catalyst during Cu mineralization process.Biotite from Dexing has similar halogen compositions to other porphyry Cu-/Mo deposits in the world.Chlorine contents of hydrothermal fluid may be critical for Cu transportation and enrichment,while consumption of Cl would promote Cu deposition.

Geochronology and Geochemistry of the Mamupu Cu-Au Polymetallic Deposit,Eastern Tibet:Implications for Eocene Cu Metallogenesis in the Yulong Porphyry Copper Belt

The Mamupu skarn-type Cu-Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt(YPCB),eastern Tibet.The Cu-Au mineralization mainly occurs as chalcopyrite in breccia,within the plate-like carbonate interlayer,being closely related to chloritization(e.g.,chlorite,magnetite and epidote)and skarnization(e.g.,diopside,tremolite and garnet).The ore-related quartz syenite porphyry(QSP)and granodiorite porphyry(GP)were emplaced at 40.1±0.2 Ma and 39.9±0.3 Ma,respectively.The QSP of Mamupu is an alkaline-rich intrusion,relatively enriched in LREE,LILE,depleted in HFSE,with no significant negative Eu and Ce anomalies,slightly high(^(87)Sr/^(86)Sr)i,lowε_(Nd)(t),uniform(^(206)Pb/^(204)Pb)i andε_(Hf)(t)values,which indicates that the porphyry magma may be caused by both the mixing of metasomatized EM II enriched mantle and thickened juvenile lower crust.The QSP in the Mamupu deposit shares a similar genesis of petrology to other ore-related porphyries within the YPCB.High oxygen fugacity and water content of the magmas are essential for the formation of porphyry and skarn Cu deposits.The QSP has similar high magmatic oxidation states and water content to the Yulong deposit,which indicates that the Mamupu has a high prospecting potential.Differences in the geological characteristics and scale of mineralization between the Mamupu and other YPCB deposits may be due to the different emplacement depths of ore-related intrusions,as well as differences in the surrounding rocks.

Geology and mineralization of the Daheishan supergiant porphyry molybdenum deposit(1.65 Bt),Jilin,China:A review

The Daheishan supergiant porphyry molybdenum deposit(also referred to as the Daheishan deposit)is the second largest molybdenum deposit in Asia and ranks fifth among the top seven molybdenum deposits globally with total molybdenum reserves of 1.65 billion tons,an average molybdenum ore grade of 0.081%,and molybdenum resources of 1.09 million tons.The main ore body is housed in the granodiorite porphyry plutons and their surrounding inequigranular granodiorite plutons,with high-grade ores largely located in the ore-bearing granodiorite porphyries in the middle-upper part of the porphyry plutons.Specifically,it appears as an ore pipe with a large upper part and a small lower part,measuring about 1700 m in length and width,extending for about 500 m vertically,and covering an area of 2.3 km^(2).Mineralogically,the main ore body consists of molybdenite,chalcopyrite,and sphalerite horizontally from its center outward and exhibits molybdenite,azurite,and pyrite vertically from top to bottom.The primary ore minerals include pyrite and molybdenite,and the secondary ore minerals include sphalerite,chalcopyrite,tetrahedrite,and scheelite,with average grades of molybdenum,copper,sulfur,gallium,and rhenium being 0.081%,0.033%,1.67%,0.001%,and 0.0012%,respectively.The ore-forming fluids of the Daheishan deposit originated as the CO_(2)-H_(2)O-NaCl multiphase magmatic fluid system,rich in CO_(2)and bearing minor amounts of CH4,N2,and H2S,and later mixed with meteoric precipitation.In various mineralization stages,the ore-forming fluids had homogenization temperatures of>420℃‒400℃,360℃‒350℃,340℃‒230℃,220℃‒210℃,and 180℃‒160℃and salinities of>41.05%‒9.8%NaCleqv,38.16%‒4.48%NaCleqv,35.78%‒4.49%NaCleqv,7.43%NaCleqv,and 7.8%‒9.5%NaCleqv,respectively.The mineralization of the Daheishan deposit occurred at 186‒167 Ma.The granites closely related to the mineralization include granodiorites(granodiorite porphyries)and monzogranites(monzogranite porphyries),which were mineralized after magmatic evolution(189‒167 Ma).Moreover,these mineralization-related granites exhibit low initial strontium content and high initial neodymium content,indicating that these granites underwent crust-mantle mixing.The Daheishan deposit formed during the Early-Middle Jurassic,during which basaltic magma underplating induced the lower-crust melting,leading to the formation of magma chambers.After the fractional crystallization of magmas,ore-bearing fluids formed.As the temperature and pressure decreased,the ore-bearing fluids boiled drops while ascending,leading to massive unloading of metal elements.Consequently,brecciated and veinlet-disseminated ore bodies formed.

岩浆演化过程中硫化物饱和对斑岩型Cu-Au矿床形成的控制

斑岩型矿床是全球铜、金、银、钼等战略性矿产的重要来源,其主要分布于汇聚板块边缘。已有研究揭示大型斑岩矿床一般起源于板片俯冲产生的岩浆作用,俯冲板块脱水诱发地幔楔部分熔融形成初始弧岩浆,在经历过一系列复杂的演化后,最终上升至近地表(3~5 km)成矿。而岩浆硫化物能强烈络合亲铜元素,对岩浆演化过程金属的富集起着重要作用,研究硫化物中亲铜元素富集与活化过程是揭示斑岩矿床成矿机理的重要一环。本文对近年来斑岩矿床中岩浆硫化物的研究成果进行系统总结,梳理硫化物饱和的控制因素与分异过程,对比分析岩浆硫化物饱和过程对斑岩矿床金属富集的控制。岩浆硫化物饱和受温度、压力、氧逸度等多种因素共同控制,其中氧逸度变化是导致硫化物饱和的关键;硫化物饱和将促使金属Cu、Au、PGE等高效浓聚,PGE元素和Au对硫化物饱和异常敏感,少量硫化物饱和会导致大量PGE和Au聚集。岩浆硫化物饱和过程对斑岩成矿潜力影响存在争议,一些研究认为硫化物饱和是斑岩成矿的关键步骤,因为饱和的硫化物将促使金属Cu、Au高效浓聚,当新的岩浆注入或岩浆氧逸度或硫逸度变化时,硫化物将被再次溶解使成矿金属重新在硅酸盐熔体中富集;一些研究则认为岩浆演化过程中硫化物饱和不妨碍斑岩成矿,因为早期少量硫化物饱和沉淀并不会降低剩余岩浆中成矿元素丰度,不影响成矿潜力。厚地壳中硫化物饱和一般发生在早期,薄地壳中硫化物在晚期饱和。

镁铁质岩浆周期性补给对云南普朗斑岩Cu-Au矿床的制约:能量约束下热力学模拟

镁铁质岩浆周期性补给于硅酸质岩浆房是形成大型斑岩矿床的关键因素。本文以普朗超大型斑岩Cu-Au矿床为例,通过能量约束体系下的热力学方法模拟浅部硅酸质岩浆房中镁铁质岩浆周期性补给过程,定量评估该过程对形成大型斑岩矿床的控制作用。普朗矿床成矿前粗粒石英闪长玢岩(CQD)和成矿期石英二长斑岩(QMP)复式岩体中均普遍发育镁铁质暗色微粒包体(MMEs),岩相学特征显示斑岩体中角闪石和黑云母发育韵律环带结构或港湾状溶蚀结构以及针柱状磷灰石的存在均指示发生了镁铁质岩浆混合作用。与单一的分离结晶模型(FC)相比,多阶段岩浆补给-分离结晶模型(R3FC)显示,镁铁质岩浆的补给一方面会抑制长石的结晶,另一方面会促进钙铁镁和铁镁等多类型角闪石的形成,并大幅提前黑云母的结晶次序。以硅酸质岩浆物质摩尔分数变化与挥发分之间相关性为参照,获得的熔体H_(2) O、SCSS(硫化物饱和时硅酸盐熔体中的S含量)和Cl溶解度显示,镁铁质岩浆补给将在岩浆演化早期提高而在晚期降低残余熔体H_(2)O含量(0.16%、0.04%、-0.30%),持续提高熔体SCSS(78.74×10^(-6)、94.44×10^(-6)和137.88×10^(-6))和Cl溶解度(0.04%、0.10%和0.20%),但对Cu含量影响有限。结果表明,能量约束体系下的R3FC和FC热力学模型不仅能够合理解释普朗复式斑岩体矿物结构特征,也定量验证了镁铁质岩浆的补给对成矿岩体异常高H_(2) O、S和Cl含量的贡献。

3D electrical structure of porphyry copper deposit:A case study of Shaxi copper deposit

Located in Lu-Zong ore concentration area, middle-lower Yangtze metallogenic belt, ShaXi porphyry copper deposit is a typical hydrothermal deposit. To investigate the distribution of deep ore bodies and spatial characteristics of host structures, an AMT survey was conducted in mining area. Eighteen pseudo-2D resistivity sections were constructed through careful processing and inversion. These sections clearly show resistivity difference between the Silurian sandstones formation and quartz diorite porphyry and this porphyry copper formation was controlled by the highly resistive anticlines. Using 3D block Kxiging interpolation method and 3D visualization techniques, we constructed a detailed 3D resistivity model of quartz diorite porphyry which shows the shape and spatial distribution of deep ore bodies. This case study can serve as a good example for future ore prospecting in and around this mining area.

Chronology and Crust-Mantle Mixing of Ore-forming Porphyry of the Bangongco: Evidence from Zircon U-Pb Age and Hf Isotopes of the Naruo Porphyry Copper-Gold Deposit

The Naruo porphyry copper-gold deposit （hereinafter referred to as the Naruo deposit） in Tibet is a potentially ultra-large, typical gold-rich porphyry copper deposit, which was recently discovered in the Bangongco-Nujiang metallogenic belt. This study analyzed U-Ph chronology and Hf isotopes of the ore-bearing granodiorite porphyry in the Naruo deposit using the LA-ICPMS dating technique. The results show that the weighted average age is 124.03±0.94Ma （MSWD=1.7, n=20）, and 2±6pb/23SU isocbron age is 126.2±2.7 Ma （MSWD=1.02, n=20）, both of which are within the error. The weighted average age represents the crystallization age of the granodiorite porphyry, which indicates that the ore-bearing porphyry in the Naruo deposit area was formed in the Early Cretaceous and further implies that the Neo-tethys Ocean had not been closed before 124 Ma under a typical island-arc subduction environment. The εGr（t） of zircons from the granodiorite porphyry varies from 2.14 to 9.07, with an average of 5.18, and all zircons have εRf（t） values greater than 0; 176Hf/177Hf ratio is relatively high （0.282725-0.282986）. Combined with the zircon age--Hf isotope correlation diagram, the aforementioned data indicate that the source reservoir might be a region that is mixed with depleted mantle and ancient crust, which possibly contains more materials sourced from depleted mantle. Rock-forming ages and ore-forming ages of the Duolong ore concentrate area are 120-124 Ma and 118-119 Ma, respectively, which indicate 124-118 Ma represents the main rockforming and ore-forming stage within the area. The Naruo deposit is located in the north of the Bangongco-Nujiang suture, and it yielded a zircon LA-ICPMS age of 124.03 Ma. This indicates the Bangongco-Nujiang oceanic basin subducted towards the north at about 124 Ma, and the Neo-tethys Ocean had not been closed before the middle Early Cretaceous. It is possible that the crust-mantle mixing formed the series of large and giant porphyry copper-gold deposits in the Bangongco.

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.

Origin of the Newly Discovered Zhunuo Porphyry Cu-Mo-Au Deposit in the Western Part of the Gangdese Porphyry Copper Belt in the Southern Tibetan Plateau,SW China

The newly discovered Zhunuo porphyry Cu-Mo-Au deposit is located in the western part of the Gangdese porphyry copper belt in southern Tibet, SW China. The granitoid plutons in the Zhunuo region are composed of quartz diorite porphyry, diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry. The quartz diorite porphyry yielded zircon U-Pb ages of 51.9±0.7 Ma（Eocene） using LA-ICP-MS, whereas the diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry yielded ages ranging from 16.2±0.2 to 14.0±0.2 Ma（Miocene）. CuMo-Au mineralization is mainly hosted in the Miocene granodiorite porphyry. Samples from all granitoid plutons have geochemical compositions consistent with high-K calc-alkaline series magmatism. The samples display highly fractionated light rare-earth element（REE） distributions and heavy REE distributions with weakly negative Eu anomalies on chondrite-normalized REE patterns. The trace element distributions exhibit positive anomalies for large-ion lithophile elements（Rb, K, U, Th and Pb） and negative anomalies for high-field-strength elements（Nb and Ti） relative to primitive mantlenormalized values. The Eocene quartz diorite porphyry yielded εNd（t） values ranging from-3.6 to-5.2,（-（87）Sr/-（86）Sr）i values in the range 0.7046–0.7063 and initial radiogenic Pb isotopic compositions with ranges of 18.599–18.657 -（206）Pb/-（204）Pb, 15.642–15.673 -（207）Pb/-（204）Pb and 38.956–39.199 -（208）Pb/-（204）Pb. In contrast, the Miocene granitoid plutons yielded ε（Nd）（t） values ranging from-6.1 to-7.3 and（87Sr/86Sr）i values in the range 0.7071–0.7078 with similar Pb isotopic compositions to the Eocene quart diorite. The Sr-Nd-Pb isotopic compositions of the rocks are consistent with formation from magma containing a component of remelted ancient crust. Zircon grains from the Eocene quartz diorite have ε（Hf）（t） values ranging from-5.2 to ＋0.9 and two-stage Hf model ages ranging from 1.07 to 1.46 Ga, while zircon grains from the Miocene granitoid plutons have ε（Hf）（t） values from-9.9 to ＋4.2 and two-stage Hf model ages ranging from 1.05–1.73 Ga, indicating that the ancient crustal component likely derives from Paleo- to Mesoproterozoic basement. This source is distinct from that of most porphyry Cu-Mo-Au deposits in the eastern part of the Gangdese porphyry copper belt, which likely originated from juvenile crust. We therefore consider melting of ancient crustal basement to have contributed significantly to the formation Miocene porphyry Cu-Mo-Au deposits in the western part of the Gangdese porphyry copper belt.

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.

Geology, Geochemistry and Origin of the Hongshan Porphyry-Cryptoexplosive Breccia Type Copper Deposit in Huichang County, Jiangxi Prvince

The Hongshan porphyry-cryptoexplosive breccia type copper deposit occurs in a metamorphic rock series of the Mesoproterozoic Zhongcun Group. Orebodies are distributed inside and outside porphyry-cryptoexplosive breccia pipes. The deposit involves five ore-forming types, i.e the porphyry type, cryptoexplosive breccia type, contact-zone veinlet-disseminated type, in-pipe fracture-zone filling-replacement type and out-of-pipe fracture-zone filling-replacement type, forming an ore-forming system of “five ore-forming types within a single rock body”. Fluid inclusion and isotope geochemical studies indicate the following: S, Pb, O and Sr were derived from the lower crust, Nd was derived from the continental crust or depleted mantle and rare earth elements (REE) and trace elements have the crustal source characters; fluids consist dominantly of formation water, metamorphic water and ***meteoric water with a part of magmatic mater, heat came from porphyry while the latter originated from partial melting caused by shear heating in the lower crust and upper mantle. According to its origin the deposit is classified as the hypabyssal and near-surface, meso- and hypothermal copper deposit associated with the late Yanshanian porphyry-cryptoexplosive breccia.

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.