bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isotopic Geochronology of the Late Paleozoic Kanggur Gold Deposit of East Tianshan Mountains, Xinjiang, NW China
Authors: ZHANG Lian–chang , LIU Tie–bing , SHEN Yuan–chao , LI Guang–ming , JI Jin–sheng 
Published: November 2008

Abstract: The Kanggur gold deposit lies in East Tianshan mountains, eastern section of Central Asia orogenic belt. The gold mineralization occurs on the northern margin of the Aqishan‐Yamansu Paleozoic island arc in the Tarim Plate. It was hosted mainly in Middle‐Lower Carboniferous calc‐alkaline volcanic rocks, and controlled by the distributions of syn‐tectonic intrusions and ductile shear zones. In order to determine ore‐forming age of the Kanggur deposit, samples were collected from ores, wall rocks, altered rocks and intrusions. The dating methods include Rb‐Sr isochron and Sm‐Nd isochron, and secondly 40Ar/39Ar age spectrum, U‐Pb and Pb‐Pb methods. Based on the mineral assemblage and crosscutting relationship of ore veins, five mineralization stages are identified. This result is confirmed by isotope geochronologic data.The first stage featuring formation of pyrite‐bearing phyllic rock, is mineralogically represented by pyrite, sericite and quartz with poor native gold. The Rb‐Sr isochron age of this stage is 2905 Ma. The second stage represents the main ore‐forming stage and is characterized by native gold–quartz–pyrite–magnetite–chlorite assemblage. Magnetite and pyrite of this stage are dated by Sm‐Nd isochron at 290.47.2 Ma and fluid inclusion in quartz is dated by Rb‐Sr isochron at 282.35 Ma. The third mineralization stage features native gold–quartz–pyrite vein. In the fourth stage, Au‐bearing polymetallic sulfide‐quartz veins formed. Fluid inclusions in quartz are dated by Rb‐Sr isochron method at 25821 Ma. The fifth stage is composed of sulfide‐free quartz–carbonate veins with Rb‐Sr age of 2547 Ma. The first and second stages are related to ductile‐brittle deformation of shear zones, and are named dynamo‐metamorphic hydrothermal period. The third to fifth stages related to intrusive processes of tonalite and brittle fracturing of the shear zones, are called magmato‐hydrothermal mineralization period. The Rb‐Sr isochron age of 2905 Ma of the altered andesite in the Kanggur mine area may reflect timing of regional ductile shear zone. The Rb‐Sr isochron age of 28216 Ma of the quartz‐syenite porphyry and the zircon U‐Pb age of 2757 Ma of tonalite in the north of Kanggur gold mine area are consistent with the age of gold mineralization (290‐254 Ma). This correspondence indicates that the tonalite and subvolcanic rocks may have been related to gold mineralization. The Rb–Sr, Sm‐Nd and U‐Pb ages and regional geology support the hypothesis that the Kanggur gold deposit was formed during collisional orogenesis process in Late Variscan.
Gold‐bearing Quartz Veins and Hydrothermal Alteration of the Paleozoic Epithermal System in the Francis Creek Area, North Queensland, Australia
Authors: Harijoko Agung , Watanabe Koichiro , Motomura Yoshinobu , Izawa Eiji 
Published: November 2008

Abstract. The Francis Creek area located at the Sybil graben in North Queensland, Australia, has some features of epithermal gold mineralization such as gold‐bearing quartz vein and silica body hosted in rhyodacitic rocks of the Late Carboniferous Hells Gate Formation. In order to understand the nature of the paleo‐hydrothermal activity in this area and to aid exploration for an economic gold deposit in this area, we carried out hydrothermal alteration mapping surrounding the veins and silica body, over an area of about 7 times 5 km2.We defined two alteration zones and inferred the center of hydrothermal activity. Fluid inclusion shows the boiling feature, and the microthermometry analysis resulted in the trapping temperature of 240°C and low salinity. This temperature is consistent with the formation temperature of clay mineral in the host rocks. On the basis of whole‐rock composition, the silica body was identified as silicified rocks. Precious metal minerals such as electrum and acanthite coexist with sulfide minerals. Iodagylite was identified as a product of weathering. The sulfide minerals imply that the low‐sulfidation epithermal gold mineralization occurred in the Francis Creek area.
Tectonic Controls on the Formation of the Liwu Cu‐rich Sulfide Deposit in the Jianglang Dome, S W China
Authors: Yan Dan‐Ping , Zhou Mei‐Fu , Song Hong‐Lin , Fu Zhao‐Ren , Sun Min 
Published: November 2008

Abstract. The Liwu Cu‐rich sulfide deposit occurs within the Jianglang dome in the eastern margin of the Tibetan plateau. The dome consists of a core, a middle slab and a cover sequence. The main deposit is hosted in the core with minor ore bodies in the middle slab. The protolith of the core consists of clastic sedimentary rocks with inter‐layered volcanic rocks.All of the ore bodies are substantially controlled by an extensional detachment fault system. The ore bodies within the core are distributed along the S2 foliation in the hinge of recumbent fold (D2), whereas ore bodies with en echelon arrangement are controlled by the mylonitic foliation of the lower detachment fault. Ore bodies within the middle slab are oriented with their axes parallel to the mylonitic foliation. Pyrite and pyrrhotite from the ores contain Co ranging from 37 to 1985 ppm, Ni from 2.5 to 28.1 ppm, and Co/Ni ratios from 5 to 71. These sulfides have δ34S values ranging from 1.5 to 7.5 % whereas quartz separates have δ18O values of 11.9 and 14.3 % and inclusion fluid in quartz has δD value of‐88.1 %. These features suggest that the deposit was of hydrothermal origin.Two ore‐forming stages are recognized in the evolution of the Jianglang dome. (1) A low‐temperature ore‐forming process, during the tectonic transport of the upper plate above the lower detachment, and the initial phase of the footwall updom‐ing at 192–177 Ma. (2) A medium‐temperature ore‐forming stage, related to the final structural development of the initial detachment at 131–81Ma. Within the core, the ore bodies of the first stage were uplifted to, or near, the brittle/ductile horizon where the ore‐forming metals were re‐concentrated and enriched. A denudation stage in which a compressional tectonic event produced eastward thrusting overprinted the previous structures, and finally denuded the deposit. The Liwu Cu‐rich sulfide deposit was formed during a regional extensional tectonic event and is defined as a tectono‐strata‐bound hydrothermal ore deposit.
The Fanshan Apatite‐Magnetite Deposit in the Potassic Ultramafic Layered Intrusion, North China
Authors: Cheng Chun , Sun Shihua 
Published: November 2008

Abstract. This article reviews work carried out on the Fanshan layered apatite (‐magnetite) deposit, which occurs in the Fanshan complex, a potassic ultramafic‐syenite layered intrusion located in North China. The Fanshan complex intruded into Proterozoic sedimentary rocks in the early Triassic. The complex comprises First‐ to Third‐Phase Intrusives. The First‐Phase Intrusive includes rhythmic Units 1 to 9, which mainly consist of clinopyroxenite and biotite clinopyroxenite. The apatite (‐magnetite) deposit is situated near the top of rhythmic Unit no. 6 of the First‐Phase Intrusive.The economical deposit comprises Orebody II and Orebody III. Orebody II, situated at the top of Unit no. 6, consists of two kinds of layer: one magnetite‐apatite rock layer at the top and a few apatite rock layers at the bottom. Orebody III is situated several meters below Orebody II, and consists of an apatite rock layer.There is controversy over the ore formation mechanism, the temperature and pressure of the magma intrusion, and the origin of the magma (including the possibility of magma immiscibility). We review these problems of this unique apatite (‐magnetite) magmatic deposit.
Talnakhite Associated with Andradite Skarn at Fuka, Okayama Prefecture, Japan
Authors: Takechi Yasushi , Kusachi Isao , Nakamuta Yoshihiro , Kase Katsuo 
Published: November 2008

Abstract. Talnakhite occurs in an andradite skarn forming adjacent to a leucocratic quartz monzonite dike intruded into limestone at Fuka. The mineral densely contains exsolution lamellae of chalcopyrite, and the talnakhite‐chalcopyrite inter‐growth is intimately associated with bornite that contains chalcopyrite as a lattice‐form exsolution. The chemical composition of the talnakhite acquired on an electron probe microanalyzer corresponds to Cu9.00Fe8.08S15.92, very close to the ideal chemical formula Cu9Fe8S16. Nickel is not detected. The X‐ray powder diffraction lines are well indexed on a body‐centered cubic cell with a = 10.589 Å. The characteristic (110) reflection of talnakhite is clearly observed at 7.49 Å. The present talnakhite retains the chalcopyrite‐like colored polished surface without tarnish in air more than a month.Talnakhite at Fuka is likely to be derived from breakdown of Cu‐rich intermediate solid solution (iss), which was in equilibrium with Fe‐rich bornite at elevated temperatures. Talnakhite thus formed has survived the subsequent cooling processes, probably because the ƒs2 was maintained in suitable levels preventing its decomposition into bornite and chalcopyrite.
A Study of Illite Kiibler Indexes and Chlorite “Crystallinities” with Respect to Shear Deformation and Alterations, Jinshan Gold Deposit, East China
Authors: Li Xiao‐feng , Hua Ren‐min , Mao Jing‐wen , Ji Jun‐feng , Wang Chun‐zeng 
Published: November 2008

Abstract. This paper presents a measurement and study of Kübler Indexes (KI) of illite, “crystallinities” of chlorite (ChC), and apparent mean crystallite sizes and lattice strain of both illite and chlorite of the Jinshan ductile shear zone in the Jinshan gold deposit of East China. It is found that the KI values and apparent mean crystallite sizes of illite decrease and the lattice strain of chlorite apparently increase, whereas the apparent mean crystallite sizes of chlorite and the lattice strain of illite remain constant, from altered mylonite to altered and higher‐strained ultramylonite in the shear zone. Only slight decrease of ChC is observed.An obvious negative correlation exists between KI and apparent mean crystallite sizes in altered mylonite with lower strain, whereas a positive correlation is found between ChC and apparent mean crystallite sizes in altered ultramylonite with higher strain. No any correlations between KI and lattice strain exist, whereas a negative correlation and a positive correlation between ChC and lattice strain occur separately in the altered mylonite and ultramylonite. It is suggested that illite Kiibler Indexes and chlorite “crystallinities” most likely reflect deformation behaviors and mechanisms of altered rocks although other factors involving water/rock ratio may apply as well.
Geochemistry and Petrogenesis of the Tongshankou and Yinzu Adakitic Intrusive Rocks and the Associated Porphyry Copper‐Molybdenum Mineralization in Southeast Hubei, East China
Authors: Wang Qiang , Zhao Zhen‐Hua , Bao Zhi‐Wei , Xu Ji‐Feng , Liu Wei , Li Chao‐Feng , Bai Zheng‐Hua , Xiong Xiao‐Lin 
Published: November 2008

Abstract. The late Jurassic Tongshankou and Yinzu plutons in southeast Hubei have been investigated for their contrasting metal mineralization features. The former is closely associated with porphyry Cu‐Mo mineralization, while the latter is barren of metal mineralization, althouth both are located very close to each other. The Tongshankou granodiorite porphyries and the Yinzu granodiorites are geochemically similar to adakites, e.g., high Al2O3 and Sr contents and La/Yb and Sr/Y ratios, enriched in Na2O, depleted in Y and Yb, very weak Eu anomalies and positive Sr anomalies. However, different geochemi‐cal characteristics exist between the two plutons: the Tongshankou adakitic rocks (1) are relatively enriched in SiO2, K2O, MgO, Cr, Ni, and Sr and depleted in Y and Yb; (2) have higher degree REE differentiation; (3) have positive Eu anomalies in contrast with very weak negative or unclear Eu anomalies in the Yinzu rocks; and (4) isotopically have relatively higher ePNd(t) values (‐5.19 to ‐5.38) and lower initial 87Sr/86Sr ratios (0.7060 to 0.7062), while the Yinzu adakitic rocks have relatively lower ePNd(t) values (‐7.22 to ‐8.67) and higher initial 87Sr/86Sr ratios (0.7065 to 0.7074).The trace element and isotopic data demonstrate that the Tongshankou adakitic rocks were most probably originated from partial melting of delaminated lower crust with garnet being the main residual mineral whereas little or no plagioclase in the source. On the contrary, the Yinzu adakitic rocks were likely derived from partial melting of thickened lower crust, with residual garnet and a small quantity of plagioclase and hornblende in the source. Interactions between the adakitic magmas and mantle peridotites possibly took place during the ascent of the Tongshankou adakitic magmas through the mantle, considering that MgO, Cr, and Ni contents and ePNd(t) values of the adakitic magmas were possibly elevated and initial 87Sr/86Sr ratios were possibly lowered due to the contamination of mantle peridotites. In addition, the Fe2O3 of the adakitic magmas was likely released into the mantle and the oxygen fugacities (ƒo2) of the latter were obviously possibly raised, which made metallic sulfide in the mantle oxidized and the chalcophile elements such as Cu were incorporated into the adakitic magmas. The ascent of the adakitic magmas enriched in Cu and Mo will lead to the formation of porphyry Cu‐Mo deposit. Nevertheless, the Yinzu adakitic magmas were possibly lack of metallogenetic materials due to not interacting with mantle peridotite, and thus unfavorable to metal mineralization.
Rhythmic Layering in the Apatite (‐Magnetite) Deposit in the Fanshan Complex, North China
Authors: Cheng Chun , Sun Shihua , Mao Qian 
Published: November 2008

Abstract. The Fanshan complex consists of three (First‐ to Third‐) Phases of intrusion. The First‐Phase Intrusive is composed of rhythmic layers. The Fanshan apatite (‐magnetite) deposit is situated near the top of no. 6 rhythmic Unit of the First‐Phase Intrusive. Two sketch maps were drawn through the deposit along no. 25 cross‐cut on 425 mL and no. 1 crosscut on 491 mL in the Fanshan mine. Through this mapping, a small‐scaled rhythmic layering (called sub‐rhythmic layering) was newly found. The sub‐rhythmic layering consists of five typical rocks: biotite clinopyroxenite, biotite rock, biotite‐apatite rock, alternation biotite‐apatite rock and apatite rock. The thickness of layers varies from four millimeters to several meters. Six units of sub‐rhythmic layering were distinguished. Each unit consists of biotite clinopyroxenite (or biotite rock and biotite‐apatite rock) layer at the bottom and apatite rock layer at the top.Major element compositions of biotite and clinopyroxene were analyzed. The trends of Mg/(Mg+Fe*+Mn) atomic ratio (Fe*: total iron) of biotite and clinopyroxene indicate that the magma evolved markedly from relatively magnesian bottom layer to less magnesian top layer in each sub‐rhythmic unit. A general trend, however, through the whole sub‐rhythmic layering sequence shows that the both minerals become relatively magnesian upwards. The hypotheses of liquid immiscibili‐ty, gravitational settling and magma mixing are against with the results obtained in the present study. This study suggests that the apatite (‐magnetite) deposit is formed through fractional crystallization process.
Variation of Cl and SO3 Contents of Microphenocrystic Apatite in Intermediate to Silicic Igneous Rocks of Cenozoic Japanese Island Arcs: Implications for Porphyry Cu Metallogenesis in the Western Pacific Island Arcs
Authors: Imai Akira 
Published: November 2008

Abstract. Determinations of SO3 and Cl contents of igneous accessory apatite were carried out on Late Cenozoic intermediate to silicic intrusive and volcanic rocks in the Japanese island arcs of the western Pacific rim including the southwestern Kuril arc (eastern Hokkaido), Northeast Japan arc (southwestern Hokkaido through northeastern Honshu to central Honshu), Izu‐Bonin arc, Kyushu‐Palau ridge, Southwest Japan arc (northern Kyushu) and northern Ryukyu arc (southern Kyushu). These were compared to those from the Western Luzon arc, Philippines, to better understand the metallogenesis of porphyry Cu deposits in the western Pacific island arcs. In addition, SO3 and Cl contents of accessory apatite in the Cretaceous magnetite‐series granitic rocks in the Kitakami belt (northeastern Honshu) and the Miocene ilmenite‐series granitic rocks in the Outer Zone of Southwest Japan (southern Kyushu) were also examined.Microphenocrystic apatites in shallow intrusions associated with porphyry Cu deposits in the Western Luzon arc contain >0.1 wt% S as SO3. Such high SO3 contents of microphenocrystic apatite are a common characteristic of hydrous mag‐matism in the Western Luzon arc, from 15 Ma old tonalitic plutonic rocks of the Luzon Central Cordillera to present‐day volcanism at Mount Pinatubo. The accessory apatite in intrusive rocks associated with porphyry Cu deposits, especially those at the Santo Tomas II deposit, show significantly high Cl contents (>2 wt%).The SO3 contents of microphenocrystic apatite in most of the hydrous silicic rocks along the volcanic front, in andesites related to native sulfur deposits, and in Miocene and younger shallow granitic intrusions in northeastern Honshu, are generally <0.1 wt%. On the other hand, the SO3 contents of apatite in such rocks from eastern Hokkaido, southwestern Hokkaido, Izu, northern Kyushu and southern Kyushu are similar to those from the Western Luzon arc. The SO3 contents of accessory apatite in the Cretaceous magnetite‐series granitic rocks in the Kitakami belt are variable, whereas those of the Miocene ilmenite‐series granitic rocks in southern Kyushu are extremely low. The Cl contents of accessory apatite in some rocks of the Northeast Japan arc, Izu‐Bonin arc and Southwest Japan arc are significantly high.In terms of the Cl and SO3 contents of microphenocrystic apatite, Cenozoic Japanese arc magmatism show similarities with arc magmatism associated elsewhere with porphyry Cu mineralization, except for the most of northeastern Honshu of the Northeast Japan arc. Apatite commonly occurs as inclusions in other phenocrystic phases. Thus the variation in SO3 contents of apatite is a feature of early stage magmatic differentiation. The SO3 contents of microphenocrystic apatite are considered to reflect the redox state of the magma source region or fluids encountered during magma generation.
Volcanic Sequences Related to Kuroko Mineralization in the Hokuroku District, Northeast Japan
Authors: Yamada Ryoichi , Yoshida Takeyoshi 
Published: November 2008

Abstract. Kuroko deposits are a representative volcanic‐hosted massive sulfide deposit and the Hokuroku district is economically the most important Kuroko containing province in Japan. There are two cycles of the bimodal volcanic sequence in the Hokuroku district. The pre‐ore volcanism started with basaltic activity and was followed by intensive felsic hyaloclas‐tic activity under bathyal conditions. The post‐ore sequence also began with basaltic activity intercalated with mudstone and was followed by alternating beds of pumice tuff with several lava flows and mudstone. Kuroko deposits are situated in the final period of the pre‐ore felsic volcanic sequence of the first bimodal volcanic cycle.Based on a detailed investigation of existing age data, it was concluded that the felsic volcanic sequences in the pre‐and post‐Kuroko formation can be divided into a pre‐ore dacite group (16–13.5 Ma), a D2 dacite group (lower unit of the post‐ore volcanic sequence, 12.7±0.6∼ ll Ma) and a Dl dacite group (upper unit of the post‐ore sequence including quartz‐porphyry and granitoid, 11sim;10 Ma) in ascending order. Field and microscopic observations show that the pre‐ore dacite is characterized by aphyric to plagioclase‐phyric lava and the post‐ore dacitic rocks are characterized by quartz‐plagioclase‐phyric aphanitic lava and dome. These three dacite groups are petrochemically discriminated by SiO2‐Al2O3 and CaO‐TiO2 diagrams, excluding altered specimens. The distribution of the normative compositions on the Q‐An‐Ab‐Or diagram suggests that the pre‐ore dacites trend on the 5 kb cotectic line (equilibrated to 10—15 km deep) and those of the post‐ore trend along the 1 kb line (a few km deep). The secular variation of the major elements indicates that the rhyolitic members genetically related to the Kuroko formation could be the most differentiated products in the pre‐ore felsic volcanism.The distribution of Nb against SiO2 content in the pre‐ and post‐ore bimodal volcanic cycles indicates that these two volcanisms could have been generated by different magmatic origins. The difference would have been caused by the tectonic conversion from a back‐arc to an island‐arc setting.
Statistical Features of Vein Systems in the Hishikari Epithermal Gold Deposit, Japan
Authors: Sasaki Munetake 
Published: November 2008

Abstract. The Hishikari epithermal gold deposit consists of parallel vertical veins hosted by the Quaternary volcanic rocks (QVR) and Cretaceous sedimentary rocks (CSR) at the shallow and deep levels, respectively. In order to reveal the litholog‐ical influence on the evolution of vein systems in the Hishikari field, vein density, width, spacing and position were statistically examined using cores sampled from three boreholes.The statistical features of the veins identified were summarized as follows, (i) The QVR have lower mean vein densities than the CSR. (ii) The former has smaller deformation degrees (ratios of total vein width per length) than the latter, (iii) Cumulative frequencies of vein density obey negative‐exponential distributions in both the types of rocks, (iv) Cumulative frequencies of vein width obey power‐law distributions with exponents of about ‐1 in both the types of rocks, but consist of two segments in the CSR. (v) Cumulative frequencies of vein spacing obey lognormal distributions with coefficients of variation between 1.8 and 3.5 in both the types of rocks. And (vi) fractal dimensions of vein position are between 0.45 and 0.52 at measure lengths between 0.1 and 10 m without distinctive difference between the two types of rocks.The feature (i) indicates higher ductility of the QVR against fracturing than the CSR. The feature (ii) implies that large deformation was accumulated in rocks themselves (e.g., alteration zones) in addition to the veins examined in the QVR compared to only the veins in the CSR. The feature (iv) suggests that the vein systems in the CSR reached a stage at which the several selected large veins grew as main conduit, that potentially provided pathways for ore‐forming fluids to ascend from deep levels. The coefficients of variation of vein spacing and fractal dimensions of vein position (features v and vi) indicate clustered distribution of the veins in the field.This study might be helpful for a better understanding of lithological influence on the evolution of vein systems not only in the Hishikari field but also in other fields.