DOI: 10.1007/s00531-014-1095-5
Scopus记录号: 2-s2.0-84925538047
论文题名: Re-equilibration history and P–T path of eclogites from Variscan Sardinia, Italy: a case study from the medium-grade metamorphic complex
作者: Cruciani G. ; Franceschelli M. ; Groppo C. ; Oggiano G. ; Spano M.E.
刊名: International Journal of Earth Sciences
ISSN: 14373254
出版年: 2015
卷: 104, 期: 3 起始页码: 797
结束页码: 814
语种: 英语
英文关键词: Mineralogical re-equilibration
; Nappe zone
; Northern Sardinia
; P–T path
; Retrogressed eclogite
; Variscan Orogeny
英文摘要: Retrogressed eclogites are hosted within the Variscan low- to medium-grade metamorphic complex near Giuncana, north-central Sardinia. These rocks are medium to fine grained with garnet and amphibole as the most abundant mineral phases along with clinopyroxene, plagioclase, quartz, biotite, chlorite, epidote, ilmenite, rutile and titanite. Four stages of mineralogical re-equilibration have been distinguished. The stage I is characterized by the occurrence of omphacite, epidote, quartz, amphibole, rutile and ilmenite in garnet poikiloblasts. The stage II is characterized by two types of symplectitic microstructures: (1) amphibole + quartz symplectite and (2) clinopyroxene + plagioclase ± amphibole symplectite. The first symplectite type replaces omphacite included in garnet, whereas the second one is widespread in the matrix. Biotite droplets and/or lamellae intimately growing with fine-grained plagioclase resemble biotite + plagioclase symplectite after phengite. The stage III is characterized by the widespread formation of amphibole: (1) as zoned porphyroblasts in the matrix, (2) as corona-type microstructure replacing garnet. Subordinate plagioclase (oligoclase) is also present in the amphibole corona. The stage IV is characterized by the local formation of biotite replacing garnet, actinolite, chlorite, albite and titanite. P–T pseudosections calculated with Perple_X give P–T conditions 580 < T < 660 °C, 1.3 < P < 1.8 GPa for the stage I. After the stage I, pressure decrease and temperature increase led to the breakdown of omphacite with the formation of clinopyroxene + plagioclase ± amphibole symplectite at ~1.25–1.40 GPa and 650–710 °C (stage II). P–T conditions of the amphibolite-facies stage III have been defined at 600–670 °C, P = 0.65–0.95 GPa. P–T conditions of the latest stage IV are in the range of greenschist facies. The P–T path of the retrogressed eclogite hosted in the medium-grade micaschist and paragneiss of Giuncana recalls the P–T trajectory of retrogressed eclogite hosted in the migmatite complex of northern Sardinia. The eclogites from Giuncana do not preserve the prograde segment of the P–T path, but, similarly to the other Sardinian eclogites, they record a slight increase in temperature, though slighter, during exhumation. This suggests that the thermal flow responsible for the amphibolitic-granulitic event post-dating the eclogitic stage recorded in the Giuncana eclogite may be tentatively referred to the slab break-off also responsible for the production of the Mg–K igneous suite in Corsica. © 2014, Springer-Verlag Berlin Heidelberg. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925538047&doi=10.1007%2fs00531-014-1095-5&partnerID=40&md5=11f6e3489230c1c8ba257d2ecbc8b79d
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/70304
Appears in Collections: 影响、适应和脆弱性 气候减缓与适应
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作者单位: Dipartimento Scienze Chimiche e Geologiche, Università di Cagliari, Cagliari, Italy; Dipartimento di Scienze della Terra, Università di Torino, Turin, Italy; Dipartimento di Scienze Botaniche, Ecologiche e Geologiche, Università di Sassari, Sassari, Italy
Recommended Citation:
Cruciani G.,Franceschelli M.,Groppo C.,et al. Re-equilibration history and P–T path of eclogites from Variscan Sardinia, Italy: a case study from the medium-grade metamorphic complex[J]. International Journal of Earth Sciences,2015-01-01,104(3)