@inproceedings{fdi:010086597,
  title = {{D}iagenetic carbonates from deep sub-seafloor organic-rich sediments influenced by magmatic sill intrusions ({IODP} {E}xp 385-{G}uaymas {B}asin, {G}ulf of {C}alifornia) [r{\'e}sum{\'e}]},
  author = {{G}ontharet, {S}. and {P}ierre {C}. and {P}elleter, {E}. and {C}aquineau, {S}andrine and {B}oudouma, {O}. and {D}emange, {J}. and {T}eske, {A}.{P}. and {L}izzaralde, {D}. and {H}{\¨o}fig, {T}.{W}. and {T}he {E}xpedition 385 {S}cientists,},
  editor = {},
  language = {{ENG}},
  abstract = {{D}uring the {I}nternational {O}cean {D}iscovery {P}rogram ({IODP}) {E}xpedition 385, diagenetic carbonates were recovered at different depths (from 10 to 534 mbsf) in six drilling sites ({U}1545, {U}1546, {U}1547, {U}1548, {U}1550 and {U}1552) distributed from the northern spreading segment of the {G}uaymas {B}asin ({G}ulf of {C}alifornia) to average 52 km away from the axial graben. {A}s this basin is a site of active sea floor spreading, hemipelagic diatomaceous and organic-rich sediments rapidly accumulating at all these drilling sites are influenced by magmatic intrusions, at depths greater than 90 mbsf. {T}he geothermal gradient observed ranges from 135 °{C}/km to 682 °{C}/km. {E}xcept in sites {U}1547 and {U}1548, both located close to a circular hydrothermal mound (called {R}ingvent), sills are in thermal equilibrium with the surrounding sediments. {C}arbonate samples (over fifty) collected during this expedition are composed of fine-grained micritic sediments and weakly to strongly lithified carbonate concretions. {T}he petrographic observations and {XRD} analyses show that stoichiometric dolomite is the dominant authigenic carbonate phase, with minor contribution of {F}e-rich dolomite, and low- to high-{M}g calcite. {C}entimeter-sized concretions composed of ankerite and {M}g-calcite also occur in the sediments collected from the northern axial graben (site {U}1550) and a site with subsurface gas hydrates ({U}1552), respectively. {O}ther authigenic minerals are often associated with these carbonates including pyrite, barite, anhydrite, zeolites and crystalline opal (opal-{CT}). {T}he carbon isotopic compositions of the bulk carbonate from these samples exhibit large variations ranging from -28.9 to +12.0? {VPDB}. {V}ery low d 13{C} values, only measured in a centimetre-seized concretion associated with cold methane seepage (site {U}1552), indicate that the bicarbonate used for carbonate precipitation is derived from anaerobic oxidation of methane ({AOM}) coupled with bacterial sulfate reduction ({BSR}). {T}he very high d13{C} values of diagenetic carbonates indicate the use of biogenic 13{C}-rich {CO}2 reservoirs related to active methanogenesis or other autotrophic microbial pathways. {T}he oxygen isotopic compositions of these carbonates cover a large range from -5.3 to +4.0? {VPDB}. {T}he decreasing d18{O} values with increasing depth reflect the effect of high geothermal gradients due to the close proximity of magmatic sills.},
  keywords = {{MEXIQUE} ; {GUAYMAS} ; {GOLFE} {DE} {CALIFORNIE}},
  numero = {},
  pages = {{EGU}22--4385 [2 ]},
  booktitle = {},
  year = {2022},
  DOI = {10.5194/egusphere-egu22-4385},
  URL = {https://www.documentation.ird.fr/hor/fdi:010086597},
}