High heat flow and ocean acidification at a nascent rift in the northern Gulf of California

Abstract

The prevailing tectonic setting in the Gulf California suggests the presence of an undetermined number of short spreading centres with associated hydrothermal systems. However, to date, active seafloor spreading phenomena have been documented in only three of the eight tectonically active basins. Here we report heat flow values as high as 15,436 mW m−2 in two of the northernmost basins of the Gulf of California, providing evidence of intense hydrothermal activity associated with the transition from continental rifting to seafloor spreading. The mean heat flow for the Wagner and Consag basins area is 1,875 mW m−2, more than 15 times higher than the mean value for oceanic crust (105.4 mW m−2). Additional evidence for vigorous hydrothermal circulation and a shallow heat source includes intense gas discharge (CO2 and CH4), widespread low pH (average 7.7), locally high 222Rn concentrations in the bottom water and a high extent of organic matter maturation in the sediments.

Consag Basin: northern Gulf of California, evidence of generation of new crust, based on seismic reflection data

“…Prol-Ledesma et al (2013) believe that the mean heat flow for the Wagner and Consag Basins area is 1875 mWm −2 , more than 15 times higher than the mean value for oceanic crust (~105 mWm −2 ). In the Wagner Basin, the sediment thickness is greater than 7 km, which impedes the rise of magma generated by seafloor spreading; this hindrance, in turn, masks any visible evidence of rifting ).…”

“…Canet et al (2010) report intense activity along the eastern margin of these two basins as seen in the emission of a large amount of gas and high geothermal flow, possibly associated with the development of new crust in the area. Prol-Ledesma et al (2013) report very high heat flow: 1875 mWm −2 ,~15 times higher than the average for young oceanic crust (~105 mWm 2 ), although such high heat flow must be in a geothermal area and is not appropriate to compare to a regional heat flow. González-Escobar et al (2010) have shown evidence of a transfer zone between the Wagner and Consag Basins.…”

Geothermal prospects in the Baja California Peninsula

“…The average heat flow in the Wagner and Consag Basins is 1875 mW/m 2 (Henyey and Bischoff, 1973;Prol-Ledesma et al, 2013), which is more than 15 times the mean oceanic heat flow (Davies and Davies, 2010). Hydrothermal activity occurs over more than 2240 km 2 and the average heat flow indicates an energy discharge of at least 4000 MWt.…”

“…However, the shallow basins, like the Wagner and Consag Basins (Fig. 1), may host hydrothermal systems that still have to be characterized (Prol-Ledesma et al, 2013).…”

“…The Wagner and Consag Faults, the most important ones, allow fluids to ascend the ocean bottom. The fluid discharge is dominated by gas, which is composed by [CO 2 ] = 78% and [CH 4 ] = 22% (Prol-Ledesma et al, 2013).…”