Paleomagnetic and mineral magnetic studies of zinc-lead ore deposits in the Metaline (Washington state, USA) and Midlands (Ireland) ore fields

详细信息    Paleomagnetic and mineral magnetic studies of zinc-lead ore deposits in the Metaline (Washington state, USA) and Midlands (Ireland) ore fields

• 出版日期：2007.
• 页数：1 online resource.
• 第一责任说明：Shanmugam Johari Pannalal.
• 分类号：a423.2 ; a261
• ISBN：9780494350942(e-book) :

MARC全文

62h0047271 20131203095527.0 cr an |||||||| 131024s2007 a fsbm |000|0 eng | NR35094 9780494350942(e-book) : CNY371.35 NGL eng NGL a423.2 ; a261 Pannalal, Shanmugam Johari. Paleomagnetic and mineral magnetic studies of zinc-lead ore deposits in the Metaline (Washington state, USA) and Midlands (Ireland) ore fields [electronic resource] / Shanmugam Johari Pannalal. 2007. 1 online resource. Description based on online resource; title from title page (viewed Oct. 24, 2013) Thesis (Ph.D.)--University of Windsor (Canada), 2007. Includes bibliographical references. Carbonate-hosted Zn-Pb deposits of the Metaline USA) and Irish Midlands Ireland) ore fields exhibit features of both MVT and SEDER deposits, and therefore, play an important role in the debate over genetic models for MVT - SEDER deposits, including the structural controls on ore mineralization, syngenetic versus epigenetic models, and the origin and migration pathways for hydrothermal fluids. The genetic controversy arises largely because of the lack of direct dates on mineralization. Paleomagnetic analyses on samples of host rock and ore mineralization from 38 sites 400 specimens) in the Metaline Zn-Pb district, Washington USA), using the known thermal history and the paleoarc method of paleomagnetic dating, indicate coeval postfolding magnetizations acquired during the Middle Jurassic 166＋/-6 Ma), in the waning stages of the Nevadan Orogeny. The thermal Th) and alternating field AF) step demagnetization, saturation isothermal anaylses SIRM), and artificial specimens tests show that the characteristic remanent magnetizations ChRM) is carried mostly by pseudosingle PSD) to single domain SD) pyrrhotite that records a primary chemical remanent magnetization CRM) in ore and a secondary ChRM in host specimens. Furthermore, the paleomagnetic Middle Jurassic age suggests an epigenetic origin for ore formation of the Zn-Pb mineralization at the Pend Oreille Mine that coincides with the timing of cooling from the regional Nevadan orogenic heating episode. Paleomagnetic analyses of the least thermally affected conodont alteration indices CAI) of <；3) Lower Carboniferous rocks at 18 sites 231 specimens) from Northern Ireland indicate posttilting ChRMs in magnetite and pyrrhotite that record a secondary CRM that was acquired &sim；3 to 4 Ma after limestone deposition. Also, paleomagnetic analyses of host rock and ore specimens in 46 sites 705 specimens) from the Galmoy and Lisheen Zn-Pb deposits from the Irish Midlands give stable postfolding ChRM, that reside in magnetite, were acquired during the Early Permian at 288＋/-8 Ma at Galmoy and 276＋/-6 Ma at Lisheen. These Early Permian paleomagnetic ages postdate the Asturian deformational phase of the Variscan orogeny and suggest an entirely epigenetic Variscan model of ore genesis in which the mineralization event occurred during the cooling from the regional Variscan thermal episode. Zinc ores ; Lead ores ; Paleomagnetism Washington (State) ; Washington (State) ; Washington (State) Electronic dissertations local. aInternet resource. aCN b010001 http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=TxUeG6TrSHM%3d 010001 Bs2770 rCNY371.35 ; h1 bs1312