Detail Investigations of faulting, magmatism, and hydrothermal activity in extensional environments Bibliografi Author: Curewitz, Daniel ; Karson, Jeffrey A. (Advisor) Topik: GEOLOGY Bahasa: (EN )    ISBN: 0-599-28793-4     Penerbit: DUKE UNIVERSITY     Tahun Terbit: 1999     Jenis: Theses - Dissertation Fulltext: 9928816.pdf (0.0B; 0 download) Abstract This dissertation comprises four separate investigations into the processes and products of faulting, magmatism and hydrothermal flow in ancient and modern extensional environments. Abstracts from each chapter, all of which are either published or in preparation, are presented below. Hydrothermal outflow occurs most commonly at the terminations of individual faults and where multiple faults interact. Concurrent migration of hydrothermal outflow sites along with these areas of elevated permeability leads to predictable patterns of hydrothermal deposition along fault zones. Dike intrusion is a fundamental process of crustal accretion at mid-ocean ridge spreading centers. Although many studies of ophiolites and spreading centers treat dikes as passive infillings of tensile fractures, observations and mechanical models from subaerial rift zones demonstrate that widespread, temporally and spatially complex mechanical effects accompany dike intrusion. Repeated dike intrusion will create systematically contrasting crustal assemblages that reflect the varying relationship between faulting and magmatism at different mid-ocean ridge spreading centers. Angular pseudotachylyte is found primarily in >10-m-wide irregular outcrops near fault zones, called reservoir zones. It is characterized by angular mineral grains and lithic fragments visible on all scales, with micron-scale fragments of mica and amphibole. Its matrix is enriched in Fe2O3, MgO, and TiO2 relative to the host rock, with minor increases in CaO and K2O, and small decreases in Na2O. Rounded pseudotachylyte is found in reservoir zones, pseudotachylyte-filled extension fractures, and small faults. These observations suggest that angular pseudotachylyte was produced by cataclasis, with enrichment in metallic oxides resulting from preferential crushing of mechanically weak amphibole and mica minerals found in the gneissic host rock. Cataclasis and concomitant frictional heating resulted in the textural and chemical modification of angular pseudotachylyte by sintering or melting, producing rounded and glassy pseudotachylyte, respectively. Structural mapping of Early Cretaceous-Tertiary sedimentary deposits in the Kangerlussuaq Region, East Greenland provides new insight into the pre-breakup tectonic history of this section of the Tertiary North Atlantic volcanic rifted margin. The composition, orientation and thickness of Early Cretaceous fluvial to marine sandstones and later shales suggest an initial period of slow (<0.5 mm/yr) regional subsidence. This subsidence may be related to thermal relaxation of the flanks of Jurassic rifts that form the Faeroe-Shetland Basin—the conjugate margin to the study area. Normal faulting and the intrusion of an extensive sill complex in the Late Cretaceous-Early Tertiary disrupted Early Cretaceous sedimentary deposits. (Abstract shortened by UMI.) Opini Anda Klik untuk menuliskan opini Anda tentang koleksi ini! Lihat Sejarah Pengadaan  Konversi Metadata   Kembali

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