In the Peloritani Mt•

RENDlCO!'<'T1 DELLA SOCIETA. ITALL\NA Dl MINERAI.OGIA E PETROLOGIA, 1985, Vol. ~O, pp. 289-294

A first occurrence of gersdorffite in the Peloritani Mt•. (Sicily N.E.)

MAURIZIO TRISCARI Istituto di Scienze della Terra dcll'Univcrsita, Via dei Verdi 75, 98100 Messina

ABSTRACT. - Geooorfflte and tetrahedrite occur fire observed for the first time in the Pelo in association with quartz and carbonate gangue ritani Mts. area, of N.E. Sicily. The only in vein mineralization from the Mts. Peloritani (N.E. Sicily). These phases were studied using previous known determination of a gersdorf X·ray, electron microprobe and optical methods. fite mineralization in Italy being the one by The gersdoffile found for the first time in the ARTINl (1903). The gersdorffite is found in Mts. Pc10ritani proved to have a 6.44 % Sb Cu-Pb-Zn-As-Sb vein deposits in the Zil1l content as well as minor amounts of Fe, Co and Cu; the tetrahoorite is a ferroan variety (4.66 % area, south of the village of Fiumedinisi Fe). The mineral assemblages arc very similar 10 (neat Messina), on the eastern flanks of the nearby Cu, Sb, Ag sulphide and complex sulphosalts Peloritani Mts· The Zilll vein system is deposits which are regarded as hydrothermal in considered to be continuation of the « S. Car origin. X.ray data confirm that this gersdorffite has a P2,3, low·temperature ordered structure as 10» Sb-Cu-Ag mineralization, a system of ex~ted from the likely deposilional conditions of uncorformable fissure veins, steeply dipping the ore deposits in the area. or almost vertical, cutting Paleozoic phyllites Key-words: Sicily, Pcloritani Mts., ore minerals, and also containing (less commonly) scheelite gersdorffite, tetraheddte. associated with sulphides and complex Sb -Cu.Pb (Ag-Fe) sulphosalts. Further infor mation on the deposit is provided by DoNATI PRIMA SEGNALAZIONE DJ GERSOORFITE NEl MONTI PELORITANI (SICILIA) et al. (1978) and TRISCARI et al. (1982). RIASSUNTO. - Viene segnalata per la prima volta la presenza di gersdorffite nei M. Peloritani (Sicilia N.E.). La mineralizzazione a gcrsdorffite e tetmedd Experimental method8 te in ganga quarwsa-carbonatica (sidedte ed anke The mineralogy and paragenesis of the rite) apparc filoniana discordante. Lo studio e: stato condotto medianle microscopia ottica in lure ri deposits were studied by reflected light Acssa, diflrattometria di polveri a RX e microsonda microscopy and X-ray powder diffractions elcltronica. La gersdorffite si dislingue per I'ele using CUKll and CoKa radiation. Chemical vato contenuto in Sb (6.44 %), come pure per (electron microprobe) analysis was carried minori Fe, Co e Cu, mcntre la tetraoorite presenta out using a Cambridge Microscan V instru un 4,66 % di Fe. La paragencsi e ampiamente confrontabilc con ana!oghe vidne mineralizzazioni ment operated with an accelerating voltage a solfuri e solfosali cli Cu, Sb e Ag considerate di of 15 KV. Pure metals were used as standard origine idrotennale. I dad dell'analisi a Raggi X except for Fe and S were pyrite was used as confermano per questa gersdorffite un gruppo spa :dale P2,) in pieno accordo con le condizioni mine standard. Results presented are mean values rogenetiche dell'area esaminala. of eight analyses, for each one, four ten seconds counts were recorded, and the data Parole chiave: Sicilia, M. Peloritani, minerali me then averaged, corrected for background and talliferi, gersdorffite. tetraeddte. deadtime, as well as for atomic number and fluorescence effects using the computer IntrodUClion program of DUNCOMB et al. (1969). The reflectance was measured using a Reichert X-ray diffraction, electron-microprobe and Spectral Microphotometer with a Zeiss WTiC optical studies were carried out on gersdorf- standard approved by the Commissi<1n on 290 M. TRISCARI

Ore Microscopy. Microhardness was mea products arc observed: limonite, malachite sured using a Vickers diamond pyramid and azurite. Gersdorffiitc in reflccted light indenter employing a load of 100 gr. is seen as cubic idiomorphic masses and euhedral crystals with typical (100) cleavage observable as characteristic triangular pits. Field occurrence All sections studied showed evidence of This occurrence of gersdorflitc lies in a intense cataclastic deformation. In some small group of discordant veins, mainly sections very rare calcopyrite was observed, quartzitic in composition, that form pan of always well rounded, quite often bordered a vein system cutting Hercynian phyllites of by an encircling rim of covelline, and always the so-alled Mandanici Unit. This unit is conrained within the quartz. The early Icgarded as part of the Calabro-Pe1oritan formed phase is gersdorffite and a second arc, considered a complex ovenhrusting episode of mineralization has brought the structure; has a medium-Iow metamorphic tetrahedrite which in part replaces the grade and it chiefly consists of phyllites, gersdorffite. It seems that the tetrahedrite is garnet and/or chloritoid phyllites, quartzites, also associated with intense cataclastic metabasites and cristalline limestones (AMo phenomena; the substituting tetrahedrite is DlO MORELLI et al., 1976; BoNUDI et al., mainly present in the mylonitic zones. Both 1982; FERLA. 1982 a, b). The deposits of phases occur togheter and sometimes the the Peloritani Mu were on~ considered to tetrahedrite contains distinct euhedral cubes be late magmatic in nature, but nowadays of gersdoffite (6g. 1 and fig. 2). are generally considered as suata bound ores The gersdorffite has been affected by {FERLA, 1982 b}, which have been secon repeated episodes of clastic deformation: darily mobilized by relatively recent hydro Euhcdral cryslals of gersdorffite show thermal activity. On the Peloritani Mts the fracturing and penetration by tetrahedrite tectonic sedimentary character of some of veinlets. Following the characteristic (100) these deposits is stiJI recognizable in a few c1eavage,·the mechanical stresses have rcdun.-J areas, where small primary Pb, Cu, Zn the gersdorffite to an aggregate of irregularly deposits of simple composition were worked shaped grains; late quarlz with undulose over the last few decades. The genesis of extinction fills the main veins. Only tetra the sulphide ores locally appears to be hedrite has been affected by an intense spatially and temporally bound to the alteration to covelline; where covcllinc is presence of basic metavolcanics ID the observed within gersdorffite it occurs only hercynian phyllites of the Mandanaci Unit as an alterarion of tetrahcdrite. Some parts (ATZORI et al., 1973; FERLA, 1982 a, b). of the veins show an abundllnce of chaleo These primary strata-bound deposits, have pyrite with tiny euhedral crystals of pyrite been reworked by late tectonic events, that diffusely scattered, also in the form of strings in the investigated area involved hydro and curved lines. Tetrahcdrite shows a grey thermal activity by which discordant veins white colour and takes a good polish, ore bodies were deposited. The veins are sometimes with a very light brownish tint: between 5 and 30 cm wide, chiefly quartzitic it is completely dark under crossed nicols. in composition, with ankerite-siderite gangue. The average strike is NNE-SSW; these veins Gersdorflite also polishes well: it is white outcrop at an height of about 250 m above in colour, sometimes with a very light sea level in the Zilll area, south of the yellowish tint. Zoning has not been observed village of Fiumedinisi some 25 Km south in this locality. All sections studied are of Messina. clearly isotropic. Although RAMDOHR (1980) reports that slight compositional variations in gersdorflite can be ascrived to submicro Mineralogy scopic intergrowth with chloantite, Ihis The main vein system consists of gersdorf mineral has not been observed optically or fite and associated tetrahedrite; gangue in XRD analysis. minerals are quartz, siderite and ankerite. Reflectance measurements on tetrahedrite Next to the surface, secondary alteration fall in the range 30.3-32.5 % at 589 nm. A FIRST OCCURRENCE OF GERSOOII.FFITI; IN THE PELORITANI MTS. 291

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Fig. I. - ChaloopyrilC: (brithl wblft'J in a Fig. 2. - EuhednJ gc:ndorffile crystals lwbiu) lc:trahc:drilC: mnlel ltrt'y), crossinc gersdorffilC: with 5UbslilUling lelrlhedrite. P.P.L. 400 x. (whild. P.P.L. 400 x.

835) are slightly different to those observed Reflectance measurements on gersdorRlte in Ihis work. Several X-ray powder dif fall in the range 44.8-47.0 % at 589 nm. fraction patterns were run for tetrahedrite These values, while in good agreement and for gersdorflite. The results are given with data from GALOPIN et al. (1972) (Te in table I and 2. From the observed d trnhedrite 30.7 - Ger,dorflite 47.5), VAU values, cell parameters were calculated fol GHAN et al. (1978) (Tetrahedrite 30-30.5 lowing the cell refinement program of Gersdorffite 46.3-53.8), PICOT et al. (1982) PREWlrT modi6ed by CoPLEY (1975). (Tetrahedrite 32.6 • Gersdocffite 45.4), show The unit cell edge measured was a. = signilicamly lower values for gersdorffite 10.377 A for tetrahedrite and ao = 5.694 A Ihan the IMAjCOM data, perhaps because for gersdorffite. of measurement of material of different composition. In 6g. 3 are shown the spectral Gangue minerals are quartz and the reflectance curves (air) for tetrahedrite and carbonates siderite and ankerite; quartz for gersdorffite. VHN values vary in the veins often show included fragments of the range 275-322 for tetrnhedrite and 634-717 host rock (phyllite). for gersdorffiites, both at 100 gr load. Secondary alteration products observed Published data are: GALOPIN et al. (1972) are malachite, azurite and limonite. In the (Tetrahedrite 328-367 and gersdorflite 665 nearby locality of « S. Carlo It' a much bigger 743), VAUGHAN et al. (1978) (Tetrahedrile vein system with the same strike directions 285·322 and gersdorffite 520·907). The and gangue minerals, studied by DoNATI et COM data for gersdorffite. refer 10 synthetic a1. (1978) and TRISCARI et al. (1982), show material {rhe material reported also in the following assemblage (in order of }.c.P.D.S.. card 12·705 and the values (782. decreasing abundance): tetrahedrite. chalco- 291 M. TRlSCARI

TA,BLE 1 -- .- Values 0/ cl ohs. and cl CIlJc.; cetl edge .. parameUrs /0' th, eXQmined tetrahedrite .. A ~, tll. ._. d C&tc.

~ • .. ~ !>.1118 .. .n 3.e7tl 3.1569 '00" ,.- 2.5l95 ...... '" '" " 2.77e 2.773 " 2.5M 2.!>95 -= n 2 .....9 ,.- ~. • 2.:123 ,.~ n. • 2.119 2.11' ,~ ,.= ,.= B • ,,, • L_ ,.- ~ M L= ,.- ro. • t.781 L", , L_ L~ , , , HO • ,.- L_ - L~ .. = , 1.&&5 ,,, n L_ ,.- n' I..M 1..91 ... 1. &611 1..67 Fig. J. _ Spectral Rellectance Curves (AIR) for 1.&11 1.412 gersdorffite (A) and tetrahedrite (8); Standard '" • Zc:in WTiC. • I.n7 L", •••.•• (lMA/COM) -n' • L", L", -- PICOT et al.. 1982 ,~ • 1.2.02 1.2.0 -- This work. ,,, • 1.111 1.111 = • L_ 1.0i3 1.057 L~ pyrite, boumonite. stromeyerite, bismuthini • te, galena, pyrite, sphalerite, pentlandite, - t,~.t& covelline, arsenopyrite. boulangerite, jameso UIH', ". • 10.377 nite. argentite, digenite as well as secondary products as malachite, azurite, goethite and for synthetic stOichiometric NiAsS (YUNO, Iimonite. 1962): it is noticeable that previous litera ture reports show that the parameter of Discu8sion natural gersdorffites range from 5.60 A (PEACOCK et al., 1940) 10 5.731 A (OLS The formula of gersdorffite is NiAsS, it HAUSEN, 1925). The crystal structures known is cubic P213. KLEMM (965) observed that for gersdorffiles (Pa3, P213, PI) were well Fe and Co can substitute for Ni, and described by BAYLlSS et a1. (1967, 1968) PALACHE et al. (1944) noted that Sb can and BAYLISS (19669, 1982 b) and the reader also substitute for As giving the variety is referred to the work of YUND (1962) corynite, ahough this has been recently and BAYUSS 0982 b) for relevant literature. proved to be only an Sb bearing gersdorffite In his study, BAYUSS (1969) of more than (BAYLlSS, 1982 a) so that use of this a dozen gersdorffites and related minerals, varietal name is unnecessary. The cell size noticed that gersdorffite with small cd1 sizes of gersdorffite from the examined locality commonly occurs with calcite and sulphides is similar to the cell size of '.69 A such as pyrite and pyrrothite, while gersdorf- A FIRST OCCURRENCE OF GERSDORFFITE IN THE PELORITANI MTS. 293

TABLE 2 TABLE 3 Va/u~s 01 d ohs. and dca/c.; etU edge RepresentatilJ~ electron microprobe ana/yses parameters lor the examin~d g~rrdorff;te 01 gersdorffite and tetrah~dr;te 0/ the pusent study ~, 1ft. ._. ....Ic...... ,. ...., m ..= ...... • .. 1< ...... •••• .... 0_", •• " >0••" u, " ,.~ ,.~- • ~ vs..) ,.~ .." .....,.. " ,.~ '" '00 ,.- , m ., 2.)2) 2.)2" ...... U...... ~ " 2.013 2.013 ~ • L_ L_ • Lm L~ (HAWLEY et al., 1961)· These two other '"m ., I.ne 1.716 phases have not been observed in the as m , 1.6"3 I.U3 semblages from the locality studied and are not mentioned in othet paragenetic sequen· ,~ 1. 57~ 1.579 ces from the Peloritani Mls. " I.~l 1.52. BAYLlSS (1982 b) also confirmed, through '"~ ", , 1."22 1."23 chemical analyses on thirteen gersdorffite '" ••3111 1.311. samples, that Co content causes a decrease '" • Lm Lm in the cubic unit cell, and As increases it. ~ • 1.21' 1.2'73 Furthermore as the (001) and (110) re ." • 1.2"'3 Lm flections may be used in space group dif ,n • 1.21'" 1.21. ferentiation (BAYLlSS, 1969) the presence ~ • 1.162 1.162 in this gersdorffite of the (11 0) reBection in , 1.116 1.116 all the examined specimens indicate a cubic .u'" L_ L_ P2 13 structure; the (001) was always looked

~ " L_ l.e1 for but never found. • Heating experiments at 500"C and 600"C »' L_ L_ • carried out by the same author, indicate a ,.~ ,.- • crystal structure change with the loss of the - (100) reflection first, and the (001) later. From these heating experiments it seems likely that the P2 13 form is the low-tem perature, ordered phase. fite with large unit cell size commonly occurs Chemical analyses (electron microprobe) with siderite lind arsenides such as skutteru are shown in table 3. Ag, Zo, Au, Cd, Pb dite and saffiorite; the presence of cobalt and Bi were also looked for in the gersdorf. and iron being ubiquitous in arsenic rich fite and Au, Cd, Te, Pb, Bi in the tetrahedri· environments. Of these accessory minerals, te, but nOt found. In the gersdorffite chemical only siderite, wich decomposes at 500u C, analyses showed a substitution of Ni by Co indicates any limitation to formation tem and Fe; it is worth also noting that the high peratures. The presence of only gersdorffite Sb and Cu contents ate probably related to rules cut temperatures higher than 700" C. the associate tetrahedrite. In the tetrahedrite Above that temperature it would be repre particularly high values are found for Sb sented by niccolite and maucherile following and Fe. The lesser commonly associated the reaction mineral phase showed normal characteristics and were quite similar to the mineral 12 NiAsS + (As) assemblages of the nearby deposits of «S. Carlo .. , the main difference consisting NiAs + Ni llAs8 + 3 As + 12 S only in the presence of gersdorffite and a M. TR1SCARI lesser number of associated minernls. Both Mts., proved to be a low-tempernture, deposits have in common strike directions ordered phase of space group P213. main minc=rnls and similar ganguc=s: chemical Acknowledgemenls. - This work was arri!!d OUI and physical data, as well as microscopic at tne Dept. of Geolotlical Science: of tne University observations and the accessory phases obser of Aston in Birmingham, with lne supporl of a ved for this mineralization of the Zilli area NATO-Consiglio Nazmale delle: Ricc:rchc: fe:Uow next to Fiumedioisi (Messina, Sicily), agr«: ship. I wish 10 thank Dr. D.}. VAUCHAN for his hdpfull critici5III of the: manuscript, the: above with the data of the previous workers: this mmtionc:d [)rc:pl. of Geology for the: kind assistance first observed gersdorffite in the Pe10ritani provided .nd Mn. C. BICK for tiping it.

REFERENCES

AMODIO MDRELLI L. et al. (1976) _ L'arco ca/abm· FEItLA P. (1982 aj - Aspeni stfutlufali e composi pe/oritano nei/'omgene appnminico-maghrebide. ziona/i delle sequenu aistalline pfealpine nei Mem. Soc. CeoJ. hal., 17, 1·60. M. PeJoritani. In «Guida alia Geologia della ARTINt E. (190}) . Note minera/ogicbe sullll VIII Sicili~ OccidentalelO, Ed. Catalano R. e D'Ar!,. sllssina. Atti Soc. hal. Se. Na!. Museo Civ. SI. nio B., Socicta Goologia haliana, Guidc Geo 0 Milano, 42, 101-117. githe: Regionali. ATZOttt P., SASSI P. (1973) - The barometric FUL\ P. (1982 b) - Inquadrllmento geologico-petro signipCllnu 0/ tbe SlIoonll pb)"/Jites (Al. Peiori· graftro delle minefllliZUlvoni metlllli/ert nei M. tani). Schwdz. Min. u. Petr. Mill., ,))/2, 24}-2')). Pe(ofitllni (Sidlill). Rc:ndk. Soc. hal. Min. Pell., BAVLlSS P., STEPHENSQ.'l N.C. (1%7) - The crystal 38, I07S·I091. structure 0/ g"sdorffitt. Min. Maa., 36, 38-42. GALOPIN R., HENIV N.FM. (1972) - Microuopic BAYLlSS P., STEPIiENSON N.C. (1%8) - The crystal study 0/ o/Nlqlle minerals. W. Hdler .. Son5 Lld., structure 0/ t.ersdorffite (Ill), 11 distorted IJnd Cambridge, England. disordered pyrite strlU'ture. Min. Maa., 36, HAWLEY jE., STAHTON' R.L., SMITH A.V. (1%1) 940-'J47. Pselld~utectic inlegfowths in IIrsenical ores /fom BAYLlSS P. (l%9j X·rll] dlltll, optical /J1fiSolropism, Sudbury. Canad. Mina., 6, '5,..5'7'. IInd lbtrmlll stlJbility 0/ coballite, gersdmffite JOINT CoMMITTEE ON PoWDEtt DIFFRACTION STAN a"d ulma"nite. Min. Maa., 37, 26.)). DAIDS (1974) - Selected powder diffraction dlltll BAVLlSS P. (1982 a) . A /urtbtr crystlll structure for min""ls. SWlnhrnore, USA. repnrment 0/ cobllltile. Amer. Mine:r., 67, 1048 Kf.El,tM DD. (196') - Syntbesen und Analyse" in Ion den Drejeck dillgrammen FeAsS£oAsS-NiAsS und BAVLlSS P. (1982 b) - A /Uft!Nr crystlll structure FdrCoSTNiS•. Neucs jahr. Abh., 103, 20.5-2". fejinement 0/ g"sdorffite. Amc:r. Mi~r., 67, OLSHAUSEN S.K.V. (192') - S"ukturuntersuchun~en 10'8-1064. naek der Debye-Schefftf Method. Zc:ir. KlISI., BoNUDI G., GIUNTA G., DE VIVO B., Lt MA A., 61, 463-'14. PEUONE V., ZUPPETTA A. (1982) • AlinerlllhUl' P"LACHE C., BElMAN H., FttONOf.L C. (l944) - Tbe zioni dell'lIrco Clllabfo-ptlOfitllno. / potesi gl'nrti· system 0/ mineralogy - Vol. I. Wilcy Sons, chI' e quadro evolutivo. BoIl. Soc. Geol. Ital., New York. 101, 141·1:55. PEACOCK M.A., BEItRY L.G. (1940) - R6ntgeno CoMMISSION ON OItE M1CltOSCOPY (1977) - IMAI grapbic observations on Ofe mineTa!s. Toronlo COM QUlIntitative DIIIII File (Editor N.F.M. Univ. Studies, Cool. ser., 44, 47-69. Henry). Applied Mineralogy Group. Mineralo PICOT P., IOHAN Z. (1982) - A/IllS 0/ ore minerals. .l\icll Society, London. B.R.G.M. EIsc:vier Pub!., Amslerdam. ClAlG ].R., VAUGHAN D.]. (1981) - Ofe miaoseopy PREWITT C.T. (1974) - A cell rejinement pfORrllm. and Qre petrogfapby. j. Wile)' 11< Sons, New York. DoNATI G., STAGNO F., TltlSCAltI M. (1978) • Ri· Opt. Hc:arth .nd Space SciencC5, New York cercbe IUlle mllni/estllvoni metaUi/efe dei M. Pe State Univcnity. Venion of august 197.5 mo 10fitlllli. Ill) Gilldmenti delle C.de S. CIINO, difi!!d by PA. Cuplcy Cambridge, England. Montllgne e lIidniori, pfesso Fiumedinisi (Mn· RAMDOHJ. P. (1980) - The ore minerllls lI"d lheif sinll). Ani Ace. Pdoritanl Pericollnri, a. Se. intergrowlhs. 2nd !!d. Pcrgamon Press, Oxford. MII. rlS. Nal., 56, 177·238. TltlSCAl1 M., SACcA C. (1982) - Scheelite lit the DuNCOMI P., jONES E.M. (1%9) - Electron PfObe «S. CllrlO" Sb-Cu·At Mine, Fiumedinisi, Messi 1ttiUOllnalysis: IIn ellSY to IIse computer Pf0t.fll1tt nil, Italy. Mina. Pctr. Acta, 26, 1.59-168. for COffectint. qlUlntitlJtive dllt•. Reporl n. 260, VAUGHAN D.j., WIG j.R. (1978) - Mit.eral cM Tube InYC5tigation Research Lab., Hinxlon, ",ist'1 0/ metal sulphides. Cambridge Univenity Saffron, England. PlCS$, Cambridgc, England.