Journal of Geosciences ，Osaka City University Vo l. 16 ，Art. 1，p. 1- 10. 恥1arch ， 1973

Stam .noi "dite-Canfiel :dite Association as . Related .tO .Vein M :ineralization at the Ashio Mine ， Japan*

Takeshi NAKAMURA and Nobuyuki AIKAWA

(With (With 1 Table ，1 Text -Figure ，and 2 Plates)

Introduction Introduction

Since Since RAMDOHR (1944) recognized four different minerals which he caUed “ Zinnkies (?I)-(?IV)" ， the mineralogical interests on and related minerals have been greatly increased. increased. The studies on the minerals of the system Cu-F か Sn -S have been promoted by the development of the electron microprobe method and the x-ray diffraction method ，and many new minerals ，namely (MARKHAM and LAURENCE ， 1965); (KATO ， 1969) 1969) which may be identical to hexastannite formerly called “ Zinnkies (?1)" (RAMDOHR ， 1960 ，MOH and OTTEMANN ， 1962) and to “ stannite jaune" (ORCEL ，1943 ，L 三VY ， 1956 and 1967); 1967); (L 三VY ，1967) ，and rhodostannite (SPRINGER ， 1968) have been proposed. In Japan ，YAMAGUCHI (1939) first described “brown stannite" from the Ikuno mine ， Hyogo prefecture. He used the name “brown stannite" due to its color. The occurrences of the mineral sim i1 ar to “brown stannite" from the Ikuno mine have been reported from the the subvolcanic hydrothermal deposits (NAKAMURA ，1954 ，YAMA ム1955 ，IMAI ，FUJIKI ，and TSUKAGOSHI ， 1967). But the detailed mineralogical studies on “brown stannite" had not been made because of its finer grain size and its complex textures associated with other sulphide sulphide minerals ， until the modes of occurrence of stannoidite from the Akenobe ，lkuno and Tada mines ，Hyogo prefecture ， I(onjo mine ，Okayama prefecture ，and Fukoku m 泊e， Kyoto prefecture ， together with the modes of occurrence of mawsonite from some of these mines ，were confirmed by the optical ， x-ray di 仔raction ，and electron microprobe methods (KATO ，1969 ，KATO and FUJIKI ， 1969). As f or the minerals of the system C 1.ト F か Sn-S from the Ashio copper mine ， the :fir st author (1954 ，1961 ，and 1970) clarified the m .o des of occurrence of “brown stannite" and “brownish orange stannite" by using the optical and x- ray powder diffraction methods ， the anisotropic anisotropic “brown stannite" being identical to stannoidite (hexastannite) and the “brownish orange stannite" to mawsonite ， but the further deta i! ed mineralogical studi es by the optical ， x- ray diffraction ，and electron microprobe methods have been needed to confirm the chemical composition and the of these n1Inerals. During the studies of copper- sulphide ores from the ore veins at the Ashio copper mine ， the authors were able to find the canfieldite-stannoidite association. This association has not yet been known from the subvolcanic hydrothermal polymetallic deposits in Japan.

The occurrence of the mineral canfieldite ~las only reported from the gold 岨 bearing silver quartz quartz veins at the Ohmidalli Mine situated in the vicinity of the Akenohe lnine ，Hyogo prefecture prefecture (SUMITA ，1969 ，KATO ，unpublished).

* Contribution from the Department of Geosciences ，No. 260. 2 Takeshi NAKAMURA and Nobuyuki AIKAWA

The present paper dealts with the canfieldite-stannoidite association as related to vein mineralization mineralization at the Ashio copper mine ， taking the modes of occurrence of stannoidite into into consideration.

Modes of Occurrence

The ore veins of the Ashio copper mine ， the subvolcanic hydrothermal ore veins with copper ， ，lead ，bismuth ，and tin ores ， occur in the Ashio rhyolitic body. Taking the mining area in the Ashio rhyolitic body as a whole ， three hypogene mineral zones ， a (central) Sn-W-Bi-Cu zone ，an (intermediate) C ル As ・Zn zone ，and a (marginal) Zn-Pb-Cu-As zone ， are are distinguished on the unit of ore vein group and single ore vein (NAKAMURA ，1954 ，1961 ， and 1970 ，KUSANAGI ， 1963). Each hypogene mineral zone shows the characteristic mineral association association as shown in the following.

Central Central Sn ・W 帽 Bl ・Cu zone: Ca ssiterite ，ferberite ， native bismuth ，bismuthinite ， native gold ，wittichenite ， ，stannite ，stannoidite ，canfieldite ，mawsonite ，

，bornite ，pyrite ，quartz ，sericite (2M t，and 2M 1 + 1M) ，-chlorite 0 (Ib ，β=90 ). Intermediate Intermediate Cu-As-Zn zone: Cassiterite ，schee Ii te ，arsenopyrite ，chalcopyrite ，pyrrho- 0 tite ， ，galena ，tetrahedrite ， ，bornite ，iron-chlorite (Ib ，β=90 ;

and IIb) ，quartz ，sericite (2M h and 2M 1 十1M) ，fiuorite ，apatite. Marginal Marginal Zn-Pb-Cu-As zone: Ar senopyrite ，chalcopyrite ，sphalerite ，galena ，stannite ， 0 pyrite ，stibnite ，iron-c h1 orite (Ib ，β=90 ) ，sericite (2M 1 + 1M ，and 1M) ，calcite ， quartz. quartz. Among these hypogene mineral zones ， the Sn-W-Bi-Cu zone characterized by the presence presence of tIn ore occurs in several places on the surface ， but it dies out suddenly with depth '. In the case of the largest Sn-W-Bi-Cu zone around the Bizendate (1 ，272.8 m above 、 sea-level ， the highest peak of the Ashio mining area) ， tin bonanza is only restricted in the

higher higher mine-levels lying above the upper 13th level (1 ，050 m above sea 圃 level) ， while the

.Cu-As 圃 Zn zone develops widely and deeply to the deeper mine-levels. The high-grade tin and copper ore (more than 1 % Sn) from the Sn-W-Bi-Cu zone is chiefly composed of cas-

siterite ，stannite ，chalcopyrite ，quartz ，and sericite (2M 1 polytype). The mineral of the ~ystem Cu-Fe-Sn-S ，namely “brown stannite" ， is often associated ¥ vith cassiterite and stannite stannite in the high-grade tin and copper ore. From the optical and x-ray powder diι fraction fraction studies the anisotropic “brown stannite" is identical to stannoidite (hexastannite). Under the ore microscope ，two types of mode of occurrence of stannoidite are dis- tinguished: tinguished: i) i) Stannoidite associated with myrmekitic intergrowth of stannite and chalcopyrite ， ii) ii) Stannoidite which occurs as granular aggregate in chalcopyrite. Canfieldite Canfieldite occurs in close association with the second type of stannoidite. Seeing Seeing from the sequence of mineralization ， the fo Il owing four main stages of minera Ii- zation zation with polyascendent character are recognized in the ore veins in the Ashio rhyo Ii tic

body: (i) earlier Sn-W 岨 Bi-Cu stage ，(ii) intermediate Cu-As 四 FeS 2 stage ，(iii) later Zn-Pb-Cu stage ，and (iv) barren stage. The deposition of stannoidite and canfieldite took place in

the the earlier Sn 圃 W-Bi-Cu stage. Stannoidite 圃 Canfieldite Association as Re/ated to Vein Mineralization 3

Ore Microscopic Properties

The studied specimen (Loc. U pper 17th .level ， Shinsei vein) was collected from the copper-tin copper-tin vein in the higher-mine levels in the central Sn-W-Bi-Cu zone. It is a massive

copper-tin copper-tin ore containing chalcopyrite ，stannoidite ，cassiterite ，and quartz as visual con 帽 stituents. stituents. Stannoidite is brass brown in color with meta l1 ic luster ，and the is dark gray. gray. U nder the ore microscope ， stannoidite occurs as granular aggregate in chalcopyrite ， and canfieldite occurs sporadica l1 y as a granular sma l1 patch in the granular aggregate of stannoidite stannoidite (P 1. 1， Fig. 1). The distribution of canfieldite patch is confined in the granular aggregate aggregate of stannoidite ，and the replacement texture of stannoidite by canfieldite is not present. present. The ore microscopic properties of stannoidite are summarized as shown in the following: Color: Color: Brownish rose. Bireflectance: Bireflectance: Distinct; granular texture observable; light salmon brown to brown in in air. More distinct in oiI ， but no significant change in tin t. Anisotropism: Anisotropism: Strong; granular texture observable; dark orange red to ye l1 0wish gray gray in air. Scarlet to gray-yellow in oi I. Internal Internal reflection: N ot present. 2 2 VHN (Vickers micro-indentation hardness in kgfmm ): 245 kgfmm for a load of 25 25 g. (VHN for the associated chalcopyrite: 22 0- 185 kg fmm 2 for a load of 25 g). The ore microscopic properties of canfieldite are summarized as shown in the fo Il owing: Color: Color: grayish white in air. Bireflectance: Bireflectance: N ot present. Anisotropism: Anisotropism: Very weak or not present. Internal Internal reflection: Not present. 2 2 VHN (Vickers micro-indentation hardness in kg fmm ): 137 kg fmm for a load of 25 25 g.

X-Ray Powder Diffraction Data

The x-ray powder diffraction data for stannoidite of the present study obtained by diffractometer diffractometer using Ni- fi1 tered Cukωradiation are listed in Table 1， together with those for

original original stannoidite (KATO ， 1969). The obtained d 圃 values of the present examination show good agreement with those of original stannoidite. In this experiment ，a very small amount of canfieldite is present in the powdered material of stannoidite ， but its amount is too little little to get the proper d-value of canfieldite.

Qualitath'e Qualitath'e Cbemical An alysis by Electron Electron Microprobe Metbod

The qualitative chemical analysis by the electron microprobe method was carried out on stannoidite and canfieldite of this study. In In the present experiment an electron microprobe analyser with a bealn diameter 1μ was used. The scanning pictures for silver (AgL~) ， copper (CuK~) ， iron (FeK~) ， tin (SnL~) and zinc (ZnK~) are shown in Pl. 2， Figs. 2，3，4，5，and 6. It is evident from the scanning 4 Takeshi NAKAMURA and Nobuyuki AIKAWA

Table Table 1. X-ray powder data for stannoidite

Stannoidite Stannoidite (original) ， Konjo Stannoidite from Shinsei mine ，Japan ，After A. KATO (1969) vein ， AshiQ copper mine

(hkl) (hkl) d(A) d (A)

200 5.4 0 55 5.39 5 011 011 5.14 E 5.15 2 103 103 4.83 10 4.82 6 112 112 4.13 3 4.15 3 211 211 3.72 2 213 213 3.11 100 3.11 100 310 310 3.00 2 312 312 020 2.70 15 2.69 15 400 006 006 215 215 2.4 6 2 、 206 206 2.39 4 2.4 0 3 305 305 413 413 2.20 2 2.20 2 017 017 2.12 1 510 510 2.00 2 503 503 303 303 420 1.906 70 1.904 50 b 026 026 600 600 1.795 2 611 611 233 233 1.621 20 b 1.623 20 b 143 143 613 613 219 219 426 1.556 3 1. 556 5 136 136 800 800 1.3 46 1.346 6

Cu/Ni Cu/Ni radiation Cu/Ni radia tion

pictures pictures that in the areas underlain by canfieldite conspicuous AgLω ー and SnL~-intensities are are recorded and in the area underlain by stannoidite conspicuous CuK~- ， FeK~- ， and SnL~-intensities are recorded. Qualitative distribution of tin (SnL~) ， iron (FeK~) ， copper (CuK~) and si1 ver (AgL~) obtained from an electron microprobe analysis along the line

A-B in P l. 1， Fig. 2 is shown in Text 圃 Fig. 1. The probe trace commences at A in stannoidite ， passes passes across quartz (black) ，then canfieldite and ends in stannoidite. The significant content

of si1 ver and tin for canfieldite and the significant content of tim ，iron ，and copper for stan 圃

noidite noidite are shown in the graphs of electron probe (Text 圃 Fig. 1). Stannoidite-Canfieldite Stannoidite-Canfieldite Association as Re/ated to Vein Mineralization 5

111111111

Stanno i. d ite ‘ Ca nf ie 1d it e IStannoi d ite Sn Lα

Ele Kα Kα

Cu Kα

10μ Ag Lα A 8 Text-Fig. Text-Fig. 1. Graphs of the electron probe showing the qua Ii tative distribution of of tin (SnL~) ， iron (FeK~) ， copper (CuK~) ， and silver (AgI~) along the the line A-B in Pl. 1 ，Fig. 2

As the presence of germ むlium in canfieldite was not detected by the electron microprobe analysis ，canfieldite of the present experiment may belong to the canfieldite proper of argyrodite-canfieldite argyrodite-canfieldite series.

This This experiment is qualitative ， but it is worthy to note that stannoidite of present ex 四 periment periment shows the presence of zinc (pl. 2， Fig. 6).

Concluding Concluding Remarks

The stannoidite "'l canfieldite association has not yet been known 'from the subvolcanic hydrothermal hydrothermal polymetallic deposits in Japan. The present paper dealts with the modes of occurrence occurrence of stannoidite and canfieldite in the ore veins at the Ashio copper mine. This mineral mineral association occurs in the copper-tin vein of the central Sn-W-Bi-Cu zone and is genetically genetically related to the earlier Sn-W-Bi-Cu stage of the vein mineralization in the Ashio •

6 Takeshi NAKAMURA and Nobuyuki AIKAWA

rhyolitic rhyolitic body.

Acknowledgement

The authors wish to acknowledge with grateful appreciation to Professor Takeo W ATANABE ，Akita University ， for giving generous support and advice during the work. Thanks are also due to the Japan Electron Optics Laboratory Co. Ltd. ， for the cooperation to the electron microprobe analysis ，and to the geological engineers of the Furukawa Mining Co. Ltd. ，and of Ashio Mining Office ， for their cooperation to the field work. The pre- paration of the plate was assisted by Mr. Taizo KIMURA to whom the authors are also indebted. indebted.

References References

Edit. Edit. Com. IMA ・IAGOD Meetings '70 (1970): Introduction to Japanese minerals. Geological Survey Survey of Japan ， p. 1-208. IMAI ，H. ，Y. FunKI ，and S. TSUKAGOS H1 (1967): Late Mesozoic to Early Cenozoic metallogenic province province in the westem Kinki district. Mining Geology ，17 ， p. 50 (in Japanese). ， KATO ，A. (1969): Stannoidite ，Cus (F e，Zn)2SnSS ，a new stannite-like mineral from the Konjo mime ，Okayama prefecture ， Japan. Bull. National Science Museum ，Tokyo ，12 ， p. 165-172. KATO ，A. and Y. Fun 阻 (1969) : The occurrence of stannoidites from the xenothermal ore deposits of of the Akenobe ，Ik ¥J1 no ，and Tada mines ，Hyogo prefecture ，and Fukoku mine ，Kyoto prefec .. ture ， Japan. Mineralogical Journal ，5， p. 417 -4 33. KUSANAGI ， T. (1963): The mineral zoning at the Ashio mine. Mining Geology ，13 ， p. 35 -4 0 (In (In Japanese). LEVY ，C. (1956): La stannite jaune du gisement de Vaulry (Haute-Vienne). Bull. Soc. Franc. Mineral. Mineral. Crist. ，79 ， p. 383-391.

L 企VY ， C. (1967): C 'o ntribution a la mineralog ie ， des sulfures de cuivre du type CU3XS4 ，Mem. Bur. Rech. Rech. Geol. Minieres ，54 ， p. 1-178. 、 MOH ，G. and J. OTTEMANN (1962): Neue Untersuchungen an Zinnkiesen und Zinnkiesverwandten. Neues Jahrb. Mineral. Abh. ，99 ， p. 1-28. NAKAMURA ， T. (1954): Tin mineralization at the Ashio copper mine Japan. Jour. Inst. Polytech. ， Osaka City Univ. ， Ser. G ，5， p. 35-52. NAKAMURA ， T. (1961): Mineralization and wall-rock alteratiort at the Ashio copper mine. Japan ， Jour. Jour. Inst.Polytech. ，Osaka City Univ. ， Ser. G ，5， p. 53-127. NAKAMURA T. (1970): Mineral zoning and characteristic minerals in the polymetallic veins of the Ashio copper mine. Volcanism and Ore Genesis ， Univ. of Tokyo Press ， p. 231-246. ORCEL ， J. (1943): Composition mineralogique et structure des zones cupriferes du minerai stan- 凶fere de Vaulry (Haute-Vienne); caracteres du nouveau type de stannite qu'elles renfermen t. Bull. Bull. Soc. Franc. Mineral. Crist. ，66 ， p. 435 -4 51. RAMDOHR ， P. (1960): Zum Zinnkiesproblem. Abh. Preuss. Akad. Wiss. ， Math.-naturw. K 1. 4， p. p. 1-30.

RAMDOHR ， P. (1960): Die Erzmlneralien und ihre Verwachsungen. 3. Auflage ，Akademie 国 Verlag ， erlin. B 'erlin.

S' PRINGER ，G. (1968): Electronprobe analyses ， of stannite and related tin minerals. Miner. Mag. 36 ， p. 1045-1051. Su 阻 TA ，M. (1969): Geology and ore deposits of Omidani mine ，especially on the Fusei deposits. Mining Geology ，19 ， p. 133-146. (in Japanese) UYTENBOGAARDT ，W. and E.A.J. BURKE (1971): Tables for microscopic ident がcation o[ ore minerals. minerals. Second rev. ed. ，Elsevier Pub l. Co. Y AMAE ，N. (1955): Microscopic study for ore minerals from the Ashio copper mine (1) stannite and bomite. bomite. Jour. Jap. Assoc. Miner. Petr. and Econ. Geol. ，39 ， p. 21-30. (in Japanese) YAMAGuem ，K.(1939):Ore deposits of the Ekuno mine and their zonal arrangement ，(I) ， (I0. Jour. Jour. Assoc. Miner. Petr. Econ. Geol. 21 ， p. 257-275; 22 ， p. 25-37 (In Japanese). •

Plate Plate 1 8

Explanation Explanation of Plate 1

Fig. Fig. 1. Photomicrogra l' h of polished section showing the mode of occurrence of canfieldite in stannoidite. stannoidite. Th e texture of granular aggregate of stannoidite is observable. One nico l. Cf: canfieldite ， Std: stannoidite ，Cp: chalcopyrite ，Q: quartz. Loc. Upper 17th level ，Shinsei vein ， Ashio Ashio copper mine.

Fig. Fig. 2. Back scattered electron picture for canfieldite and stan n. oidite. The line A-B marks the trace trace ofthe electron microprobe analysis shown in Text-Fig.1. Cf: canfieldite ， Std: stannoidite ， Cp: chalcopyrite ，Q: quartz. Loc. Upper 17th level ，Shinsei vein ， Ashio copper mine.

、

'. T. T. NAKAMURA & N . AIKAWA: Stannoidite-Canfieldite Association Plate 1

0 '.1 rnm

20μ a -

Flate Flate 2 10 10

Explanation Explanation of Plate 2

1 Fig. Fig. 1 • Back scattered electron picture showing the distribution of canfieldite (Cf) ，stannoidite (Std) ，chaleopyrite (Cp) ，and quartz (Q). The scanning pictures of Figs. 2ム4，5，and 6， are obtained obtained on the same field as shown in Fig. 1 respectively. Loc. Upper 17th level ，Shinsei vein ，Ashio copper mine.

Fig. Fig. 2. Scanning picture fOF si1 ver (AgL~)

Fig.3. Fig.3. Scanning picture for copper (CuK~)

Fig. Fig. 4. Scanning picture for iron (FeK~)

Fig.5. Fig.5. Scanning picture for tin (SnL~)

Fig.6. Fig.6. Scanning picture for zinc (ZnK~)

、 •

T. T. NAKAMURA & N. AIKAWA: Stannoidite 圃 Canfieldite Association Plate 2 2

50μ50μ 3 4

50μ50μ a ・ 5 6

50μ50μ