A weakening mechanism for intermediate-depth seismicity? Detailed petrographic and microtextural observations from blueschist facies pseudotachylytes, Cape Corse, Corsica

Gabbro-and peridotite-hosted pseudotachylytes from the Alpine Schistes Lustres Unit in Corsica, previously determined to have formed at blueschist to lawsonite-eclogite facies conditions, have been causally linked to the generation of intermediate-depth earthquakes, which occur at depths of 50-300 km. Detailed petrographic and microtextural analyses of these pseudotachylytes suggest that their initiation may be controlled by a thermally-activated shear runaway process that is controlled by rheology rather than mineralogy. This is documented by sheared out, prolate, kinked and twinned wallrock clasts that have been peeled off and entrained into the pseudotachylyte vein as sigmoid survivor clasts. The presence of metastable high temperature crystallisation products in the pseudotachylyte, such as hoppers and dendrites of olivine, enstatite and diopside (peridotite) and Al-rich omphacite and Fe-rich anorthite in metagabbro, are suggestive of a short-lived hightemperature event resulting from thermal instability. These high temperature mineral assemblages are overprinted by ones indicating a return to ambient conditions of lower temperatures, but still high pressures: glaucophane, albite and epidote in metagabbro and clinochlore; and fine-grained granoblastic olivine, enstatite and diopside in peridotite. The observations from this detailed study of natural samples suggest that intermediate-depth seismicity may be generated by a thermal runaway process

Epidemiologic Characteristics of Women With Idiopathic Recurrent Vulvo-vaginal Candidiasis

Objective: To evaluate risk factors related to anamnestic variables, sexual behavior, feminine hygiene habits, and microbiologic findings in women with idiopathic recurrent vulvovaginal candidiasis. Methods: We conducted a multivariate observational study comparing sociodemographic, anamnestic, clinical, and microbiologic variables between 86 patients with recurrent vaginal candidiasis and 180 controls with nonrecurrent infection. Results: In logistic regression analysis, women with recurrent candidal vaginitis were more likely than controls to use contraceptive pills (adjusted odds ratio 2.0, 95% confidence interval [CI] 1.02-3.91; P = .04) and commercially available solutions for either vulvoperineal cleansing (adjusted odds ratio 2.2, 95% CI 1.25-3.88; P = .007) or vaginal douching (adjusted odds ratio 1.8, 95% CI 1.0-3.26; P = .05). The rate of isolation of non-albicans candida species was significantly higher among cases than controls (adjusted odds ratio 3.0, 95% CI 1.50-6.04; P = .005). Finally, increasing frequency of monthly sexual intercourse was significantly correlated (chi2 for trend = 4.87; P = .027) with recurrent infection. Conclusion: Several behavioral factors seem to influence the occurrence of relapses in recurrent vulvovaginal candidiasis. Appropriate counseling about contraception, sexual activity, and personal hygiene habits could be an important preventive measure in these cases

Earthquakes in the Mantle? Insights From Rock Magnetism of Pseudotachylytes

Ultramafic pseudotachylytes have been regarded as earthquake fossils formed at mantle depths (i.e., >30 km). Here we show that pseudotachylytes hosted by ultramafic rocks from three localities have distinct magnetic properties. Fresh host peridotites contain only small amounts of coarse-grained magnetite. In contrast, the ultramafic pseudotachylytes contain variable amounts of significantly finer magnetite that formed coseismically through melting. Among each locality, magnetite abundance in the pseudotachylytes ranges over several orders of magnitude (4\u20132,000 ppm), and magnetic grain size varies considerably (from single domain to multidomain). Because the host peridotites are compositionally similar, the pseudotachylyte magnetic properties are interpreted to primarily reflect the physical and cooling conditions prevailing during seismic slip. Further, the examination of laboratory-produced ultramafic pseudotachylytes shows that quenching does not produce superfine magnetite. We hypothesize that the magnetic properties of ultramafic pseudotachylytes are controlled by fO2 and in consequence vary systematically with depth of formation. Therefore, these properties can be used to assess if the ruptures producing the earthquakes that these pseudotachylytes represent nucleated at actual mantle depths or at shallow depths during exhumation of mantle rocks

Earthquakes in the mantle? Insights from rock magnetism of pseudotachylytes

Ultramafic pseudotachylytes have been regarded as earthquake fossils formed at mantle depths (i.e., >30 km). Here we show that pseudotachylytes hosted by ultramafic rocks from three localities have distinct magnetic properties. Fresh host-peridotites contain only small amounts of coarse-grained magnetite. In contrast, the ultramafic pseudotachylytes contain variable amounts of significantly finer magnetite that formed coseismically through melting. Among each locality, magnetite abundance in the pseudotachylytes ranges over several orders of magnitude (4~2000 ppm), and magnetic grain size varies considerably (from single domain to multidomain). Because the host-peridotites are compositionally similar, the pseudotachylyte magnetic properties are interpreted to primarily reflect the physical and cooling conditions prevailing during seismic slip. Further, the examination of laboratory- produced ultramafic pseudotachylytes shows that quenching does not produce superfine magnetite. We hypothesize that the magnetic properties of ultramafic pseudotachylytes are controlled by fO2 and in consequence vary systematically with depth of formation. Therefore these properties can be used to assess if the ruptures producing the earthquakes that these pseudotachylytes represent nucleated at actual mantle depths or at shallow depths during exhumation of mantle rocks. This research was originally published in Journal of Geophysical Research. Solid Earth. © 2017 Wile