Unraveling the origins and P-T-t evolution of the allochthonous Sobrado unit (Ordenes Complex, NW Spain) using combined U-Pb titanite, monazite and zircon geochronology and rare-earth element (REE) geochemistry

被引：1

作者：

Manuel Benitez-Perez, Jose ^{[1
,3
]}

Castineiras, Pedro ^{[2
]}

Gomez-Barreiro, Juan ^{[3
]}

Martinez Catalan, Jose R. ^{[3
]}

Kylander-Clark, Andrew ^{[4
]}

Holdsworth, Robert ^{[5
]}

机构：

[1] Univ Lisbon, Ctr Ciencias & Tecnol Nucl, Inst Super Tecn, Estr Nacl 10 Km 139,7, P-2695066 Bobadela, Portugal

[2] Univ Complutense Madrid, Fac Ciencias Geol, Dept Mineral & Petrol, C Jose Antonio Novais 12,Ciudad Univ, Madrid 28040, Spain

[3] Univ Salamanca, Dept Geol, Pza Caidos S-N, Salamanca 37008, Spain

[4] Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA

[5] Univ Durham, Earth Sci Dept, Sci Labs, Durham DH1 3LE, England

来源：

SOLID EARTH | 2020年 / 11卷 / 06期

关键词：

WEST-AFRICAN CRATON; PROGRADE METAMORPHIC REACTIONS; NORTHWESTERN IBERIAN MASSIF; CABO-ORTEGAL COMPLEX; TRACE-ELEMENT; ACCESSORY MINERALS; TECTONIC EVOLUTION; ION MICROPROBE; GRANITIC-ROCKS; OROGENIC BELT;

D O I：

10.5194/se-11-2303-2020

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

The Sobrado unit, within the upper part of the Ordenes Complex (NW Spain) represents an allochthonous tectonic slice of exhumed high-grade metamorphic rocks formed during a complex sequence of orogenic processes in the middle to lower crust. In order to constrain those processes, U-Pb geochronology and rare-earth element (REE) analyses of accessory minerals in migmatitic paragneiss (monazite, zircon) and mylonitic amphibolites (titanite) were conducted using laser ablation split stream inductively coupled plasma mass spectrometry (LASS-ICP-MS). The youngest metamorphic zircon age obtained coincides with a Middle Devonian concordia monazite age (similar to 380 Ma) and is interpreted to represent the minimum age of the Sobrado high-P granulite facies metamorphism that occurred during the early stages of the Variscan orogeny. Metamorphic titanite from the mylonitic amphibolites yield a Late Devonian age (similar to 365 Ma) and track the progressive exhumation of the Sobrado unit. In zircon, cathodoluminescence images and REE analyses allow two aliquots with different origins in the paragneiss to be distinguished. An Early Ordovician age (similar to 490 Ma) was obtained for metamorphic zircons, although with a large dispersion, related to the evolution of the rock. This age is considered to mark the onset of granulite facies metamorphism in the Sobrado unit under intermediate-P conditions, and related to intrusive magmatism and coeval burial in a magmatic arc setting. A maximum depositional age for the Sobrado unit is established in the late Cambrian (similar to 511 Ma). The zircon dataset also record several inherited populations. The youngest cogenetic set of zircons yields crystallization ages of 546 and 526 Ma which are thought to be related to the peri-Gondwanan magmatic arc. The additional presence of inherited zircons older than 1000 Ma is interpreted as suggesting a West African Craton provenance.

引用

页码：2303 / 2325

页数：23