Liquid immiscibility in the Archean Greenstone Belt of Piumhi (Minais Gerais,Brazil) |
| |
| Affiliation: | 1. Istituto di Mineralogia, Università di Ferrara, Corso E. I d''Este, 32, 44100 Ferrara Italy;2. Instituto de Geocencias, Cidade Universitaria, Universidade do São Paulo, São Paulo Brazil;1. Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, 05508-900, Brazil;2. Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Via Campi, 103, I-41125, Modena, Italy;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Earth Dynamics Research Group, ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Sciences, Curtin University, WA 6845, Australia;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Department of Geosciences, Eberhard Karls University Tuebingen, Tuebingen 72076, Germany;1. Laboratorio de Paleomagnetismo Daniel A. Valencio, Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires (IGEBA), Departamento de Cs. Geologicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina;2. University of Western Australia, Australia;3. Laboratorio de Geofísica y Geotectónica, Departamento de Geología, Facultad de Ciencias, Universidad de la República, Uruguay;4. IANIGLA (Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales), CCT-Mendoza, CONICET, Argentina;5. Instituto de Geocronología y Geología Isotópica (INGEIS), UBA-CONICET, Buenos Aires, Argentina;1. Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology, Shahrood, Iran;2. School of Mining, College of Engineering, University of Tehran, Tehran, Iran |
| |
| Abstract: | Liquid immiscibility has been used for explaining several modern situations either in effusive or in intrusive rocks. Liquid immiscibility is also proposed for explaining the variolitic structures in the Archean rocks of the Abitibi Greenstone belt, Ontario.The volcanic sequence of the lower portion of the Greenstone belt of Piumhi (Minas Gerais, Brazil) shows the occurrence of variolitic structure, that may have been formed by liquid immiscibility.This possibility is supported by the following points: (a) the contact between varioles and matrix is very sharp; (b) spinifex texture occurs both in the varioles and in the matrix and the single crystal may cross the varioles; (c) the varioles and the matrix show contrasting compositions: the latter has the composition of a basaltic komatiite and the former varies form that of an alkali-basalt to andesite; and (d) a test by a thermodynamic model from literature shows that, although with some doubt, the free energy of the possible parent liquid is higher than that of the two unmixed liquids. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
