bluuebunny/crossref_metadata_2025 huggingface dataset:
Late Miocene Magmatic‐Hydrothermal Systems in the Jozankei‐Zenibako District, Southwest Hokkaido, Japan
Authors: WATANABE Yasushi , OHTA Eijun
Published: November 2008

Abstract: Hydrothermal systems related to magmatic intrusions in the Jozankei‐Zenibako district, southwest Hokkaido are examined, based on field observations, K‐Ar ages, and alteration mineral assemblages. The study reveals five major magmat–ic–hydrothermal systems of Late Miocene in age, comprising Ogawa (9. 7 Ma), Jozankei (9. 5–9. 0 Ma), Otarunaigawa (8. 7 Ma), Asarigawa (8. 8 and 6. 7 Ma) and Hariusu (6. 7 Ma). The Ogawa system is related to granodiorite, and the Jozankei, Otarunaigawa and Asarigawa systems are related to quartz porphyry.

The Ogawa system includes potassic, sericitic, propylitic and advanced argillic alteration as well as base‐metal mineralization, represented by the Toyotomi deposit. The Jozankei and Otarunaigawa systems lack significant potassic alteration, and are accompanied by sericitic and propylitic alteration. The Otarunaigawa system is associated with base‐metal mineralization at Toyohiro and Inatoyo. The Asarigawa and Hariusu systems include advanced argillic and argillic alteration, as well as iron sulfide deposits. The presence of potassic alteration only in the Ogawa system is ascribed to deeper emplacement (˜3 km from the surface) of the intrusive magma. These systems formed in terrestrial environments that existed from ca. 11 Ma to 8. 5 Ma and after 7. 5 Ma in the district.

Age–data compilation shows that the major advanced argillic alteration events in southwest Hokkaido, including those in the Jozankei‐Zenibako district, formed during the periods from 9. 7–6. 5 Ma and 3. 5–1. 5 Ma. These periods correspond to the timing of normal subduction of the Pacific plate beneath the Northeast Japan arc. Normal, in contrast to oblique, plate subduction is characterized by andesitic, polygenetic volcanism and associated advanced argillic alteration.
Spinifex Texture of Native Sulfur: A Cooling Product of Sulfur Flow Eruptions at Shiretoko‐Iwozan Volcano, Hokkaido, Japan
Authors: IMAI Akira , GESHI Nobuo
Published: November 2008

Abstract: Several native sulfur specimens, collected from Shiretoko‐Iwozan volcano, eastern Hokkaido, Japan, exhibit spinifex texture, which appears to resemble that often observed in komatiite. The spinifex texture is exhibited by yellow‐colored elongated skeletal native sulfur crystals up to 5 cm long settled in medium gray‐colored fine–grained clayey matrix. One surface of a specimen is coated by layers of micro pillow lava of native sulfur. Such specimens were rarely found as clasts or fragments around the 1936 No. 1 crater that erupted native sulfur flows, together with the most common monomineralic native sulfur fragments of native sulfur flows having pahoehoe surface and of native sulfur dikes. The elongated spinifex native sulfur crystals presently consist of aggregated polygrains of orthorhombic sulfur crystals formed through crystallo‐graphic transition from the single crystal of monoclinic sulfur initially crystallized. The spinifex texture exhibited by elongated skeletal native sulfur crystals is a product of rapid cooling of sulfur melt.

Many lithic fragments of altered country rocks are present in the specimens exhibiting native sulfur spinifex texture. This suggests that segregation of the sulfur melt from the mixture of lithic fragments and sulfur melt was incomplete because the mixture was chilled before the melt segregation. Elongated skeletal native sulfur crystals may have nucleated and crystallized directly from the molten sulfur liquid. Lithic fragments mixed in the melt are supposed to have acted as nuclei for the nucleation of the native sulfur crystals. On the other hand, the most of native sulfur flows consist of monomineralic massive native sulfur with very scarce lithic fragments. Such massive monomineralic native sulfur crystallized from the supercooled, solidified amorphous sulfur. Such supercooled amorphous state may have been attained due to the lack of nuclei because of the scarcity of lithic fragments. The unique structures exhibited by native sulfur lava flow, including pahoehoe surface and spinifex texture, are due to the characteristic physical property of molten sulfur liquid, that is, low viscosity.
Hydrogeochemical Characteristics of Acid Mine Drainage around the Abandoned Youngdong Coal Mine in Korea
Authors: CHON Hyo–Taek , KIM Ju–Yong , CHOI Si–Young
Published: November 2008

Abstract: To determine the geochemical characteristics of the Imgok creek impacted by acid mine drainage (AMD) generated from the abandoned Youngdong coal mine in Korea, chemical analyses of water samples and precipitates and the geochemical modelling of the precipitates were conducted. Acid mine drainage drained from the mine adit and coal refuse piles shows a low pH, high conductivity and high concentrations of Fe, Al, SO4 and heavy metals such as Co, Cu, Ni and Zn. In the Imgok creek, the concentrations of heavy metals and major cations besides Fe are decreased by dilution, but concentrations of Fe are decreased by the formation of precipitates as well as dilution. From the results of geochemical modelling, goethite is oversaturated, and schwertmannite is the most stable solid phase in the Imgok creek. Yellowish red Fe‐precipitates collected at the Imgok creek are recognized as amorphous or poorly crystallized minerals from XRD patterns and Feox/Fetotratios, and as containing chemically bonded SO4 and OH by an IR analysis. The mole ratios of Fe/S in these precipitates, which are determined by EPMA, are 5. 1 and 6. 1.
Geology and K‐Ar Ages of the South, Huh Bulgiin Hundii, Saran Uul, Taats Gol and Han Uul deposits in the Bayankhongor Region, Mongolia
Authors: WATANABE Yasushi , TURMAGNAI Daramjav , BYAMBASUREN Dolgor , OYUNCHIMEG Gurjav , TSEDENBALJIR Yadamtsoo , SATO Yoichi
Published: November 2008

Abstract: The Bayankhongor region in central Mongolia consists of a Paleozoic subduction system including Precambrian microcontinents (Baidrag and Burd Gol zones), obducted ophiolites and accretionary sedimentary rocks (Bayankhongor and Dzag zones), and forearc sedimentary rocks (Khangay zone). Arc magmatism in the Bayankhongor region is characterized by dominance of Early Paleozoic ilmenite‐series and Late Paleozoic magnetite‐series granitoids. These granitoids accompany many hydrothermal deposits of such various types as porphyry, skarn and vein. K‐Ar dating on four deposits in the region revealed that the South porphyry Cu‐Au, Huh Bulgiin Hundii skarn Cu‐Au, Han Uul shear zone‐hosted Au and Taats Gol pegmatite W‐Au deposits formed at 240±5 Ma, 252±5 Ma, 283±6 Ma and 329±7 Ma, respectively.

Thus the former three are related to the Permian to earliest Triassic magnetite‐series granitoids, whereas the W‐Au pegmatite at Taats Gol to the Early Carboniferous ilmenite‐series granitoids. Porphyry and skarn Cu‐Au mineralization occurred at latest Permian to earliest Triassic, when the Andean‐type arc magmatism was immediately followed by the collision between the Baidrag and Tarbagatai microcontinents.
Mineralizations of Base Metal Deposits of Acid‐Sulfate Type Coexisting with Adularia‐Sericite Type
Authors: IMAI Hideki
Published: November 2008

Abstract: Two types of ores are recognized in the Huanzala mine, Peru. Zinc and lead ore of adularia‐sericite type, is accompanied by pyrite body and skarn. Orthoclase (adularia), sericite and calcite are found in the skarn and altered country rocks. On the other hand, copper and silver (tin) ore of acid‐sulfate type, is characterized by enargite, luzonite and bornite, accompanied by tin, silver and tellurium minerals. Although sericite and calcite are found only at the earlier stage in the mineralization of acid‐sulfate type, kaolinite appears in the country rocks at a subsequent stage. It is interpreted that the ore‐forming fluid of the acid‐sulfate type separated from the adularia‐sericite type by boiling in the early stage of mineralization. The separated fluid was nearly neutral just after boiling and changed into acidic by the oxidation of H2S into HSO4‐. Both types of mineralizations are studied in terms of fo2‐fs2‐pH‐temperature diagrams. The adularia‐sericite type might correspond to the hot‐water system of a geothermal area, and the acid‐sulfate type to the vapor‐dominated system.

The copper ores from the Teine mine, Hokkaido, Japan and the Chinkuashih mine, Taiwan are acid‐sulfate type, characterized by the occurrence of enargite and luzonite. However, zinc and lead ores of the adularia‐sericite type are also present in these deposits. Both types in the Teine and Chinkuashih deposits are supposed to have formed in the similar relation as in the Huanzala deposits. The enargite and luzonite ores in the Hokuetsu mine, Japan are closely associated with native sulfur of solfataric origin.
Genesis of the Mamut Porphyry Copper Deposit, Sabah, East Malaysia
Authors: IMAI Akira
Published: November 2008

Abstract: The Mamut deposit of Sabah, East Malaysia, is a porphyry type Cu‐Au deposit genetically related to a quartz monzonite (“adamellite”) porphyry stock associated with upper Miocene Mount Kinabalu plutonism. The genesis of the Mamut deposit is discussed based on petrology of the intrusives in the Mount Kinabalu area combined with ore– and alteration–petrography, fluid inclusion and sulfur isotope studies.

Groundmass of the adamellite porphyry at Mamut is rich in K which suggests vapor transport of alkaline elements during the mineralizing magmatic process, while the groundmass of the post‐ore “granodiorite” porphyry at Mamut contains small amounts of normative corundum suggesting depletion in alkaline elements at the root zone of the magma column. Sub‐dendritic tremolitic amphibole rims on hornblende phenocrysts in the Mamut adamellite porphyry suggest interaction between the mineralizing magma and the exsolved fluids. Occurrences of clinopyroxene microphenocrysts and pseudomor‐phic aggregates of shredded biotite and clinopyroxene after hornblende phenocrysts in the barren intrusives imply lower water fugacity and decreasing in water fugacity, respectively. Compositional gap between the core of hornblende phenocrysts and the tremolitic amphibole rims and those in the groundmass of the Mamut adamellite porphyry suggests a decrease in pressure. Higher XMg (=Mg/(Mg+Fe) atomic ratio) in the tremolitic amphibole rims in the Mamut adamellite porphyry compared to those of the barren intrusions suggests high oxygen fugacity. High halogen contents of igneous hydrous minerals such as amphiboles, biotite and apatite in the Mamut adamellite porphyry suggest the existence of highly saline fluids during the intrusion and solidification of the mineralizing magma. Fluid inclusions found in quartz veinlet stockworks are characterized by abundant hypersaline polyphase inclusions associated with subordinate amounts of immiscible gaseous vapor.

Both Cu and Au are dispersed in disseminated and quartz stockwork ores. Chalcopyrite and pyrrhotite as well as magnetite are the principal ore minerals in the biotitized disseminated ores. Primary assemblage of intermediate solid solution (iss) and pyrrhotite converted to the present assemblage of chalcopyrite and pyrrhotite during cooling.

Subsequent to biotitization, quartz veinlet stockworks formed associated with retrograde chlorite alteration. The Cu‐Fe sul–fides associated with stockwork quartz veinlet are chalcopyrite and pyrite. Overlapping Pb and Zn and subsequent Sb mineralizations were spatially controlled by NNE‐trending fractures accompanying the phyllic and advanced argillic alteration envelope.

Sulfur isotopic composition of ore sulfides are homogeneous (about +2%) throughout the mineralization stages. These are identical to those of the magmatic sulfides of Mount Kinabalu adamellitic rocks.
Geochemistry and Radioactive Potentiality of Um Naggat Apogranite, Central Eastern Desert, Egypt
Authors: EL–AFANDY Adel H. , ABDALLA Hamdy M. , ALY Mohsen M. , AMMAR Fathy
Published: November 2008

Abstract: The northern part of Um Naggat granite massif (UNGM) has suffered extensive post‐magmatic metasomatic reworking which results into the development of (Zr, Hf, Nb, Ta, U, Th, F)– and albite‐enriched and greisenized apogranite body (UNAP) of 600 m thick, and more than 3 km in the strike length.

Albitization produced an enrichment in Zr (av. 2384 ppm), Hf (61), Nb (419), and U (43). The Th/U ratio ranges between 1. 33 and 1. 90. Extreme albitization (i. e. the albitite rock) is characterized by sharp decrease in the rare metals contents. However, extreme greisenization (i. e. endogreisen bodies) is characterized by a considerable enrichment in Zr (av. 5464 ppm), Hf (143), Nb (2329), Ta (152), U (66) and Th (178). The Th/U ratio ranges between 1. 57 and 3. 60. In contrast to extreme greisenization, it seems that extreme albitization does not apparently change the fluid pH and therefore poor amounts of rare metals are localized in the albitites.

It is suggested that the presence of Na+, H+ and F‐ in the ore fluids was essential to stablize complexes of Zr, Hf, Nb, Ta, U, Th, and HREE during extraction and transportation. In contrast, contemporaneous decrease of temperature and increasing pH due to decreasing pressure are considered the essential factors for localization of disseminated mineralization of Zr and Nb in the apical parts of the UNAP. The enhanced uranium content in the alteration facies of UNAP coupled with the absence of significant uranium mineralization may indicate the metalliferous rather than mineralized nature for the UNAP. The high uranium contents are stabilized in refractory accessory minerals. However, with repect to Zr and Nb, the UNAP especially the albitized and greisen facies, can be categorized as a mineralized productive granite.
Cation Leaching from the Basalt JB–1a by 2M NaCl Hydrothermal Solutions
Authors: UCHIDA Etsuo , TSUTSUI Ken
Published: November 2008

Abstract: The basalt JB–1a was reacted with 2M NaCl solutions, and the leaching behavior of the cations Na, K, Ca, Mg, Fe, Mn, Zn and Co was monitored. The experiments were carried out using standard cold‐seal pressure vessels in the temperature range from 300 to 800C under the constant pressure of 1000 bars and also in the pressure range from 500 to 1000 bars at 600°C.

The concentrations of Fe, Mn, Zn and Co in the hydrothermal solutions increased significantly with increasing temperature and with decreasing pressure. The thermodynamic analysis of the experimental results suggests that this is due to the formation of trichloro‐complexes and also partly due to the temperature dependence of ion exchange between augite and aqueous chloride solution. The Na concentration in the aqueous solution decreases with increasing temperature and with decreasing pressure. On the other hand, the behavior of K, Ca and Mg is complex and their concentrations seem to be controlled by the coexisting minerals.

Judging from the experimental results, it is concluded that the transition elements are effectively leached from the basalt under higher temperatures and lower pressures. This means that higher temperature and lower pressure conditions are preferable for the production of ore‐forming hydrothermal solutions.
Hydrothermal Fluid Evolution Associated with Gold Mineralization at the Wenyu Mine, Xiaoqinling District, China
Authors: JIANG Neng
Published: November 2008

Abstract: The Wenyu mesothermal gold deposit is located in the Xiaoqinling district about 1000 km southwest of Beijing in central China. It occurs in the Late Archean to Early Proterozoic metamorphosed volcanic and sedimentary rocks. Three distinct stages of veins have been identified: (I) gold‐poor quartz–pyrite veins, (II) gold‐rich sulfide–quartz veins, and (III) gold‐poor carbonate–quartz veins. Stage II can be subdivided into IIa and IIb. Gold typically occurs as fracture‐fillings associated with chalcopyrite and galena.

Fluid inclusions were examined in quartz samples from veins of both stage I and II. Three types of fluid inclusions are identified: CO2–H2O, CO2–rich, and aqueous inclusions. The first two types are of primary in origin. The last type occurs in two ways: coexisting with CO2–H2O and CO2–rich inclusions and thus primary in origin; and occurring along late healed fractures and hence secondary in origin. CO2–H2O inclusions display progressively decreasing Th and increasing Thco2, from the highest Th (311–408C) and lowest Thco2 (average 18C) in stage I quartz through middle Th (284–358C) and ThCO2(average 25C) in stage IIa quartz to the lowest Th (275–314C) and highest ThCO2 (average 28C) in stage IIb quartz, indicating an evolving H2O–CO2–NaCl fluid system. CO2–rich and primary aqueous inclusions show consistent ThCO2 or Th with their coexistent CO2–H2O inclusions. Whereas the secondary aqueous inclusions in stage I and IIa quartz have almost the same Th and salinity as the primary aqueous inclusions in stage IIb quartz. Comparing with CO2–H2O inclusions, these non–CO2, low salinity aqueous inclusions may come from different origin, most probably meteoric water.

Unlike in both stage I and IIa quartz, fluid inclusions in stage IIb do not show evidence of fluid immiscibility. The fact that most of gold is associated with stage IIa and IIb veins and not with veins of stage I which is the main stage of vein formation suggests that gold deposition occurs at the later stage of fluid immiscibility. The continuing phase separation led to the deposition of large amounts of gold at the Wenyu mine.
Occurrence of Almandine, and Its Implications for Ancient High Temperature Activity of the Orakeikorako Geothermal Field, Taupo Volcanic Zone, New Zealand
Authors: BIGNALL Greg
Published: November 2008

Abstract: Exploration drilling at Orakeikorako provides information on the hydrologic and thermal regime of the geothermal system, which is presently as high as 265C. The presence of almandine in Drillhole OK–1, at 1312. 5m drilled depth, is the only known occurrence of hydrothermal garnet in an active geothermal system from New Zealand. The formation temperature of the almandine, is not consistent with measured (bore) temperatures, but does coincide with fluid inclusion data and temperatures inferred from other secondary minerals, which suggest it formed at >240C, and possibly as much as 310C. Almandine is an important mineral geothermometer in active hydrothermal systems, and implications for its occurrence should not be discounted in fossil (mineralised) epithermal‐type hydrothermal systems.
Preliminary Examinations of the Ore‐forming Process by Fluid Mixing – a Test of MIX99
Authors: HOSHINO Kenichi , YAMAMOTO Yuki , GU Xiangping , LEE Su Young , WATANABE Makoto
Published: November 2008

Abstract: Possible ore deposition by fluid mixing was preliminarily examined using MIX 99, a FORTRAN program developed for simulating water‐rock interactions. We consider mixing of two fluids, the low fO2 and high temperature source fluid and the high fO2 and low temperature seawater. Oxygen fugacity of a mixed fluid formed by titration of seawater into the source fluid gradually decreases with decreasing temperature (model A). Sequential precipitation of ore‐forming minerals was examined in this model. On the other hand, simultaneous precipitation of the minerals could be followed by simulation of instantaneous overall mixing of the two fluids (model B). Results of simulation of the both models revealed that a temporal sequence of mineralization observed in the Karuizawa mine, NE Japan, can be formed by model A, while model B is suitable for the mineralization of an active chimney found in the Rainbow hydrothermal area of the Mid‐Atlantic Ridge.
Geological and Geochemical Characteristics of the Hydrothermal Clay Alteration in South Korea
Authors: KOH Sang‐Mo , TAKAGI Tetsuichi , KIM Moon–Young , NAITO Kazuki , HONG Sei–Sun , SUDO Sadahisa
Published: November 2008

Abstract: Hydrothermally altered areas forming pyrophyllite‐kaolin‐sericite‐alunite deposits are distributed in Chonnam and Kyongsang areas, Cretaceous volcanic field of the Yuchon Group. The Chonnam alteration area is located within depression zone which is composed of volcanic and granitic rocks of late Cretaceous age. The clay deposits of this area show the genetic relationship with silicic lava domes. The Kyongsang alteration area is mainly distributed within Kyongsang Basin comprising volcanic, sedimentary and granitic rocks of Cretaceous and Tertiary age. Most of the clay deposits of this area are closely related to cauldrons. Paleozoic clay deposit occurs in the contact zone between Precambrian Hongjesa granite gneiss and Paleozoic Jangsan quartzite of Choson Supergroup.

Cretaceous igneous rocks of the both alteration areas belong to high K calc‐alkaline series formed in the volcanic arc of continental margin by subduction‐related magmatism. Chonnam igneous rocks show more enrichment of crustal components such as K, La, Ce, Sm, Nd and Ba, higher (La/Yb)cn ratio, and higher initial 87Sr/86Sr ratio (0. 708 to 0. 712) than those of Kyongsang igneous rocks. This might be due to the difference of degree of crustal contamination during Cretaceous magmatism.

The most characteristic alteration minerals of Chonnam clay deposits are alunite, kaolin, quartz, pyrophyllite and diaspore which were formed by acidic solution. Those of Kyongsang clay deposits are sericite, quartz and pyrophyllite which were formed by weak acid and neutral solution. The formation ages of the clay deposits of two alteration areas range from 70. 1 to 81. 4 Ma and 39. 7 to 79. 4 Ma, respectively. The Daehyun clay deposit in Ponghwa area of Kyongsang province shows the alteration age range from 290 to 336 Ma. This result shows the different alteration episode from the hydrothermal alteration of Cretaceous to early Tertiary in the Kyongsang and Chonnam alteration areas. These data indicate, at least, three hydrothermal activities of Tertiary (middle to late Eocene), late Cretaceous (Santonian to Maastrichtian) and Paleozoic Carboniferous Periods in South Korea.
Crystallization of Podiform Chromitites from Silicate Magmas and the Formation of Nodular Textures
Authors: ZHOU Mei‐Fu , MALPAS John , ROBINSON Paul T. , SUN Min , LI Jian‐Wei
Published: November 2008

Abstract: Podiform chromite deposits consist of numerous individual accumulations of chromite in the mantle sequences of ophiolites, suggesting formation in separate, mini‐magma conduits in the upper mantle. They may show unique nodular and orbicular textures. Simple mixing of two distinct magmas, invoked for chromite deposits in layered intrusions, is inadequate to explain the formation of podiform chromite deposits. More likely, melt/rock interaction triggers the precipitation of chromite by addition of newly‐formed droplets of melt to the main body of magma passing through a conduit, a process similar to that of magma mingling but involving a turbulent, moving magma so that newly‐formed melt droplets behave like snowballs. These droplets concentrate chromite to form an outer shell and, while the magma is moving upwards, less dense silicate melts are squeezed out of the droplets as the shell collapses to form a nodule. Upon cooling, both orbicular and nodular textures are preserved in the chromitite.
Timing and Duration of Hydrothermal in the Oligocene Hamad Cauldron, SW Japan: Evidence from K‐Ar Ages of Sericites
Authors: Imaoka Teyruyoshi , Nakashima Kazuo , Itaya Testumaru , Okada Toshinori
Published: November 2008

Abstract: Crystallinity, chemical compositions and K‐Ar ages of sericites in highly‐sericitized granites and associated fissure‐filling veins were examined to delineate the timing and duration of the hydrothermal activity in the Oligocene Hamada cauldron in the San‐in district, SW Japan. Sericite separates (>2 μm) from the highly‐sericitized granites consist mainly of 2M1 polytype having high crystallinity and low Kübler indices of 0.22–0.35, while those in the fissure‐filling veins have lower 2M1/1Md ratios and crystallinity, and high Kübler indices of 0.29–0.35. This suggests that the sericites in highlysericitized granites were formed at a higher temperature than the vein sericites.

Sericites from the highly‐sericitized granites of the Kumogi pluton give K‐Ar ages of 30.0±0.7, 30.4±0.7, 30.6±0.7, 30.6±0.7, 32.1±0.7, 32.3±0.7 and 33.0±0.7 Ma (1s̀), while those of the central plutons, 33.8±0.7 and 33.8±0.7 Ma. Sericites in the fissure‐filling veins of the Kumogi granite give K‐Ar ages of 31.0±0.7, 31.5±0.7, 31.6±0.7, 31.7±0.7 and 32.3±0.7 Ma. Biotite separates from the fresh Kumogi granite give K‐Ar ages of 31.7±0.8, 32.0±0.8, 32.7±0.7 and 33.5±0.7 Ma. The K‐Ar age data revealed that the hydrothermal alteration began at about 33 Ma and ended by about 30 Ma and that the period of sericite alteration was nearly synchronous with the cooling of the granite intrusions in the Hamada cauldron.

Despite intense hydrothermal alteration, the Oligocene granitoids have not accompanied with any economic base metal mineralization. The bulk chemical analyses of sericite separates in the veins indicate that the post‐magmatic fluids were originally barren in heavy metals.
Generation and Evolution of Ore Fluids for Porphyry Cu‐Au Mineralization of the Santo Tomas II (Philex) Deposit, Philippines
Authors: IMAI Akira
Published: November 2008

Abstract: The Santo Tomas II (Philex) deposit is a porphyry Cu‐Au deposit, located in the southern part of the Baguio mineral district, Benguet Province, northern Luzon, Philippines. The Santo Tomas II deposit is associated with an intrusive complex consisting of four rock types that are distinguished based on petrography. They are 1) post‐ore clinopyroxene‐bearing hornblende andesite porphyry, 2) ore‐generating hornblende andesite porphyry, 3) hornblende quartz diorite porphyry and 4) porphyritic hornblende quartz diorite. K‐Ar age of hydrothermal biotitization was estimated to be 1.5±0.4 Ma.

A number of intrusive bodies having broadly similar petrography and K‐Ar age occur in the vicinity of the Santo Tomas II deposit, such as at Clifton, Ligay (Binang), Bumolo (Waterhole) and Philex Main Camp areas. The intrusions at the Santo Tomas II deposit and in the vicinity are characterized by high XMg (Mg/[Mg+Fe] atomic ratio, about 0.7 or higher) of mafic silicate phenocrysts such as hornblende, and high sulfur contents (> 0.2 wt% as SO3) in accessory microphenocrystic apatite, suggesting a highly oxidizing condition. Sulfur is accommodated dominantly as oxidized species since the crystallization of phe‐nocrysts. Sub‐dendritic rim of tremolitic amphibole on hornblende phenocryst in the ore‐generating andesite porphyry at the Santo Tomas II deposit suggests interaction of magma and aqueous fluid(s) exsolved due to decompression during intrusion.

Dissemination of magnetite is associated with hydrothermal biotitization and is followed by sheeted and stockwork quartz veinlets having silician magnetite and rare titanohematite instead of Cu‐Fe sulfides. The silician magnetite‐rich quartz veinlet was formed at fO2 near the hematite‐magnetite buffer at nearly magmatic temperature, where sulfur dominantly existed as oxidized species such as SO2. Chalcopyrite and bornite, which commonly exhibit micrographic texture often accompanying Pd telluride and native gold/Au‐rich electrum, are associated with subsequent anhydrite (‐quartz) veinlets and stringers. Both intermediate solid solution (iss) and bornite solid solution (bnss) are thought to have coprecipitated primarily at above 500°C based on fluid inclusion microthermometry and sulfur isotope thermometry applied for anhydrite and associated chal‐copyrite and bornite. The initial iss is considered to have converted to chalcopyrite partly replacing bnss during cooling. The hypersaline polyphase fluid inclusions abundantly found in the sheeted and stockwork quartz as well as anhydrite veinlets with scarce gaseous inclusions suggest that they have been trapped in the two aqueous fluid immiscible region.

The western Luzon arc associated with porphyry Cu mineralization is characterized by oxidized hydrous magmatism and shallow emplacement, and by the source of sulfur enriched in 34S.
Stratigraphic Correlation of the Malusok Volcanogenic Massive Sulfide Deposits, Southern Mindanao, Philippines
Authors: QUERUBIN Cliff L. , YUMUL Graciano P.
Published: November 2008

Abstract: Two adjacent volcanogenic massive sulfide (VMS) deposits, the Main Malusok and the Malusok Southeast, are delineated within Barangay Tabayo, Siocon, Zamboanga del Norte, Mindanao, Philippines. These deposits comprise massive to semi‐massive sulfide lenses representing the down‐dip equivalent of oxidized gossans. The massive sulfides have a primary mineral assemblage of pyrite‐chalcopyrite‐sphalerite with significant amounts of supergene copper in the form of chal‐cocite. Owing to structural and metamorphic overprinting combined with intense alteration, primary textures are generally obliterated. Rock types are classified according to dominant mineral assemblages whereas the main lithologic units comprising the Malusok volcanic package are divided based on the position of each unit relative to the mineralized zone. The main lithologic units are designated as the hanging wall, the host, and the footwall sequences. In correlating the stratigraphy of the Main Malusok zone with that of the Malusok Southeast zone, a chlorite/epidote‐rich interval located at the base of the hanging wall sequence serves as a distinct stratigraphic marker from which all lithologies are referred to. Comparisons between the stratigraphy of the two areas show that massive to semi‐massive sulfide lenses are confined within a single stratigraphic interval representing the favorable horizon for the entire Malusok area. However, differences exist relative to style of mineralization and configuration of the altered interval between the Main Malusok and the Malusok Southeast VMS deposits. Based on characteristics exhibited by each individual deposit, it is inferred that the Main Malusok VMS deposit overlies a feeder zone whereas the Malusok Southeast sulfide lenses represent satellite deposits and transported blocks.
Application of Image Analysis to Observe Microstructure in Sandstone and Granite
Authors: CHEN Youqing , NISHIYAMA Takashi , ITO Toshihide
Published: November 2008

Abstract: Advanced techniques are examined to observe microstructure of rocks using image analysis combined with methods such as the fluorescent approach and the application of optical characteristics of minerals. Analyzed are discrimination of grains in rocks, distribution patterns of grain orientation in sandstone, changes of grain shape as weathering advances and distribution patterns of microcracks in granite. In Shirahama sandstone, relatively large and flat grains are orientated parallel to the bedding on the plane perpendicular to the bedding, while grains on the plane parallel to the bedding show random patterns. In weathered granite, it is clarified that the grain surface becomes complex as weathering advances and differences among three major mineral species are identified. In Inada granite, intracrystalline cracks predominate over intercrystalline cracks and grain boundary cracks both in total length and number. Furthermore, three types of microcracks show different orientations; the intercrystalline cracks show a dominant orientation which coincides with the orientation of the rift plane, the easiest plane to split, while the intracrystalline cracks and grain boundary cracks show no preferred orientation.
Preliminary Study on the Chemical Mapping of Individual Fluid Inclusion by Synchrotron X‐ray Fluorescence Microprobe
Authors: HAYASHI Ken–ichiro , IIDA Atsuo
Published: November 2008

Abstract: Synchrotron X‐ray fluorescence analyses on individual hypersaline fluid inclusions were tested to using synchrotron source at Tsukuba (KEK), Japan. The XRF instrumentation at KEK meets the purpose of fluid inclusion analysis, nondestructive, multi–element, ppm detection limits, with micro spatial resolution. In practice, however, the quantitative chemical analysis of fluid inclusion requires further considerable data accumulation. Semi‐quantitative distribution of elements (mass number > 25) in single fluid inclusion was obtained.
A Gold‐bearing Alkaline Pluton in Eastern Linxi District, Inner Mongolia: Its Geochemistry and Metallogenic Significance
Authors: ZHU Yongfeng , SUN Shihua , JIANG Neng
Published: November 2008

Abstract: The Biliutai pluton, as the host of a small gold deposit, containing dark‐gray enclaves, intruded into the Lower Permian volcanic‐sedimentary formations in east Inner Mongolia, China. The host rocks and enclaves formed simultaneously at about 200 Ma (Rb–Sr isochron age with initial 87Sr/86Sr of 0.704). The Nd (T) values for the enclaves (from +4.4 to +4.6) are similar to their host rocks (+3.2 to +4.8), although the values for the host rocks are relatively variable. Both enclaves and host rocks are enriched in large ion lithosphere elements and light rare earth elements but depleted in high field strength elements and heavy rare earth elements. These observations suggest that the magma was produced from subduction‐modified mantle sources. The age of the mantle enrichment event, evaluated using depleted mantle Nd model ages, is 0.61 ‐ 0.83 Ga. These geochemical characteristics constrain the metallogeny of the Biliutai pluton, and imply that the ore‐forming materials probably were derived from lithospheric mantle.
Mineralogy, Geochemistry, and Age Constraints on the Beni Bou Ifrour Skarn Type Magnetite Deposit, Northeastern Morocco
Authors: RHAZI Mohammed EL , HAYASHI Ken–ichiro
Published: November 2008

Abstract: The Beni Bou Ifrour deposit of northeastern Morocco is a skarn type magnetite deposit. K‐Ar age determination suggests that the mineralization occurred at 7.040.47 Ma. The spatial relationship between skarn and dikes of microgran‐odiorite derived from the batholith of Wiksane Granodiorite, and the similarity of age (8.020.22 Ma), confirms that the Wiksane Granodiorite is the igneous rock most probably related to mineralization. The skarn is distributed asymmetrically in the limestone, and magnetite ore was developed just below the calc‐silicate skarn as two parallel beds separated by 100 m of barren limestone and schist.

The mineralization can be divided into three stages. The early stage is characterized by the formation of calc‐silicate minerals, mainly clinopyroxene (80–70 % diopside) and garnet (early almost pure andradite to the late 60 % andradite). The main stage is characterized by the formation of a large amount of magnetite. Epidote and quartz formed simultaneously with magnetite. Fluid temperatures exceeded 500 C during the early to main stages. Fluid with very high salinity (50–75 wt% NaCl equiv.) was responsible for the formation of the magnetite ore. The oxygen isotope composition, together with the fluid inclusion data, suggests that magmatic fluid was significant for the formation of calc‐silicate skarn minerals and magnetite. Low temperature (‐230C) and low salinity (‐10 % NaCl equiv.) hydrothermal fluids dominated by meteoric water were responsible for the late stage quartz and calcite formation.
Biogeochemical Prospecting of Sulphide Minerals in Winder Valley, Balochistan, Pakistan
Authors: NASEEM Shahid , SHEIKH Shamim Ahmed
Published: November 2008

Abstract: The Mor Range is mountainous terrain in southern Balochistan dominantly occupied by exposures of rocks of the Ferozabad Group which is comprised of Lower‐Middle Jurassic carbonates and siliciclastics. This group contains syngenetic and epigenetic Zn–Pb–Ba mineralization classified as Stratiform Sediment‐Hosted (SSH) and Mississippi Valley Type (MVT) deposits. Three important flora of the Saharo–Sindian, phytogeographical region of Pakistan, namely Tamarix aphyl–la, Salvadora oleoides and Acacia arabica have been studied as a mineralization prospecting tool. Samples of these species were collected from Winder Valley adjoining the Mor Range to prospect for new areas of mineralization, besides the known sulphide deposits. This study revealed the Draber, Thorar, Raj, Mithi and Kanrach localities as new prospect. Quantitative estimation of biophile elements (Zn–Cu–Pb) from the three species was made. A number of new Zn, Cu and Pb anomalies were distinguished in the area. The variation in the constituents of these species from different localities possibly varies with nature and distance from bedrock, mobility, climate, average abundance in the plant ash and exclusion mechanism of the flora. Acacia arabica with deep penetrating roots shows the best results and could be used to delineate new horizons of mineralization. In these species Zn and Cu are relatively concentrated whereas Pb shows limited enrichment. Lead therefore is the element best suited for pinpointing the mineralization owing to its relatively less mobile character.

Relationships among Zn–Cu–Pb have been established using scattergrams and triangular variation diagram, which also demonstrate their genetic affiliation. Statistical analyses, such as determination of mean, mode, median, standard deviation, and coefficient of correlation, were also made to improve the raw geochemical data. These biogeochemical methods appear to be suitable in arid climate of Balochistan, if proper attention is paid to species selection.
A Fluid Inclusion Study on Columnar Adularia from the Hishikari Low‐sulfidation Epithermal Gold Deposit, Japan
Authors: ETOH Jiro , IZAWA Eiji , TAGUCHI Sachihiro
Published: November 2008

Abstract: In the Hishikari low‐sulfidation epithermal gold deposit, Japan, columnar adularia crystals commonly precipitated directly on to the fracture surface of wall rock, and then electrum precipitated on the columnar adularia with fine‐grained adularia and quartz. To reveal the characteristics of mineralizing fluids and the elevation of paleo‐water tables at the earliest stage of mineralization in the Honko‐Sanjin zone of the Hishikari deposit, the fluid inclusions in the columnar adularia in gold‐bearing quartz–adularia veins were studied.

Coexistence of vapor‐rich and liquid‐rich two–phase primary fluid inclusions indicates the deposition of columnar adularia from boiling fluids. The precipitation temperatures range from 175 to 215C, and generally increase with depth. The temperatures of final melting point of ice range from –1.2 to –0.1C with an average of –0.5C, corresponding to salinity ranging from 0.2 to 2.1 wt% NaCl equivalent with an average of 0.9 wt% NaCl (eq.). Concentrations of non‐condensable gases such as CO2 were under the detection limit of a laser Raman microprobe spectrometer. From the precipitation temperature of columnar adularia in the Hosen–2 vein and the boiling point – depth curve for a 0.9 wt% NaCl (eq.) fluid, paleo‐water table was estimated to be at an elevation of about +170 m. The elevation of the paleo‐water tables for other veins was estimated to range from +140 to +215 m.
Carbonate Minerals in the Warrawoona Group, Pilbara Craton: Implications for Continental Crust, Life, and Global Carbon Cycle in the Early Archean
Authors: NAKAMURA Kentaro , KATO Yasuhiro
Published: November 2008

Abstract: The occurrences of the Early Archean carbonate minerals are compiled and their precipitation processes are investigated for the Warrawoona Group, Pilbara Craton. Sedimentary carbonate rocks such as limestone and dolostone are very rare, and only a small amount of sedimentary carbonate minerals are sometimes contained in the hydrothermal bedded chert, implying that a sink of CO2 was minor in the Early Archean sediments. Moreover, it is very likely that the activity of cyanobacteria forming stromatolites was considerably low in the Early Archean. Microfossils and carbonaceous matter in the hydrothermal cherts are probably derived from a non‐photosynthetic microorganisms related to the seafloor hydrothermal activity. Their preservation in sediments may play a very minor role in carbon sink of the Earth's surface.

On the other hand, carbonatized volcanic rocks subjected to seafloor hydrothermal alteration occur ubiquitously in the Early Archean greenstone belts such as the Warrawoona Group, suggesting that the hydrothermally altered oceanic crust had large amounts of CO2 as carbonate minerals. Global carbon cycle in the Early Archean is considered to have been controlled by the intense seafloor hydrothermal alteration. Large amounts of CO2 were sunk into the oceanic crust by the alteration. The carbonatized oceanic crust was partly accreted to the continents and/or island–arcs, and partly subducted into the mantle without decomposition. Significant amounts of carbonate minerals in the carbonatized oceanic crust were very likely to store in the accretionary prisms and mantle, consequently giving rise to a decrease of atmospheric and oceanic CO2.
Trend Surface Modelling of Karlapat Bauxite Deposit, Eastern Ghat Group, Orissa, India
Authors: NAYAK Bijaya Ketana , SAHU Santanu Kumar , SAHOO Rama Krishna
Published: November 2008

Abstract:The Karlapat bauxite deposit occurs in the Eastern Ghat Group of rocks in Orissa and has developed in the khondalites. Mineralogical and physical observations on bore hole samples reflect the presence of a maximum of six weathered zones from top to bottom. These zones are termed as topsoil, siliceous laterite, ferruginous laterite, bauxite, lithomarge and altered khondalite. Four‐dimensional trend surface models are developed for the data of 45 and 36 bore holes from north and south blocks, respectively, on Al2O3and SiO2to delineate the zones of metallurgical grade bauxite (SiO25 % and Al2O340 %). The results indicate about 15 m thickness of bauxite in the north block while it could be up to 20 m thick in the south block, leaving about 10 m of lat‐erites at the top of each block. High grade bauxite (>47 % Al2O3) is also encountered at specific locations.
Paleozoic Epithermal Au and Porphyry Cu Deposits in North Xinjiang, China: Epochs, Features, Tectonic Linkage and Exploration Significance
Authors: Qin Kezhang , Sun Shu , Li Jiliang , Fang Tonghui , Wang Shulai , Liu Wei
Published: November 2008

Abstract. Based on field investigation of large number of ore deposits including some latest discoveries and multidiscipline comprehensive research, we demonstrated the general features of metallic deposits and we suggest that Paleozoic archipelago‐type collisional orogen at North Xinjiang, northwestern China show intimate similarity with the metallogenesis of Southeast Asia Cenozoic archipelago. We briefly described the characteristics of major porphyry‐type, skarn‐type Cu deposits and typical high‐sulfidation type (HS‐type) and low‐sulfidation type (LS‐type) epithermal Au deposits as well as some latest discoveries. Systematic isotopic age‐dating on the Tuwu‐Yandong superlarge porphyry Cu deposits revealed that they formed in Late Devonian to Early Carboniferous in an accretionary arc setting. The tectonic settings of epithermal Au deposits and its linkage with porphyry Cu deposits are further discussed. The formation condition for porphyry Cu deposits is more strict than epithermal Au deposits. The distribution width for porphyry Cu deposits in the orogenic belts is more limited than epithermal Au deposits. The discovery and prospecting progress of the Kalatage HS‐type Cu‐Au deposit were reported. The significance in further exploration was suggested.
Hydrothermal Alteration and Cu‐Au Mineralization at Nena High Sulfidation‐type Deposit, Frieda River, Papua New Guinea
Authors: Espi Joseph Onglo , Kajiwara Yoshimichi , Hawkins Mike A. , Bainbridge Tony
Published: November 2008

Abstract. The Nena Cu‐Au deposit, located in the Frieda River mineral district of northwestern mainland Papua New Guinea, is a composite structurally‐lithologically controlled high sulfidation (HS) system. Its hydrothermal alteration and Cu‐Au mineralization are presented in this paper. Initially propylitized andesitic volcanics veined by epithermal quartz were pervasively superimposed by zoned HS alteration. The zonation grades from vuggy silica core to sulfur‐rich, pyritic silica‐alunite halo followed by pyrophyllite‐dickite‐kaolinite interval and finally to thin illite‐smectite margin, suggesting progressive decrease in temperature and increase in pH. This zonation is enveloped by chlorite‐epidote‐calcite‐gypsum alteration.

The acid altered rocks were then invaded by multiple phases of pyrite, subsequently crosscut by quartz, vein alunite and barite. Then sequential deposition of bladed covellite, enargite, luzonite and stibioluzonite occurred from the NW to the SE portions of the deposit, forming a zonation suggestive of progressive decrease in temperature, sulfur fugacity and sulfidation stage. Most ore mineralization occurs in the vuggy silica core. Gold mineralization commenced from the transition of enargite to luzonite and continued throughout the stibioluzonite stage. Associated with gold deposition are Au‐rich pyrite, tennantite‐tetrahedrite, chalcopyrite‐bornite, native tellurium, electrum, calaverite, bismuthinite and galena. Native sulfur occupied the remaining cavities and represents the waning stage of the hydrothermal system.

Fluid inclusions studies distinguished magmatic (>300–350d̀C, 9–15 wt% NaCl equiv.) and meteoric (<150–200d̀C, 1–2 wt% NaCl equiv.) fluids (Holzberger et al., 1996). Temperatures and salinities of fluid inclusions from barite associated with Cu sulfides show a general decrease from NW (330d̀C, 9–15 wt% NaCl equiv.) to SE (172d̀C, 10 wt% NaCl equiv.) parts of the deposit, indicating gradual entrainment of ground water (Hitchman and Espi, 1997). Interaction of magmatic fluids with meteoric water accompanied by changes in temperature, salinity, acidity and oxidation state of the resultant fluids is interpreted to have been the main cause of metal precipitation. Finally, supergene processes generated Au zone with an underlying chalcocite‐covellite‐digenite blanket over the primary sulfides at depth. Gold occurs as lattice constituent in scorodite, limonite‐goethite and jarosite. Chalcocite is more abundant and widespread than other Cu sulfides. Acidic fluids deposited powdery alunite and kaolinite, vein alunite and amorphous silica. Weakly secondary biotite‐quartz altered porphyry located below the known HS Cu‐Au deposit contains chalcopyrite‐bornite and is overprinted by quartz‐alunite‐pyro‐phyllite‐pyrite assemblage. This feature indicates close temporal, spatial and genetic relation between the two deposit types.
Cikidang Hydrothermal Gold Deposit in Western Java, Indonesia
Authors: Rosana Mega F. , Matsueda Hiroharu
Published: November 2008

Abstract. The Cikidang gold deposit, discovered in 1991, is located within the Bayah dome, a Tertiary‐Quaternary volcanic zone at west end of Java, which is well known as a gold district (e.g., Pongkor and Cikotok mines). Typical low‐sulfidation quartz‐adularia‐sericite(‐calcite) vein deposits represent the gold deposit in the district.

The Cikidang vein system comprises four sub‐parallel quartz‐adularia‐sericite(‐calcite) veins that are rich in manganese oxide and limonite with very poor amount of sulfides. These vary from 0.5 to 2.7 m thick and extend for up to 1,000 m long. The vein trends roughly N‐S and dip 60d̀ to 86° toward west. The ore grades vary from trace to 74.9 g/t Au and 1.2 to 225.0 g/t Ag. A K/Ar age determination on adularia yielded 2.4 Ma for the Cikidang vein.

The ore minerals are represented by electrum, argentite, aguilarite and pyrite. Electrum shows the compositional ranges of Ag (50–65 atom %). The gangue minerals are dominated by quartz with variable amounts of calcite, sericite, adularia, clay minerals, manganese oxide and limonite. The vein textures are so variable as banded, colloform, comb, brecciated and massive. Host rocks, composed of Miocene lapilli tuff and breccia, suffered from pervasive hydrothermal alterations. Wall rocks adjacent to the vein are characterized by argillic and propylitic alteration.

The fluid inclusion study of the Cikidang vein shows homogenization temperatures ranging from 170 to 260°C. Salinities are low, generally below 3 wt% NaCl equivalent. Oxygen isotope results suggest meteoric water in origin for ore fluids responsible for the Cikidang deposit.