Isotopic composition (δ¹⁸ O y δD) of silica speleothems of the Algar do Carvão and Branca Opala volcanic caves (Terceira Island, Azores, Portugal)
DOI:
https://doi.org/10.3989/egeol.41717.315Keywords:
speleothems, opal-A, isotopes, lava tubeAbstract
The volcanic caves of Algar do Carvão (a pit with a complex genesis) and of Branca Opala (a lava-tube cave), differ from other caves on the island of Terceira by having speleothems composed only by opal. This kind of speleothems, in volcanic caves, suggests that the silica origin can be related to hydrothermal activity. The objective of this study is to determine the speleothem isotopic composition in δ¹⁸OSMOW and δDSMOW to determine their geochemical signature and conditions of formation. The studied samples from Algar do Carvão pit are stalactites and flowstones/gours that have been formed in subaerial conditions, while those from the Branca Opala lava tube have been defined as underwater silica stromatolites. dD data of speleothems from both caves are relatively similar (−102.0 ± 10.5‰ in Branca Opala and −103.7 ± 11.1‰ in Algar do Carvão) and it can be assumed that the fluids involved in the silica deposition may be similar. Moreover the δ¹⁸OSMOW data show that the Algar do Carvão speleothems have higher values (δ¹⁸OSMOW 39,4 ± 0,3‰), relatively to the Branca Opala stromatolites (δ¹⁸OSMOW 35,2 ± 0,8‰). The diagenesis that affected the opal A may explain, in part, the observed differences. However, other genetic factors are also influencing such as the fact that Algar do Carvão stalactites are formed in sub aerial conditions, under the influence of evaporation processes, while Branca Opala speleothems were formed in underwater conditions. However, it is also possible, that the water that originated the Branca Opala speleothems was 10,7 °C warmer than the water that formed the Algar do Carvão stalactites.
Downloads
References
Aubrecht, R.; Barrio-Amoros, C.L.; Breure, A.S.H.; Brewer-Carías, C.; Derka, T.; Fuentes-Ramos, O.A.; Gregor, M.; Kodada, J.; Kováčik, L.; Lánczos, T.; Lee, N.M.; Liščák, P.; Schlögl, J.; Šmída, B.& Vlček, L. (2012). Venezuelan tepuis: their caves and biota. Acta Geologica Slovaca Monograph, Bratislava, 168 pp.
Aubrecht, R.; Brewer-Carías, C.; Šmída, B.; Audy, M.& Kováčik, L. (2008). Anatomy of biologically mediated opal speleothems in the World's largest sandstone cave: Cueva Charles Brewer, Chimantá Plateau, Venezuela. Sedimentary Geology, 203: 181–195. http://dx.doi.org/10.1016/j.sedgeo.2007.10.005
Borges, P.; Silva, A.& Pereira, F. (1992). Caves and pits from the Azores with some comments on their geological origin, distribution and fauna. 6th International Symposium on Vulcanospeleology (Hilo, Hawaii), National Speleological Society, Proceeding Book, 121–151.
Bustillo, M.; Aparicio, A.& Carvalho, M. (2010). Estromatolitos silíceos en Espeleotemas de la Cueva de Branca Opala (Isla Terceira, Azores). Macla, 13: 51–52.
Calvert, A.T.; Moore, R.B.; McGeehin, J.P.& Rodrigues da Silva, A.M. (2006). Volcanic history and 40Ar/39Ar and 14C geochronology of Terceira Island, Azores, Portugal. Journal of Volcanology and Geothermal Research, 156: 103–115. http://dx.doi.org/10.1016/j.jvolgeores.2006.03.016
Cioccale, M.A.; Pasquini, A.I.& Depetris, P.J. (2008). Hallazgo de espeleotemas silíceas en rocas graníticas del batolito de Achala, Sierras Pampeanas de Córdoba. Asociación Geológica Argentina, 63: 417–420.
Carvalho, M.R.; Nunes, J.C.& França, Z. (2004). Controlo hidrogeológico das estalactites siliciosas do Algar do Carvão (Ilha Terceira, Açores). III Pico Island International Volcanological Meeting (Ilha do Pico, Açores), Abstract Book, 21–23.
Carvalho, J.M.; Coelho, L.; Nunes, J.C.& Carvalho, M.R. (2013). Geothermal Energy Use, Country Update for Portugal. European Geothermal Congress 2013 (Pisa, Italy), Abstract Book, 11 pp.
Clayton, R.N.; O'Neil, J.R.& Mayeda, T.K. (1972). Oxygen isotope exchange between quartz and water. Journal of Geophysical Research, 77: 3057–3067. http://dx.doi.org/10.1029/JB077i017p03057
Daza, R.; Bustillo, M.A.; Carvalho, M.R.; Nunes, J.C.& Pereira, F. (2012). Distribución, composición y génesis de depósitos silíceos en la cueva volcánica de Branca Opala (Terceira, Islas Azores). Geogaceta, 52: 37–40.
Daza, R.& Bustillo, M.A. (2014). Exceptional silica speleothems in a volcanic cave: a unique example of silicification and sub-aquatic opaline stromatolite formation (Terceira, Azores). Sedimentology, http://dx.doi.org/10.1111/sed.12130
Ferreira, T. (1994). Contribuição para o estudo das emanações gasosas associadas a processos de vulcanismo no arquipélago dos Açores. Provas de Aptidão Pedagógica e Capacidade Científica. Universidade dos Açores, Ponta Delgada, 183 pp.
Forjaz, V.H.; Nunes, J.C.& Barcelos, P. 2004. Algar do Carvão volcanic pit, Terceira island (Azores): geology and volcanology. 11 International Symposium on Volcanospeleology (Maio, Madalena, Pico), Abstract Book, 24.
Forti, P. (2001). Biogenic speleothems: an overview. International Journal of Speleology, 30: 39–56. http://dx.doi.org/10.5038/1827-806X.30.1.4
Forti, P. (2005). Genetic processes of cave minerals in volcanic environments: An overview. Journal of cave and Karst Studies, 67: 3–13.
França, Z.; Cruz, J.V.; Nunes, J.C.& Forjaz, V.H. (2003). Geologia dos Açores: uma perspectiva actual. Acoreana, 10: 11–140.
Herdianita, N.R.; Browne, P.R.L.& Rodgers, K.A. (2000). Mineralogical and textural changes accompanying ageing of silica sinter. Mineralium deposita, 35: 48–62. http://dx.doi.org/10.1007/s001260050005
Hill, C.A.& Forti, P. (1997). Cave minerals of the world. National Speleological Society. Huntsville, 463 pp.
Jones, J.B.& Segnit, E.R. (1971). The nature of opal I. Nomenclature and constituent phases. Journal of the Geological Society of Australia, 18: 57–68. http://dx.doi.org/10.1080/00167617108728743
Knauth, L.P.& Epstein, S. (1976). Hydrogen and oxygen isotope ratios in nodular and bedded cherts. Geochimica et Cosmochimica Acta, 40: 1095–1108. http://dx.doi.org/10.1016/0016-7037(76)90051-X
Miller, A.; Pereira, M.; Calaforra, J.M.; Forti, P.; Dionisio, A.& Saiz-Jimenez, C. (2014). Siliceous Speleothems and Associated Microbe-Mineral Interactions from Ana Heva Lava Tube in Easter Island (Chile). Geomicrobiology Journal, 31: 236–245. http://dx.doi.org/10.1080/01490451.2013.827762
Moschen, R.; Lücke, A.; Parplies, J.; Radtke, U.& Schleser, G.H. (2006). Transfer and early diagenesis of biogenic silica oxygen isotope signals during settling and sedimentation of diatoms in a temperate freshwater lake (Lake Holzmaar, Germany). Geochimica et Cosmochimica Acta, 70: 4367–4379. http://dx.doi.org/10.1016/j.gca.2006.07.001
Nunes, J.C. (2000). Notas sobre a geologia da Ilha Terceira (Açores). Acoreana, 9: 205–215.
Nunes, J.C. (2004). Atlas Básico dos Açores. Observatório Vulcanológico e Geotérmico dos Açores, Ponta Delgada, 112 pp.
Nunes, J.C.; Barcelos, P.; Pereira, F.; Forjaz, V.H.& Borges, P.A. (2004). Monumento Natural Regional do Algar do Carvão (Ilha Terceira). Biodiversidade e Geodiversidade. Atlântida 49: 279–286.
Nunes, J.C.; Calvert, A.; Medeiros, S.; Lima, E.; Pereira, F.; Costa, M.P.; Barcelos, P.& Carvalho, M.R. (2014). Geological mapping of volcanic caves in central area of Terceira Island (Azores, Portugal): associated volcanostratigraphy, ages and genetic implications on the Malha-Balcões-Chamusca lava caves system. IX Congresso Nacional de Geologia (Porto, Portugal). in press.
Self, S.& Gunn, B. (1976). Petrology, volume and age relations of alkaline and saturated peralkaline volcanics from Terceira, Azores. Contributions to Mineralogy and Petrology, 54: 293–313. http://dx.doi.org/10.1007/BF00389409
Vidal, J.R.; Sanjurjo, J.; Vaqueiro, M.& Fernández, D. (2010). Speleothems of Granite Caves. Comunicações Geológicas, 97: 71–80.
Vidal, J.R.& Vaqueiro, M. (2007). Types of granite cavities and associated speleothems: genesis and evolution. Nature Conservation, 63: 41–46.
Vogt, P.R.& Jung, W.Y. (2004). The Terceira Rift as hyper-slow, hotspot-dominated oblique spreading axis: A comparison with other slow-spreading plate boundaries. Earth and Planetary Science Letters, 218: 77–90. http://dx.doi.org/10.1016/S0012-821X(03)00627-7
Webb, J.A.& Finlayson, B.L. (1987). Incorporation of Al, Mg, and water in opal-A-evidence from speleothems secondary minerals found in caves. American Mineralogist, 72: 1204–10.
Willems, L.; Compère, P.; Hatert, F.; Pouclet, A.; Vicat, J.P.; Ek, C.& Boulvain, F. (2002). Karst in granitic rocks, South Cameroon: cave genesis and silica and taranakite speleothems. Terra Nova, 14: 355–362. http://dx.doi.org/10.1046/j.1365-3121.2002.00429.x
Williams, L.A.& Crerar, D.A. (1985). Silica diagénesis II. General mechanisms. .Journal of Sedimentary Petrology, 55: 312–321.
Wray, R.A.L. (1999). Opal and chalcedony speleothems on quartz sandstones in the Sydney region, southeastern Australia. Australian Journal of Earth Sciences, 46: 623–632. http://dx.doi.org/10.1046/j.1440-0952.1999.00732.x
Wray, R.A.L. (2011). Alunite formation within silica stalactites from the Sydney Region, South-eastern Australia. International Journal of Speleology, 40: 109– 116. http://dx.doi.org/10.5038/1827-806X.40.2.3
Published
How to Cite
Issue
Section
License
Copyright (c) 2014 Consejo Superior de Investigaciones Científicas (CSIC)
This work is licensed under a Creative Commons Attribution 4.0 International License.
© CSIC. Manuscripts published in both the printed and online versions of this Journal are the property of Consejo Superior de Investigaciones Científicas, and quoting this source is a requirement for any partial or full reproduction.All contents of this electronic edition, except where otherwise noted, are distributed under a “Creative Commons Attribution 4.0 International” (CC BY 4.0) License. You may read here the basic information and the legal text of the license. The indication of the CC BY 4.0 License must be expressly stated in this way when necessary.
Self-archiving in repositories, personal webpages or similar, of any version other than the published by the Editor, is not allowed.
