Mantle Origin of CO2 and Carbonate Budget of Oceans and Travertine Deposits – Examples from Turkey and Szeklerland

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The Pamukkale Travertine was deposited along the Burdur-Fethye fault zone. The main source of the significant amount of CO2 converted into bicarbonate should be of mantle origin, as proven by the nearby presence of borate deposits in the Bigadiç borate Basin.

Carbonate budget in the oceans of the Earth and in continental domains, as well, basically depends on the availability of CO2 in aqueous solutions, which might be a function of the mantle CO2 release by oceanic floor volcanic activity, in a given geological period. Wilson includes the enrichment in volatiles, halogens and CO2, among the general characteristics of continental rift zone magmatism (Wilson, 1989). Solubility of CO2 in magmas increases with pressure and magma alkalinity (Lowenstern, 2001).

Mantle origin CO2 is commonly present in active strike-slip zones, either as bicarbonate ion in aqueous solutions, or as dry CO2, and may give birth to significant continental carbonate deposits in the form of travertines, like in Pamukkale, Turkey, or the Yellowstone carbonate travertines in the USA. For example, the Ol Doinyo Lengai volcano of the East African Rift, Tanzania, is producing natrocarbonatite lava, accompanied by a flux of 6000–7200 tonnes CO2 d−1 (Koepenick et al., 1996). It is very difficult to disproof the mantle origin of these enormous CO2 fluxes.

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Small size Holocene carbonate tufa dome at Tălișoara/ Olasztelek, Szeklerland, Romania

Distribution of massive CO2 occurrences and that of larger carbonate tufa domes is related to deep crustal faults, and thus surface carbonate tufa deposits can be used to trace deep seated crustal faults, hence we consider them as integral parts of the GSST mapping techniques. A minor carbonate tufa dome is above from Tălișoara/ Olasztelek, which together with the Bálványos carbonate tufa domes delineate a major W to E trending deeper crustal fault system in Szeklerland/ Romania. Another synthetic fault to the master is coming from the Racoș/ Alsórákos neovolcanic area via the Ozunca Băi/ Uzonkafürdő carbonate tufa dome.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.

Accommodation Space Budget in the Mediterranean Area During the Messinian Salinity Crisis

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Recent shoreline  with uplifted Pleistocene sediments in Antalya, Turkey. History has recorded that the Manavgat River was navigable several centuries ago. While Venice is tectonically subsiding, Manavgat is rising.

The motor of basin opening mechanisms and subsequent subsidence in the Mediterranean Basin is best described in terms of strike-slip tectonics, related to the plate-velocity contrast of the African and Eurasian Plates during their eastward journey. In this approximation, the Mediterranean area represents an intercontinental mega-shear zone,  obviously with numerous transtensional zones, which evolved into isolated, small subbasins (Martínez-Garcia et al., 2013), featuring transform margins Tari et al. (2012), internal strike-slip zones (our experience in the Pantelleria Island area), and several push-up ranges, which in many parts of the Mediterranean area evolved into orogens, like in the case of the Atlas, Apennine, Alpine, Carpathian orogens. This continental scale tectonic evolution was enabled by several microplates and even nanoplates, in GSST wording.

The Atlas Microplate is found at the northern margin of the African Plate. Besides the High Atlas Nanoplate, which underlies the Atlas orogene, it includes two other, smaller nanoplates, the Gibraltar and Sicily Nanoplates. This microplate shows particularly intense strike-slip tectonics, and at the same time, we believe that it holds the main responsibilities for the accommodation space budget in the Mediterranean area, what has as a direct consequence that strike-slip tectonics should be considered as the main controlling factor for the Messinian Salinity Crisis, obviously exploiting the existing background climate factors.

According to Salé et al. (2012), the Mediterranean basins are showing very similar depositional trends and sedimentary architecture. They found however that the Late Messinian cyclicity of non-marine and fully marine sediments is related to climate changes, admitting that cyclicity is enhanced by tectonic activity in their study area, which is located over the Serrata-Carboneras strike-slip zone in Spain.

Looking after clues in the sedimentary record, we found that Late Messinian sediments are evidencing sedimentary intervals described as seismicites (Fortuin and Dabrio, 2008) and explosive fluid expulsion events (Bertoni and Cartwright, 2015).

In conclusion, it is more likely that causes of the Messinian Salinity Crisis should be attributed to the joint management of the Mediterranean accommodation space budget. Whatever is the subsidence of the individual subbasins, the total volume of available sea water counts in desiccating subbasins. It should be also noted that not every subbasin contains Messinian Salt, just those which met the desiccation criteria of the communicating vessels (subbasins).

Given the strike-slip related deformations recorded by the Atlas orogene, it is not hard to believe that the Atlas Microplate, certainly accompanied by the other microplates and orogens involved,  had a significant impact on  driving the vertical basin-floor oscillation, and ultimately changes in basin volume, all orchestrated by the regional strike-slip stress field.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.