大江鉱床の変質ハローの形成の過程は,緑泥石化を主とする(II)相の変質が,現在の鉱脈が存在する位置を中心として起り,同時にその外側に原岩と(II)相の漸移相としての(I)相をつくった.その後一部の場所にパイロフィライト化を主とする(P)相が形成され,さらに現在の鉱脈の裂かを中心に珪化・絹雲母化を主体とする(III)相と(IV)相が形成されたものと考えられる.
鉱床探査のために追跡すべき標的は,鉱脈に密接な関係をもって分布し,かつ,ある程度の分布の広さをもつ(III)相の変質岩である.その追跡にあたっては,特に試錐の観察におけるRQDの値が極めて有効な情報を提供してくれる.

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The Akenobe deposit has been cited as one of the best-known examples of the xenothermal tin-bearing polymetallic vein-type mineralization. It occurs in a formation of slate, basic tuff and basic lava of middle to late Permian Maizuru group as well as Yakuno basic complexes. Detailed examination on the distribution of metals in each vein and the entire mineralization field revealed that the mineralization is roughly divided into three groups; Cu-Zn type, Cu-Sn type and Cu-Zn-Sn type and that a positive correlation exists between zonal arrangement of ores and type of mineralization. In general, Cu-Sn type is dominant in the central portion of the mining field, mainly along NE-SW trending major faults. On the other hand, Cu-Zn type is distributed in the outer zone, especially in the northwestern and southeastern areas.
The Chiemon vein swarm and Ginsei vein both belong to Cu-Zn-Sn type, although they are quite different each other in their metal zoning patterns. The former is composed of Cu-Zn and Cu-Sn type mineralizations which occurred with a considerable tectonic gap, while the latter seems to have been a product of more or less continuous ascending of ore solutions with copper, zinc and tin.
Taking into consideration the mineral zoning patterns and results of stress field analysis, it is concluded that the Chiemon vein swarm has been formed under NW-SE trending compressional stress and the No. 3 fault has served as channelways for ascending ore solutions. Recent exploration works based on these conclusions seem to be quite successful.

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The newly discovered Ezuri kuroko deposits are located in the southwestern part of Hokuroku area in Akita Prefecture, Japan. Detailed geological study on the stratigraphy of acidic volcanic activities in the Fukazawa-Ezuri district had indicated possible existence of the kuroko-bearing formation in this particular area. As a result of a few drillings, favourably altered acidic volcanic rocks were encountered and a systematic exploration program started which included geochemical examination of the behavior of alkali and alkaline earth metals in pre-mineralization acidic volcanic lavas, geophysical survey (time domain IP method), magnetic susceptibility measurement, and systematic grid drillings.
In May 1975, the Iwagami deposit and in July 1976 the Ezuri deposit were discovered. The Ezuri mine comprising these deposits, now has possible or reserved ore of about 3 million tons with a grade of 0.89% Cu, 3.3% Pb, 10.1 % Zn. Since October 1979, the mine has been in operation on a scale of 7, 500 tons per mounth.
The geology of the area is characterized by an intensive volcanic activity. Pyroclastic rocks, lavas and intrusive rocks of the Nishikurosawa and Onnagawa stages of the Miocene age are the major constituents. These are subdivided into three units, Yukisawa, Kagoya, and Shigenai formations in the ascending order, which can be correlated with the stratigraphic column in the nearby Fukazawa area. The orebodies occur at the top of dacitic volcanics of Yukisawa formation and is overlain by a sheet like porphyritic dacite and in turn by basic tuff. Each orebody is mainly composed of stratiform black ores accompanied with minor amount of yellow ores, dissemi-nated or stockwork ores and gypsum ores.

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フリエダ鉱床は,いわゆるニューギニア・モービルベルト地帯にあり,中期中新世の安山岩質火成岩コンプレックスに伴われる.フリエダ周辺にある同一マグマ起源と思われる種々の貫入岩はK-Ar法によって13.5～16.6×10⁶年前に貫入したものとされている.
このコンプレックスは安山岩質砕屑岩と熔岩からなる噴出岩と安山岩斑岩～石英閃緑岩の貫入岩によって構成されている.これらの噴出岩と早期貫入岩の分布方向と広範囲に認められている"Acid変質"(石英,カオリナイト,明ばん石,絹雲母～パイロフィライト,黄鉄鉱,硫黄)およびポーフィリーカッパー変質の分布方向はいずれもNW系であり,これらの火成活動と変質活動がSE-NW方向の応力により規制されたことを示している.後期に貫入した非変成閃緑岩は火山構造性陥没地帯に沿って貫入したものと考えられる.最末期に貫入したNE方向の岩脈と噴出岩中にNW方向の褶曲があることは火成活動の末期に応力の方向がSE-NWからSW-NE方向に変化したことを示している.
フリエダにはポーフィリー型鉱床とは異なるAs-Cu-Ba-Au鉱床も認められている.これは塊状黄鉄鉱と硫砒銅鉱―ルソン銅鉱―重晶石脈からなる."Acid変質"の構成鉱物である石英,明ばん石,黄鉄鉱,硫黄等はこのAs-Cu-Ba-Au鉱化に調和して分帯配列しているように思われる.
As-Cu-Ba-Au鉱床の探鉱は十分に行なわれていないので鉱量計算をする段階までには達していないが,ポーフィリー型鉱床の探鉱はかなり進んでおり,Ivaal鉱床,Horse鉱床,Koki鉱床の概略はほぼ明らかにされている.これらの3鉱床では,計7億6千万トン,0.47% Cu,0.28g/t Au,約40g/t Moの鉱量が確認されている.
ポーフィリー型鉱床の主要鉱物は黄鉄鉱と黄銅鉱で,斑銅鉱,輝銅鉱,輝水鉛鉱,磁鉄鉱を伴う.これらは変質鉱物である黒雲母,正長石,石英,絹雲母～パイロフィライト,緑泥石,緑簾石,曹長石,紅柱石,硬石膏と共に割れ目充填,脈,鉱染状に産出する.変質鉱物累帯は母岩の化学的性質によって,それぞれのポーフィリー型鉱床間で若干異なっている.Ivaal鉱床では中心部から外縁部に向って,黒雲母の多いPotassic帯,石英脈の多いTransitional帯,Sericite-Quartz-Chlorite帯,Sericite-Quartz-Andalusite帯,Propylitic帯へと漸移している,しかしHorse鉱床とKoki鉱床ではSericite Quartz-Andalusite帯を欠き,さらにKoki鉱床はTransitional帯とSericite-Quartz-Chlorite帯もあまりはっきりしない.これらのポーフィリー型鉱床や他の2～3ケ所で探鉱中のポーフィリー型鉱化の中心部には常にHorse microdioriteが存在しており,Horse microdioriteは当地域のポーフィリー型鉱化の運鉱岩であると考えられる.
Ivaal鉱床とHorse鉱床の一部には溶脱帯と共に二次富化帯があり,ブランケット状に約4千万トン,0.85～0.90%Cu,0.3g/t Auの鉱量がある.この二次富化帯では輝銅鉱と少量の斑銅鉱,銅藍が黄鉄鉱,黄銅鉱を交代しており,初生Cu品位の1.7倍のCu品位を示す.フリエダのポーフィリー型鉱床には中心のPotassic帯から外縁のPropylitic帯にかけて大量の硬石膏がもたらされているが,上部は天水により溶脱されている.この硬石膏溶脱帯は二次富化ブランケットの下面からさらに150～200m下位まで達しており,天水の影響はCu溶脱帯と二次富化ブランケットの形成だけでなく,さらに下部までおよび,硬石膏溶脱帯の形成にも関与している.
フリエダで認められている2つのタイプの鉱床――ポーフィリー型鉱床と"Acid変質"に伴うAs-Cu-Ba-Au鉱床――は同一シリーズの火成活動による一連の熱水作用によってもたらされたものであろう.前者は比較的地表下深部で起きたポーフィリーカッパー鉱化作用によってもたらされ,後者は地表近くで起きた噴気性鉱化作用によってもたらされたものと考えられるが,フリエダはこれら2つの鉱化作用の成因関係を明らかにするための恰好のフィールドを提供しているように思われる.

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The Huanzala mine is a copper, lead and zinc deposit in Peruvian Andes. Being emplaced in a limestone formation of Cretaceous age, the orebodies are bedded or lenticular in form and occur in limited horizons. A few sheets of quartz porphyry exist close to the ore horizons.
Ore deposit of the Huanzala mine is considered to be a product of skarnization and succeeding hydrothermal replacement processes related to the activity of the quartz porphyry. On the basis of their mode of occurrence and mineral assemblage, Pb-Zn ores are divided into three types; pyritic ore, skarn ore and "shiroji" ore (argillized ore). "Shiroji" ore is a hydrothermal alteration product of pyritic and skarn ores. Cu ores are also divided into three types; pyritic, "shiroji" and vein-like. Main Cu minerals of each of the three ore types are chalcopyrite, bornite+chalcopyrite, and tennantite, respectively.
In the Huanzala mine, two types of sphalerite are recognized. One is the iron-rich type, called "red sphalerite" because of its reddish and/or brownish color, occurring in the pyritic and skarn ores. The other is the iron-poor type, called "black sphalerite", which is microscopically black due to the numerous small dots of chalcopyrite inclusion. This type of sphalerite is generally accompanied by "shiroji" ore. Microscopic examination indicates that the "red sphalerite" has formed earlier than the "black sphalerite".
The sequence of the mineralization in the Huanzala deposit is considered to be as follows; pyritization nearly simultaneous with quartz porphyry intrusion→skarnization and "red sphalerite" mineralization→galena mineralization followed by chalcopyrite mineralization→"shiroji" alteration and "black sphalerite" mineralization→bornite+chalcocite mineralization→tennantite mineralization.
Although the pattern is not very simple, zonal distributions of elements and ores which can be related to the paragenetic sequence are distinct in the deposit. Systematic analysis of these data is very useful for an exploration guide and some encouraging results have already been obtained.

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Ore-prospecting and engineering geological survey have so many common grounds as to their technique and object that the two fields should cooperate more closely. Among the techniques and knowledges employed in the engineering geological survey, the following may be of particular importance to ore-prospecting, that is, seismic survey, numerical analysis of fault-and fracture-systems based on rock mechanics, knowledge of rock mass classification and groundwater hydrology. On the contrary, application of the ore-prospecting techniques to engineering geological survey may be most useful in surface and underground geological survey, geophysical and geochemical surveys, drilling, etc. Because of the growing trend of larger scale civil engineering construction these days, underground geologic data such as those required in mining geology are becoming more and more important in engineering geological survey. In view of the close relationship between the above two fields of the applied geology, it is desirable for young geologists working in either field to have experience of the counter field as much as possible.

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