Geology, Wall-rock Alteration and Vein Paragenesis of the Bilimoia Gold Deposit, Kainantu Metallogenic Region, Papua New Guinea

The Bilimoia deposit (2.23 Mt, 24 g/t Au), located in the eastern Central Mobile Belt of mainland Papua New Guinea, is composed of fault‐hosted, NW–NNW‐trending Irumafimpa–Kora and Judd–Upper Kora Au‐quartz veins hosted by Middle–Late Triassic basement that was metamorphosed to medium‐grade greenschist facies between Middle–Late Triassic and Early–Middle Jurassic. Mineralizing fluids were introduced during crustal thickening, rapid uplift, change of plate motions from oblique to orthogonal compression, active faulting and S₃ and S₄ events in an S₁–S₄ deformation sequence. The Bilimoia deposit is spatially and temporally related to I‐type, early intermediate to felsic and late mafic intrusions emplaced in Late Miocene (9–7 Ma). Hydrothermal alteration and associated mineralization is divided into 10 main paragenetic stages: (1) chlorite–epidote‐selvaged quartz–calcite–specularite vein; (2) local quartz–illite–pyrite alteration; (3) quartz–sericite–mariposite–fuchsite–pyrite wall‐rock alteration that delimits the bounding shears; (4) finely banded, colloform‐, crustiform‐ and cockade‐textured and drusy quartz ± early wolframite ± late adularia; (5) hematite; (6) pyrite; (7) quartz ± amethyst‐base metal sulfides; (8) quartz–chalcopyrite–bornite–Sn and Cu sulfides–Au tellurides and Te ± Bi ± Ag ± Cu ± Pb phases; (9) Fe ± Mn carbonates; and (10) supergene overprint. Fluid inclusions in stage 4 are characterized by low salinity (0.9–5.4 wt% NaCl equivalent), aqueous–carbonic fluids with total homogenization temperatures ranging from 210 to 330°C. Some of the inclusions that homogenized between 285 and 330°C host coexisting liquid‐ and vapor‐rich (including carbonic) phases, suggesting phase separation. Fluid inclusions in quartz intergrown with wolframite have low salinity (0.9–1.2 wt% NaCl equivalent), aqueous–carbonic fluids at 240–260°C, defining the latter’s depositional conditions. The ore fluids were derived from oxidized magmatic source initially contaminated by reduced basement rocks. Wall‐rock alteration and involvement of circulating meteoric waters were dominant during the first three stages and early part of stage 4. Stage 5 hematite was deposited as a result of stage 4 phase separation or entrainment of oxygenated groundwater. Gold is associated with Te‐ and Bi‐bearing minerals and mostly precipitated as gold‐tellurides during stage 8. Gold deposition occurred below 350°C due to a change in the sulfidation and oxidation state of the fluids, depressurization and decreasing temperature and activities of sulfur and tellurium. Bisulfides are considered to be the main Au‐transporting complexes. The Bilimoia deposit has affinities that are similar to many gold systems termed epizonal orogenic and intrusion‐related. The current data allow us to classify the Bilimoia deposit as a fault‐controlled, metamorphic‐hosted, intrusion‐related mesothermal to low sulfidation epithermal quartz–Au–Te–Bi vein system.     

Does heavy oil pollution induce bacterial diseases in Japanese flounder Paralichthys olivaceus?

As basic research for the effect of heavy oil on the fish immune system, in this study, the number of leukocyte was counted in Japanese flounder Paralichthys olivaceus, after exposure to heavy oil at a concentration of 30 g/8L for 3 days. To compare the numbers of bacteria in the skin mucus between oil-exposed and control fish, viable bacteria were enumerated by counting colony forming unit (CFU). Compared with 5.79+/-1.88 x 10(7)leukocytes/mL in the controls, the exposed fish demonstrated higher counts, averaging 1.45+/-0.45 x 10(8)cells/mL. The bacterial numbers of control fish were 4.27+/-3.68 x 10(4)CFU/g, whereas they were 4.58+/-1.63 x 10(5)CFU/g in the exposed fish. The results suggest that immune suppression of the fish occurred due to heavy oil stressor, and bacteria could invade in the mucus, resulting in the increasing leukocyte number to prevent infectious disease.     

Primary productivity and solar radiation off Sanriku in May 1997

We measured the in situ primary production at four stations from the surface to 80 m off Sanriku in late May 1997. The depth-integrated daily primary production in the upper 80 m was estimated to be 391, 468, and 855 mgC m⁻²d⁻¹ in water from the Oyashio, and 336 mgC m⁻²d⁻¹ in the warm-core ring. The variation in the primary production was primarily due to the variation in phytoplankton activity (chlorophyll α-specific primary production). A combination of previous and present studies in water from the Oyashio and the warm-core ring suggested that phytoplankton activity is proportional to light intensity between 12 and 50 Ein m⁻²d⁻¹ which is close to the usual light condition (61–75 Ein m⁻²d⁻¹) off Sanriku in May and June. Light may be a limiting factor for phytoplankton off Sanriku in late spring and early summer.     

Mitigation of earthquake-induced damage of breakwater by geogrid-reinforced foundation

A strong earthquake often precedes a tsunami, and a breakwater may settle during the earthquake. Such seismic subsidence of the breakwater may reduce its ability to block the tsunami, and the tsunami may easily enter coastal areas by overflowing it. This study deals with the instability of a breakwater due to an earthquake. In addition, to protect a breakwater from damage caused by an earthquake, a new concept of using geogrid for reinforcing the foundation of a breakwater is introduced. To determine the behavior of unreinforced foundation and to evaluate the effectiveness of the proposed reinforced foundation under different earthquake loadings, a series of shaking table tests were performed. It was observed that the earthquake generated excess pore water pressures and deformations of foundation ground were main reasons of failure of the breakwater. The reinforced foundation was found effective to reduce the earthquake-induced damage of the breakwater, and finally it makes the breakwater resilient against earthquake-induced forces. Numerical simulations were also performed to elucidate the mechanism of reinforcement–breakwater–soil–water system under different earthquake loadings.     

NATURE OF PRECIPITATION AND ACTIVITY OF CUMULUS CONVECTION DURING THE 1991 MEIYU SEASON OF CHANGJIANG-HUAIHE RIVER BASIN

Seasonal variability regarding the nature of precipitation and the activity of cumulus convectionduring the 1991 Meiyu season of Changjiang-Huaihe River Basin(Jianghuai)has been investigatedby calculating apparent heat source/apparent moisture sink and analyzing TBB(cloud-topblackbody radiation temperature)data.It is found that three periods of strong ascending motionduring the Meiyu season lead to three episodes of heavy rain,and the latent heat due to theprecipitation is of the sole heat source of the atmosphere.The nature of precipitation showsdistinct seasonal variability,from frontal precipitation of the first episode to the extremely strongconvective precipitation of the third episode.TBB field of East Asia may well reflect not only theintensity of convection and rainfall,but also the movement of rain belt and convection belt.In thewhole Meiyu season.convection belt mainly stays in Jianghuai.but may shift within the domain ofEast Asia.Its locating in Jianghuai or not determines the maintenance or break of Meiyu.In thethird episode,the narrow convection belt over Jianghuai is mainly caused by southwest monsoonwhich takes moist and convective atmosphere from tropical ocean.     

TBB资料揭示的亚澳季风区季节转换及亚洲夏季风建立的特征

发展了一个用于台风路径预报的初始场人造台风方案。该方案除包含对称台风环流外,也考虑了非对称风的作用。使用双向移动套网格模式作的试验预报结果表明,初始场中引入人造台风后能明显提高径预报的水平。     

A new one-dimensional simple energy balance and carbon cycle coupled model for global warming simulation

Global warming and accompanying climate change may be caused by an increase in atmospheric greenhouse gasses generated by anthropogenic activities. In order to supply such a mechanism of global warming with a quantitative underpinning, we need to understand the multifaceted roles of the Earth's energy balance and material cycles. In this study, we propose a new one-dimensional simple Earth system model. The model consists of carbon and energy balance submodels with a north–south zonal structure. The two submodels are coupled by interactive feedback processes such as CO₂ fertilization of net primary production (NPP) and temperature dependencies of NPP, soil respiration, and ocean surface chemistry. The most important characteristics of the model are not only that the model requires a relatively short calculation time for carbon and energy simulation compared with a General Circulation Model (GCM) and an Earth system Model of Intermediate Complexity (EMIC), but also that the model can simulate average latitudinal variations. In order to analyze the response of the Earth system due to increasing greenhouse gasses, several simulations were conducted in one dimension from the years 1750 to 2000. Evaluating terrestrial and oceanic carbon uptake output of the model in the meridional direction through comparison with observations and satellite data, we analyzed the time variation patterns of air temperature in low- and middle-latitude belts. The model successfully reproduced the temporal variation in each latitude belt and the latitudinal distribution pattern of carbon uptake. Therefore, this model could more accurately demonstrate a difference in the latitudinal response of air temperature than existing models. As a result of the model evaluations, we concluded that this new one-dimensional simple Earth system model is a good tool for conducting global warming simulations. From future projections using various emission scenarios, we showed that the spatial distribution of terrestrial carbon uptake may vary greatly, not only among models used for climate change simulations, but also amongst emission scenarios.     

Fractionated Ilmenite-series Granites in Southwest Japan: Source Magma for REE-Sn-W Mineralizations

Abstract. Various leucocratic biotite granites, low-temperature I-type, from the middle zone of the Sanyo ilmenite-series granitic terrane were studied chemically. These granites are locally associated with REE-Sn-W mineralizations, and were compared with unmineralized granites and batholithic Ryoke granites in three areas of the Chubu, Kinki and Chugoku Districts. They are unique in the region because they have extremely low ferromagnesian components but high Rb/Sr and 10000Ga/Al ratios. These granites are divided petrographically into the main phase, finer-grained marginal phase and younger sheets and dikelets. These rocks have increasing of HREE+Y and Nb+Ta contents in this order, which is also followed by decreasing zircon saturation temperature from 780 to 725C. Together with the mode of occurrence of these granites, the leucogranitic magmas are considered to have formed by in-situ fractionation of the host granitic magmas near the top of the magma chambers. The concentration of HREE, Y, Nb and Ta in these Sanyo Belt leucogranites is principally controlled by magmatic fractionation.     

Resource Evaluation and Some Genetic Aspects of Indium in the Japanese Ore Deposits

Abstract. There have been two primary sources for industrial indium; one from massive sulfides, while the other is dissemination-veins and skarns, related to felsic igneous rocks. The latter group of the In-bearing deposits is abundant in the Japanese Islands. Indium occurs as In-minerals such as sakuraiite, roquesite, laforetite and many unidentified minerals, but the majority is contained as an impurity in sphalerite, and tin and copper sulfides. Average grades of the ores from which indium has been extracted vary from a few ppm (e.g., Kosaka mine) to more than 300 ppm (Toyoha mine). The amount of indium in all the major basemetal deposits is estimated by analyzing representative samples. The main indium deposits are subvolcanic and tin-poly-metallic vein types. The largest one is Toyoha mine (4,700 tons hi) and the Ashio mine (ca. 1,200 tons In) was found to be the second largest. Many small occurrences, were recognized in the Miocene magnetite-series belt, besides the classic occurrences in the ilmenite-series granitic terrains of SW Japan, including the Ikuno and Akenobe tin(-tungsten) polymetallic veins, located in the northern margin of the late Cretaceous Sanyo ilmenite-series province. Magnetite-series magmas with deep source are necessary to concentrate sulfur in the magma chamber but sedimentary source rocks and their reducing agents are needed to collect and to precipitate indium. The Japanese islands are essentially accretionary terrains intruded by various deep oxidized magmas; thus forming magnetite/ilmenite-series paired belts, which are sometimes mixed. This unique geologic setting may be the most fundamental reason why indium is rich in vein-type deposits of the Japanese Island arcs.