資源地質
Online ISSN : 2185-4033
Print ISSN : 0918-2454
ISSN-L : 0918-2454
50 巻, 1 号
選択された号の論文の6件中1~6を表示しています
  • 吉成 明夫, 黒木 宏治
    2000 年 50 巻 1 号 p. 1-10
    発行日: 2000/05/15
    公開日: 2009/06/12
    ジャーナル フリー
    The Tizapa mine located in Mexico State, Mexico, started production in 1994 and is now producing 40, 000t/month of crude ore by the Minera Tizapa S.A de C.V., a joint venture among Penoles, Dowa Mining Co., Ltd. and Sumitomo Corporation.
    The Tizapa deposit is a strata-bound volcanogenic massive sulfide (VMS) type deposit and its characteristics are very similar to that of Kuroko deposits in Japan. Though the present shape of the ore deposit looks composed of several layers of ore bodies because of many folding and thrust faults, the ore deposit is thought to be originally a single lenticular ore body emplaced at the contact of footwall sericite-chlorite schist and hanging wall graphite schist.
    The footwall sericite-chlorite schist can be distinguished in appearance, one greenish colored "chlorite schist" and whitish "sericite schist". Immobile element study, however, shows that the protolith of "chlorite schist" and "sericite schist" are both classified into andesitic to dacitic rock and doesn't show significant geocherrlical difference.
    The alteration halo of the footwall sericite-chlorite with Alteration Index more than 70 is observed around the ore deposit. This fact suggests the original alteration zone in the footwall volcanic rocks of the Tizapa VMS deposit is preserved even after the metamorphism.
    Low resistivity zone detected by transient electromagnetic (TEM) method has a good correlation with the location of the ore deposit. It is understood that the hanging wall graphite schist is the cause of the low resistivity and the TEM method is effective to interpret the structure and to predict the depth of ore horizon at the Tizapa area.
    The Tizapa deposit is older in geological age (before early Cretaceous) than Kuroko deposits in Japan (middle Miocene), but both have very similar characteristics and the same exploration method can be applied. It is proposed that most effective exploration method in the Tizapa area is to clarify the stratigraphy and to pursue the ore horizon with the guidance of the alteration halo in the footwall unit.
  • 椛島 太郎, 荒井 英一, 細井 義孝
    2000 年 50 巻 1 号 p. 11-22
    発行日: 2000/05/15
    公開日: 2009/06/12
    ジャーナル フリー
    The Metal Mining Agency of Japan carried out the helicopter-based magnetic and radiometric survey using a stinger mounted magnetometer over the Shakotan Peninsula referred to as Block 2 region in the southwest Hokkaido last year. Magnetic data and also potassium, uranium and thorium gamma-ray spectral data with high resolution were acquired along flight lines oriented 30 degree clockwise from the North. spaced 200m apart and with a mean terrain clearance of 60-80m.
    The hydrothermal activities associated with mineralization and alteration might have led the destruction and redistribution of magnetic minerals such as magnetite in the host rocks, and the formation of various K-bearing minerals such as adularia, illite and alunite. These the hydrothermal alteration halos can often cover an area of at least several square kilometers, and can be detected by reconnaissance surveys utilizing high resolution airborne magnetic and radiometric sensors.
    The magnetic data were processed using the vertical derivative filter, pseudo-depth slicing, Euler deconvolution and analytic signal in order to obtain information on linearment and fault systems. Some promising sites were recognized by interpreting some maps in terms of magnetic data and those related to radiometric data. By considering these promising sites, we set five highly prospected areas with the known geologic information, the images of Landsat-TM and SPOT, and geochemical anomalies on the stream sediment.
    At least 25 small discrete zones of potassium enrichment are observed within the very large semicircular volcanic complex located at the southeast of Yoichi in the Yamato-Otarumatsukura Prospect. In the Todoroki-Nakanosawa Prospect, several zones of anomalous potassium, uranium and thorium gamma-ray spectral values are present topographically below volcanic rocks of the Yobetsu Formation and along the prominent NNW-trending fracture zone within which the Todoroki and Nakanosawa mineral-izations are placed. In the Tamagawa-Taishu Prospect, Cenozoic pultons intrude the main NW-trending anticlinal dome. There are some mineralizations at the boundaries between plutons and the anticline. These areas are rated as having a very high potential for hosting mineralization.
  • 笹尾 英嗣, Llyle SAWYER
    2000 年 50 巻 1 号 p. 23-34
    発行日: 2000/05/15
    公開日: 2009/06/12
    ジャーナル フリー
    Reflectance spectra have potential as a useful tool to confirm the mineral composition of rock chip and drilling core quickly and easily, even during field investigation.
    The total of 99 samples of hydrothermally altered rocks, collected in the northern part of the Alligator Rivers Uranium Field, Australia, were investigated in order to check the accuracy of the identification and quantification of clay minerals by means of the short wavelength infrared reflectance spectra of 1300-2500nm. In the case of a binary mixture of chlorite and mica clay mineral and that of kaolinite and mica clay mineral, the ratio of each end mineral was calculated by comparing measured spectra with reference spectra in a range of 2100 to 2500nm. The following results were obtained from the comparison on the mineral proportion determined by the reflectance spectra method and the X-ray diffraction method:
    1. The ratio of kaolinite to mica clay mineral can be accurately estimated for their binary mixtures.
    2. In a mixture of chlorite and mica clay mineral, the ratio of those minerals can be estimated with reasonable accuracy.
    3. Smectite and vermiculite are distinguishable from each other by a shape of spectra.
    4. It is difficult to identify mineral species for samples containing hematite, because reflectance spectra do not show any clear absorption pattern.
    5. Estimation of the ratios of chlorite to mica clay minerals and that of kaolinite to mica clay minerals is found to be more accurate using reflectance data in the range of 2100 to 2500nm than estimation of the ratios using reflectance data in the range of 1300 to 2500nm.
  • 松本 勝時, 皿田 滋
    2000 年 50 巻 1 号 p. 35-43
    発行日: 2000/05/15
    公開日: 2009/06/12
    ジャーナル フリー
    As a part of the deep sea mineral exploration program of the Metal Mining Agency of Japan (MMAJ), a twenty day drilling program was conducted around the Suiyou seamount in the Izu-Ogasawara Arc between December 8 and 27, 1999. The seamount is located about 240km northwest of Chichi Island and is characterized by the submarine hydrothermal polymetallic mineralization of back-arc basin type. Three of five drill holes intersected polymetallic mineralized parts enriched in Au, Ag, Cu, and Zn and characterized by pyrite, chalcopyrite and zincblende, making which is the first recovery of a modem hydrothermal deposit.
  • 迫田 昌敏, 児玉 敬義, 井上 常史
    2000 年 50 巻 1 号 p. 45-60
    発行日: 2000/05/15
    公開日: 2009/06/12
    ジャーナル フリー
    The Ohmori (Iwami) mine in the southwestern Japan is composed of two types of deposit. One is disseminated Ag deposit called the Fukuishi deposit (the Iwami Ag deposit), and the other is vein type auriferous Cu deposit called the Eikyu deposit (the Ohmori deposit). The two deposits occur in dacites of the Plio-Pleistocene Oe-Takayama volcano group, which are divided into the S-type, the Y-type and the I-type in the Ohmori mining area.
    K-Ar age data and geological information show that the S-type dacite erupted at 2.2 to 1.8Ma, the Y-type dacite solid-ified at 1.8 to 1.6Ma, and the I-type dacite intruded into the Y-type dacite at 1.5 to 1.2Ma. It is suggested that the Fukuishi deposit in the S-type dacite formed in association with the intrusion of the I-type dacite, and the Eikyu deposit formed at 1.1Ma along ENE-WSW faults in the I-type dacite.
  • 正路 徹也
    2000 年 50 巻 1 号 p. 61-71
    発行日: 2000/05/15
    公開日: 2009/06/12
    ジャーナル フリー
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