minerals Article Valentinite and Colloform Sphalerite in Epithermal Deposits from Baia Mare Area, Eastern Carpathians Gheorghe Damian 1,2, Andrei Buzatu 2, Ionut Andrei Apopei 2,* , Zsolt László Szakács 1 , 1,3 1 2 Ioan Denut, , Gheorghe Iepure and Daniel Bârgăoanu 1 North University Centre of Baia Mare, Technical University of Cluj-Napoca, 430083 Baia Mare, Romania; [email protected] (G.D.); [email protected] (Z.L.S.); [email protected] (I.D.); [email protected] (G.I.) 2 Department of Geology, Faculty of Geography and Geology, “Alexandru Ioan Cuza” University of Ias, i, 700505 Ias, i, Romania; [email protected] (A.B.); [email protected] (D.B.) 3 County Museum of Mineralogy, “Victor Gorduza”, 430212 Baia Mare, Romania * Correspondence: [email protected] Received: 9 December 2019; Accepted: 26 January 2020; Published: 30 January 2020 Abstract: Valentinite forms through the alteration of stibnite in sulphide deposits. Colloform sphalerite is a widespread mineral in low-temperature deposits, particularly those of the Mississippi-Valley type. We identified valentinite and colloform sphalerite in hydrothermal deposits occurring in the Baia Mare area. The Baia Mare metallogenic district of Neogene age occurs in the northwestern part of the Neogene volcanic chain within the Eastern Carpathians. The Neogene volcanism from Baia Mare area is related to the subduction processes of the East European plate under two microplates, Alcapa and Tisza-Dacia/Tisia, in the post-collisional compressive phase. We have identified valentinite in the Dealul Crucii and Baia Sprie deposits, associated with other epithermal minerals, in the absence of the stibnite. Valentinite is deposited in the final phase of the epithermal process after calcite and manganese-bearing calcite. Micro-Raman and microprobe determinations indicate the presence of valentinite. The formula of valentinite is close to stoichiometric Me2O3 and contains small amounts of tin as an antimony substituent. Colloform sphalerite was identified in the Baia Sprie ore deposit associated with minerals formed in the final epithermal phase. It was deposited on idiomorphic crystals of stibnite, which it corrodes. Its structure and an alternate banding, exhibited on the nano-/microscale, were identified by optical microscopy, SEM (scanning electron microscopy), and BSE (backscattered electron microscopy) imaging. These structures are typical for colloform sphalerite and suggest a genesis due to episodic precipitation. The spherical nano/micro-particles (nodules) are characteristic of the colloform sphalerite from Baia Sprie. Raman analysis indicates the presence of a colloform sphalerite with low iron content. The typical diffraction lines for sphalerite were identified in X-ray diffraction: 3.118 Å (111), 1.907 Å (220), 1.627 Å (311). Microprobe analysis certifies the presence of sphalerite with the stoichiometric formula close to ZnS. Iron content is low (0%–0.0613%), but Sb (0.7726%–2.6813%), Pb (0.56%–1.1718%), Bi (0%–0.1227%) are also present. The negative correlation between Zn and Sb suggests the simultaneous deposition from the same epithermal fluids. Valentinite and colloform sphalerite were formed at low temperatures (100–150 ◦C) at the end of the epithermal process. Keywords: valentinite; colloform sphalerite; Dealu Crucii; Baia Sprie; Baia Mare; Eastern Carpathians 1. Introduction Valentinite and colloform sphalerite are very rare minerals in epithermal deposits. Valentinite has been discovered in the Dealul Crucii (Crucii Hill) and Baia Sprie ore deposits and colloform Minerals 2020, 10, 121; doi:10.3390/min10020121 www.mdpi.com/journal/minerals MineralsMinerals 20202020,, 1010,, 121121 22 ofof 1919 has been discovered in the Dealul Crucii (Crucii Hill) and Baia Sprie ore deposits and colloform sphaleritesphalerite inin BaiaBaia SprieSprie oreore deposits,deposits, respectivelyrespectively (Figure(Figure1 1))[ [1].1]. Hydrothermal oreore depositsdeposits fromfrom BaiaBaia MareMare miningmining districtdistrict are internationallyinternationally recognized for the minerals that were firstfirst described here: andoriteandorite [[2],2], semseyitesemseyite [[3],3], felsöbanyitefelsöbanyite [[4],4], klebelsbergiteklebelsbergite [[5],5], dietrichitedietrichite [[6],6], szmikiteszmikite [[7],7], inin thethe BaiaBaia SprieSprie area,area, fülöppitefülöppite [[8]8] DealulDealul Crucii,Crucii, andand fizfizélyiteélyite [[9]9] atat Herja.Herja. FigureFigure 1.1. Sketch of the map of Baia Mare area with the location of ore deposits Dealul Crucii andand Baia Sprie,Sprie, withwith modificationsmodifications afterafter [[1].1]. ValentiniteValentinite occursoccurs in in many many locations locations around around the the world, world, for example,for example, in France in France at Chalanches at Chalanches mine, northmine, ofnorth Allemont, of Allemont, Isere, and Isere, in otherand in occurrences other occurre [10nces]. They [10]. are They formed are formed during theduring alteration the alteration process ofprocess stibnite of andstibnite other and minerals other richminerals in antimony rich in andantimony are associated and are withassociated senarmontite with senarmontite and kermesite. and kermesite.Colloform sphalerite occurs in low-temperature deposits, especially those of the Mississippi-Valley TypeColloform (MVT) in carbonate-hosts sphalerite occurs [11 ].in Accordinglow-temperature to this author, deposits, colloform especially sphalerite those isof cryptocrystallinethe Mississippi- toValley fibrous Type and (MVT) shows ain banded carbonate-hosts structure. [11]. The originAccording of colloform to this sphaleriteauthor, colloform has been discussedsphalerite byis Rogerscryptocrystalline (1917) [12 ],to indicating fibrous and that shows it was a banded formed struct fromure. colloidal The origin and meta-colloidal of colloform sphalerite substances, has in been the opendiscussed space. by There Rogers were (1917) authors [12], who indicating indicated that the non-colloidalit was formed origin from of thecolloidal colloform and texturesmeta-colloidal [13,14]. Roeddersubstances, (1968) in the [13 open] demonstrated space. There by were electron-microprobe authors who indicated analysis the (EMP) non-colloidal and scanning origin electron of the microscopycolloform textures (SEM) that[13,14]. the Roedder banded structures(1968) [13] of demonstrated the Pine Point by field electron-microprobe (Northwest Territories, analysis Canada) (EMP) areand due scanning to the variation electron inmicroscopy iron content. (SEM) Pfaff etthat al. (2011)the banded [15] supported structures that of colloform the Pine now Point is mostly field accepted(Northwest as aTerritories, descriptive Canada) morphological are due and to not the as vari a genetication in term. iron content. Pfaff et al. (2011) [15] supportedMVT orethat deposits colloform occur now in is Pinemostly Point accepted Canada as [a13 descriptive], in Wisconsin, morphological Missouri, and Illinois not statesas a genetic from USAterm. [ 16–18], in Réocin, Noth Spain, in Trèves, South France, and Krakow-Silesia, Poland [19]. AMVT major ore MVT deposits deposit occur is locatedin Pine inPoint the WieslochCanada [13] area, in of Wisconsin, southwest Germany,Missouri, whichIllinois is states controlled from byUSA the [16–18], graben-related in Réocin, faults Noth of Spain, the Upper in Trèves, Rhinegraben South France, [19]. Thisand Krakow-Silesia, deposit occurs inPoland Middle [19]. Triassic limestonesA major [19 MVT]. The deposit Schwarzwald is located orein the district Wiesloch is located area of in southwest the southern Germany, part ofwhich the Wieslochis controlled MTV by deposits.the graben-related The hydrothermal faults of veinsthe Upper in the SchwarzwaldRhinegraben ore[19]. district This deposit are comparable occurs in to Middle the formations Triassic fromlimestones the Wiesloch [19]. The MVT Schwarzwald deposit [15 ].ore district is located in the southern part of the Wiesloch MTV deposits. The hydrothermal veins in the Schwarzwald ore district are comparable to the formations from the Wiesloch MVT deposit [15]. MineralsMinerals 20202020,, 1010,, 121121 33 ofof 1919 Colloform sphalerite also occurs in the Bleiberg Pb-Zn deposit in the Drau Range (Eastern Alps) in Alpine-TypeColloform sphalerite (APT) Triassic also occurs carbonate-hosted. in the Bleiberg Pb-ZnIn this deposit deposit, in thedifferent Drau Rangetypes (Easternof sphalerite: Alps) incolloform Alpine-Type schalenblende (APT) Triassic and carbonate-hosted.crystalline sphalerite, In this co-occur deposit, in di thefferent same types sample of sphalerite: [20]. colloform schalenblendeIn the present and crystalline study, we sphalerite,examine the co-occur occurrence in the of same valentinite sample [and20]. colloform sphalerite from epithermalIn the presentore deposits study, from we examinethe Baia theMare occurrence area, Eastern of valentinite Carpathians. and The colloform aim of sphaleritethis study fromis to epithermalcharacterize ore these deposits minerals, from formed the Baia at low Mare temperatures. area, Eastern Carpathians. The aim of this study is to characterize these minerals, formed at low temperatures. 2. Geological Settings 2. Geological Settings The metallogenetic district of Baia Mare represents the northwestern part of the Neogene The metallogenetic district of Baia Mare represents the northwestern part of the Neogene Volcanic Volcanic Chain from the inner side of the Eastern Carpathians. This volcanic chain was formed Chain from