RHEOLOGY AND MICROSTRUCTURES OF EXPERIMENTALLY DEFORMED QUARTZ AGGREGATES (FLOW LAWS, PIEZOMETRY, ROCK MECHANICS).

摘要

Circular cylinders (12.7 mm long, 6.4 mm in diameter) of Simpson quartzite (d(,i) (TURN) .21 mm) and Arkansas novaculite (d(,i) (TURN) 7.5 (mu)m) were deformed ductiley in compression to mechanical steady-state at two nominal "wetnesses" using Griggs-Blacic solid medium apparatuses. Experimental conditions were in the range 750-1000(DEGREES)C, .91-1.52 GPa, 1.25 x 10('-7) -2.53 x 10('-4)s('-1), .22-2.74 GPa flow stress; all samples were quenched rapidly under differential stress.;(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI).;2.72 (+OR-) .19, 134 (+OR-) 32 (kJ.mol('-1)) for "dry" quartzite; 5.05 E-6 (+OR-) 5.59 E-9 (MPa('-2.61)s('-1)), 2.61 (+OR-) .15, 145 (+OR-) 17 (kJ.mol('-1)) for "wet" quartzite; and 3.72E-2 (+OR-) 3.39E-2 (MPa('-2.35)s('-1)), 2.35 (+OR-) .20, 210 (+OR-) 17 (kJ.mol('-1)) for "wet" novaculite. For either starting material, "dry" experiments were stronger than comparable "wet" experiments. Comparing the two starting materials deformed "dry", novaculite was stronger. In "wet" experiments, relative strengths vary with temperature. Grain boundary effects were correlated to neither "wetness" nor flow stress and were inconsistent with either Hall-Petch or superplastic behavior.;Microstructures produced in these experiments were analogous to those observed in many natural quartz tectonites. Recrystallization was present in all but a few "dry" samples and contributed to local stress relaxation in all the specimens observed by TEM. Recovery processes were important at flow stresses below (TURN)500 MPa.;Data from the (alpha)-quartz field are well described by both power {(epsilon) = A(,1) (sigma)('n)exp(-Q/RT)} and hyperbolic sine laws. Power law constants A(,1), n, and Q are respectively.;Samples with simple strain histories appeared to have reached microstructural steady-state. Several microstructures were measured to determine piezometric relations of the form y = b((sigma)(,1)-(sigma)(,3))('Y) where y is the measured microstructure and b and Y are empirically determined constants which did not appear to depend upon "wetness" or initial grain size and which were respectively 490 ((mu)m.MPa('.59)) and -.59 for recrystallized grain size; 137 ((mu)m.MPa('.54)) and -.54 for subgrain size; and 19.8 ((mu)m.MPa('.32)) and -.32 for the spacing of deformation lamellae. Such a relationship was not determinable for dislocation density. Data gathered in both the (alpha)- and (beta)-quartz fields are in good agreement as are measured subgrain sizes and lamellar spacings.