• Journal of the Mineralogical Society of Korea
• /
• v.15 no.3
• /
• pp.205-220
• /
• 2002

The gold-silver deposits in the Casado district were formed in the sheeted and stockwork quartz veins which fill the fault fractures in volcanic rocks. K-Ar dating of alteration sericite (about 70 Ma) indicates a Late Cretaceous age for ore mineralization. These veins are composed of quartz, adularia, carbonate, and minor of pyrite, sphalerite, chalcopyrite, galena, Ag-sulfosalts (argentite, pearceite, Ag-As-Sb-S system), and electrum. These veins are characterized by chalcedonic, comb, crustiform and feathery textures. Based on the hydrothermally altered mineral assemblages, regional alteration zoning associated with mineralization in the Gasado district is defined as four zones; advanced argillic (kaolin mineral-alunite-quartz), argillic (kaolin mineral-quartz), phyllic (quartz-sericite-pyrite) and propylitic (chlorite-carbonate-quartz-feldspar-pyroxene) zone. Phyllic and propylitic zones is distributed over the study area. However, advanced argillic zone is restricted to the shallow surface of the Lighthouse vein. Compositions of electrum ranges from 14.6 to 53.7 atomic % Au, and the depositional condition for mineralization are estimated in terms of both temperature and sulfur fugacity: T=245。$~285^{\circ}C$, logf $s_2$=$10^{-10}$ ~ $10^{-12}$ Fluid inclusion and stable isotope data show that the auriferous fluids were mixed with cool and dilute (158。~253$^{\circ}C$ and 0.9~3.4 equiv. wt. % NaCl) meteoric water ($\delta^{18}$ $O_{water}$=-10.1~8.0$\textperthousand$, $\delta$D=-68~64$\textperthousand$). These results harmonize with the hot-spring type of the low-sulfidation epithermal deposit model, and strongly suggest that Au-Ag mineralization in the Gasado district was formed in low-sulfidation alteration type environment at near paleo-surface.

• Economic and Environmental Geology
• /
• v.13 no.3
• /
• pp.167-184
• /
• 1980

The granitic plutons associated with Ogcheon geosynclinal zone can be grouped into three different subzones; SE-Subzone for the migmatitic and schistose granites of the southeast margin, 101-181m.y. old; NW-Subzone for those of the northwest margin, 112-163m. y. old; and C-Subzone for those of central part of the zone, 63-183m.y. old. The intrusives in C-Subzone are further subdivided into the older, adamellite to granodiorite (148-183m.y. old) and the younger, perthitic granites (63-106m,y. old). The metallogenic distribution of South Korea suggests that, in the Ogcheon Zone, it is possible to delineate an elongated polymetallogenic province in the general orientation of the zone intimately related with the migmatite and plutonic zones mentioned. Moreover, the mineralization in the province was basically controlled by the patterns of local geology involving country rocks and related igneous bodies, that permit subdivision of the province into the following three parts: Northeast (NE) Province consists dominantly of thick Paleozoic calcareous sediments; Middle (M) Province is characterized by predominant argillaceous and partly calcareous sediments of Precambrian to Late Paleozoic age; and Southwest (SW) Province consisting mainly of volcanic and arenaceous sediments of Mesozoic age. The three different plutonic zones with three different country rock provinces above mentioned make a combination which consists of nine classes. Each class can be assumed to be characterized by specific mineralization type. In order to classify the mineralization types, the present study sampled twenty six ore deposits and mineralized areas in Ogcheon zone as shown figure 2; eight ore deposits from plutonic SE-Subzone, ten from the plutonic NE-Subzone and eight from the plutonic C-Subzone. The characteristics of the classes are as follows: NE-SE is predominant in Au-Ag vein and Sn-migmatite of katazonal occurrence; NE-C is most productive in Pb-Zn and remarkable in Fe contact deposit in mesozone and partly Pb-Zn-Cu skarn in limestone and subordinate in mesozone and partly Pb-Zn pipes; M-SE is considerable in Au-Ag vein and rare elements (Nb, Ta, etc.) of pegmatite; M-C is predominant in F-veins in epizone and Mo-W, Fe, Cu veins occur in replacement type; M-NW is productive in Fe metamorphic and skarn types, partly remarkable in Cu, Pb-Zn contact; SW-SE is barren in mineralization related to Jurassic igneous rocks; SW-C is predominant in alunite and pyrophyllite in tuffs; and SW-NW is scarece in Pb-Zn, Cu, As and Au-Ag veins.

• Economic and Environmental Geology
• /
• v.4 no.2
• /
• pp.77-90
• /
• 1971

About four hundred deposits of iron, talc, fluorite, tungsten, molybdenum, lead, zinc and other polymetallic mineral deposits were plotted on the Ore Distribution Map of the Ockcheon Geosynclinal Area. These mineral deposits plotted on the map can be divided into the several metallogenic zones by the consideration of their geologic background including the sedimentary and tectonic cycles and the igneous activities in the geosynclinal evolution, as follows: a. Chungju iron and talc zones. b. Cheong-san copper bearing iron sulphide zone c. Kumsan-Muju fluorite-polymetallic zones. d. Cheong-an Puyong and Ein Suckseong gold zone e. Hwang-gan Seolcheon and Sangju gold zones. Chungju iron zone originated in the iron bed in the Kemyongsan Series corresponding to the Pre-Ockcheon Cycle of evolution history. In early period of the Ockcheon Cycle, Hyangsanri quartzite and Munjuri phyllitic formation corresponding to the lower terrigenous sequence were not mineralized while the next sequence of the Samsungsan basic igneous-metamorphic formation and the Changri limestone formation were mineralized by the copper bearing iron sulphide and the fluorite-polymetallic deposits respectively. Two generations of the gold zones are recognized. The earlier generation distributes directionaly in the outside of the Ockcheon sedimentary belt was followed by the earlier grantitic invasion of Jurasic in age, while the later generation scatters at random which was related to the nondirectional Cretaceous granitic intrusion of the Post-Ockcheon Cycle. Conclusively speaking, it was disclosed that the endogenic mineralization in the Ockcheon geosyn clinal zone was not conspicuous in its inner sedimentary belt except its limestone area but in its outer peripheral granitic or gneissic zones, and the related igneous activities occured in the Post-Ockcheon Cycle of evolution history.

• Economic and Environmental Geology
• /
• v.27 no.4
• /
• pp.325-333
• /
• 1994

Gold and/or silver mineralization in the southeast province, Korea, occurred in hydrothermal quartz vein that fills fracture zones in Cretaceous volcanic and sedimentary rocks of the Gyeongsang basin or granites and Precambrian gneiss. Most of the gold-silver-bearing veins in the province occur in Hapcheon, Suncheon and Haman-Gunbuk area where they are associated with Cretaceous Bulgugsa granites. On the basis of the Ag/Au ratio on amounts produced and ore grades, mode of occurrence, and associated mineral assemblages, hydrothermal Au-Ag deposits in southeast province, Korea, can be classified as follows: pyrite-type gold deposit (Group IIB, Samjeong and Sangchon deposits), antimony-type gold-silver deposit (Group IV, Gisan and Geochang deposits), and antimony-type silver deposit (Group V, Sanggo, Seweon, Seongju and Gahoe deposits). All of the gold-silver deposits in the province are generally characteristics of the gold-silver or silver-dominant type deposit which contains more silver-bearing minerals than those deposits in central Korea. The gold-silver mineralization in the deposits consist of two generation; the early characterized by gold precipitation and the late represented by silver-rich (as silver-bearing sulfosalts minerals) mineralization. All but one deposit (Samjeong deposit) having relatively lower Au content in electrum values between ${\approx}20$ and ${\approx}50$ atomic %. The mineralogical data on electrum-sphalerite and/or arsenopyrite geothermometry and fluid inclusion data indicate that the gold and silver mineralizations were occurred at temperatures of $190{\sim}280^{\circ}C$ and $150{\sim}180^{\circ}C$, respectively. These suggest that the gold-silver mineralization in the province occurred in the lower temperature and pressure conditions as epithermal-type hydrothermal vein deposit.

• Economic and Environmental Geology
• /
• v.48 no.6
• /
• pp.525-536
• /
• 2015

Trapiche project corresponds to the advanced exploration stage which is thought to be a part of various porphyry copper deposits occurring in the margin of Andahuyalas-Yauri metallogenic belt. This deposit is genetically related to the monzonitic porphyry intrusion and Oligocene breccia pipe. Mineralization consists of primary sulfides such as pyrite, chalcopyrite, bornite, and molybdenite and secondary sulfides such as chalcocite, covellite and digenite. It occurs malachite, tenorite and cuprite as copper oxide. As a result of lixiviation or enrichment process, mineralization shows untypical zonation structure. Breccia and porphyry areas characterize the vertical zonation patterns. In the northern area, lixiviation zone, secondary enrichment zone, transitional zone and primary mineralized zone are distributed in northern area. In the western area of deposit, oxidation zone and mixed zones are narrowly occurred. Inferred resources of deposit is estimated to be 920 Mt @ 0.41% Cu with the cut-off grade of 0.15%.

• Economic and Environmental Geology
• /
• v.8 no.1
• /
• pp.25-56
• /
• 1975

Most fluorite deposits of South Korea are distributed in three metallogenic zones namly as: Hwacheon, Hwangangni and Geumsan metallogenic zones. Fluorite deposits of each zone show The characteristic features owing to the geological setting, the structural patterns and their forming processes. deposits of the Hwacheon metallogenic zone are wholly fissure filling hydrothermal veins emThe bedded in shear fractures of the granite gneiss or schists of Precambrian age or in the cooling fractures of the granite and acidic hypabyssal rocks which are assumed to be a differentiated sister rock of the granite. Localization of most fluorite veins of the region is structurally controlled by NW and EW fracture systems and genetically related to the granite intrusion which ascertained as motivating rock of the fluorite mineralization. Fluorites are in most cases accompanied by quartz, chalcedony mainly and rarely agate, calcite, barite and sulphide base metals in some localities. The deposits of the Hwangangni metallogenic zone were formed at the last stage of hydrothermal polymineralization of W, Mo, Cu, Pb, Zn. The majority of the fluorite ore bodies were originated from replacement in limestone beds of Great Limestone Series or in calcareous interbeds of metasediments, whereas some cavity-filling ore bodies were embedded in phyllites and schists of the Ockcheon system and along the fissures in the replaced beds which were originated by volume decrease. The localization of fluorite deposits in this region is genetically related to the Moongyong granite which has been dated as middle Cretaceous, and controlled structurally by the $N20^{\circ}{\sim}50^{\circ}W$ extension fracture system or axial planes of folds, and by faults of NE direction that acted as paths of ore solution. The deposits of the Geumsan metallogenic zone are seemed to be formed through the similar process as that of Hwangangni metallogenic zone, but characteristic distinctions are in that they are more prevailing fracture filling veins and large number of the deposits are localized in roof-pendants or xenolithes of limestone in granites and porphyries. Igneous rocks that presumably motivated the mineraltzation are middle Cretaceous Geumsan granite and porphyries. Metallogenic epoch of the fluorite mineralization of South Korea are puesumably limited in early-middle Cretaceous. Studies of the fluid inclusions in fluorites of the region reveal that the homogenization temperature of the fluorite deposits are as follows: Hwacheon metallogenic zone : $95^{\circ}C{\sim}165^{\circ}C$; Hwangangni metallogenic zone : $97^{\circ}C{\sim}235^{\circ}C$; Geumsan metallogenic zone : $93^{\circ}C{\sim}236^{\circ}C$. Judging from the above results, the deposits of the Hwancheon region were formed at the epithermal stage, and those in the Hwangangni and Geumsan regions, were deposited at epithermal stage preceded by mesothermal mineralization of small scale in which some sulphide minerals were deposited. The analytical data of minor elements in the fluorites reveal that ore solutions of Hwangangni metallogenic zone seemed to be emanated in more acidic stage of magma differentiation than Hwacheon metallogenic zone did.

• Proceedings of the KSRS Conference
• /
• 1999.11a
• /
• pp.158-164
• /
• 1999

This paper investigated and evaluated the NASA's Shuttle Imaging Radar-C (SIR-C) multiple frequency SAR data for differential backscattering effects of microwave from the surface geological materials overlying the skarn type mineralization. Although an integrated approach in mineral exploration is more cost effective and is well in use, there are still many technical and scientific issues to be further investigated and researched. In this study we have reprocessed several sets of previously surveyed exploration data and experimented with fuzzy logic digital fusion of the preprocessed data with respect to chosen exploration targets. Among the numerous fuzzy logic operators, which are currently available for a data driven integrated exploration strategy, we used varying combinations of fuzzy MIN, fuzzy MAX, and fuzzy SUM operators along with Gamma operator for fusion of exploration data, including the contact metamorphic zone information. The final exploration target tested was a skarn type W-Mo-F mineralization in the study area. The fuzzy logic derived mineral potential anomaly almost exactly matched the differential backscattering anomalies on the C-band and L-band SIR_C data when overlaid on each other. Although this high degree of correlation between these two data sets is remarkable, the differential backscattering anomaly over the skarn type W-Mo-F mineralization in the study area requires further investigation.

• Economic and Environmental Geology
• /
• v.53 no.3
• /
• pp.259-269
• /
• 2020

The use of the geophysical method in mining prospecting has been studied in the Asdaf region (South-East of Morocco). The objective of the study is to examine the aptitude of the electrical technique, in this case induced polarization (IP) and electric tomography, combined with the electromagnetic method (VLF), in the exploration of barite . The result obtained by the pseudo-sections of electrical tomography and that of KH filtration highlighted anomalies of resistant contact (greater than 400Ω.m) and of high charge chargeability (5mV / V). These contacts are hosted in less resistant Devonian age shale and sandstone. The resistivity response obtained at their level is characteristic of the venous structures associated with barite mineralization. The direction of the mineralized veins is parallel to the direction of the fractured zones (NE-SW), which indicates that the mineralization in place is due to the tectonic movements of the Hercynian orogeny (from Devonian to Permian). These veins are aligned with the locations of abandoned mine shafts and with surface mining areas. Geophysical technique therefore seems to play a key role in barite mining exploration.

• Economic and Environmental Geology
• /
• v.8 no.4
• /
• pp.183-201
• /
• 1975

The south and southwestern parts of Jeonra-namdo has been known as an alunite province in Korea. The alunite deposits investigated for the present study are Okmaisan, Seongsam, Bugog, Gasado south, Gasado north, Jangsando, Dogcheon and Jungyongri deposits. The main purpose of this study is to depict the genetical origin of the alunite deposits. The rocks distributed in the areas mentioned above consist chiefly of rhyolitic tuff, breccia tuff and andesitic tuff of Cretaceous age which represent different episodes of volcanic activities during Cretaceous epoch. The attitude of bedding of the tuffaceous rocks varies from place to place but generally dips very gently. The alunite deposits are embedded mostly in the rhyolitic tuff so that they appear as layered deposits, this occurrence may be the result of stratigraphic and lithologic controls. The result of this study can be summarized as below. The mineral sequence studied by the mineral paragenesis and the result of the spectrograph anlyses is such that (1) alunite was formed at first and pyrophyllite was nearly contemporaneous with alunite but pyrophyllite formation can be recognized as a secondary mineralization products, (2) kaoline was succeeded to form later and hematite finally deposited, and (3) pyrite was deposited from the begining to the end of the above mineralization period. The compositional change of host rocks is such that CaO, $SiO_2$ and $Na_2O$ were largely removed from the parent rocks and some $Al_2O_3$ and $SO_3$ were transported by the solution so as to enrich the rocks. The sequencial process of such mineralization has resulted in forming those distinguish mineral zones; alunite, kaoline, pyrophyllite, silicifide and sulphide zone which manifest irregular shape. These deposits were formed by hydrothermal solution which was possibly low temperature and contained sulphuric acid originated from $H_2S$ and $SO_2$ gases.

• Economic and Environmental Geology
• /
• v.7 no.4
• /
• pp.157-173
• /
• 1974

The Red Hill deposit of the Dongjom Copper Mine is the most promising deposit of the mine and under intensive exploration at present although there are eight more deposits of vein type. With total 2160m drilling of 9 holes completed and 400m drilling on two holes underway, the nature of the Red Hill deposit has come more clear. The copper content in the whole ore body is meager so far as the exploration done up to present indicates, but there are evidences that mineralization covers all over the granodiorite cupola at the Red Hill area. The petrological work and assay on the samples taken by the writers indicate that granodiorite rocks can be divided into fresh zone and alteration zone. Alteration zone consists of potassic and argillic zones accompanyied by silicification zone on basis of Lowell and Guilbert model Argillic zone has closely related with a mineralization in the Red Hill deposit. It has been cleared that the alteration acompanyied with the mineralization took place not only &long vertical fissures but also in the irregular lateral zone, the nature of which is unknown. Judging from the results of exploration and petrochemical study on the Red Hill deposit which is imbedded in a southern part of the granodiorite cupola, it can be concluded by the writer's opinion that the Red Hill deposit is possibly a porphyry copper deposit, because the shape of the ore body, mineral zoning and paragenesis and wall rock alteration resemble to those of typical porphyry copper deposits. It is the writers' opinion that more exploration work is required so as to evaluate the deposit.