bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photo‐oxidative Stress Impacts the Expression of Genes Encoding Iron Metabolism Components in Chlamydomonas†
Authors: Long Joanne C. , Merchant Sabeeha S. 
Published: November 2008

AbstractChlamydomonas, like other organisms, regulates iron assimilation very tightly through differential expression of iron assimilation components. Nevertheless, in the presence of excess iron, cells do overaccumulate iron but without an evident phenotype. As iron toxicity is attributed to reactive oxygen species, we tested the impact of photon flux density (PFD) on cells with increased iron content. We noted that growth at >500 μmol m−2 s−1 is inhibited as iron content of the medium is increased, suggesting that high light exacerbates the systems of iron toxicity and vice versa. Cells grown in high light selectively down‐regulate the abundance of iron assimilation components, ferroxidase and FEA1, and storage protein ferritin1. At the RNA level, the abundance of ferroxidase (FOX1), iron reductase (FRE1), iron assimilatory protein (FEA1) and ferritin (FER1) mRNAs is also decreased. The time course of the response to high light compared to the response to Rose Bengal and H2O2 treatments suggests that both singlet oxygen and H2O2 may be implicated in the high light response. This hypothesis is supported by the recapitulation of some but not all of the high light responses in the carotenoid‐deficient, high light–sensitive npq1lor1 strain. We conclude that responses to iron nutrition and PFD are connected, and the determination of an optimum for photosynthetic growth for each is dependent on the other. This work defines a fourth stage of iron nutrition in Chlamydomonas, the iron excess situation, which can be molecularly and physiologically distinguished from the iron‐limited, iron‐deficient and iron‐replete stages, described previously.
Geophysical Expression of Low Sulphidation Epithermal Au‐Ag Deposits and Exploration Implications –Examples from the Hokusatsu Region of SW Kyushu, Japan–
Authors: FEEBREY Craig A. , HISHIDA Hajime , YOSHIOKA Ken , NAKAYAMA Ken 
Published: November 2008

Abstract: Low sulphidation epithermal Au‐Ag deposits constitute a major exploration target for many mining companies worldwide. These deposits are commonly characterized by quartz vein systems which formed at temperatures often in the range 150–250°C giving rise to major alteration halos. Accompanying mineralization and associated alteration is the destruction and redistribution of magnetite in the host rocks and the formation of various K‐bearing minerals such as adularia, illite and alunite. These alteration halos can often cover an area of at least several square kilometres and as such have the potential to be detected during reconnaissance geological surveys utilizing high resolution airborne aeromagnetic and radiometric sensors.Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au‐Ag deposits are characterized by several distinct geophysical features varying with the degree of post‐mineralization cover and level of erosion. Several deposits coincide with extensive magnetic “flat” and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan.
Geology and Genesis of Barite Deposits of Lasbela and Khuzdar Districts, Balochistan, Pakistan
Authors: AHSAN Syed Nayyer , MALLICK Khalil Ahmed 
Published: November 2008

Abstract: Geology and genesis of the sediment‐hosted barite deposits in the Lasbela and Khuzdar districts of Balochistan, Pakistan have been studied and described. Hot solutions generated in rifting environments during the initial stage of separation of the continental crustal block related to the Gondwanaland fragmentation subsequently reposed in Jurassic rocks, most probably played an important role on barite formation.Paragenetic relationships indicate that the period of barite mineralization was distinctly later than that of zinc‐lead sulphide mineralization in the Lasbela and Khuzdar districts. The barite deposits occur on top and in peripheral to the zinc‐lead sulphides. The earliest barite mineralization took place in the clastic rock sequence of the lower Spingwar Formation as cross cutting veins. Younger mineralization as stratabound‐replacement type occurred within the platform limestones of Loralai Formation, just above the Spingwar Formation. The youngest mineralization as stratiform is hosted within black shales, mudstones and argillaceous limestones of Anjira Formation at the top of Loralai Formation. In the light of the evidences gathered from field and laboratory investigations a genetic model has been deduced.
Rare Earth Elements as an Indicator to Origins of Skarn Deposits: Examples of the Kamioka Zn‐Pb and Yoshiwara‐Sannotake Cu(–Fe) Deposits in Japan
Authors: Kato Yasuhiro 
Published: November 2008

Abstract: Systematic data of rare earth elements (REEs) are presented in order to put some constraints on the origin of hydrothermal fluids responsible for two contrastive skarn deposits in Japan; the Kamioka Zn‐Pb and Yoshiwara‐Sannotake Cu(‐Fe) deposits. Carbon and oxygen isotopic studies have demonstrated that the hydrothermal fluids responsible for the Kamioka Zn‐Pb deposits are of meteoric water origin whereas those for the Yoshiwara‐Sannotake Cu(‐Fe) deposits are of magmatic water origin. The REE abundances of epidote skarn derived from aluminous rocks, garnet and clinopyroxene in calcic exoskarn derived from limestone, and interstitial calcite associated with sulfide minerals were determined for these contrastive skarn deposits by inductively‐coupled plasma mass spectrometry (ICP‐MS).A significant difference in the REE concentrations is not found between epidote skarn and aluminous original rock (plagioclase‐clinopyroxene rock, called Inishi rock) from the Kamioka Zn‐Pb deposits, indicating that the REEs are generally immobile during the formation of epidote skarn, and that the REE concentrations of the hydrothermal fluid are considerably low relative to the aluminous original rock. In contrast, the epidote skarn exhibits enrichment of Eu with increasing total REE concentrations relative to the aluminous original rock (quartz diorite) in the Yoshiwara‐Sannotake Cu(‐Fe) deposits, implying a contribution of magmatic fluid derived from granitoids during the skarn formation.Limestone generally has much lower REE concentrations related to surrounding aluminous rocks, and thus the REE concentrations of garnet and clinopyroxene in calcic exoskarn, originated from limestone, are variable due to the interaction with the hydrothermal fluids. The chondrite‐normalized REE patterns of garnet, clinopyroxene, and interstitial calcite exactly provide useful information on origins of hydrothermal fluids. The REE patterns of these minerals from the Kamioka Zn‐Pb deposits show lower (Pr/Yb)cn ratios, and negative Ce and Eu anomalies inherited from limestone with the decrease of This suggests that the hydrothermal fluids responsible for the Kamioka Zn‐Pb deposits were depleted in REEs, and were not magmatic water in origin, but presumably meteoric one. In striking contrast, the REE patterns of exoskarn minerals and calcite from the Yoshiwara‐Sannotake Cu(‐Fe) deposits exhibit a positive Eu anomaly, and high (Pr/Yb)cn ratios with the considerable increase of σREE and the disappearance of negative Ce anomaly, implying that the fluids were dominantly of magmatic origin. The REE indices are very likely to be an excellent indicator to origins of the skarn deposits.
Geology and Hydrothermal Alteration of the Milyang Pyrophyllite Deposit, Southeast Korea
Authors: TAKAGI Tetsuichi , KOH Sang–Mo , KIM Moon–Young , NAITO Kazuki , SUDO Sadahisa 
Published: November 2008

Abstract: The Milyang pyrophyllite deposit, which is embedded in the Late Cretaceous Yuchon Group of the Kyongsang Supergroup, is one of the largest hydrothermal clay deposits in the Kyongsang basin, southeast Korea. Host rocks of the deposit are porphyritic andesite lava and minor andesitic lapilli tuff. In the Milyang district, a hydrothermally altered zone is about 2 × 3 km in extent; we can recognize the concentric arrangement of advanced argillic, propylitic, and sericitic alteration zones from the central to peripheral parts of the zone. The Milyang pyrophyllite deposit forms a part of the advanced argillic alteration zone.The Milyang pyrophyllite deposit is subdivided into the following four zones based on mineral assemblages: the pyrophyllite zones 1, 2, 3, and the silicified zone. The pyrophyllite zone 1, which occupies the central part of the deposit, comprises mainly pyrophyllite, kaolinite, and diaspore without quartz. Diaspore nodules often concentrate in beds 40–50 cm thick. Andalusite, dumortierite, and tourmaline locally occur as network veins, crack‐filler, or small spherulitic spots. The Al2O3 content of the ore ranges from 27 to 36 wt%. The pyrophyllite zone 2, which constitutes a major part of the deposit, comprises mainly pyrophyllite, kaolinite, and quartz. The Al2O3 content of the ore ranges from 15 to 24 wt%. The pyro‐phyllite zone 3 is the hematite‐rich marginal facies of the deposit. The silicified zone, which occurs as beds and septa, is mostly composed of quartz with minor pyrophyllite and kaolinite; the SiO2 contents range from 79 to 90 wt%. Comparing chemical compositions of the high‐Al ores with those of unaltered host andesite, the Fe, Ca, alkalis, HFSE, and HREE contents are significantly depleted, whereas S, B, As, Sr, and LREE are enriched.The hydrothermal alteration of the Milyang pyrophyllite deposit can be classified into the following four stages: 1) extensive sericitic and propylitic alteration, 2) medium‐temperature (200–250°C) advanced argillic alteration, 3) high‐temperature (250–350°C or more) advanced argillic alteration, and 4) retrograde low‐temperature alteration. The heat and some volatile components such as B and S would be derived from the Pulguksa Granite intruded underneath the deposit.
A Special Orogenic‐type Rare Earth Element Deposit in Maoniuping, Sichuan, China: Geology and Geochemistry
Authors: WANG Denghong , YANG Jianmin , YAN Shenghao , XU Jue , CHEN Yuchuan , PU Guangping , LUO Yaonan 
Published: November 2008

Abstract: The Maoniuping REE deposit is the second largest light rare earth elements deposit in China, explored recently in the northern Jinpingshan Mountains, a Cenozoic intracontinental orogenic belt in southwestern China. It is a vein‐type deposit hosted within, and genetically related to, carbonatite‐alkalic complex. Field investigation and new geochemical data of the carbonatites from the carbonatite‐alkalic complex support an igneous origin for the Maoniuping carbonatites and related REE mineralization. Carbonatite itself carries rare earth elements which were enriched by hydrothermal solution.It is known that most of the REE deposits related to carbonatite‐alkalic complexes were formed in relatively stable tectonic setting such as cratonic or rifting environment. The Maoniuping deposit, however, was formed during the processes of Cenozoic orogeny. Although the Maoniuping deposit is located in the north sector of the Panxi paleo‐rift zone, the rift had been closed before early Cenozoic and evolved into an intracontinental orogenic belt, i.e., the Jinpingshan Orogen, which was formed since later Mesozoic to early Cenozoic. Geochronological and geochemical data also prove that the Maoniuping REE deposit was formed in an intracontinental orogenic belt instead of rift system or stationary block.The Maoniuping REE deposit is similar to the Mountain Pass REE deposit in many respects such as the high contents of bastnaesite and barite, the low content of niobium, and the common occurrence of sulfides. The discovery of the Maoniuping deposit and other REE deposits during the past two decades suggest a good potential for prospecting REE deposits along the alkalic complex belt located on the eastern side of the Qinghai–Xizang–West Sichuan Plateau.
Geochemical Cycles of Bio‐essential Elements on the Early Earth and Their Relationships to Origin of Life
Authors: KAKEGAWA Takeshi , NODA Masakazu , NANNRI Hideyuki 
Published: November 2008

Abstract: The bio‐essential elements are demanded for the metabolic action of all living organisms. These elements are continuously supplied to biosphere through the elemental cycle on the surface Earth. The geochemical cycle of bio‐essential elements was most likely different in the pre‐biotic era (ca. 4.4 to 4.0 Ga) compared to the modern Earth. The difference was probably made by the absence of continents and biological mediation in the pre‐biotic environments. Geochemical cycle models of bio‐essential elements (P, B and Mo) on the pre‐biotic Earth are proposed in this study, and these models are examined using available geochemical data.The input flux of phosphorous in pre‐biotic oceans was probably dominated by submarine hydrothermal activities associated with carbonatized oceanic crusts. Such input flux by submarine hydrothermal activities is not known in the present‐day oceans, and probably a unique flux in the pre‐biotic oceans. Boron chemistry of pre‐biotic oceans was also controlled by submarine hydrothermal input flux. The Mo exchange between the pre‐biotic ocean and lithosphere may have restricted only at the submarine hydrothermal areas. These suggest that the submarine hydrothermal discharging areas were only locations to obtain bio‐essential elements for the earliest life. This model is consistent with the previously proposed model for hydrothermal origin of life.
Late Cenozoic Metallogeny of Southwest Hokkaido, Japan
Authors: WATANABE Yasushi 
Published: November 2008

Abstract: This paper reviews the Miocene to Pleistocene tectonic framework, geology, magmatic style and stress field of southwest Hokkaido, Japan, and compiles deposit form, type, ore and alteration minerals, strike and length of mineralized veins, and associated igneous activity. The late Cenozoic tectonic regime of the Sapporo‐Iwanai ore district is divided into five periods on the basis of the subduction mode of the Pacific plate: Period 1 (15.0–12.1 Ma) oblique‐subduction setting with an orthogonal convergence rate (OCR) of 51–81 mm/y; Period 2 (12.1–6.2 Ma) normal subduction with an OCR of 81–94 mm/y; Period 3 (6.2–3.6 Ma) oblique subduction setting with an OCR of 73–99 mm/y; Period 4 (3.6–1.5 Ma) normal‐subduction setting with an OCR of 99–103 mm/y and Period 5 (1.5–0 Ma) oblique‐subduction setting with an OCR from 99 to 57 mm/y.The hydrothermal deposits in the district include Kuroko deposits of Period 1 and epithermal vein‐type deposits of Periods 2 to 5. The Kuroko deposits were accompanied by submarine monogenetic rhyolite volcanism associated with tholeiitic basalt in the backarc region. In contrast, Late Miocene to Pliocene epithermal vein‐type deposits were associated mainly with polygenetic andesite and monogenetic rhyodacite volcanism of calc‐alkaline series. These different styles of magmatism occurred in an extensional tectonic regime (Period 1), and weakened extensional (Periods 2–3) or neutral tectonic regimes (Periods 4). Periods 2–5 epithermal vein‐type deposits are divided into base‐metal and precious‐metal deposits. The base‐metal deposits are associated mainly with large (>5 km in diameter) polygenetic andesitic volcanoes and subvol‐canic intrusions. The precious‐metal deposits are associated with small (<5 km in diameter) polygenetic or monogenetic volcanoes and/or subvolcanic intrusions of andesite, dacite and rhyolite near the volcanic arc front. This difference in distribution is ascribed to different states of horizontal differential stress.Productive vein‐type deposits, such as Toyoha, Inakuraishi, Ohe and Chitose, formed in the neutral regime with a large horizontal differential stress during Period 4, which may have promoted strike‐slip faulting and non–extrusive, subvol‐canic intrusion. This tectonic regime and stress field resulted from the normal subduction of the Pacific plate with elevated velocity. This observation leads to the conclusion that large metallic deposits in southwest Hokkaido are expected to have formed primarily during Pliocene magmatic‐hydrothermal activity, when the orthogonal convergence rate was highest and strike‐slip faulting was active.
Petrochemistry of Volcanic Rocks in the Hishikari Mining Area of Southern Japan, with Implications for the Relative Contribution of Lower Crust and Mantle‐derived Basalt
Authors: Hosono Takahiro , Nakano Takanori 
Published: November 2008

Abstract. This study presents the petrographical, mineralogical, and geochemical characteristics of Late Pliocene‐Pleistocene volcanic rocks distributed in the Hishikari gold mining area of southern Kyushu, Japan, and discusses their origin and evolution. The Hishikari volcanic rocks (HVR), on the basis of age and chemical compositions, are divided into the Kurosonsan (2.4–1.0 Ma) and Shishimano (1.7–0.5 Ma) Groups, which occur in the northern and southern part of the area, respectively. Each group is composed of three andesites and one rhyodacite. HVR are characterized by high concentrations of incompatible elements compared with other volcanic rocks in southern Kyushu, and have low Sr/Nd and high Th/U, Th/Pb, and U/Pb ratios compared with typical subduction‐related arc volcanic rocks.Modal and whole‐rock compositions of the HVR change systematically with the age of the rocks. Mafic mineral and augite/hypersthene ratios of the andesites decrease with decreasing age in the Kurosonsan Group, whereas in the Shishimano Group, these ratios are higher in the youngest andesite. Similarly, major and trace element compositions of the younger andesites in the former group are enriched in felsic components, whereas in the latter group the youngest andesite is more mafic than older andesites. Moreover, the crystallization temperature of phenocryst minerals decreases with younger age in the former group, whereas the opposite trend is seen in the latter group. Another significant feature is that rhyodacite in the Shishimano Group is enriched in felsic minerals and incompatible elements, and exhibits higher crystallization temperatures of phenocryst minerals than the rhyodacite of the Kurosonsan Group.Geochemical attributes of the HVR and other volcanic rocks in southern Kyushu indicate that a lower subcontinental crust, characterized by so‐called EMI‐type Sr‐Nd and DUPAL anomaly‐like Pb isotopic compositions, is distributed beneath the upper to middle crust of the Shimanto Supergroup. The HVR would be more enriched in felsic materials derived from the lower crust by high‐alumina basaltic magma from the mantle than volcanic rocks in other areas of southern Kyushu. The Kurosonsan Group advanced the degree of the lower crust contribution with decreasing age from 51 %, through 61 and 66 % to 77 %. In the Shishimano Group, the younger rhyodacite and andesite are derived from hotter magmas with smaller amounts of lower crust component (58 and 57 %) than the older two andesites (65 % and 68 %). We suggest that the Shishimano rhyodacite, which is considered to be responsible for gold mineralization, was formed by large degree of fractional crystallization of hot basaltic andesite magma with less lower crustal component.
Subsurface Occurrence of Natural Gas Hydrate in the Nankai Trough Area: Implication for Gas Hydrate Concentration
Authors: Uchida Takashi , Lu Hailong , Tomaru Hitoshi 
Published: November 2008

Abstract. The Nankai Trough runs along the Japanese Islands, where extensive BSRs have been recognized in its forearc basins. High resolution seismic surveys and site‐survey wells undertaken by the MITI have revealed the gas hydrate distribution at a depth of about 290 mbsf. The MITI Nankai Trough wells were drilled in late 1999 and early 2000. The highlights were successful retrievals of abundant gas hydrate‐bearing cores in a variety of sediments from the main hole and the post survey well‐2, keeping the cored gas hydrate stable, and the obtaining of continuous well log data in the gas hydrate‐dominant intervals from the main hole, the post survey well‐1 and the post survey well‐3. Gas‐hydrate dominant layers were identified at the depth interval from 205 to 268 mbsf. Pore‐space hydrate, very small in size, was recognized mostly filling intergranular pores of sandy sediments. Anomalous chloride contents in extracted pore water, core temperature depression, core observations as well as visible gas hydrates confirmed the presence of pore‐space hydrates within moderate to thick sand layers. Gas hydrate‐bearing sandy strata typically were 10 cm to a meter thick with porosities of about 40 %. Gas hydrate saturations in most hydrate‐dominant layers were quite high, up to 90 % pore saturation.All the gas hydrate‐bearing cores were subjected to X‐ray CT imagery measurements for observation of undisturbed sedimentary textures and gas‐hydrate occurrences before being subjected to other analyses, such as (1) petrophysical properties, (2) biostratigraphy, (3) geochemistry, (4) microbiology and (5) gas hydrate characteristics.
Redox and Compositional Parameters for Interpreting the Granitoid Metallogeny of Eastern Australia: Implications for Gold‐rich Ore Systems
Authors: Blevin Phillip L. 
Published: November 2008

Abstract. Granitoids and related rocks of eastern Australia can be classified according to their metallogenic potential using a scheme based on compositional character, degree of compositional evolution, degree of fractionation, and oxidation state. The scheme is based on empirical and theoretical considerations and satisfactorily describes the known distribution of granite‐related mineralisation.The granitoids range from unevolved, mantle compatible compositions to highly evolved and fractionated. They exhibit age‐ and region‐specific variations in silica content, compositional evolution and oxidation state. The most unevolved intrusive igneous rocks comprise those of the Ordovician of the Lachlan Orogen, and the Devonian of the New England Orogen. Strongly fractionated and evolved I‐type granites occur in western Tasmania, the southern New England Orogen, and far north Queensland. Other fractionated suites tend to occur relatively rarely in the Lachlan Orogen and elsewhere. Oxidation states vary markedly. The most consistently oxidised rocks occur in the Ordovician of the central Lachlan Orogen, and the northernmost New England Orogen. The Carboniferous I‐types of the northeastern Lachlan Orogen are consistently more oxidised than other Lachlan Orogen I‐types.Gold‐rich, Cu‐poor systems associated with felsic I‐types in eastern Australia are associated with W‐Mo mineralised suites with gold occurring within a predictable metallogenic zonation. Gold mineralised I‐types comprise weakly to moderately oxidised, high‐K granitoid suites that, at least in the east Australian context, have low K/Rb ratios and show strong fractionation trends. Gold is readily removed from granitic magmas through the early precipitation of sulfides, or to a lesser extent by magnetite. Crystallisation of Fe‐poor, silica‐rich granitic magmas in a relatively narrow oxidation window between the FMQ and NNO buffers may provide conditions where retention of Au in magmas in felsic granitic magmas is optimised.