Evidence of hydrothermal fluid circulation driving elemental mass redistribution in an active fault zone

Important fault zone processes can be discerned from the characterization of fracture damage and chemical transformations associated with active seismic sources. To characterize the 2010 M7.2 El Mayor-Cucapah rupture zone, continuous samples of fault core and 23 samples of damaged rock were collected perpendicular to strike of the Borrego fault. Samples were analyzed for clay mineralogy, bulk geochemistry, and bulk and grain density from which porosities and volumetric strains were derived. Prior to the Borrego fault forming, the tonalitic protolith, containing chlorite, epidote, and titanite, was subjected to temperatures of ∼330–340 °C during deuteric alteration. Rocks within the damage zone are partially pulverized and contain abundant cataclastic seams. Porosity and volumetric strain peak in zones 1.5 m–10.5 m from the core. Within these zones, losses in Ca and P mass, increases in Mg and Na mass, along with the conservation of Fe and Si mass are consistent with oxidizing acidic conditions at < 200 °C. Gains in LOI are attributed to increases in clay content. The above data support a model of Mg- and Na-rich oxidizing fluid circulation within the damage zone of the Borrego fault

Early carboniferous brachiopod faunas from the Baoshan block, west Yunnan, southwest China

38 brachiopod species in 27 genera and subgenera are described from the Yudong Formation in the Shidian-Baoshan area, west Yunnan, southwest China. New taxa include two new subgenera: Unispirifer (Septimispirifer) and Brachythyrina (Longathyrina), and seven new species: Eomarginifera yunnanensis, Marginatia cylindrica, Unispirifer (Unispirifer) xiangshanensis, Unispirifer (Septimispirifer) wafangjieensis, Brachythyrina (Brachythyrina) transversa, Brachythyrina (Longathyrina) baoshanensis, and Girtyella wafangjieensis. Based on the described material and constraints from associated coral and conodont faunas, the age of the brachiopod fauna from the Yudon Formation is considered late Tournaisian (Early Carboniferous), with a possibility extending into earlyViseacutean.<br /

Host-specific pit-forming epizoans on Silurian crinoids

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75404/1/j.1502-3931.1978.tb01229.x.pd

Carboniferous and Permian Rugosochonetidae (Brachiopoda) from West Spitsbergen

The rugosochonetid brachiopod species Lissochonetes geinitzianus from the Kazimovian of the Nordenskioldbreen Formation, and Dyoros (Dyoros) mucronata sp. nov., Dyoros (Dyoros) spitzbergianus and Lissochonetes superba from the Artinskian to latest Permian Kapp Starostin Formation in West Spitsbergen are described and figured. Dyoros is generally restricted to the Boreal Realm, whereas Lissochonetes is mostly distributed in the Boreal Realm, but occasionally present in the Palaeoequatorial and Gondwanan Realms<br /

Mesozoic cataclastic rocks in the Boyden Cave roof pendant and their regional significance

he Boyden Cave pendant is an elongate northwesterly trending body consisting of metamorphosed miogeosynclinal lithologies in the west and eugeosynclinal lithologies in the east. The miogeosynclinal sequence is derived from pelitic shales, quartz sandstones, marls, and limestones, while the eugeosynclinal sequence is derived from intermediate volcanics and subordinate pelitic shales. Field and microscopic relations in a cross-sectional portion of the Bovden Cave pendant suggests that the pendant has undergone two periods of deformation and regional metamorphism and one period of contact metamorphism. The first deformation affecting the pendant produced a quartz-biotite schistosity in pelitic rocks and N70°E trending isoclinal to slightly open, similar style folds. The second deformation is a cataclastic event which disrupted the first generation structures and produced nearly isoclinal N15°W trending chevron style folds, mineral and crenulation lineations, and a cataclastic foliation subparallel to second generation axial planes. The second generation structures dominate the macroscopic fabric of the pendant and the Lightning Creek Granodiorite (Moore and Marks, 1972), thus suggesting that the pendant and pluton largely comprise a fault zone. Although Jones and Moore (1973) extracted a early Jurassic ammonite from vi slates in the eastern portion of the pendanc, the cataclastic nature of the rocks indicates that only the small tectonic unit where the fossil was found is of early Jurassic age. The Boyden Cave structures are reflections of regional deformations, as they have counterparts in the Western Metamorphic Belt (Baird, 1962, Wetzel and Nokleberg, 1976) and in the lower Kings River pendant (Nokleberg, 1975) . It is concluded that the first deformation affecting the western Sierra Nevada foothills occurred in the late Triassic-early Jurassic and the second deformation occurred in the late Jurassic

Descriptions of new species ol Upper Paleozoic fossils from China

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