Brittle Fracture in Oceanic Basalts

Basalt samples dredged from the ocean floor were experi­mentally fractured in tension while being observed microscopi­cally. Five basaltic textural types were chosen: (1) cotectic crystallization of olivine, plagioclase, and pyroxene Juan de Fuca, (2) dark glass matrix with phenocrysts of plagioclase and clinopyroxene Gorda Ridge, (3) vesicular black glass matrix with trachytic micro-phenocrysts Mid Atlantic Ridge Rift Valley, (4) black glass pillow with an hollow-centered phenocrysts Mid Atlantic Ridge Rift Valley, (5) black glass matrix with micro-­phenocrysts of olivine, pyroxene, plagioclase Mid Atlantic Ridge Rift Valley. Fracturing was done in the ¼ inch direction of precisely machined chips 1 x ¾ x ¾ inches. Test conditions were dry at 20°C, wet at 20°c, and 300°c. Modal integration of the crack path length and general modal analyses indicate that regardless of texture or test parameter: (1) the fracture path seeks out voids, glass, and grain boundaries to the exclusion of mineral grain cleavage, (2) a propagating fracture is offset by pre-existing frac­tures perpendicular to the propagation direction, (3) within the locus of the propagation direction, a pro­pagating fracture coalesces with a pre-existing parallel or sub-parallel fracture. The off-setting behavior of pre-existing fractures for newer fractures bears a striking geometric resemblance to the Mid Atlantic Ridge and its transform faults.

Grantor dc:publisher

Temple University. Libraries

Year dc:date.issued

1972

Author dc:creator

• Koons, Mary-Linda

Advisor dc:contributor.advisor

• Ulmer, Gene Carleton, 1937-2015

Committee members dc:contributor.committeemember

• Myer, George H.
• Platt, Lucian B., 1931-

• Geology
• Basalt

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Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/20.500.12613/8425

OAI record oai:identifier

https://scholarshare.temple.edu/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Ascholarshare.temple.edu%3A20.500.12613%2F8425