Manganese Skarn in the Shizhuyuan Polymetallic Tungsten Deposit, Hunan, China

Home , Rhodonite, Spessartine, Tephroite

RESOURCE GEOLOGY, 46(1), 1•`11, 1996

Jingwen MAO*, Bernard GUY**, Louis RAIMBAULT*** and Hidehiko SHIMAZAKI****

Abstract: Manganese skarns in the Shizhuyuan supergiant W-Sn-Mo-Bi-Be deposit consist of spessartine, almandine- spessartine garnet, rhodonite, tephroite, helvite, alabandite, Mn-bearing salite, manganese hedenbergite, Mn-bearing phlogopite and rhodochrosite. The development of the skarn is related, in time and space, to the greisenization-mineralizations subsequent to calcic skarnization and related retrograde alteration. Complexity of mineral assemblages and manganese contents of the minerals increase with distance from the, contact zone of the Qianlishan granite stock. The manganese content of host rocks of the deposit is low, and the source of manganese in the skarn is supposed to be mainly from the hydrothermal solution associated with Yanshanian granite emplacement.

tope compositions of the ore are characterized by Introduction ordinary lead of single stage evolution, and Pb-Pb The Shizhuyuan supergiant polymetallic tung- model ages are in accordance with that of emplace- sten deposit is one of the largest nonferrous metal ment of the Qianlishan granite stock. Based on light deposits in the world, and is characterized by ex- stable isotope data, ZHANG(1989) has proved that tensive development of skarnization and greiseni- the hydrothermal solution responsible for the for- zation. The geologic setting, granitic intrusion, mation of the deposit, is mainly derived from the calcic skarn, and major gangue and ore minerals granite stock in the proximal contact zone, and have been intensively studied in the past ten years mixed with meteoric water in the distal contact by WANG et al. (1982,1987), YANG (1982), LIU et zone. al. (1983), WANG and ZHANG (1988), CHEN et al. It would be worthy to mention that the term gre-

(1992) among others. According to these works, isen (and greisenization) has been used by previ- the Shizhuyuan polymetallic tungsten deposit is ous investigators of the Shizhuyuan deposit with believed to be genetically associated with the somewhat different meaning from the usual one.

Qianlishan Yanshanian granite stock, and strong Greisen in the Shizhuyuan deposit means network skarnization and greisenization are responsible for to massive body mainly consisting of quartz with the precipitation of various kinds of metals. minor fluorite, topaz, feldspars, micas, beryl, After studying sulfur and lead isotopes of ore scheelite, wolframite, bismuth minerals, cassiter- veins, XU et al. (1989) described that ƒÂ34S values ite and pyrite, superimposed on early stage skarns. of galena, sphalerite, pyrite, molybdenite and bis- In the deposit, calcic skarn is predominant and muthinite range mostly from +3 to 9 •ñ; lead iso- magnesian skarn is rare. Development of some Received on November 21, 1994, accepted on March 28, manganese skarns overlapping to the major calcic 1995. skarn has recently been noticed and drawing at- * Institute of Mineral Deposits, Chinese Academy of Geo- tention of many investigators. In the present pa- logical Sciences, Beijing 100037, China ** Departement Geochimie , Ecole des Mines de Saint- per, the characteristics and major skarn-forming Etienne, France minerals of the manganese skarn and the direction *** Centre d'Informatique Geologique, Ecole des Mines de of its formation and evolution will be described Paris, France and discussed. **** Geological Institute, University of Tokyo, Hongo, Tokyo 113, Japan Geologic Setting Keywords: Shizhuyuan tungsten deposit, Polymetallic; Man- The Shizhuyuan polymetallic tungsten deposit ganese skarn, Spessartine garnet, Yanshanian granite, China is situated 13 km southeast of Chengzhou City, 2 J. MAO, B. GUY, L. RAIMBAULT and H. SHIMAZAKI RESOURCE GEOLOGY:

Hunan Province, China. In the Shizhuyuan area, the stratigraphic sequence consists of Precambrian metagraywacke, middle Devonian sandstone of the Tiaomajian Group, dolomitic limestone of the Qiziqiao Group, upper Devonian limestone and marls of the Shetianqiao Group, and dolomitic limestone of the Xikuangshan Group. The Shetian- qiao and Qiziqiao Groups are the main country rocks for the skarnization and mineralization. The mining area is located at the northern end of the Dongpo-Yuemei synclinorium which consists of several subordinate folds, Jinshiling syncline, Gutang anticline, Zhongshan syncline, Chalukou anticline and Jinchuantang syncline. There are a number of faults which can be divided into three groups, striking NE, nearly NS and NW. The first two are large in scale and are characterized by tec- tonic pulsation and inheritance, and act as the con- straints for the magmatic activities and metallogenesis in the area. The last one is rare and weak, and is usually formed after the skarnization and mineralization. It should be emphasized that the fractures striking NNE and NE developed so well Fig. 1 Geologic map of the Shizhuyuan area. that they cut through each other to construct a 1: Quaternary. 2: Upper Devonian dolomitic limestone of closed stockwork fracture system. They show close Xikuangshan Group. 3: Upper Devonian limestone and marls of Shetianqiao Group. 4: Middle Devonian dolo- relationship to the formation of skarns including mitic limestone of Qiziqiao Group. 5: Middle Devonian calcic skarns and manganese skarns, retrograde sandstone of Tiaomajian Group. 6: Sinian metagraywacke. altered rocks and greisen veins. 7: Pseudoporphyritic biotite granite. 8: Equigranular bi- The Qianlishan granite stock occurs in the cen- otite granite. 9: Granite porphyry. 10: Diabase dike. 11: ter of the Dongpo-Yuemei synclinorium. Its out- Sn-Cu mineralized pseudoporphyritic biotite granite. 12: Massive greisen. 13: Massive calcic skarn. 14: Geologic crop is about 10 km2. The granite stock is a com- boundary. 15: Fault. posite one, and is composed, from early to late, of pseudoporphyritic biotite granite (152 Ma), The occurrence of manganese skarn is rather lim- equigranular biotite granite (137-136 Ma), granite ited compared with that of the calcic skarn in the porphyry (131 Ma) and diabase dike. The earlier area. Manganese skarnization develops during the two phases of granite are associated in time and greisenization and base metal mineralization, and space with the polymetallic tungsten deposit. is getting stronger away from the contact zone. The The skarn in the Shizhuyuan area is mainly cal- time and space relations show that the manganese cic skarn, which develops around the Qianlishan skarn is genetically related to the equigranular bi- granite stock as shown in Fig. 1. The calcic skarn otite granite activity. consists of garnet, pyroxene, vesuvianite and wol- It should be emphasized that all of skarns and lastonite. The study by MAO(1991) indicates that greisens in the Shizhuyuan area include some kinds the calcic skarn and massive biotite greisen ob- and some amounts of ore minerals. Recent study served in roof pendants of the granite stock, are by MAO et al. (1993) shows that the two periods of genetically related to pseudoporphyritic biotite mineralizations can be distinguished: (1) skarn- granite. The equigranular biotite granite is respon- greisen W-Sn-Mo-Bi mineralization period asso- sible for the garnet-vesuvianite skarn veins super- ciated with pseudoporphyritic biotite granite, con- imposed on the massive calcic skarn and exten- sisting of the calcic skam W-Sn-Bi stage, porphyry sive greisen veins. Sn-Cu stage, retrograde altered W-Sn-Bi stage and 46(1),1996 Manganese skam in the Shizhuyuan polymetallic tungsten deposit 3

Table I Characteristics of manganese skarn and its zoning.

massive greisen W-Sn-Mo-Bi stage, and (2) greisen W-Sn-Mo-Bi-Be-Pb-Zn-Ag mineralization period associated with equigranular biotite granite, consisting of the stockwork greisen vein W- Sn-Mo-Bi stage, fine stockwork greisen vein Sn- Cu-Be stage, garnet vein W-Mo-Sn stage and Pb- Zn-Ag-Sb vein stage.

Distribution of Manganese Skarn Manganese skarns in the Shizhuyuan area are closely related to greisenization associated with equigranular biotite granite. The greisenization in this period is resposible for the mineralization zon- Fig. 2 Diagram showing the relationship among manga- ing in the Shizhuyuan area. The mineralization nese skarn veins, greisen veins and retrograde altered zone, from the cupolas of the granite stock upward, rocks. 1: Retrograde altered rock. 2: Greisen veins. 3: are successively stockwork greisen W-Sn-Mo-Bi Manganese skarn veins. ore vein zone hosted by massive calcic skarn, fine stockwork greisen Sn-Cu-Be ore vein zone hosted hosted rocks, generally retrograde altered rocks as by marble, distal greisen Sn-W-Be mineralization shown in Fig. 2. When reaching to the calcic skam, ore hosted by marble, and base metal ore zone the veins of manganese skarn disappear rapidly in hosted by marble (Table 1). most cases. Proximal manganese skarn The manganese skarn in this area contains pre- The proximal manganese skarn develops near the dominant almandine-spessartine garnet, minor Mn- contact zone of the Qianlishan granite stock, and bearing pyroxene, helvite, quartz, scheelite and cas- is superimposed on massive calcic skarns, retro- siterite. Pargasite and/or chlorite usually develop grade altered rocks and greisens. The manganese beside the veins of manganese skarn. In the Sn- skarn forms stockwork veinlets up to several doz- Be-Cu ore zone, the manganese skam occurs as ens of centimeters long, and frequently occurs at variable veinlets, such as spessartine veins, the boundaries between the greisen veins and spessartine-rhodonite veins and spessartine-helvite 4 J. MAO, B. GUY, L. RAIMBAULTand H. SHIMAZAKI RESOURCE GEOLOGY:

veins, which are intergrown with many kinds of tephroite skarn consists of an intergrowth of other veins, for example, tiny greisen veins, mus- tephroite and rhodonite, or predominant rhodonite covite veins, tourmaline-fluorite veins and chlo- and interstitial tephroite as well as pyrite, pyrrho- rite-sulfide veins. All veins almost always inter- tite, alabandite, arsenopyrite, galena, sphalerite, sect each other and have very complex mineral fluorite, chlorite and Mn-bearing phlogopite. compositions: as major gangue minerals observed Spessartine-rhodonite skarn, the best developed are muscovite, calcite, fluorite and tourmaline, and association in the area, consists of coarse-grained minor quartz, biotite, margarite, plagioclase, K- spessartine, medium-grained rhodonite and fluo- feldspar,chlorite, epidote,spinel, topaz, phlogo- rite, and minor sphalerite, pyrrhotite, galena, py- pite, apatite, barite, prehnite and zeolites; and as rite, tourmaline, biotite and/or phlogopite. Some- major ore minerals are pyrrhotite, cassiterite and times, manganese skarn enclosed by rhodochrosite pyrite, and minor scheelite, chalcopyrite, sphaler- assemblage are found in the marble. This type of ite, stannite, magnetite, marcasite, molybdenite, manganese skarn is accompanied by Pb-Zn miner- bismuthinite, galenobismutite, native bismuth, ga- alization. Furthermore, some veinlets of spessartine lena, arsenopyrite, bavenite, taaffeite, helvite, Be- and cassiterite are superimposed on the manganese bearing margarite, phenacite, beryl and chryso- skarn veins, especially on the sepssartine-helvite beryl. veins. Those tiny veins are brown in color; and Distal manganese skarn cassiterite crystal generally shows an obvious The distal manganeseskarn mainlydevelops in zoned structure. the Jinchuantang,Henshanling, and Shexinpingar- eas, 0.8-7 kmsouthwest away from the Qianlishan Mineralogy and Paragenesis granitestock (Fig. 1). Manganeseskarns in these The identified manganese-bearing minerals of areas occur as swarms of veins, which are up to manganese skarns in the Shizhuyuan polymetallic several dozens of meters long and several milli- tungsten deposit are spessartine, almandine- metersto centimeterswide. Based on the relation- spessartine garnet, manganese hedenbergite, Mn- ship to the mineralizations,the manganeseskarn bearing salite, rhodonite, tephroite, helvite, alaban- veins can be classifiedinto two types. dite, rhodochrosite and Mn-bearing phlogopite. The first type containspyroxene skarn and gar- The changes in major mineral compositions and net-pyroxeneskarn. The pyroxeneskarn is char- mineral assemblages are a monitor of the evolu- acterized by extensivedevelopment of pyroxene tion of manganese skarns. and fluorite with minor Mn-bearing phlogopite, Garnet: In the manganese skarn, garnet is the quartz, K-feldspar,calcite and rare garnet. The most important mineral. It occurs as subhedral to gamet-pyroxeneskarn characterized by enrichment euhedral and fine-grained aggregates in the proxi- in garnetand pyroxene generally shows a clearzon- mal contact zone, and as euhedral and coarse- ing pattern, consistingof quartz zone, pyroxene- grained, ranging from 0.4 to 1.5 cm in diameters, fluorite zone and garnet-fluoritezone from center aggregates in the distal contact zone. Based on the to outward. Thesetwo typesof skarnscontain zir- time and space relation, garnet can be divided into con, apatite,scheelite, molybdenite, bismuthinite, five types, i.e., (1) garnet in garnet-pyroxene veins arsenopyriteand pyrite. This type of manganese around the stockwork greisen veins in the proxi- skarnis associatedin timeand spacewith low-grade mal contact zone hosted by massive calcic skarn; W-Mo-Bimineralizations, and is formed earlier (2) garnet in garnet veins or garnet-rhodonite veins than the secondtype manganeseskarn. in the Be-Sn-Cu ore zone hosted by marble in the The second type contains helvite-spessartine, proximal zone; (3) garnet in spessartine- rhodonite-tephroiteand spessartine-rhodoniteas- manganoan pyroxene veins nearby mineralized sociations,which are in generalpink or yellowish greisen veins in the distal zone; (4) garnet in gar- pink in color. Thehelvite-spessartine skarn is com- net-rhodonite veins and garnet-helviteveins accom- posed of major spessartineand minor sphalerite, panied by Pb-Zn mineralization in the distal zone; galena,pyrrhotite, helvite, phenacite,alabandite, and (5) garnet in garnet-cassiterite veins superim- scheelite,tourmaline and phlogopite. Rhodonite- posed on the gamet-helvite veins in the distal zone. 46(1),1996 Manganese skarn in the Shizhuyuan polymetallic tungsten deposit 5

Table 2 Representative microprobe analyses of garnets.

Note And: Andradite. Gr: Grossular, Am:Almandine, Sp: Spessartine, Py: Pyrope Electron microprobe analyses show that the first type of garnet belongs to almandine-spessartine garnet (Nos. 78-83 in Table 2). The composition of the almandine-spessartine garnet are plotted in the range of 43.7-51.9 mole % of almandinewith averagevalue of 48.7 mole %, and 3.9-8.2 mole % of grossularplus andradite with average of 5.8 mole %. The ratios of andradite to grossular change from 0 to 1.25. The second type of garnet is,spessartine-grossular garnet whose compositions are in the range of 63.7-86.4 mole % spessartine, 1.4- 25.4 mole % of grossular, and 0.7-8.2 mole % of almandine (Nos. 104-108 in Table 2). All of the third, fourth and fifth types of garnet are in the distal zone. Their compositions show that they are more enriched in spessartine component than those in the first Fig. 3 Chemical compositions of garnet plotted on the triangle dia- and second types from the proximal zone. The gram of spessartine-almandine-grossular+andradite ratios of almandine to grossular are generally 1: Manganese skarn around stockwork greisen veins hosted by mas- about 1.5 to 5 except for a few analyses (Nos. sive calcic skarn in the proximal contact zone. 2: Manganese skarn 1-135 in Table 2). Among them, the third type hosted by marble in the proximal contact zone. 3: Manganese skarn of garnet shows scattered plotted points in Fig. associated with greisenization in the distal zone. 4: Manganese skarn 3. All points are plotted either near the al- associated with base metal mineralization in the distal zone. 5: spessartine-cassiterite veins superimposed on spessartine-helvite mandine-spessartine join or near the grossu- veins. lar-spessartine join, and are characterized by 6 J. MAO, B. GUY, L. RAIMBAULT and H. SHIMAZAKI RESOURCE GEOLOGY:

Table 3 Representative microprobe analyses of pyroxene.

Note: Di: Diopside, Hed: Hedenbergite, Joh: Johannsenite high contents of spessartine molecule ranging from 64 to 95 mole %. The fourth type of garnet in garnet-rhodonite veins is enriched in spessartine, ranging from 81.8 to 87.3 mole %. Their contents of almandine, grossular and andradite are respectively lower than 10 mole %. The garnet in gamet-helvite veins also belongs to spessartine-rich garnet in the range of 68.9-80.6 mole % of spessartine, and 10.0- 16.4 mole % of almandine, with average of 12.8 mole % of grossular plus andradite. The fifth type of garnet consists of spessartine with average value of 67.4 mole %, almandine of 17.1 mole %, and grossular of 14.5 mole %. On the whole, the garnet compositions change toward manganese end-member from calcium-poor almandine-spessartine series, through iron-poor spessartine-grossular to predominant spessartine, Fig. 4 Chemical compositions of clinopyroxene plotted from the proximal zone to the distal zone as shown on the triangle diagram of diopside-hedenbergite- in Fig. 3. In other words, from early to late metal- johannsenite. 1:Pyroxene in the proximal contact zone. logenic stages, the garnet is enriched in spessartine 2: Pyroxene in the distal contact zone. component. A coarse-grained garnet crystal with eight millimeters diameter from a garnet-helvite ish at the center to dark green at the rim, and usu- vein was systematically analyzed for compositional ally develops on the margin of garnet-pyroxene zoning. The result shows that the content of spes- veins. Pyroxene compositions listed in Table 3 and sartine is successively rising whereas grossular plotted in Fig. 4 show that they belong to Mn-bear- decreasing from center to rim. ing salite with 5-15 mole % of johannsenite. Pyroxene: Pyroxene occurs in both the proxi- The pyroxene in the distal zone is pale green in mal and distal zones. In the proximal zone, pyrox- color with pink tune, short or long prismatic in ene is short prismatic in shape, and green in color form, and frequently occurs as aggregates. These with color zoning under the microscope from green- pyroxenes correspond to johannsenite-hedenbergite 46(1), 1996 Manganese skarn in the Shizhuyuan polymetallic tungsten deposit 7

Table 4 Microprobe analyses of rhodonite.

solid solutions with 26-44 mole % of johannsenite molecule (Table 3). According to the definition by ZHAOet al. (1990), the pyroxene with such high manganese contents is named as manganese hedenbergite. Variations of pyroxene compositions in Fig. 4 indicate that they are enriched in MnO from the proximal contact zone of the Qianlishan granite stock to outward. Rhodonite: DEERet al. (1978) pointed out that rhodonite is never pure MnSiO3 but always contains a certain amount of CaO. Rhodonites, pink in color and generally developing as aggregates with radiated structure, are recognized in both the proximal and distal contact zones in the Shizhuyuan deposit. In the proximal zone, the rhodonite oc- Fig. 5 Chemical compositions of rhodonite plotted on the curs as subhedral aggregates and is intergrown with triangle diagram of MnSiO3-CaSiO3-FeSiO3. 1: Rhodonite in the proximal contact zone. 2: Rhodo- margarite, chlorite, scheelite and cassiterite. The nite from rhodonite-spessartine assemblage in the dis- compositions of rhodonite show great changes as tal contact zone: 3: Rhodonite from rhodonite-tephroite shown in Table 4; 46.8-70.0 mole % of MnSiO3, assemblage in the distal zone. 4: Rhodonite in the Bajiazi Pb-Zn deposit (DONG, 1986). 5: Rhodonite in the 13.6-34.0 mole % of CaSiO3 and 12.2-19.3 mole Makeng Fe-Pb-Zn deposit (ZHAOet al., 1983). % of FeSiO3. These rhodonites are composition- ally similar to those from the Makeng Fe-Pb-Zn 1986)(Fig. 5). The rhodonites in the distal zone deposit, Fujian, China (ZHAOet al., 1983), and the are developed together with spessartine or Bajiazi Pb-Zn deposit, Liaoning, China (DONG, tephroites. It seems, on the whole, that the rhodo- 8 J. MAO, B. GUY, L. RAIMBAULT and H. SHIMAZAKI RESOURCE GEOLOGY:

Table 5 Microprobe analyses of tephroite in the distal zone.

nites in the distal zone are richer in MnSiO3 component than those in the proximal zone. They con- tain 72.3-81.1 mole % of MnSiO3, 9.4-16.7 mole % of CaSiO3, and 9.8-11.3 mole % of FeSiO3. Tephroite: The mineral is an end-member of the tephroite-fayalite join, and Mn2+is always replaced by some Fe2+ and Mgt+. Tephroite in the Shizhuyuan area is minor in amount, and occurs as tephroite-rhodonite veins or as interstitials among rhodonite granular crystals. It is anhedral to short prismatic in shape, and colorless under the microscope. Microprobe analyses indicate that the composition of tephroite therein is very uniform Fig. 6 Chemical compositions of tephroite plotted on the with 78.8-82.0 mole % of Mn2SiO4, 13.0-15.4 triangle diagram of Mg2SiO4-Fe2SiO4-Mn2SiO4. mole % of Fe2SiO4and 4.9-7.9 mole % of Mg2SiO4 1: Tephroite from tephroite-rhodonite veins. 2: Teph- (Table 5 and Fig. 6). Some exceptions are analy- roite as interstitials in rhodonite skarn. 3: Tephroite ses given as Nos. 377-379 in Table 5 showing that from Cornwall, England (RUSSELL, 1946). 4: Manga- noan fayalite from Bluebell, British Columbia they are transitional members in tephroite-fayalite (MOSSMANand PAWSON,1976). 5: Manganoan fayalite join with 23.5-23.6 mole % of Fe2SiO4. from Santa Eulalia, Mexico (MEGAW, 1990). 6: Teph- Tephroite is reported from various occurrences roite from Uchucchacua, Peru (BUSSELLet al., 1990). such as the Cornwall manganese deposit (RUSSELL, 1946), Broken Hill Pb-Zn deposit (MASON,1973) 1976), the Primorye Pb-Zn deposit (KAZACHENKO and Uchucchacua polymetallic manganese deposit et al., 1979), the Bajiazi Pb-Zn deposit (ZHAOet al., (BUSSELLet al., 1990). Besides them, manganoan 1990)and the SantaEulalia Pb-Zn deposit (MEGAW, fayalites, knebelites, have also been reported in the 1990). Compared with the tephroites from other Bluebell Pb-Zn deposit (MOSSMANand PAWSON, deposits, the compositions of tephroite in the 46(1), 1996 Manganese skarn in the Shizhuyuan polymetallic tungsten deposit 9

Shizhuyuan deposit are slightly richer in Mg2SiO4 uted within 0-1 kmaway from the contact zone of molecule (Fig. 6). The tephroite with short pris- the Qianlishangranite stock, and base metal min- matic shape being intergrown with rhodonite con- eralization,distributed in 0.8-7 kmaway from the tains less manganese than that being interstitial contactzone. The manganeseskarn begins to de- crystals among the rhodonite aggregates (Fig. 6). velopduring the greisenstage in the secondperiod Helvite: Helvite in the Shizhuyuan deposit is of mineralizationin the Shizhuyuanarea. From subhedral to anhedral in shape, 0.3 to 4 mm long, vicinityto far from the granitecontact, maganese and is often accompanied by spessartine and phlo- contentin manganeseskarn as well as the variety gopite. It contains a lot of tiny opaque minerals. of minerals increase. In particularat the deposi- Electron microprobe analyses show that the helvite tional stage of base metal sulfides, the maganese is characterized by a high content of manganese skarn developsextensively, and thevariety of man- (40.4-42.3 wt % MnO), and contains about 90 mole ganeseminerals and theirmanganese contents still % of helvite molecule. increasein the skarn. Whereis the sourcefor manganesefixed in the Discussion and Conclusion manganese skarn ? The host rocks of the skarns Since the end of 1970's, several scientists have and related mineralizationsin the Shizhuyuande- paid attention to the abundance and behavior of posit are limestone and marl of the Shetianqiao manganese in skarns associated with tungsten de- Group and dolomitic limestone of the Qiziqiao posits. SHIMAZAKI(1977), GUY (1979, 1980), Group of Devonian age. Manganesecontents of DOBSON(1982), NEWBERRY(1982, 1990), DICK the carbonates in the Shetianqiao and Qiziqiao and HODGSON(1982), COELHOet al. (1985), ZAHM Groupsare 223ppm in averageof 76 analysesrang- (1987) have found in different deposits that the ing from 199 to 259 ppm, and 864 ppm in average chemical composition of garnet changes from an- of 174 analyses ranging from 536 to 1600 ppm, re- dradite-rich to spessartine+almandine-rich through spectively (Xu et al., 1989), which are lower than intermediate grossular-rich garnets from early to the average value of their corresponding rocks late stages of skarn formation, and even in a single given by TUREKIAN (1969). Therefore, it is im- garnet crystal from the center to rim. Guy (1979) possible for the strata to provide enough manga- and NEWBERRY(1990) found that pyroxene is nese to form manganese skarns. johannsenite at the latest stage of skarnization in It should be, however, emphasized that the man- some tungsten deposits, such as Costabonne, ganese skarn is a product during the hydrothermal France and Pine Creek, the United States. EINAUDI metallogenic process and related alteration, which and BURT (1982) made a preliminary discussion is closely related to granite activity. Thus the source on this point. Compared with these deposits, the of manganese in the skarn is supposed to be mainly Shizhuyuan polymetallic tungsten deposit seems from the hydrothermal solution associated with to show a more extensive development of manga- Yanshanian granite emplacement. Manganese nese skarnization. could be tranported as chloride complex in hydro- As mentioned above, the Qianlishan granitoid thermal solutions, and its concentration is strongly stock genetically associated with the mineraliza- dependent on temperature and chloride content of tion in, the Shizhuyuan deposit is a composite in- the solution (HOLLAND, 1972). Lowering of tem- trusion. The first pseudoporphyritic biotite gran- perature and dilution of the solution by meteoric ite and second equigranular biotite granite have waters, as suggested by ZHANG (1989), could have been proved to be associated in time and space with caused relatively complete breakdown of manga- mineralizations in the deposit (MAO et al., 1993). nese chloride complex in the solution, as well as The first stage of polymetallic mineralization in- other base metal chloride complexes such as zinc cludes the processes of skarnization, retrograde and lead, and resulted in the increase of manga- alteration and greisenization in the roof pendants nese contents of the skarn with the distance from of the pseudoporphyritic biotite granite. The sec- the granitestock. ond period of polymetallic tungsten mineralization Acknowledgements:We are much gratefulto ev- consists of the processes of greisenization, distrib- eryone who helped us during the field work for 10 J. MAO, B. GUY, L. RAIMBAULTand H. SHIMAZAKI RESOURCE GEOLOGY:

this investigation, in particular to senior geologists tungsten, molybdenum, bismuth, tin (beryllium) deposit. WANGChanglie and XU Youzhi. The paper is a Geol. Explor., 19, 8•`14 (in Chinese). part of the result obtained in a research project en- MAO, Jingwen (1991): Geological characteristics and geochem- titled "The Shizhuyuan polymetallic tungsten de- istry of the Shizhuyuan skarn polymetallic tungsten deposit, China. Sci. Rept., Ecole des Mines de Paris et Ecole des

posit and associated granite", jointly sponsored by Mines de Saint-Etienne, 114p.

Financial Committee of Geological Development MAO, Jingwen, Li, Hongyan, RA MBAULT, L., GUY, B. (1993):

of China and Ministere de l'Industrie et du Com- Spatial-temporal evolution and substance source of the

merce Exterieur, France. The manuscript has been Qianlishan granite stock and its relationship to polymetallic improved through critical reviews by Masaaki tungsten deposit in the Shizhuyuan district. In Current SHIMIZUand an anonymous referee. Research in Geology Applied to Ore Deposits (P.F. HACH- ALI, J. TORRES-RUIZ and F. GERVILLA eds.), 633•`636.

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中華人民共和国湖南省柿竹園多金属タングステン鉱床のマンガンスカルン

毛景文・ベルナールギイ・ルイラムボウ・島崎英彦

要旨:柿竹園巨大W-Sn-Mo-Bi-Be鉱床にみられるマも伴って,このマンガンスカルンが形成された.鉱物共ンガンスカルンは,満バン柘榴石,鉄バン-満バン柘榴生の複雑さと鉱物中のマンガン含有量は,千里山花崗岩石,バラ輝石,テフロ石,ヘルビン,閃マンガン鉱,含体との接触部から離れるに従って大きくなる.鉱床の母マンガンサーラ輝石,マンガン灰鉄輝石,含マンガン金岩である石灰岩やドロマイト中のマンガン含有量は低い雲母,菱マンガン鉱からなる.本鉱床ではまず石灰質スので,マンガンは熱水溶液を通じて主として燕山期花崗カルン化作用とその後退変質があり,引き続いて起こっ岩よりもたらされたと考えられる. たグライゼン化作用・鉱化作用に,時間的にも空間的に