Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/12089
Authors: Marques, J. M.* 
Etiope, Giuseppe* 
Neves, M. O.* 
Carreira, P. M.* 
Rocha, C.* 
Vance, S. D.* 
Christensen, L. F.* 
Miller, A. Z.* 
Suzuki, S.* 
Title: Linking serpentinization, hyperalkaline mineral waters and abiotic methane production in continental peridotites: an integrated hydrogeological-bio-geochemical model from the Cabeço de Vide CH4-rich aquifer (Portugal)
Issue Date: 2018
Series/Report no.: /96 (2018)
DOI: 10.1016/j.apgeochem.2018.07.011
URI: http://hdl.handle.net/2122/12089
Abstract: Continental active serpentinization of ultramafic rocks is today recognized as a key process triggering a sequence of phenomena involving the passage from inorganic, to organic and metabolic reactions. These may have a role in the origin of life, and may explain the occurrence of abiotic hydrocarbons on Earth and other planets. Production of hyperalkaline waters and abiotic methane (CH4) are two critical steps in this sequence. They were described independently by specific hydrogeological and geochemical models. Here, we update and combine these models into a unified scheme using and integrating geological, hydrogeological, hydrogeochemical, gasgeochemical and microbial analyses acquired from 2002 to 2014 in the Cabeço de Vide (CdV) study site, Portugal. The hyperalkaline (pH > 10.5), Na-Cl/Ca-OH mineral water of CdV evolve from groundwater-peridotite interaction (serpentinization) generating hydrogen (H2), which, according to multiple theoretical, laboratory and field evidence, likely reacted with CO2 within metal- (catalyst) rich rocks, abiotically producing CH4 (up to 1.2 mg/L; -24.4°/oo < δ13C-CH4 < -14.0°/oo and -285°/oo < δ2H-CH4 < -218°/oo). The hyperalkaline water hosts hydrogen oxidizing bacteria “Serpentinomonas”, which may explain the paucity of H2 observed in the dissolved gas. The CdV gas-rich mineral waters ascend along a fault at the boundary of the peridotite intrusion. Temporal changes of pH and CH4 concentration result from episodic mixing with shallower Mg-HCO3-type waters. Soil-gas analyses show that methane migrates to the surface along the fault, also independently from the water emergences, consistently with non-aqueous abiotic CH4 production. Our integrated model is generally compatible with observations from other gas-bearing continental serpentinization sites.
Appears in Collections:Papers Published / Papers in press

Files in This Item:
File Description SizeFormat 
Marques et al 2018 CdV.pdf6.15 MBAdobe PDFView/Open
Show full item record

Page view(s)

7
Last Week
0
Last month
checked on May 27, 2019

Download(s)

12
checked on May 27, 2019

Google ScholarTM

Check

Altmetric