High-pressure granulites from Carir¨¦, Borborema Province, NE Brazil: Tectonic setting, metamorphic conditions and U-Pb, Lu-Hf and Sm-Nd geochronology

详细信息    查看全文

• 作者：Wagner da Silva Amaral ; Ticiano Jos¨¦ Saraiva dos Santos ; Eberhard Wernick ; Jos¨¦ de Ara¨²jo Nogueira Neto ; Elton Luiz Dantas ; Massimo Matteini
• 关键词：Granulites ; High pressure ; Metamorphic conditions ; U&ndash ; Pb ; Borborema Province
• 刊名：Gondwana Research
• 出版年：2012
• 出版时间：November, 2012
• 年：2012
• 卷：22
• 期：3-4
• 页码：892-909
• 全文大小：4128 K

文摘

In the northwest region of the Cear¨¢ Central Domain, Borborema Province, an elongate area of mylonitic diorites and granodiorites is structurally controlled by NE-SW-trending strike-slip faults. Granitic material and layers and lenses of felsic and mafic granulites occur along the main shear zones. We present and discuss petrographic, geothermobarometric, and geochronological (LA-MC-ICPMS U-Pb and Lu-Hf in zircon and Sm-Nd whole-rock) data for these rocks. Felsic granulites are composed of orthopyroxene + clinopyroxene + plagioclase + quartz ¡À hornblende ¡À garnet ¡À biotite ¡À feldspar, while the mafic granulites comprise clinopyroxene + plagioclase + garnet + hornblende ¡À rutile ¡À quartz. The P-T conditions recorded range from 9.4 to 8.3 kbars and from 804 to 870 ¡ãC for the felsic granulites and from 13.6 to 10.2 kbars and 910 to 750 ¡ãC for the mafic granulites. U-Pb zircon ages of granodiorite host rocks are 2157 and 2044 Ma. The felsic granulites yield a U-Pb age of 2110 Ma, while the mafic granulites yield U-Pb zircon ages of 613 and 589 Ma for the metamorphic recrystallization. Sm-Nd and Lu-Hf T_DM ages for the mafic granulites are similar (1.6-1.3 Ga) and share positive values of ¦Å_Nd and ¦Å_Hf, which suggests that these mafic rocks were derived from a juvenile Mesoproterozoic crust. In addition, the felsic granulites and the granodiorites have similar T_DM-Nd and U-Pb ages (with positive values of ¦Å_Nd), indicating a Paleoproterozoic mantle source for these rocks.