التفاصيل البيبلوغرافية
| العنوان: |
C-O-H fluids and redox processes at subduction zones |
| المؤلفون: |
MALASPINA, NADIA, Tumiati, S, Fumagalli, P, Poli, S. |
| المساهمون: |
Malaspina, N, Tumiati, S, Fumagalli, P, Poli, S |
| بيانات النشر: |
Società Geologica Italiana |
| سنة النشر: |
2014 |
| المجموعة: |
Università degli Studi di Milano-Bicocca: BOA (Bicocca Open Archive) |
| مصطلحات موضوعية: |
C-O-H fluids, carbonate, diamond, redox state, oxygen fugacity, GEO/07 - PETROLOGIA E PETROGRAFIA |
| الوصف: |
C-O-H fluids are released by dehydration, partial melting and/or decarbonation of the slab and transferred to the mantle, where they interact with the surrounding rocks, prompting the growth of carbonates, hydrous minerals and C polymorphs. In the pure C-O-H system, C-saturated fluid speciation is a function of the oxygen chemical potential. Therefore, in natural systems, the fluid speciation can be imposed by the redox state of the rock-forming phases. Alternatively, C-O-H fluids may control the bulk oxidation state of the rock system by redox reactions with the mineral phases. Complexities in the speciation of such fluids are demonstrated by discoveries of hydrates, carbonates and carbon polymorphs in polyphase inclusions, and also by high-pressure H2- or CH4-bearing fluid inclusions in mantle harzburgites, suggesting that the composition of C-bearing hydrous fluids closely relates to the oxidation state of the system. We selected three case studies of garnet-bearing ultramafic rocks (Ulten zone, Italy; Sulu, China; Bardane, Norway), which record metasomatic processes driven by C-O-H fluids at the interface between a subducting slab and the overlying mantle wedge. All these rocks contain carbonates (dolomite-only at P < 1.9 GPa at 900 °C, magnesite- only at P > 2.4 GPa at 900 °C, dolomite + magnesite in between) and hydrous phases (amphibole, phlogopite) equilibrated at some stages in the garnet stability field. The fO2 values, estimated by analysing the Fe3+ content (skiagite mole fraction) in garnet, indicate that the Ulten and Sulu peridotites record high oxygen fugacities (FMQ to FMQ+2) and a retrograde path with decreasing P and T. The fO2 values obtained for the Bardane garnet websterites, which record a prograde path with increasing T and P, are up to -2 log units lower than the FMQ. When combined with data for subduction-zone systems (arc lavas and their mantle sources), the studied ultramafic rocks define a trend of decreasing fO2 with increasing pressure. The Bardane websterites contain ... |
| نوع الوثيقة: |
conference object |
| اللغة: |
Italian |
| العلاقة: |
ispartofbook:Rendiconti Online della Società Geologica Italiana; Congressi SGI-SIMP 2014; firstpage:411; lastpage:411; numberofpages:1; journal:RENDICONTI ONLINE DELLA SOCIETÀ GEOLOGICA ITALIANA; http://hdl.handle.net/10281/52887Test |
| الإتاحة: |
http://hdl.handle.net/10281/52887Test |
| رقم الانضمام: |
edsbas.5D89CD59 |
| قاعدة البيانات: |
BASE |
