資源地質
Online ISSN : 2185-4033
Print ISSN : 0918-2454
ISSN-L : 0918-2454
47 巻, 2 号
選択された号の論文の6件中1~6を表示しています
  • 矢島 太郎, 松本 泰三, 吉岡 謙, 中山 健
    1997 年 47 巻 2 号 p. 45-58
    発行日: 1997/04/30
    公開日: 2009/06/12
    ジャーナル フリー
    勢多の低硫化系浅熱水性金鉱床は日本において最も最近に発見された金鉱床である.現地性シリカシンター,カオリン鉱床,水銀鉱床,熱水爆発角礫岩等の熱水活動の地表近くの兆候がよく保存されており,これらが金鉱床発見の手がかりとなった.主鉱化帯は現地表面下約250m付近に位置しており,比較的浅所で金の沈殿が生じたと考えられる.
    鉱化作用は(i)所々角礫化した白色の縞状石英脈,(ii)黒色の硫化物に富む熱水角礫岩に分けられ,いずれも主として凝灰角礫岩や安山岩中に発達している.前者は掘進長で最大19mの幅を有し,部分的にAu50g以上の高品位部を伴う.これは中性熱水の湧昇によって形成されたと考えられる.脈は調査地域の北部では急傾斜で北西―南東に連続するが,南部~南西部では不規則な細脈群となり,さらに南部では水平脈に移行する.このことから,北部から南部に向かう導水勾配に規制された熱水の流れが示唆される.後者は,北西一南東方向の規制を受けた4列の雁行配列をなして産出し,最大幅25mに達するところがあるが金品位は一般に低い.これはH2Sの酸化により生成した酸性水と上昇する中性熱水が混合するところに形成されたものであり,地下水位の低下を反映しているものと考えられる.
  • 笹尾 英嗣, Joseph DRAKE-BROCKMAN, 山田 康夫
    1997 年 47 巻 2 号 p. 59-69
    発行日: 1997/04/30
    公開日: 2009/06/12
    ジャーナル フリー
    Egg-shaped uraninite nodules were discovered near Yambla creek in central Australia during work carried out on the Arunta uranium exploration project by Power Reactor and Nuclear Fuel Development Corporation.
    The Yambla area is geologically situated in the eastern part of the Arunta Inlier which consists of several lower Prot-erozoic metamorphic sequences. The distribution and mode of occurrence of the uraninite nodules has been investigated by detailed surface mapping, intensive mapping and sampling in trenches. It was found that the uraninite nodules are distributed over a 1 km north-south trend on the surface and in the trenches are intimately associated with plagioclase-scapolite phase (white phase) and amphibole-rich phase (dark phase) in an amphibolite host rock. The surface trend parallels the strike of the host sequence.
    From chondrite-normalized REE pattern, radiometric age dating and high thorium content, the uraninite is estimated to be produced by high temperature mineralizing fluids at some 360 million years age which corresponds to the Carboniferous Alice Springs Orogeny. The white and dark phases originated by metasomatic replacement during injection of a high temperature (above 400°C) fluid along fractures and metamorphic foliation planes.
  • 茂田 直孝
    1997 年 47 巻 2 号 p. 71-79
    発行日: 1997/04/30
    公開日: 2009/06/12
    ジャーナル フリー
    This paper introduces our recent trials on geophysical surveys used in exploration for uranium deposits in the Athabasca basin, northern Saskatchewan, Canada. The uranium deposits are associated with the unconformity between the Helikian (Middle Proterozoic) Athabasca sandstone and an older crystalline basement.
    The current standard geophysical exploration flow in this area consists of a series of geophysical methods with electromagnetic methods as its core. That is, in view of the association between non-magnetic basement graphitic metasediments and the uranium deposits, air-borne magnetic and electromagnetic methods are the primary reconnaissance tools, and they are followed by ground electromagnetic methods to delineate the graphitic horizons prior to exploratory drilling.
    Here, I show that three-component time domain electromagnetic measurements can provide a more accurate estimation of the locations of the conductor axes (intersections between the graphitic horizons and the unconformity) than conventional two-component measurements, and that direct current resistivity mapping is effective for picking shallow alteration zones.
  • 山川 正, 松村 稔, 松尾 重明, Gilberto Ruy DERZE, 羽藤 正実
    1997 年 47 巻 2 号 p. 81-87
    発行日: 1997/04/30
    公開日: 2009/06/12
    ジャーナル フリー
    It is indispensable for mineral exploration program that alteration zone which is closely related to the mineralization is clarified on its characteristics and is delineated from an investigation area. In this paper, Fazenda Brasileiro mine as a lode type of gold ore deposits pregnated in the greenstone was selected as a study area, aiming at extracting alteration zone, which is considered to be associated with primary alteration, around the ore body, by the use of remote sensing techniques.
    As the results, spectral analysis using field spectroradiometer against surface soils might be important tool for further exploration program in the preliminary stage. Through this spectral analysis, kaolinite, which is produced by weathering process, was focused as one of the indices showing wall rock alteration in this study area.
  • 廣岡 知
    1997 年 47 巻 2 号 p. 89-94
    発行日: 1997/04/30
    公開日: 2009/06/12
    ジャーナル フリー
  • 正路 徹也
    1997 年 47 巻 2 号 p. 95-108
    発行日: 1997/04/30
    公開日: 2009/06/12
    ジャーナル フリー
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