MINERALOGIJA IN GEOMIKROBIOLOGIJA V JAMSKIH OKOLJIH Z AKTIVNIM VULKANIZMOM V SREDNJI AMERIKI

Recently, the study of mineralogical and geomicrobiological interactions in volcanic caves is gaining relevance, because there are many factors to consider them as Mars analogues for astrobiology and planetary sciences. In addition, sulfuric acid caves have also shown to be an important field of study for the understanding of chemolithoautotrophic metabolic pathways, especially in regard to the biogeochemical cycle of sulfur compounds. Hitherto, sulfur-rich volcanic caves found in Central America were almost unknown to the scientific community. This work presents the mineralogical and microbiological diversity and the potential geomicrobiological links found in active volcanic settings, such as Cueva los Minerales (CMI) and Cueva los Mucolitos (CMU) at Irazú volcano (Costa Rica), and Cueva Hoyo de Koppen (CHK) at El Hoyo volcano (Nicaragua). The volcanic caves at Irazú volcano (Costa Rica) are located in the northwest (NW) foothills of the main crater. These caves became accessible after the partial collapse of the NW sector of the Irazú volcano in 1994, offering the opportunity to investigate in situ active minerogenetic processes. Detailed mineralogical and geochemical analyses were performed to study the speleothems at CMI and CMU. Mineralogical analyses included X-ray diffraction (XRD) and Raman spectroscopy, while geochemical characterization was done using Energy Dispersive X-ray spectroscopy (EDX) coupled to Scanning Electron Microscopy (SEM). In noveladdition, measurements of cave environmental parameters, cave drip water, and a compilation of geochemical analyses of the Irazú volcanic lake (located ca. 150 m above the cave level) and fumarole analyses, were conducted between 1991 and 2014. Forty-eight different mineral phases were identified, mostly rare hydrated sulfates of the alunite, halotrichite, copiapite, kieserite and rozenite groupsthirteen of which are described here, as cave minerals, for the first time, i.e. aplowite, bieberite, boyleite, dietrichite, ferricopiapite, ferrinatrite, lausenite, lishizhenite, magnesiocopiapite, marinellite, pentahydrite, szomolnokite, and wupatkiite. The presence of other novel cave minerals, such as tolbachite, mercallite, rhomboclase, cyanochroite, and retgersite, is likely, but this was not possible to confirm by the various mineralogical techniques employed in this study. It was determined that uplifting of sulfurous gases, water percolation from the Irazú volcanic lake, and hydrothermal interactions with the volcanic host rock are responsible for such extreme mineralogical diversity. Moreover, acidic (pH < 2) viscous biofilms, known as snottites, were observed hanging from both, walls and ceiling, of the caves at Irazú volcano, in close relation with the presence of sulfate minerals. Knowledge about snottites in volcanic caves is scarce, being biofilms present in carbonated rocks the most studied, e.g. at Frasassi and Acquasanta caves (Italy), and Cueva de Villa Luz and Luna Azufre (Mexico). 16S rRNA techniques (with primers for target Bacteria and Archaea), together with bioinformatics analyses, were used to investigate the snottites from CMU and CMI. The results indicated that both prokaryotic groups in the snottites offer a vast metabolic potential to execute various reactions, including redox reactions. The phylogenetic findings revealed that approximately 65% of the identified taxa corresponded to species related to sulfur-oxidizing metabolic pathways (e.g., Leptospirillum, Mycobacterium, Acidithiobacillus and Acidiphilium), while just 0.04% corresponded to sulfur-reducing species (Desulfosporosinus). Since sulfur-oxidizing microorganisms appeared to be dominant in the acidic snottites, induced-gypsum precipitation by changes in micro environmental conditions, is strongly suggested as the path for biomineralization at the studied caves. 34S isotope signature of sulfur minerals presented negative values (from -16.2 to -3.4 ‰), comparable with data obtained...V zadnjem času postaja proučevanje mineraloških in geomikrobioloških interakcij v vulkanskih jamah vse pomembnejše, saj so številne podvržene podobnim dejavnikom, ki kažejo, da bi lahko bile Marsov analog za astrobiologijo in planetarno znanost. Poleg tega so se tudi žveplene jame izkazale pomembne za razumevanje kemolitoautotrofnih metabolnih poti, zlasti biogeokemijskega cikla žveplovih spojin. Vulkanske jame, bogate z žveplom na območju Srednje Amerike, so znanstveni skupnosti praktično nepoznane. V pričuječem delu proučujemo mineraloško in mikrobiološko raznolikost ter potencialne geomikrobiološke interakcije v aktivnih vulkanskih okoljih, kot so jame Cueva los Minerales (CMI) in Cueva los Mucolitos (CMU) v vulkanu Irazú (Kostarika), ter Cueva Hoyo de Koppen (CHK) v vulkanu El Hoyo (Nikaragva). Jame vulkana Irazú (Kostarika) se nahajajo na severozahodnem vznožju glavnega kraterja. Postale so dostopne po delnem podoru SZ sektorja vulkana Irazú leta 1994, kar je omogočilo raziskati aktivne procese nastajanja mineralov v vulkanskih jamskih okoljih na tem geografskem območju. Opravljene so bile podrobne mineraloške in geokemijske analize jamske sige v CMI in CMU. Mineraloške analize so vključevale rentgensko difrakcijo (XRD) in ramansko spektroskopijo, medtem ko je geokemična karakterizacija vključevala energijsko disperzijsko rentgensko spektroskopijo (EDX) v navezavi z vrstično elektronsko mikroskopijo (SEM). Opravljene so bile meritve okoljskih parametrov v jamah ter analize preniklih voda v jamah, poleg tega pa še analiza zbranih geokemijskih podatkov vulkanskega jezera Irazú (~ 150 m nad nivojem jame) in fumarol za obdobje med letoma 1991 in 2014. Identificirali smo 48 različnih mineralnih faz, večina so redki hidrirani sulfati, aluniti, halotrihiti, kopiapiti, kieseriti in rozenititrinajst jih je tukaj opisanih prvič kot jamski minerali, tj. aplowit, bieberit, boyleit, dietrichit, ferikopiapit, ferinatrit, lausenit, lishizhenit, magneziokopiapit, marinelit, pentahidrit, szomolnokit in wupatkiit. Prisotnost drugih novih jamskih mineralov, kot so tolbahit, merkalit, rombomklaz, cianohroit in retgersite, je verjetna, vendar tega ni bilo mogoče potrditi z uporabljenimi mineraloškimi tehnikami. Ugotovljeno je bilo, da je vzrok za tako ekstremno mineraloško raznolikost izhajanje žveplenih plinov, pronicanje vode iz vulkanskega jezera Irazú in hidrotermalne interakcije z okoliško vulkansko kamnino. Kisli viskozni biofilmi (pH < 2), znani kot snotiti (mukozni stalaktiti) v vulkanskih jamah vulkana Irazú visijo na stenah in stropih jam in so v tesni povezavi s sulfatnimi minerali. O snotitih v vulkanskih jamah je malo znanega, še največ vemo o tovrstnih biofilmih iz primerov bolj raziskanih podzemnih jam v karbonatnih kamninah in sicer, jamah Frasassi in Acquasanta (Italija), Cueva de Villa Luz ter Luna Azufre (Mehika). Molekularne metode proučevanja 16S rRNA (z oligonukleitidnimi začetniki za Bakterije in Arheje) so bile skupaj z bioinformatskimi analizami uporabljene za proučevanje mukoznih stalaktitov iz CMU in CMI. Rezultati so pokazali, da imata obe prokariontski skupini mikroorganizmov velik metabolični potencial za različne biokemijske reakcije, vključno z oksidoredukcijskimi. Filogenetske analize so pokazale, da približno 65% identificiranih taksonov ustreza vrstam, povezanim z metabolizmom za oksidacijo žvepla (npr. Leptospirillum, Mycobacterium, Acidithiobacillus in Acidiphilium), medtem ko je samo 0,04% taksonov pripadalo vrstam, ki lahko reducirajo žveplo (Desulfosporosinus). Rezultati kažejo, da so v kislih snotitih mikroorganizmi, ki oksidirajo žveplo prevladujočito pa lahko pomeni, da so za biomineralizacijski proces za izločanje sadre v proučevanih jamah ključne spremembe mikrookoljskih pogojev. 34S izotopske vrednosti so bile za minerale negativne (-16,2 ‰ do -3,4 ‰) in so primerljive z vrednostmi iz drugih žveplenih jam, npr. Frassasi, Cueva de Villa Luz, Lechuguilla in Provalata, kjer so bile dokazane..