Chemical deposits inside evaporite (gypsum, anhydrite and halite) caves are far less common than those developed within limestone or volcanic cavities. Moreover they exhibit a lower scarce ...mineralogical variability due to several reasons, the most important of which are: 1) calcium sulfate and sodium chloride are by far less reactive than calcium carbonate; 2) evaporite outcrops normally have a low mineralogical variability within the cave recharge areas. Therefore these karst environments were less investigated from this point of view in the past: no general paper exists on speleothems developing in halite and anhydrite caves until present, while the last printed one on gypsum (and anhydrite) karst appeared around 20 years ago. Several mineralogical studies were carried out in the last decades in caves from different evaporite areas proving that some of them host peculiar minerogenetic mechanisms, which are, at the moment, exclusive for these areas, and sometimes also brought to light to rare or even new cave minerals. In the present paper, together with an overview on all the actually known minerogenetic mechanisms active within the evaporite caves, the related chemical deposits and speleothems are shortly described. Far from being exhaustive, the recent mineralogical research on evaporite caves puts in evidence their unexpected richness in peculiar hosted speleothems and rare cave deposits. Seven out of the fifty known evaporite cave minerals, and around 10 speleothem types/subtypes are exclusive to these environments. Taking into account that only a few evaporite areas have been, so far, studied, it is highly probable that in the near future many more new cave deposits will be discovered, thus increasing the mineralogical interest of these unique caves.
Perhaps man’s first motivation to explore caves, beyond using them as shelter, was the search for substances that were not availableelsewhere: most of them were minerals. However, for a long time it ...was believed that the cave environment was not very interestingfrom the mineralogical point of view. This was due to the fact that most cave deposits are normally composed of a singlecompound: calcium carbonate. Therefore, the systematic study of cave mineralogy is of only recent origin. However, although onlya limited number of natural cavities have been investigated in detail, about 350 cave minerals have already been observed, someof which are new to science. The presence of such unexpected richness is a direct consequence of the variety of rocks traversedby water or other fluids before entering a cave and the sediments therein. Different cave environments allow the development ofvarious minerogenetic mechanisms, the most important of which are double exchange reactions, evaporation, oxidation, hydrationdehydration,sublimation, deposition from aerosols and vapors, and segregation. The cave temperature and pH/Eh strictly controlmost of them, although some are driven by microorganisms. The cave environment, due to its long-term stability, can sometimesallow for the development of huge euhedral crystals, such as those found in the Naica caves (Mexico), but the presence of extremelysmall yet complex aggregates of different minerals is far more common. Future development in the field of cave mineralogy will likelybe focused mainly on hydrothermal and sulfuric-acid caves and on the role played by micro-organisms in controlling some of the mostimportant minerogenetic processes in caves.
Evaporite karst in Italy: a review De Waele, Jo; Piccini, Leonardo; Columbu, Andrea ...
International journal of speleology,
05/2017, Letnik:
46, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Although outcropping rarely in Italy, evaporite (gypsum and anhydrite) karst has been described in detail since the early 20th century. Gypsum caves are now known from almost all Italian regions, but ...are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum mines in Piedmont. During the late 80s and 90s several multidisciplinary studies were carried out in many gypsum areas, resulting in a comprehensive overview, promoting further research in these special karst regions. More recent and detailed studies focused on the gypsum areas of Emilia-Romagna and Sicily. Sinkholes related to Permian-Triassic gypsum have been studied in Friuli Venezia Giulia. This article reviews the state of the art regarding different aspects of evaporite karst in Italy focusing on the main new results.
Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these ...caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskite-blödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars.
The network of lava tubes is one of the most unexploited natural wonders of the Galapagos Islands. Here, we provide the first morphological, mineralogical, and biogeochemical assessment of ...speleothems from volcanic caves of the Galapagos to understand their structure, composition, and origin, as well as to identify organic molecules preserved in speleothems. Mineralogical analyses revealed that moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves were composed of calcite, opal-A, and minor amounts of clay minerals. Extracellular polymeric substances, fossilized bacteria, silica microspheres, and cell imprints on siliceous minerals evidenced microbe-mineral interactions and biologically-mediated silica precipitation. Alternating depositional layers between siliceous and carbonate minerals and the detection of biomarkers of surface vegetation and anthropogenic stressors indicated environmental and anthropogenic changes (agriculture, human waste, and cave visits) on these unique underground resources. Stable isotope analysis and Py-GC/MS were key to robustly identify biomarkers, allowing for implementation of future protection policies.
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•Speleothems from lava tubes of Galapagos are archives of anthropogenic stressors•Moonmilk and coralloids are composed of calcite, opal-A, and clay minerals•Microbe-mineral interactions promote mineral dissolution and precipitation•Biomarkers of surface vegetation and anthropogenic impacts detected by Py-GC/MS
Earth sciences; Geochemistry; Geology; Volcano
During the 2011 speleological expedition to the Puerto Princesa Underground River (Palawan, Philippines) a drapery characterized by several close-to-horizontal ribs has been noticed. Even without ...sampling and analyzing its internal growth layers, a detailed morphological study allowed to present a possible genetic model. The presented model helps to explain its evolution, which is mainly controlled by variation in water flow as a consequence of the Palawan climate. When validated by further analyses, the same genetic mechanism could define also the evolution of the very common but still unexplained complex flowstones, which exhibit several close-to-horizontal steps, widenings and narrowings along their growth axis.
Fascinating and fragile environments as are the underground estuaries, need to be studied, understood and protected for present and future generations. Even if wide and abundant bibliography related ...to tides and their behaviour with respect to the external estuaries is available, none dealed with the estuary caves and the related hydrogeology. This paper aims to partially fill this gap presenting a preliminary study done at the Puerto Princesa Underground River (PPUR), in the Palawan Island (Philippines). The data was collected during the last expedition (November 2016) organised by La Venta, in which some of the authors took part. During the survey, the cave has been instrumented with in continuous diver data-logger devices (CTD) recording temperature (T), electrical conductivity (EC) and water level fluctuations. Longitudinal and vertical water hydrogeological profiles of the cave were realised with the aim of understanding the dynamics of the waters during different hydrogeological regimes in combination with salt water intrusion. In addition, a bathymetric profile was done to better identify the point where to realise the vertical logs. A significant rainstorm occurred during the expedition, lasting for approximately 12 hours resulting in 80 mm of rain, and its effects gave the researchers the opportunity to analyse the hydrodynamics of the flowing waters during a flood. In normal flow conditions, the longitudinal logs highlighted the presence of freshwater inlets and the vertical logs testified to a clear stratification of the waters (freshwaters at the surface and brackish waters at the bottom). During floods, the EC and T data showed evidence of a fast substitution of the resident waters. Key words: anchialine caves, sea water intrusion, hydrodynamics, karst springs, PPUR, Philippines. Učinek močnega naliva na hidrodinamiko podzemske reke Puerto princese (Palawan, Filipini) Očarljivo in občutljivo okolje, kot so podzemni estuariji, je treba preučevati, razumeti in zaščititi za sedanje in prihodnje generacije. Četudi imamo na voljo široko in bogato bibliografijo o plimovanju in delovanju plimovanja v zunanjih estuarijih, nobeno delo ne obravnava estuarskih jam in s tem povezane hidrogeologije. Namen tega članka je delno zapolniti to vrzel in predstaviti predhodno študijo na podzemni reki Puerto Princesa (PPUR) na otoku Palawan (Filipini). Podatki so bili zbrani med zadnjo ekspedicijo (novembra 2016), ki jo je organizirala La Venta, v kateri so sodelovali tudi nekateri avtorji. V raziskavi je bila jama opremljena z zveznimi merilci (CTD) temperature (T), električne prevodnosti (EC) in nihanja nivojev vode. Vzdolžni in navpični hidrogeološki vodni profili jame so bili izmerjeni, da bi razumeli dinamiko voda med različnimi hidrogeološkimi nivoji in med vdori morske vode. Poleg tega je bil opravljen tudi batimetrični profil, da bi lažje določili, kje izvesti navpične meritve. Med ekspedicijo se je zgodil močan naliv, ki je trajal približno 12 ur, padlo je 80 mm dežja, njegov učinek pa je raziskovalcem omogočil analizo hidrodinamike tekočih voda med poplavo. V običajnih vodostajih so vzdolžne meritve pokazale na dotoke sveže vode, vertikalne meritve pa so pokazale jasno stratifikacijo lastnosti vode (sveža voda na površini in brakična voda na dnu). Med poplavami so podatki EC in T potrdili hitro zamenjavo vode. Ključne besede: anhialine jame, vdor morske vode, hidrodinamika, kraški izviri, PPUR, Filipini.
Peculiar iron and manganese deposits coating walls, floors and ceilings of many galleries are one of the special features of the ElSoplao Cave (Cantabria, Spain). These speleothems appear to have ...been deposited over wall clay deposits, as well as formingpart of flowstones. Structure of crusts is essentially amorphous but several manganese and iron oxides were identified like goethiteand birnessite, though all occur with a low degree of crystallinity. In the outer layer of the crusts, alteration iron minerals appear thatderive from previous minerals in a process probably mediated by microorganisms. EDX microanalyses report fairly high values of Feand Mn in the crusts, though the Mn/Fe ratio varies considerably as a function of distance from the substrate/bedrock. The presentstudy proposes a genetic model for crust speleothems in El Soplao, based on oscillations of the phreatic level. The origin of thesedeposits is related to mobilization, under phreatic conditions, of polymetallic sulfides in the host rock. Metal ions (including Fe²+ andMn²+) released into the cave under reducing conditions, are oxidized and fixed in a process mediated by bacteria, giving rise to oxidesand hydroxides of low crystallinity. The presence of various black intercalated layers in aragonite flowstones indicate periods whencave conditions suddenly changed from vadose, when aragonite is precipitated, to phreatic and epiphreatic conditions, when theMn-Fe deposits are precipitated. Subsequently, vadose conditions were re-established, leading to the final stages of precipitation ofaragonite recorded in the flowstone and recent aragonite helictites on the surface of the Mn-Fe crusts.
V Savdski Arabiji je bilo raziskanih in izmerjenih več velikih vulkanskih jam v različnih poljih lave. Ena največjih je Ghar Al Hibashi na polju lave Harrat Buqum-Nawasif. To je v glavnem raven rov ...(400 m dolg in 15 m širok), dostopen skozi majhno brezno, ki se odpira v stranskem rovu. Jama je dolgo služila za skrivališče netopirjem, hijenam, volkovom in lisicam. Zaradi tega je dno jame, deloma iz debelih plasti nesprijetega peska, prekrito s številnimi kostmi in koproliti ter razmeroma velikimi kupi gvana. Nekateri so se bili vneli, zaradi česar so deloma zgorele tudi na njih ležeče kosti. Edine prave kapnike predstavlja nekaj majhnih, rumenih in prosojnih stalaktitov. Tekom treh odprav 2003 je bilo iz jame vzetih nekaj sekundarnih kemičnih odkladnin za mineraloške preiskave. Kljub majhnemu številu vzorcev je bilo do sedaj zaznanih vsaj 19 različnih mineralov, največ takih, ki so povezani z biogeno mineralizacijo kosti in gvana. Trije od teh, pyrocoproite, pyrophosphite in arnhemite, so izredno redke organske spojine, izključno vezane na goreči gvano. Do danes so bili ti minerali znani le iz nekaj jam v Afriki. Zahvaljujoč tem odkritjem ni jama Hibashi le najpomembnejša vulkanska jama v Savdski Arabiji, ampak tudi tamkajšnje daleč najbogatejše mineraloško nahajališče. Zato te raziskave, ki še zdaleč niso končane, potrjujejo novejše domneve, da so v jamskem okolju prav vulkanske jame najprimernejše za razvoj različnih mineralogenih mehanizmov. Several large lava tubes have been explored and mapped in different lava fields around the Saudi Arabia. One of the largest is Ghar Al Hibashi, located in the Harrat Buqum-Nawasif lava field. It mainly consists of a huge rectilinear gallery (over 400 m long and 15 m wide) the access to which is through a small vertical pit reaching a side corridor. The cave was long used as a shelter for bats, hyenas, wolves and foxes. Therefore the entire cave floor, consisting of locally thick uncemented sand, is scattered with a great amount of bones and coprolites, while some rather large guano deposits are also found. Some of these guano deposits caught fire, which partially burnt the bones overlaying them as well. The only true speleothems consist of a few small yellow translucent stalactites. During three expeditions in 2003, a few samples of secondary chemical deposits were collected inside this lava tube to be analysed from the mineralogical point of view. Despite the scarcity of these samples, at least 19 different minerals have already been detected, most of which are related to the biogenic mineralization of bones and guano deposits. Three of them, pyrocoproite, pyrophosphite and arnhemite are extremely rare organic compounds strictly related to the guano combustion, which have been observed until now only in a few caves in Africa. Thanks to these findings Hibashi lava tube is not only the most important volcanic cave of Saudi Arabia but also by far the richest mineralogical shelter of the country. Therefore this research, which is far from coming to an end, confirms the recently advanced opinion that amongst the different cave environments, volcanic cavities are very favourable for the development of different minerogenetic mechanisms.
The stone book PAOLO FORTI
Travaux de l'Institut de spéologie Emile Racovitza,
01/2018, Letnik:
57, Številka:
2018
Journal Article
Odprti dostop
The aesthetic value of a wild and/or tourist cave is well known everywhere. Anyway, presently only few people are aware that caves are the most important natural laboratories, in which it is possible ...to complete studies and researches that, in some cases, would be impossible in any other plac
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