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SUMMARY:Altering volcanic rocks at the Earth’s surface: A progress repor
 t - Lou Derry\, Cornell University\, USA
DTSTART:20170504T130000Z
DTEND:20170504T140000Z
UID:TALK72447@talks.cam.ac.uk
CONTACT:Alexandra Turchyn
DESCRIPTION:While much work on weathering and alteration processes has foc
 used on granitoid compositions that represent typical continental crust\, 
 the subaerial weathering of volcanic rocks is an important part of the geo
 chemical cycle.  The alteration of volcanics is a strong sink for CO2 in p
 art because of their compositions\, hydraulic properties and chemical reac
 tivity. On a global scale weathering of volcanics contributes disproportio
 nately to CO2 consumption fluxes\, and appears to depend strongly on tempe
 rature.  Ocean island and arc settings are particularly important because 
 they continuously generate new substrate\, are geomorphically active\, and
  are commonly wet.  The coupled geochemical-hydrological evolution of the 
 surface of volcanic islands differs substantially from most continental se
 ttings\, is poorly understand\, and can lead to substantial underestimates
  of weathering fluxes. The processes that control basalt alteration in a s
 oil profile are also incompletely understood\, in part because of the pres
 ence of complex amorphous phases in both primary and altered materials.  W
 e have used reactive transport modeling with a chronosequence of basaltic 
 soils to better understand the roles of affinity\, water saturation\, acid
 ity and ligand complexation in the weathering of basalt under humid condit
 ions. Finally\, the major province for volcanic alteration is the oceanic 
 crust\, where oxidative alteration is a major part of the global redox cyc
 le.  An interesting question is how the oceanic crust was coupled to the g
 lobal redox cycle under conditions of low seawater sulfate and oxygen in D
 eep Time. \n
LOCATION: Harker 2\, Department of Earth Sciences\, Downing Street
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