A Remote-Sensing-Based Alteration Zonation Model of the Duolong Porphyry Copper Ore District, Tibet

Remote sensing (RS) of alteration zones and anomalies can provide information that is useful for geological prospecting and exploration. RS is an effective method for porphyry copper mineral exploration and prospecting prediction. More specifically, the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) data, which include 14 spectral channels from visible light to thermal infrared, are useful in such cases. This study uses visible-shortwave infrared and thermal infrared ASTER data together with surface material spectra from the Duolong porphyry copper ore district to construct an RS-based alteration zonation model of the deposit. In this study, an RS alteration zoning model is established based on ground-spectral alteration zoning results. The methods include PCA (Principal Component Analysis), Ratio, and Slope methods. The information obtained by each method is different. RS-based alteration zonation is developed based on the intersection of maps, resultant from the different methods for extracting information related to different minerals. The alteration zonation information extracted from ASTER RS data is consistent with geological observations. Using information from the RS-based model, we mapped the alteration minerals and zones of the Duolong ore district, thereby identifying prospecting target areas of the deposit

A Remote-Sensing-Based Alteration Zonation Model of the Duolong Porphyry Copper Ore District, Tibet

Remote sensing (RS) of alteration zones and anomalies can provide information that is useful for geological prospecting and exploration. RS is an effective method for porphyry copper mineral exploration and prospecting prediction. More specifically, the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) data, which include 14 spectral channels from visible light to thermal infrared, are useful in such cases. This study uses visible-shortwave infrared and thermal infrared ASTER data together with surface material spectra from the Duolong porphyry copper ore district to construct an RS-based alteration zonation model of the deposit. In this study, an RS alteration zoning model is established based on ground-spectral alteration zoning results. The methods include PCA (Principal Component Analysis), Ratio, and Slope methods. The information obtained by each method is different. RS-based alteration zonation is developed based on the intersection of maps, resultant from the different methods for extracting information related to different minerals. The alteration zonation information extracted from ASTER RS data is consistent with geological observations. Using information from the RS-based model, we mapped the alteration minerals and zones of the Duolong ore district, thereby identifying prospecting target areas of the deposit

Devonian porphyry Cu deposits in NW China: the Xiaotuergen example

<p>The Nuoerte Basin in northern Altay contains numerous mineral discoveries, including the Xiaotuergen porphyry Cu, Kumasu VMS Pb–Zn, and Hongshanzui orogenic Au deposits. This deposit, newly discovered by the 4th Geological Team of XJBGMR – the Xiaotuergen porphyry Cu deposit – is mainly hosted along the contact zone between the granodiorite porphyry and the Nuoerte Formation volcanic-sedimentary rocks. Disseminated, veinlet, veinlet-disseminated, and stockwork Cu mineralization occur in the granodiorite porphyry. Wall-rock alteration styles include mainly potassic (K-feldspar and biotite), silicic, carbonate, sericite, pyrite, chlorite, and epidote alterations. In this study, we used LA-ICP-MS zircon dating for the various rock types in the Xiaotuergen Cu ore district. The tuff at the periphery of the ore district has been newly dated to be ca. 411 Ma. This, together with stratigraphic correlation, suggests that the local stratigraphy is the Lower Devonian Nuoerte Formation, rather than the Lower Carboniferous Hongshanzui Formation as previously assumed. The ore-hosting granodiorite porphyry, quartz porphyry, biotite monzogranite, and granite porphyry are dated to be ca. 405 Ma, 400 Ma, 398 Ma, and 397 Ma, respectively. This constrains the Cu mineralization to be slightly younger than 405 Ma, and indicates that they may have belonged to the same Early Devonian intrusive event. Magmatism at Xiaotuergen had recommenced in the Late Devonian, as represented by minor granite porphyry dikes (ca. 370 Ma) intruding the ore-hosting granodiorite porphyry.</p

Geochemistry and Sr–Nd–Hf isotopes of Middle Devonian igneous rocks of the Sarsuk polymetallic Au deposit: implications for understanding the tectonic evolution of the south Altay Orogenic Belt, Northwest China

<p>The medium-tonnage Sarsuk polymetallic Au deposit is located in the Devonian volcanic–sedimentary Ashele Basin of the south Altay Orogenic Belt (AOB), Northwest China. Within the deposit, the rhyolite porphyries and diabases are widespread, emplaced into strata. The orebodies are hosted by the rhyolite porphyries. We studied the petrography, geochemistry, and Sr–Nd–Hf isotopes of the rhyolite porphyries and diabases, in order to understand the petrogenesis of these rocks and their tectonic significance. They display typical bimodality in geochemistry compositions. The diabases are characterized by SiO₂ contents of 44.84–59.77 wt.%, high Mg# values (43–69), enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), depletion in Nb and Ta, low (⁸⁷Sr/⁸⁶Sr)<i>_i</i> (0.706687–0.707613) values, positive <i>ε</i>_Nd(<i>t</i>) (4.8–6.8) values, and positive and high <i>ε</i>_Hf(<i>t</i>) (7.15–15.19) values, suggesting a depleted lithosphere mantle source that might have been metasomatized by subduction-related components. The rhyolite porphyries show affinity to sanukitoid magmas contents [high SiO₂ (78.6–81.82 wt.%) and MgO (3.38–5.94 wt.%, one sample at 0.61 wt.%), and enrichments in LILE and LREE], they were derived from the equilibrium reactions between a mantle source and subducted oceanic crust materials. Those characteristics together with the positive <i>ε</i>_Nd(<i>t</i>) (4.1–8.4) and <i>ε</i>_Hf(<i>t</i>) (2.88–15.17) values indicate that the diabases and rhyolite porphyries were generated from the same mantle peridotite source. But the rhyolite porphyries underwent fractional crystallization of Fe–Ti oxides, plagioclase, and apatite due to their negative Eu (<i>δ</i>Eu = 0.21–0.28) and P anomalies. According to the geochemical and isotopic data, the Sarsuk Middle Devonian igneous rocks are considered to be the products of the juvenile crustal growth in an island arc setting. The Sarsuk polymetallic Au deposit formed slightly later than the Ashele Cu–Zn deposit in the Ashele Basin, but they have the same tectonic setting, belonging to the trench–arc–basin system during extensional process in the south AOB.</p

新疆阿尔泰阿舍勒VHMS型铜锌矿床成矿流体的氦—氩同位素示踪/Helium and Argon Isotopes Tracing for Sources of Ore-forming Fluid in the Ashele Volcanogenic-host Massive Sulfide Copper—Zinc Deposit, Chinese Altay[J]

阿舍勒大型铜锌矿是我国典型的海相火山岩块状硫化物(VHMS)型矿床,赋存于阿舍勒盆地早—中泥盆世阿舍勒组海相火山—沉积岩系中.1号主矿体呈似层状或大透镜体状,矿石呈块状、浸染状、条带状、层纹状、细脉状.本文对块状、浸染状、条带状矿石的黄铁矿中流体包裹体He和Ar同位素进行了研究.黄铁矿中流体包裹体的4He含量为(64.5～173.0)×10-7cm3STP/g,n(3He)/n(4He)值为(0.1358 ～0.379) Ra,幔源He的含量为1.79％～ 5.55％,表明成矿流体中He主要来源于地壳.40Ar含量为(0.318 ～ 4.69)×10-7cm3STP/g,n(40Ar)/n(36Ar)值变化于389.1～9425,40Ar*含量为24.06％ ～96.89％,表明成矿流体中存在含有放射性成因Ar的海水加入.结合矿床的氢、氧、硫同位素特征,认为成矿流体来源为海水和幔源岩浆热液

新疆阿尔泰南缘克因布拉克铜锌矿床成矿流体的氦-氩同位素示踪/Helium and Argon Isotopes Tracing for Sources of Ore-forming Fluid in the Keyinbulake Copper-zinc Deposit,Southern of Altay,Xinjiang[J]

克因布拉克铜锌矿床赋存于二长花岗岩外接触带的上志留-下泥盆统康布铁堡组黑云石英片岩、变质石英砂岩中，矿体呈似层状、透镜状及脉状。本文对铜锌矿石中的黄铁矿流体包裹体氦和氩同位素组成进行了研究。黄铁矿中流体包裹体的4He含量为0.241×10-7~5.288×10-7 cm3STP/g，Rc/Ra值为0.95~1.89，幔源He的含量为14.1%~28.8%，表明成矿流体中氦主要来源于地壳，存在幔源氦的加入。40Ar 含量为4.345×10-8~7.752×10-8 cm3STP/g，40Ar/36Ar比值变化于302.10~436.96，40Ar*含量为2.2%~32.4%，表明成矿流体中存在含有放射性成因氩的大气降水加入。结合矿床地质特征及氢、氧、碳、硫同位素特征，认为成矿流体来源于高温深源壳幔混合成因的岩浆流体，具大气氩同位素组成特征的低温大气降水

新疆准噶尔北缘玉勒肯哈腊苏铜(钼)矿床流体包裹体和稳定同位素研究/Fluid inclusion and stable isotope study of Yulekenhalasu copper-(molybdenum) deposit in northern margin of Junggar, Xinjiang[J]

玉勒肯哈腊苏中型斑岩型铜(钼)矿主要赋存在闪长玢岩中,有少量矿化产在北塔山组火山岩及似斑状黑云母石英二长岩中.矿化呈细脉状、细脉-浸染状和浸染状.围岩蚀变主要为钾化、硅化、绢云母化、石膏化、磁铁矿化、绿泥石化、绿帘石化.矿床的形成经历了斑岩期、剪切变形期和表生期,铜和钼矿化主要形成于斑岩期的硫化物-钾硅酸盐阶段和辉钼矿阶段.石英和方解石中的流体包裹体可划分为H2 O-NaCl型和H2O-CO2(±CH4 /N2)-NaCl型.硫化物-钾硅酸盐阶段的成矿温度为141～500℃,主要集中在200～340℃;流体的ω(NaCleq)为2.96％～14.97％;流体的密度为0.60～ 0.98 g/cm3.碳酸盐阶段的流体以中-低温度(140～320℃)和低盐度[ω(NaCleq)为2.74％～10.61％]为特征.硫化物的δ34S值集中于-4.5‰～0.1‰,峰值为-3.5‰,表明硫来自深源岩浆.石英和方解石的δ18OSMOW值为9.1‰～13.2‰oo,δ18OH2O值为2.05‰～6.28‰,δD值为-120‰～ 97‰,表明主成矿阶段的成矿流体主要是岩浆水,混合有大气降水;碳酸盐阶段的流体主要为大气降水,混合有岩浆水.成矿时代为中泥盆世[(373.9±2.2 Ma)],成矿作用与闪长玢岩的侵入有关.温度和压力的降低导致流体沸腾,同时,水-岩交换反应、流体成分的改变等在铜钼成矿过程中起着主导作用

新疆阿尔泰南缘乌吐布拉克铁矿成矿机制研究/Study on the ore-forming mechanism of the Wutubulake iron deposit in the southern of Altay,Xinjiang[J]

乌吐布拉克中型铁矿床赋存于上志留统-下泥盆统康布铁堡组变质火山-沉积岩系中,矿体呈似层状、透镜状,矿体及其周围发育大量矽卡岩矿物组合.早期矽卡岩阶段包裹体均一温度为256～534℃,盐度为11.90％ - ＞73.96％ NaCleqv,密度为0.56 ～0.96g/cm3,表明成矿流体为高-中温、高-中盐度、高-中密度的NaCl-H2O体系;退化蚀变阶段包裹体均一温度为188～313℃,盐度为12.30％～＞39.76％ NaCleqv,密度为0.83 ～ 1.05g/cm3,表明成矿流体为中温、中-低盐度、高-中密度的NaCl-H2O体系.石英-硫化物-碳酸盐阶段包裹体均一温度为162 ～ 320℃,盐度为2.90％～15.57％ NaCleqv,密度为0.70～1.02g/cm3,成矿流体为NaCl-H2O-CO2±CH-4或N2型流体.石榴子石氢氧同位素表明早期矽卡岩阶段成矿流体主要来源于岩浆水,石英及方解石的氢氧同位素暗示石英-硫化物-碳酸盐阶段存在低温、低盐度的大气降水的加入.方解石的碳、氧同位素表明流体中碳主要来自深部岩浆.硫化物硫同位素表明硫来源于岩浆硫.成矿机制可能为早三叠世岩浆热液交代上志留-下泥盆统康布铁堡组火山岩形成矽卡岩矿物,在矽卡岩退化蚀变过程中形成铁矿体