Electrical Conductivity of Eclogite, Amphibolite and Garnet-Quartz-Mica Schist with Implications for the Conductivity in
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Electrrical Coonductivvity of Eclogite E e, Amph hibolitee and GarnetG Quarttz-Micaa Schist with Im mplicatiions forr the Coonductivity in th he Qian ngtang Terrane T e of Norrthern Tibetan T n Platea au Yi Cao *1, Xiinzhuan Guo o2, 1, Jinxue Du D 3 1. State Keyy Laboratory off Geological Proocesses and Mineral Resourcees, School of Eaarth Sciences, Chinaa University of Geosciences, Wuhan W 430074, China 2. Keyy Laboratory foor High‐Temperrature and Highh‐Pressure Stud dy of the Earth’ss Interior, Instiitute of Geochem mistry, Chinnese Academy of Sciences, Guiiyang 550081, China C 3. School of Earth E Sciences and Resourcess, China Univerrsity of Geoscieences, Beijing 100083, China Yi Cao: https:///orcid.org/0000 0-0001-9197-07763 AB BSTRACT: Un nderstanding the t electrical coonductivity of high pressure metamorphic rocks is essen ntial to constrain the compositions in i the subducttion zone and continental c cru ust. In this stu udy, we calcula ated thee electrical con nductivity for such rocks sam mpled from th he central Qian ngtang metamoorphic belt in the noorthern Tibetan Plateau. Thee results reveaal that, when aqueous a fluids are absent, th he conductivity y of meeta-mafic rock ks (e.g., eclogitee and amphiboolite) is strikingly higher than n that of metaa-felsic rocks (ee.g., gaarnet-quartz-m mica schist). Th he conductivityy of eclogite deecreases due too the enrichmeent of amphibo ole, bu ut this effect iss diminished when w a critical degree of amp phibolization is i reached. Ou ur calculated conc du uctivity of ecloggite and amph hibolite differs greatly from the t experimen ntally derived rresults for the ecloggites from oth her localities, partly p owing to t the strong effects e of diffeerent mineral assemblages and a ch hemical compositions on the conduction mechanisms m and d efficiencies. However, the disparity of conc du uctivity betweeen our calculated and the preeviously measu ured results forr a similar amp phibole-rich ecclogitte sampled froom the same loocality suggests that trails off highly condu uctive rutile-ilm menite aggrega ates maay contribute to the higher bulk-rock b conductivity in th he laboratory measurements m . Moreover, since thee calculated coonductivity of eclogite and amphibolite is not n high enouggh at the temp peratures relev vant to their metamorphic thermal condition, parrtial melts or aqueous a fluidss originated froom the upwellling astthenosphere are more likelyy to explain thee anomalously y high electricaal conductivityy zones in mag gnetottelluric imagess in the Qiangttang terrane in n the northern Tibetan Plateaau. KE EY WORDS: electrical e condu uctivity, eclogitee, amphibolite, felsic schist, higgh pressure meetamorphic rocck. 0
INTRODU UCTION Eclogite is a meta-maficc rock consistinng mainly of garnet g (Grt) and ompphacite (Omp) that t are formed by high-pressuure to ultrahigh-presssure (HP-UHP) metamorphism m. Tectonically, eclogite commonlyy represents the mafic componeents in the subduucted oceanic/continnental crust or inn the thic
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