Hydrogenous Deposits, Which Mainly Includ

MINING GEOLOGY,40(3),159•`173,1990

Geochemistry of Manganese Deposits in the Tokoro Belt, Northeastern Hokkaido, Japan*

Jai Ho CHOI** and Yu HARIYA**

Abstract: Strata-bound manganese oxide and manganiferous iron deposits are distributed in the Tokoro Belt. The manganiferous iron deposits are found between the bedded chert and greenstone whereas the manganese oxide deposits usually occur within the radiolarian chert. These deposits are regarded to have been formed by submarine hydrothermal activities, as inferred from the mode of occurrence of the country rocks. The manganese oxide ores are characterized by low Fe/Mn ratios which are similar to those of the submarine hydrothermal deposits. The average Fe/Mn ratios of manganese oxide and manganiferous iron deposits are 0.017 and 6.41, respectively. It is considered that the fractionation between Fe and Mn takes place during their formation. According to the distribution of the trace elements (Co, Ni, Cu, and Zn) in the manganese oxide ores, two types can be distinguished: one type has rather high chemical concentrations as hydrogenous deposits, the other has low concentrations as submarine hydrothermal deposits. These compositional trends and geological evidences on the occurrence of manganese deposits suggest that they are syngenetic and have been formed by precipitation from submarine hydrothermal activities with limited hydrogenetic effects during early Cretaceous.

of hydrothermal mounds near the Galapagos 1. Introduction Rift. It has been proposed that the deposits of The ferromanganese deposits on the ocean this area have been formed by submarine floor fall largely into two major categories; volcanic processes. It is considered that the hydrogenous deposits, which mainly include concentration of elements in ferromanganese the ferromanganese nodules and encrusta- deposits distributed around the submarine vol- tions, and submarine hydrothermal deposits. canic areas is enriched by hydrogenous effects Submarine hydrothermal deposits, which can which take place before and after volcanic ac- be correlated to the hydrogenous deposits, are tivities. It is thought that these deposits result characterized by low Fe/Mn ratios and low from both submarine hydrothermal and hy- concentrations of the trace elements (Co, Ni, drogenous origin. Cu, and Zn). The discoveries of manganese- Accumulation of the geochemical data of rich and ferromanganese-rich crusts near ac- manganese deposits from various present-day tive spreading centers of the oceans are be- marine environments and better understan- lieved to suggest that these deposits have ding of their origin make it possible to apply originated mainly by hydrothermal activity these data to deduce the origin of terrestrial (BONATTIand JOENSUU,1966; BOSTROMand manganese deposits. As compared with fer- PETERSON,1966). CORLIsset al. (1978), how- romanganese deposits on the oceans, those on ever, reported hydrogenous Fe-Mn coatings the land, which occur within the sedimentary rock sequences, have been considered to be Received on February 3, 1990, accepted on April 27, formed primarily by submarine hydrothermal 1990. activities (BONATTIet al., 1976; SNYDER, 1978; * Part of this study was presented at the Annual Meeting BOSTROMet al., 1979; MAGARITZand BRENNER, of Mineralogical Society of Japan (June 12, 1989) 1979; VARENTSOVet al., 1988). ** Department of Geology and Mineralogy, Faculty of Several manganese oxide and manganifer- Science, Hokkaido University, Sapporo 060, Japan ous iron deposits occur within the Tokoro Keywords: Manganese oxide deposits, Manganiferous Belt located in the northeastern part of Hok- iron deposits, Hydrothermal deposits, Hydrogenous deposits kaido. These deposits are of little economic

159 160 J. H. CHOI and Y. HARIYA MINING GEOLOGY: value because of their small size, but their geochemical study should provide informations on the formation environments of the Tokoro Belt. The ore deposits in this area are assumed to have been derived from submarine volcanoes, as inferred from the mode of occurrence of the country rocks (SUZUKI and OHMACHI, 1956). Based on these facts, the Tokoro manganese oxide and manganiferous iron deposits are thought to be ancient analogues of present submarine hydrothermal manganese deposits. In the present study, we describe the possible origin of several manganese deposits in the Tokoro Belt, viz. Wakasa, Hokkaido, Syotosibetu, Koryu, Hinode, Nikura, and Kokuriki mines, on the basis of geological observations and results of geochemical analysis of samples.

2. Geological Setting The regional geology and distribution of manganese oxide and manganiferous iron Fig. 1 Generalized geological map of the Tokoro deposits in the Tokoro Belt are presented in Belt (after SAKAKIBARAet al., 1986) and locality of Fig. 1. Three stratigraphic units, namely: manganese oxide and manganiferousiron deposits . Yubetsu, Saroma, and Nikoro Groups, have been recognized within the Tokoro Belt (SAKAKIBARAet al., 1986). The Nikoro Group is Cherts are usually red to reddish brown in col- represented by Upper Jurassic to Lower or and composed principally of radiolarian

Cretaceous greenstone complex with subor- tests. The ore bodies strike NE to N30•‹E and dinate cherts and limestone beds. On the con- dip 20•‹ to 40•‹NW. The ore bed possesses trary, Saroma and Yubetsu Groups are com- variable thickness (0.5 to 2.5 meters) and posed of clastic sedimentary rocks of Upper shows an irregularly lenticular shape. The ores Cretaceous age. Conglomerate, sandstone, are characteristically rich in silica, but poor in shale, and alternating beds of sandstone and iron (URASHIMA and TSUTSUMI, 1956). It is com-

shale constitute the Saroma Group. The Yubet- posed of braunite, caryopilite, and orientite su Group consists mainly of alternating beds (OSAWA et al., 1989). of sandstone and mudstone. Hokkaido Mine: The Hokkaido mine occurs The manganese oxide and the manganifer- 4.5 km northwest of Kunneppu Town. Man- ous iron deposits are confined to the Nikoro ganese ores are concentrated within lenticular Group. The former deposits, which are con- bedded cherts. It is up to 0.5-3 meters in formable, stratiform, and strata-bound, occur thickness and 3-10 meters in length (KISHI- in the radiolarian cherts. The latter are dis- MOTO and WATANABE, 1956). The dominant tributed between the bedded chert and green- minerals which constitute ore bodies are braun- stone. The cherts usually occur towards the ite, rhodonite, hematite, and quartz. This hanging walls of the ore deposits. mine produced 500 metric tons of ore with Wakasa Mine: The Wakasa mine is situated at 40%Mn in average. the tributary of the Bushi River. Manganese Hinode Mine: The Hinode mine is located deposits typically occur in the bedded cherts . near a junction of the Ponoromushi River and 40(3), 1990 Geochemistry of manganese deposits in the Tokoro belt 161 the Oromushi River, about 10 Km southwest from each mine. The samples were crushed us- of Kitami City. Manganese ores were ex- ing a tungsten-carbide mill and pulverized in ploited from three pits during 1948(?)-1955 an agate mortar. Approximately 0.7 g of the ig- (HASEGAWA et al., 1983). Manganese deposit of nited sample powder and five times flux of this mine was known to be 20-80 cm thick and anhydrous lithium tetraborate (Li2B4O7)were had an extension of several meters (Doi et al., mixed and fused to make a glass bead to deter- 1965). This deposit exists in red bedded cherts mine the major elements, using an X-ray and has a strike of N20•‹-60•‹E and a dip of fluorescence spectrometer (Philips PW 1404) 20•‹-50•‹SE. Manganese ores consist mainly of with Rh anode. Another 2.5 g of finely ground braunite and with minor amounts of hollan- sample mixed with 3.5 cc polyvinyl alcohol dite and Mn-pumpellyite. solution was pressed into a pellet to determine Syotosibetu Mine and Koryu Mine: These trace elements. Analytical procedures and con- mines occur near the Hinode mine. Strata- ditions are similar to those described bound manganese oxide deposits usually oc- elsewhere (CHOI and HARIYA (in press); cur in red bedded cherts. In the Syotosibetu TSUCHIYAet al., 1989). X-ray diffractometer mine, the manganese beds intercalated in (XRD) analysis were performed to determine cherts exhibit similar attitudes. The ore bodies constituent minerals. occur in close association with cherts. It 4. Analytical Results and Discussion means that manganese and silica were originally precipitated together. Well-fractionated 4.1 Ores manganese ores with the separation of cherts Braunite is the major ore constituent were formed later by diagenesis (FUJIWARA et mineral in most manganese oxide ores from al., 1962). The strike of manganese deposit of the Tokoro Belt. Hollandite, cryptomelane, the Syotosibetu mine is NE5•‹-38•‹, and it has todorokite, and birnessite are common. a dip of 46•‹-72•‹SE. Minerals identified in the Todorokite and birnessite were presumably manganese ores of this mine are: braunite, formed during supergene oxidation of the hollandite, todorokite, and birnessite. deposits (HEWETTand FLEISCHER,1960). The Kokuriki Mine and Nikura Mine: These manganiferous iron ores are made up mainly manganiferous iron ore deposits are located of very fine-grained or dusty hematite and 20 Km north of Kitami City. The ore bodies quartz crystals associated with braunite and generally lie between the cherts and green- bixbyite (AKASAKAet al., 1988). Table 1 shows stone. Cherts overlie the ore bodies whereas the manganese minerals identified in bedded the greenstone underlies them. The thickness type deposits of the Tokoro Belt. The and extension of lenticular ore bodies are mineralogy of manganese deposits of this area extremely variable. Bodies found are from 50 is described by HARIYA(1961) and YOSHIMURA meters long with 1 meter thick to 700 meters (1969). long with 10 meters thick (BAMBA, 1984). The The main constituent element of the man- ores, which are dark brown in color, are gen- ganese oxide ores is manganese while iron is erally compact and massive and consist of very present in minor amounts (Table 2). The man- fine-grained hematite and quartz associated ganese oxide ores studied are characterized by with braunite, Mn-pumpellyite, and okhotsk- low Fe/Mn ratios and the average Fe/Mn ite. Radiolarian tests replaced by quartz are ratio of ores is 0.0165 which is similar to those distributed in the matrix of chalcedony and of submarine hydrothermal deposits. In con- dusty hematite in the cherts (TGGARI et al., trast, the Fe/Mn ratio of the hydrogenous 1988). deposits is about 1. This means that Fe/Mn ratios of the manganese oxide ores from the 3. Analytical procedure Tokoro Belt are similar to those of manganese Fresh samples of country rocks (radiolarian deposits found near present-day submarine chert and greenstone) and ores were collected hydrothermal centers where they form by rap- 162 J. H. CHOI and Y. HARIYA MINING GEOLOGY:

Table 1 Manganese minerals identified at the manganese oxide and manganiferous iron deposits in the Tokoro Belt

XXX: Abundant; XX: Common; X: Rare

Fig. 2 Ternary diagram of CRERARet al. (1982) with the analyzed samples from the Tokoro Belt and fields of deep- sea manganese nodules and submarine hydrothermal deposits . Also shown are fields of Franciscan samples after CRERARet al. (1982), Apennine samples after BONATTIet al. (1976), Orthrys and Perachora samples after PANAGOS and VARNABAS(1984), and Alpine and Oman samples after PETERS(1988) .

id precipitation from hydrothermal solutions . chemical stability limits of compounds of iron The average Fe/Mn ratio of manganiferous and manganese show that iron tends to pre- iron deposits is 6.41. The Fe/Mn ratio of cipitate first at lower Eh and pH which is manganiferous iron deposits is approximately close to the source, while manganese main- three hundred times greater than that of man- tains a longer residence time in solution . ganiferous oxide deposits. The mechanism for Therefore, the Fe/Mn ratio is found to be this separation of iron and manganese can be higher in the manganiferous iron deposits . explained as follows (KRAUSKOPF,1957; BONA- The analytical data of manganese ores general- TTIet al., 1972). In the process of formation of ly fall in the hydrothermal area in the Mn-Fe- submarine hydrothermal deposits , the (Cu+Ni+Co)•~10 ternary diagram (Fig. 2). 40(3), 1990 Geochemistry of manganese deposits in the Tokoro belt 163

Table 2 Chemical composition of ore deposits and associated rocks in the Tokoro Belt (SiO2•`P2O5: wt.%,

Ba-Zr: ppm) 164 J. H. CHOI and Y. HARIYA MINING GEOLOGY:

Table 2 Continue 40(3), 1990 Geochemistry of manganese deposits in the Tokoro belt 165

Table 2 Continue

Concentrations of trace elements (Co, Ni, Cu, and Zn) in the Tokoro manganese oxide ores are generally lower compared with those in hydrogenous deposits. According to the distribution. of the trace elements in the manganese oxide ores studied, two type can be distinguished (Fig. 3): HN1, K1, and K2 show rather high chemical concentrations as in the hydrogenous deposits, whereas S8, H3, and W13 show low chemical concentrations which are similar to those of submarine hydrothermal deposits. Submarine hydrothermal Mn-oxide deposits such as those found in the EPR (East Pacific Rise) and the Galapagos areas generally contain trace element (Co, Ni, Cu, and Zn) concentration well in excess of nor- mal pelagic sediments but have an order of magnitude lower than in the hydrogenous ferromanganese deposits (CRONAN,1980). The trace elements of manganese ores from the

Fig. 3 Representative trace element profiles for Tokoro Belt are classified into two types even manganese oxide ores from the Tokoro Belt. S: though the ore deposits have been thought to Syotosibetu mine H: Hokkaido mine W: Wakasa be formed by the submarine hydrothermal mine HN: Hinode mine K: Koryu mine origin. The variable amounts of trace elements 166 J. H. CHOI and Y. HARIYA MINING GEOLOGY:

over 1 percent are usually occurred in the mineralogical assemblage which includes hollandite. The average Ba content of manganese oxide deposits is higher than those of manganiferous iron deposits. The lower Ba content of the latter is simply due to its precipitation more closer to the sources. The Ba-enrichment in deep-sea sediments has been interpreted by three principal processes: (a) biological activity in surface layers, (b) lower accumulation rates, (c) hydrothermal supply (PETERS,1988). It is thought that the Ba-enrichment in the manganese oxide deposits is related to absorption by the Mn oxides during the time where these deposits were in contact with sea water. It is suggested that the rate of Fig. 4 Zn-Co-Ni diagram for manganese oxide precipitation of Mn phases was lower and ores. Solid triangles: hydrogenous deposits (deep- their residence time was greater so that the ab- sea manganese nodules) from various environment sorption was higher. MURRAY(1975) reported (after CRONAN, 1980); solid circles: submarine that Ba is enriched by adsorption into certain hydrothermal deposits (after CRONAN,1980). hydrous manganese dioxide. 4.2 Country rocks are thought to indicate that the elements have The country rock of the ore deposits con- differing origins. sists of bedded cherts, usually red in color. The relationship between the two types of Cherts are composed mainly of fine-grained deposits are indicated in Fig. 4, where the ma- quartz in which abundant radiolarian fossils jority of submarine hydrothermal deposits are are observed. The radiolarian chert was plotted on the line between Ni and Zn in the originally biogenic siliceous ooze similar to field of low concentration of Co. The that forming in the modern ocean basins (CHIP- hydrogenous deposits occupy a field which is PING, 1971). The cherts of the Wakasa, Hok- relatively high and towards the Co corner of kaido, Koryu, Hinode, Syotosibetu,. and the Zn-Co-Ni triangle. Some samples in- Kokuriki mines yield early Cretaceous (middle cluding HN1, K1, and K2 from the Hinode, Barremian-early Aptian) radiolarian fossils Syotosibetu and Koryu mines are plotted in such as Thanarla conica, Eucyrtis micropora, the fields characteristic for hydrogenous Diborachlas tytthopora, Podobursa tricola, origin. On the contrary, the samples including and ,Irchaeodictyomitra lacrimula. The fossil S8, H3, and W.13 from.the Hokkaido, and data show that manganese oxide and Wakasa mines fall in the submarine hydrother- manganiferous iron deposits in the Tokoro mal origin area. The trace elements such as Belt were formed almost simultaneously dur- Cu, Ni, and Zn are primarily hydrothermal in ing a relatively short period around ca. 110- origin whereas Co is considered to be of 120 Ma (IWATAet al., in press). predominantly hydrogenous origin (CRERARet Various elements and the average chemical al., 1982). Co has an exceptional crystal field composition of country rocks from the preference for adsorption by tetravalent Mn manganese oxide deposits and manganiferous oxides (BURNS,1976). iron deposits are shown in Table 3. Ba is usually considered to be enriched in As compared with the cherts of manganif- hydrothermal fluids. In our samples the Ba erous iron deposits, those of manganese oxide contents are highly variable ranging between deposits are enriched in TiO2, Al2O3, MnO, 100 ppm and 4 percents. Ba concentrations and K2O and are depleted in Ba, Co, Ni, Cu, 40(3), 1990 Geochemistry of manganese deposits in the Tokoro belt 167

Table 3 Average chemical composition of manganese oxide and manganiferous iron ores and siliceous country

rocks in the Tokoro Belt (SiO2-P2O5: wt.%; Ba•`Zr: ppm)

Zn, Pb, Th, and Sr. The high concentrations of, Al2O3 and TiO2 show the presence of detrital material and CaO is a product of nor- mal pelagic sedimentation (PANAGOS and VARNAVAS,1984). Considering trace elements, it is notable that the concentration of Co, Ni, Cu, Zn, and Ba is lower in the manganese deposits than in the manganiferous iron deposits. The relatively high trace elements (Co, Ni, Cu, Zn, and Ba) reflect the submarine hydrothermal influence during the formation. The origin of the silica in these samples may be deduced by comparing their Si versus Al concentrations (TOTH, 1980). In the Si-Al Fig. 5 Si-Al discrimination diagrams. Besides the discrimination diagram (Fig. 5), most of the analysed samples, the fields of hydrothermal and data of the Tokoro manganese oxide deposits hydrogenic deposits according to CRERAR et al. fall in the hydrothermal deposit area except (1982) are indicated. 168 J. H. CHOI and Y. HARIYA MINING GEOLOGY:

hydrothermal and biogenic origins as mention- ed above. This mined out area is considered to have been controlled by the strong influence of solutions from the source rocks such as recent submarine hydrothermal deposits (HONNOREZ et al., 1981; CRONANet al., 1982). This is con- sistent with field observations which show that greenstone is always found at the manganiferous iron deposits in the Tokoro Belt. The trend of MnO is different from that of Al2O3. It reflects that the scavenging of Mn phases was almost non-existent because of high precipitation rates and short residence time of Mn phases in the sea water. In the Koryu mine (manganese oxide

Fig. 6 Correlation diagram for Ti02 and Al2O3 deposit), manganese horizons are intercalated from the Tokoro samples. with red cherts (Fig. 8). The element profiles of the Koryu mine show that a good correlation exists between Al2O3 contents and that of for some data from the Koryu mine. Accor- major elements except SiO2 and MnO. It is ding to a model. proposed for the formation of thought that these elements are primarily the Tokoro manganiferous deposits by BAMBA detrital because submarine hydrothermal (1984), ferruginous silica gel has been formed manganese deposits generally precipitate far by submarine effusive processes. However, away from the source and have relatively a round or oval shaped radiolarian tests replac- limited effects of hydrothermal activities. Ac- ed by quartz are distributed in the matrix of cording to their concentrations, trace elements chalcedony and dusty hematite in the cherts. (Co, Ni, Cu, Zn, and Ba) show good correla- This suggests that chests of the Tokoro Belt tion with MnO. It is considered that the were formed by hydrothermal silica as well as scavenging of Mn compounds occurred biogenic silica. The Al is primarily detrital, be- because of the low precipitation rates and long ing added to the sediment in clay minerals residence time of Mn compounds in the sea (CRERARet al., 1982). water. MURRAYand BREWER(1977) showed The element Ti is basically immobile in that Co, Ni, Cu, Zn, and Ba are enriched by hydrothermal solution and considered to be a adsorption from sea water into certain measure of clastic input (SUGISAKI,1984). The tetravalent Mn compounds. As a result of relatively high TiO2 values in manganese oxide high adsorption capacity of Mn compounds, deposits suggest some mixing of detrital trace elements are strongly enriched in sub- material during precipitation. Such an origin marine ferromanganese nodules (KRAUSKOPF, is supported by the extremely good correlation 1956; BURNSand BURNS,1979). of Al with Ti (Fig. 6). 4.3 Formation of the Tokoro manganese Geological data and chemical profiles of the deposits Nikura mine (manganiferous iron deposit) The distribution and field relations of show that greenstone forms the stratigraphic manganese oxide and manganiferous iron base and the contact with the overlying Fe-Mn deposits in the Tokoro Belt are similar to horizon and cherts (Fig. 7). A1203 shows good those of present submarine hydrothermal correlation of major elements (TiO2, Fe2O3, volcanoes (RONA, 1978; LALOU, 1983). These MgO, CaO, Na2O, and P2O5) and all trace ore deposits were formed almost simultaneous- elements in the concentration profiles across ly during early Cretaceous time. The country the outcrop. Silica is inferred to be of both rocks and ores are concordant, and both have 40(3), 1990 Geochemistry of manganese deposits in the Tokoro belt 169

Fig. 7 Chemical profiles for the samples from the Nikura mine. Sample locations are shown in the outcrop sketch map. 1-2: Fe-Mn horizon (N2- N3; N1 was sampled this horizon but chemical profiles are not shown in this diagram). 3-5: chert (N4-N6). 6-12: greenstone (N7-N13). 13- 14: chert (N14-N15).

similar features. Thus, ores and country rocks cesses: have been formed in the same environment (1) Penetration of cold seawater through and were subjected to similar geologic pro- deep fracture areas characterized by high heat cesses since their deposition. flow. The formation of the Tokoro manganese ox- (2) Occurrence of seawater-volcanic rock ide and manganiferous iron deposits is con- reactions leading to ascent of metal-enriched sidered to have involved the following pro- hot solutions through gradients of decreasing 170 J. H. CHOI and Y. HARIYA MINING GEOLOGY:

Fig. 8 Chemical profiles for the samples the Koryu mine. Sample locations are shown in the outcrop sketch map. 1-4: chert (K9-K12). 5-7: Mn horizon (K13-K15). 8-10: chert (K16-K18).

temperature and pressure. Such a process is (3) Precipitation of Fe phases occurred in an suggested by experiments on the seawater- environment with low Eh and pH values as basalt interaction by BISCHOFFand DICKSON those for the source rock, while the deposition (1975). They show that substantial amount of of Mn phases took place at a later stage in an trace elements such as Mn, Fe, Ni, and Cu can higher Eh and pH because of their higher be dissolved and transported to the sea floor solubilities. by the altered seawater and precipitated as (4) Enrichments in trace elements in some metalliferous sediment. manganese oxide deposits due to hydrogenous 40(3), 1990 Geochemistry of manganese deposits in the Tokoro belt 171 influence which probably occurred subsequent Piemontite from the manganiferous hematite ore to submarine hydrothermal activities. It is con- deposits in the Tokoro Belt, Hokkaido, Japan. sidered that the formation of submarine Miner. and Pet., 38, 105•`116. hydrothermal ferromanganese deposits or BAMBA, T. (1984): The Tokoro Belt, A tectonic unit of the highly fractionated iron and manganese central axial zone of Hokkaido. Jour. Fac. Sci. Hok- deposits is ultimately controlled by the process kaido Univ., ser. IV, 21, 21•`75. of hydrogenous deposition either at the site of BISCHOFF, J. L. and DICKSON, F.W. (1975): Seawater- basalt interaction at 200•Ž and 500 bars: implica- volcanism or close it (Roy, 1981). tions for origin of sea-floor heavy-metal deposits and

Thus, we assume that manganese oxide and regulation of sea-water chemistry. Earth Planet. Sci. manganiferous iron deposits in the Tokoro Lett., 25, 385•`397. Belt have been mainly formed by submarine BONATTI, E. and JOENSUU, O. (1966): Deep sea iron hydrothermal activities during early Creta- deposits from the South Pacific. Science, 154, ceous time. 643•`645. BONATTI, E., KRAEMER, T. and RYDELL, H. (1972):

5. Conclusions Classification and genesis of submarine iron-

manganese deposits. In Ferromanganese Deposits on (1) The manganese oxide and manganif- the Ocean Floor (HORN, D. ed.), Lamont Doherty erous iron deposits in the Tokoro Belt were geological observatory of Columbia University, mainly formed by submarine hydrothermal Palisades, NY, 149•`166.

activity. BONATTI, E., ZERBI, M., KAY, R. and RYDELL, H. (1976): (2) The trace elements (Co, Ni, Cu, and Metalliferous deposits from the Apennine ophiolites: Zn) of manganese oxide deposits reflect a Mesozoic equivalents of modern deposits from change from hydrothermal condition to oceanic spreading centers. Geol. Soc. Amer. Bull., hydrogenous condition. 87, 83•`94. (3) Fossil data show that these deposits BOSTROM K. and PETERSON M. N. A. (1966): Precipitates were formed almost simultaneously during a from hydrothermal exhalations on the East Pacific short period of ca. 110-120 Ma. Rise. Econ. Geol., 61 1258•`1265. BOSTROM, K., RYDELL, H. and JOENSUU, O (1979):

(4) The geology and chemical profiles Langban; an exhalative sedimentary deposit?. Econ. show that the formation of manganiferous Geol., 74, 1002•`1011. iron deposits is largely associated to sub- BURNS, R. G. (1976): The uptake of cobalt into fer-

marine hydrothermal activities whereas forma- romanganese nodules, soils, and synthetic manganese

tion of manganese oxide deposits had less (IV) oxides. Geochim. Cosmochim. Acta, 40, effects of such activities. 95•`102. Acknowledgments: We would like to thank to BURNS, R. G. and BURNS, V. M. (1979): Manganese oxide. Prof. S. Yui of Hokkaido University for In Marine Minerals (BURNS, R. G. ed), Mineral. Soc. critical reading and valuable suggestions. We Amer. Short Course Notes, Vol. 6. Washington are indebted to Dr. K. Iwata of Hokkaido D.C., 1•`46. University for the identification of radiolarian CHIPPING, D. H. (1971): Paleoenvironmental significance fossils. We wish to thank to Messrs. S. Terada of chert in the Franciscan Formation of western California.. Geol. Soc. Amer. Bull., 82, 1707•`1712. and T. Kuwajima of technical officers of Hok- CHOI, J. H. and HARIYA, Y.: Trace element concentrations kaido University for XRF facility and prepar- of manganese deposits in the Tokoro Belt, Hok- ing the samples. We are grateful to Dr. P. kaido, Japan. Jour. Fac. Sci. Hokkaido Univ., ser Gautam of Tribhuvan University for language IV, (in press). revision. One of us (J.H.C.) gratefully CORLISS, J. B., LYLE, M. and DYMOND, J. (1978): The acknowledges the financial support obtained chemistry of hydrothermal mounds near the through a Japanese Government Student Galapagos Rift. Earth Planet. Sci. Lett., 40, 12•`24. Scholarship. CRERAR,D. A., NAMSON,J., CHYI, M. S., WILLIAMS,L. and FEIGENSON,M. D. (1982): Manganiferous cherts Reference of the Franciscan Assemblage: I. General geology, ancient and modern analogues,. and implications for AKASAKA, M., SAKAKIBARA,M. and TOGARI, K. (1988): 172 J. H. CHOI and Y. HARIYA MINING GEOLOGY:

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北海道常呂帯に分布するマンガン鉱床の地球化学的特徴

崔宰豪・針谷宥

要旨:北海道常呂帯の中生代層には酸化マンガン鉱床と Zn)の含有量は水成起源のような高いものと熱水起源の含マンガン鉄鉱床が分布している.含マンガン鉄鉱床はような低いものに分類される. 放散虫チャートの薄層を上盤とし,枕状溶岩を下盤とすこれらの地質関係と化学分析の結果,常呂帯のマンガる層状鉱床であり,酸化マンガン鉱床は放散虫チャートン鉱床は白亜紀初期頃,部分的に水成起源の影響を受け中に存在する層状鉱床である.これらの鉱床はチャートてはいるが,主に海底熱水活動によって金属元素の濃集. のような珪堆積岩を伴っていることから海底における火が行われて形成されたと考えられる.

山-堆積性鉱床と考えられる. 固有名詞の漢字表記含マンガン鉄鉱石と酸化マンガン鉱石のFe/Mn比の Hinode:日の出,Hokkaido:北海道,Kokuriki:国力, 平均値は6.41と0.017であり,酸化マンガン鉱石は現在 Koryu:興隆,Nikoro:仁頃,Nikura:仁倉,Saroma:

の深海底熱水鉱床のような低いFe/Mn比で特徴づけら佐呂間,Syotosibetu:小利別,Tokoro:常呂,Wakasa: れる.酸化マンガン鉱石中の微量成分(Co, Ni, Cu, and 若佐,Yubetsu:湧別