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Scarcity of precipitation in the western Canary Islands prevents dissolution of gypsum speleothems. The constant supply of ions from sea spray, air currents in the cave, and the fast, but partial, evaporation due to the high relative humidity in the lava tube favours accumulation of major amounts of gypsum and subordinately halite. Two probable vias for ions input into the lava tube are considered: 1) sea spray circulating through the lava tube 2) low-frequency rain infiltration leaching the marine spray salts precipitated at the surface. These data support the idea that gypsum precipitates in the lava tube by evaporation of marine spray or solutions derived from marine spray. ⁸⁷ Sr/ ⁸⁶ Sr from speleothems (0.708665–0.708976) suggests that the main source of Ca is seawater, but additional Ca contributions from aeolian dust have reduced the Sr isotope values. δ ³⁴ S and the δ ¹⁸ O of gypsum speleothems (δ ³⁴ S is 20.97‰ V-CDT and δ ¹⁸ O is 9.78‰ V-SMOW) is similar to that of sulphate dissolved in seawater. Uranium series dating of speleothems show ages ranging from 6217 ± 1644 yr to 40,039 ± 4748 yr.
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Those composed of macrocrystalline gypsum with millimetric-size tabular and lenticular crystals are: crusts and stalactites. Speleothems composed of microcrystalline gypsum (up to 150 μm long) are: coatings, globules, or extensive white powder accumulations covering the tube floor. Mineralogical analyses of the speleothems from El Covón and Chifletera lava tubes show that gypsum is the dominant mineral with minor amounts of halite. Lava tubes from Lanzarote Island in the Canary Archipelago commonly show white speleothems that stand out from the black basaltic rock. Ofdeposition (dry conditions) and dissolution (jlood conditions). Its genesis is related to seasonal variations Observations show that the dust is composed of small aggregate grains ofgypsum cryslals partially cementedīy very small calcite grains (3-5% CaC03 total dust composition). Gypsum dust is a powdery deposit (crystal size range between 15-30Jl) located on the wallsĪnd ceiling ofthefirst 300-500 m ofPark's Ranch Cave, close lo lhe entrance. They are lhe product ofĮvaporatían and air jlow direction and velocity, which factors control deposition and the expansion level of Gypsum trays are a type ofstalactite with sub-horizontal developmentĪnd a maximum axis of elongation outwards from the wall (Rocking Chair Cave). In two cases the gypsum speleothems were identified which now or have neverīeen described before in the literature. Inside ofthese caves gypsum speleothems are widespread and more developed than in the other gypsum The speleothems are located in the Pennú:m-age gypsum karstĪrea ofNew Mexico, in several caves close to Carlsbad and Roswell (Rocking Chair Cave and Park's RanchĬave).
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In Ihis paper two new types of speleolhems are described, and lheir genesis is discussed on lhe basis of lheĪvaible climatic and hydrodynamic data.
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