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リンク⇒こちら| 鉱床とは| 鉱床の分類| |
斑岩銅鉱床| カーボナタイト鉱床| 火山性塊状硫化物鉱床| ミシシッピーバレイ型鉛・亜鉛鉱床| 鉄酸化物銅・金鉱床| その他 |
鉱床学の本| 有用元素| |
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地下(Underground、Subsurface)の資源(Resource)となる物質を多く含む岩石(Rock)を鉱石(Ore)と呼ぶ。鉱石が集まった場所を鉱床(Ore
Deposit、Mineral Deposit)と呼ぶ。鉱床について、それらの資源となる物質が濃集したメカニズム(Concentration Mechanism)を解明するための学問が鉱床学(Economic Geology、Ore Geology)である。従って、資源の探査(Exploration)や採掘(Mining)のためには必須の学問であり、また資源となる物質の性質等も明らかにする学問であるから選鉱(Dressing)や製錬(Smelting)にとっても重要である。ただし、化石燃料(Fossil Fuel)関係では、単なる鉱床学という名称は一般的に用いられないようである。 資源となる物質が濃集するには、液体状態(Liquid State)が最も効率が良い。鉱石は異常な岩石(Abnormal Rock)であるが、岩石の一種であるから、岩石の成因(でき方)(Rock Genesis)に類似させて考えれば、液体状態は『マグマ(Magma)』と『熱水(Heated Water、Hot Water、Hydrothermal)』である。これらは、火成作用(Igneous Activity)に伴って生成する。マグマの場合、普通の岩石を形成するのはケイ酸質(Siliceous)のマグマ本体であるが、鉱石を形成するのは水を主とする揮発成分(Volatile Constituent)の多いマグマである。一方、熱水の場合、このようなマグマに含まれていた水も存在するが、一般的にはマグマの熱によって熱水〔または場合によっては水蒸気(Water Vapor)も〕となった地下水(Groundwater)の循環(Cycle)によって鉱石が形成される場合が多い。熱水〔地表付近では温泉水(Hot Spring Water)とも呼ばれる〕は地下の岩石に含まれる物質を循環の間に溶かし込む。そして、地表部の低温・低圧条件下で、鉱石となるような物質を沈殿させる(Precipitate)。地下の割れ目(Fracture)などが熱水の通路(Passage)として適しているために、そのような場所に鉱石を沈殿させることが多い。いわゆる、鉱脈鉱床(Vein-type Deposit)である。目立った通路が無く、散点的に広範囲に存在すれば、交染鉱床(Disseminated Deposit)となる。 鉱床は、このように形状(Form)で分類されることもあるが、普通には鉱種(Ore-type)別〔元素(Element)別〕に分類される(Classify)ことの方が多い。例えば、金鉱床(Gold Deposit)とか、鉄鉱床(Iron Deposit)とか、銅鉱床(Copper Deposit)とかである。これは、研究者が特定の鉱種を対象に研究することが多いためである。 また、鉱床学は英語ではEconomic Geology(直訳すれば経済地質学)とされていることからも判るように、資源の開発(Exploitation)において経済的に採算がとれるかどうかが重要である。 なお、実際の開発(Development)のための学問は資源工学(Resource Engineering)などと呼ぶ。 |
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■苣木浅彦 先生 2010年4月(肺癌)ご逝去(享年87歳) ■広渡文利 先生 2007年7月(脳出血)ご逝去(享年82歳) ■関根良弘 先生 2004年5月 ご逝去(享年80歳) 【見る→】 ■添田 晶 先生 1998年 ご逝去 ■立見辰雄 先生 1997年10月(肺炎)ご逝去(享年81歳) ■片山信夫 先生 1997年3月(腎不全)ご逝去(享年87歳) ■吉村豊文 先生 1990年 ご逝去(享年85歳) ■渡辺武男 先生 1986年12月 ご逝去(享年79歳) ■宮久三千年 先生 1983年2月(喘息+急性肺炎)ご逝去(享年54歳) |
| 鉱床とは |
| 鉱床の分類 |
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![]() Figure 1: Map of world showing the distribution of major deposits plotted on digital elevation model with draped geology from Geological Survey of Canada, Open File 2915d, 1995. Data from the synthesis of ore deposits. Data plotted and diagrams prepared by W.D. Goodfellow. Natural Resources Canada > Earth Sciences Sector > Priorities > Geological Survey of Canada > Consolidation and Synthesis of Mineral Deposits Knowledgeの『World』の『Figure 1』から |
![]() Figure 13 Schematic illustration of the major geological characteristics of major mineral deposit types that typically occur in continental arc and back-arc environments. (大陸弧と背弧環境に典型的に生成する主要な鉱床の主な地質学的特徴の図示) ![]() Figure 14 Schematic illustration of the major geological characteristics of mineral deposit types that typically occur in oceanic arc environment and back-arc spreading centres. (海洋弧環境と背弧拡大中心に典型的に生成する主要な鉱床の主な地質学的特徴の図示) ![]() Figure 15 Schematic illustration of the major geological characteristics of mineral deposit types that typically occur in ore-forming environments within the interior regions of continents. (大陸の内部地域の鉱石形成環境に典型的に生成する主要な鉱床の主な地質学的特徴の図示) カナダ地質調査所(Geological Survey of Canada)による『Mineral Deposits of Canada Maps of deposits and resources(world)』から |
| Epigenetic |
Porphyry Large, low grade deposits usually associated with a porphyritic intrusive body. |
Cu-Mo |
| Cu (-Au) | ||
| Mo (-W) | ||
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Skarn Mineral deposits formed by replacement of limestone by ore and calc-silicateminerals, usually adjacent to a felsic or granitic intrusive body. |
W-Cu (-Zn, -Mo) | |
| Zn-Pb-Ag (-Cu, -W) | ||
| Cu (-Fe, -Au, -Ag, - Mo) | ||
| Fe (-Cu, - Au) | ||
| Sn (-Cu, -W, -Zn) | ||
| Au (-As, -Cu) | ||
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Vein Fracture filling deposits which often have great lateral and/or depth extent but which are usually very narrow. |
Hypothermal - Cu (-Au) | |
| Mesothermal - Cu-Pb-Zn-Ag-Au | ||
| Epithermal - Au-Ag (-Hg) | ||
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Mississippi Valley Named for the region where they were first described, these deposits formed within porous carbonate rocks (limestone reefs or caves). They are Pb-Zn deposits with low Ag values. |
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| Syngenetic |
Volcanic Massive Sulphide (VMS) These deposits formed as massive (over 60% sulphide) lens-like accumulations on or near the sea floor in association with volcanic activity. |
Felsic volcanic hosted - Cu-Pb-Zn-Ag-Au |
| Mafic volcanic hosted - Cu (-Zn, -Au) | ||
| Mixed volcanic/sedimentary - Cu-Zn (-Au) | ||
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Sedimentary Massive Sulphide (Sedex) These are formed by hydrothermal emanations on or near the sea floor in association with the deposition of sedimentary rocks. |
Pb-Zn-Ag | |
| Ba | ||
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Magmatic- layered mafic intrusion During the crystallization of a magma, usually mafic or ultramafic, heavy, metal-rich liquids settle and accumulate at specific sites, often at the base, within the intrusion. |
PGM (Platinum group metals) | |
| Chromite | ||
| Ni-Cu (-PGM) | ||
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Placer Formed within sediments by the concentration of heavy resistant minerals (Au diamond, cassiterite) by stream or wave action. |
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![]() Figure 5 Diagram illustrating the plate tectonic setting in hich several ma or types of mineral deposits are formed The diagram shows a divergent plate boundary (spreading center) where tectonic plates are moving apart from each other and lava flows are extruded on the ocean floor forming a line of undersea mountains that encircle the Earth. Iceland, in the north Atlantic, is the tip of one part of this mountain range. Volcanogenic massive sulfide (VMS) deposits (described in the text) are an example of mineral deposits that form on the sea floor. Also shown are convergent plate boundaries where an oceanic plate is being subducted beneath a continental tectonic plate forming folded and faulted mountains (orogen) and volcanoes. The subduction of oceanic tectonic plates is accompanied by strong earthquakes and the generation and movement of tmagma (molten rock) and hydrothermal fluids that form a variety of mineral deposits, including porphyry copper deposits and associated gold and silver veins and polymetallic replacement deposits and associated gold and silver veins and polymetallic replacement deposits described in this report. Continental rift zones are areas where the crust is stretched (extended) forming linear depressions characterized by faults, volcanoes, sedimentary basins, and a variety of mineral deposit types including sediment-hosted (sedex) lead-sinc, sediment-hosted copper, and evaporite deposits. See text for further discussion. Modified from Kious and Tilling (1996). USGSのGeology and Nonfuel Mineral Deposits of Africa and the Middle Eastから |
![]() 図14 沈み込み様式・広域応力場・火成活動様式および鉱床タイプとの模式的関係図 渡辺 寧氏によるプレートの沈み込み様式と鉱床タイプから |
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梶原・正路(1997)による〔『エネルギー・資源ハンドブック』(1015-1020p)から〕 |
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金田・正路(1993)による〔『地球環境工学ハンドブック』から |
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佐藤(1979)による『地球の資源/地表の開発』から |
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| 鉱床全体 |
![]() Fig. 1. Structure and processes beneath an oceanic island arc (sources: Tatsumi and Eggins, 1995; Schmidt and Poli, 1998; Winter, 2001; Poli and Schmidt, 2002; Fumagalli and Poli, 2005). Primary hydrous basaltic arc magmas are derived from partial melting of the metasomatized asthenospheric mantle wedge. Mineral zones shown in the subducting plate indicate lower limits of stability of hydrous phases in the basaltic oceanic crust and peridotitic mantle lithosphere. Abbreviation: Ctd=chloritoid. ![]() Fig. 3. Schematic section through a continental arc, showing the development of a MASH or “hot zone” at the base of the crust where basaltic arc magmas pool at their level of neutral buoyancy, differentiate, and interact with crustal rocks and melts. Evolved, less dense, andesitic magmas rise into the mid-to-upper crust where they pool at their new level of neutral buoyancy to form batholithic complexes. Along with volcanic structures, porphyry and epithermal deposits may form at shallower levels above these batholithic complexes where exsolved magmatic fluids ascend, cool, and interact with near-surface upper crustal rocks.Modified fromRichards (2003, 2005); sources: Hildreth andMoorbath (1988),Winter (2001), Annen et al. (2006), and Sillitoe (2010). ![]() Fig. 4. Post-subduction tectonic environments conducive to the formation of porphyry and epithermal deposits by remobilization of previously subduction-modified lithosphere (modified from Richards, 2009). (a) Porphyry Cu±Mo deposits formed in normal arc settings; a continental arc is shown, but similar processes can occur in mature island arcs. (b-d) During post-subduction tectonic processes, previously subduction-modified sub-continental lithospheric mantle (SCLM) or lower crustal hydrous cumulate zones residual from previous arc magmatism (black layer) may undergo small-volume partial melting. Such magmas may remobilize Au as well as Cu±Mo left behind in residual sulfide phases by arc magmatism, leading to the potential formation of porphyry Cu±Au±Mo and alkalic-type epithermal Au deposits. Magmas may be characterized by high Sr/Y and La/Yb ratios due to the presence of hornblende (±garnet, titanite) in the amphibolitic lower crustal source rocks. See text for discussion. ![]() Fig. 7. Schematic cross-section through a typical coupled arc batholith.cupola.volcanic system, with associated porphyry Cu±Au and linked high sulfidation Cu.Au epithermal deposits. Also shown are the thermal structure, fluid flow pathways and characteristics during the main stage of hydrothermal activity, and overlapping hydrothermal alteration zones. Propylitic alteration by circulating heated groundwaters can be assumed to affect all the supracrustal rocks in the field of view, with greatest intensity (epidote, actinolite) close to the intrusions, fading to background distally. Modified from Richards (2005); sources: Sillitoe (1973, 2010), Dilles (1987), Shinohara and Hedenquist (1997), Hedenquist et al. (1998), and Fournier (1999). Richards(2011)による『Magmatic to hydrothermal metal fluxes in convergent and collided margins』から |
| 鉱床各論 |
![]() Figure A1. Phanerozoic porphyry belts, porphyry deposits, and representative porphyry copper deposits summarized in Appendix 2 (red labels). Modified from Seedorff and others (2005, their Fig. 1). ![]() Figure B1. General setting of porphyry copper and associated deposit types (modified from Sillitoe and Bonham, 1990). John,D.A.(ed.)(2010)による『Porphyry Copper Deposit Model』から |
![]() Figure 1. Location of explored Nb- and REE-carbonatite deposits included in the database and grade and tonnage models. USGSによる『Carbonatites of the World, Explored Deposits of Nb and REE−Database and Grade and Tonnage Models』から |
![]() Figure 24. World map showing the distribution of volcanogenic massive sulfide deposit subtypes. USGSによる『Volcanogenic Massive Sulfide Deposits of the World−Database and Grade and Tonnage Models』から |
![]() Figure 1. Global distribution of Mississippi Valley-Type lead-zinc deposits and districts. USGSによる『A Deposit Model for Mississippi Valley-Type Lead-Zinc Ores』から |
Iron
oxide Cu-Au deposits are veins and breccia-hosted bodies of hematite
and/or magnetite with disseminated Cu + Au ± Ag ± Pd ± Pt ± Ni
± U ± LREE minerals formed in sedimentary or volcano-sedimentary
basins intruded by igneous rocks. Deposits are associated with
broad redox boundaries and feature sodic alteration of source
rocks and potassic alteration of host rocks.USGSによる『Descriptive and Grade-Tonnage Models and Database for Iron Oxide Cu-Au Deposits』から |
【その他】
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![]() Figure 1. Ficklin plot of the sum of the base metals Cd, Co, Cu, Ni, Pb, and Zn versus pH illustrating the variation of mine drainage chemistry as a function of the geologic characteristics (type) of specific mineral deposits. Modified from Plumlee and Nash (1995), and Plumlee (1999). USGSによる『Progress on Geoenvironmental Models for Selected Mineral Deposit Types』から |
| 鉱床学の本 |
| 有用元素 |