HR: 14:55h
AN: T43E-06    [Abstracts]
TI: Experimental study of the effect of mica on pressure solution of single crystal calcite
AU: * Karcz, Z
EM: zvi.karcz@exxonmobil.com
AF: Corporate Strategic Research. ExxonMobil Research and Engineering, 1545 Route 22E, Annandale, NJ 07901, United States
AU: Laronne, L
EM: leehee@wisemail.weizmann.ac.il
AF: Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, Sussman 202, Rehovot, 76100, Israel
AU: Polizzotti, R S
EM: richard.s.polizzotti@exxonmobil.com
AF: Corporate Strategic Research. ExxonMobil Research and Engineering, 1545 Route 22E, Annandale, NJ 07901, United States
AU: Ertas, D
EM: deniz.ertas@exxonmobil.com
AF: Corporate Strategic Research. ExxonMobil Research and Engineering, 1545 Route 22E, Annandale, NJ 07901, United States
AU: Aharonov, E
EM: einat.aharonov@weizmann.ac.il
AF: Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, Sussman 202, Rehovot, 76100, Israel
AB: Field and experimental studies suggest that clays and micas accelerate the rate of pressure solution in various geomaterials. It is not clear however whether the "clay effect" is purely mechanical (i.e., maintaining a thick conduit for fluids at the contact) or whether its surface chemistry plays a critical role. A case in point is the insoluble clay filling of stylolites, which are thought by some to be merely an inert byproduct of dissolution, or by others to be a necessary feature for the propagation of the seam. To study the effect of mica on carbonate pressure solution, the corner of a cleaved calcite single crystal rhomb was polished into a triangular face (edge length ~ 200micron) and pressed against either muscovite or quartz discs to yield a nominal stress of 10-20MPa. Immersing the contact in pre-saturated (with respect to microcrystalline calcite) solutions of distilled water or 0.25M NH4Cl caused axial shortening of the crystal. This axial strain was measured with a capacitance sensor (<0.5nm/h resolution) while the contact morphology was imaged in situ with a confocal microscope (3micron spatial resolution). In pre-saturated water solution the axial shortening of calcite loaded against muscovite is ~1nm/h, and no significant changes in contact morphology are detected. In pre-saturated NH4Cl solution however, both calcite- quartz and calcite-muscovite contacts evolve in two stages: the first stage is characterized by low axial strain rates (<5nm/h) during which the original contact area inside the triangle (as determined by interference fringes) shrinks and its perimeter roughens. The second stage is distinguished by high axial strain rates (~40nm/h) and changes in the size and spatial position of isolated contacts (diameter< 10 microns) in a dynamic channel-island morphology covering the entire triangular region. Post-experiment SEM analysis suggests dissolution in this region and precipitation on the free faces adjacent to it. At this point we see no significant difference between the calcite quartz and calcite muscovite experiments under similar load conditions.
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3902 Creep and deformation
DE: 3947 Surfaces and interfaces
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting