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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.

Izdelana je bila predhodna podrobna studija jame Modrica, se preden bi jo uredili za turisticni obisk. Meljasta ilovica z guanom vsebuje mnogo kremena, ilita in taranakita ter manjse kolicine vivianita in visoke koncentracije bakra (2869 mg/kg), cinka (951 mg/kg) in kadmija (28 mg/kg). Sedimenti, pomesani z guanom, so obogateni z rahlim REE in s povisanimi koncentracijami U, Th in Hg. Sedimenti z delci kosti vsebujejo kremen, ilit, kalcit in hidroxylapatit, a manj carnalita in nizke vrednosti težkih mineralov. Vsi analizirani sedimenti kažejo razlicno stopnjo kontaminacije Cu in Zn zaradi razsutega guana. Vecina Zn in Cu v jamskih sedimentih kot tudi hidroxylapatitna skorja so v zvezi z železovim in manganovim hidroksidom ter organskimi delci. Organski delci v vzorcih sedimentov so pomembni, ker kažejo neposredni vpliv guana in hidroxylapatitnih skorij, medtem ko je v vzorcih sedimentov z drobci kosti najpomembnejsi hidroksid. V dveh primerih smo opazovali vpliv guana na prenikajoco vodo v levem rovu, kjer je vecja koncentracija ortofosfatov glede na hidroxylapatit A comprehensive study of Modric cave was undertaken to evaluate the baseline conditions before its utilization for tourism. Silty loams with guano contain abundant quartz, illite and taranakite and minor vivianite and high concentrations of Cu (2869 mg/kg), Zn (951 mg/kg) and Cd (28 mg/kg). Also sediments mixed with guano are enriched with light REE as well as elevated concentrations of U, Th, Rb and Hg. Sediments with bone fragments contain abundant quartz, illite, calcite and hydroxylapatite and minor carndallite and lower contents of heavy metals. All sediments analysed showed various degrees of contamination by Cu and Zn from dispersed guano. Most of the Zn and Cu in cave sediments and the hydroxyl-apatite crusts are mainly controlled by the iron and manganese hydroxide and the organic fractions, the organic fraction plays an important role in sediment samples with direct influence of guano and in hydroxylapatite crusts while in samples with bone fragments the hydroxide control is dominant. Guano influence on the percolating waters was observed in two cases in the left channel where due to the higher content of orthophosphates saturation in respect to hydroxyl-apatite is present.

International audience; This paper documents the occurrence of tinsleyite in the "dry" Cioclovina Cave, Sureanu Mountains, Romania. This is the first mention of tinsleyite as a cave mineral and the second find of this mineral species in the world. The mineral occurs in small quantities, as a rare authigenic, early diagenetic mineral, in the bat guano deposits in this cave. Low (alpha) quartz is the only closely associated mineral. This assemblage corresponds to a possible reaction in the natural guano - clay system upon decomposition of illite. Chemical analyses show variable leucophosphite contents (up to 31.68 mol.%). The unit-cell parameters calculated for an iron-poor sample are a = 9.638(5) Å, b = 9.522(4) Å, c = 9.540(4) Å and ß = 103.10(3)°, whereas those determined for an iron-rich sample are a = 9.639(6) Å, b = 9.538(8) Å, c= 9.553(7) Å and ß = 103.04(4)°. Thermal analyses show that water is lost in three steps and that the loss of molecular water is complete before 250°C. The fully dehydrated material is completely X-ray amorphous. Ammonium is expelled at about 490°C. The infrared spectrum of tinsleyite affords reasonable evidence for the presence of PO4, NH4 and OH groups, together with H2O molecules. The punctual symmetry of the PO4 groups is Cs.