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DOI	10.1016/j.tecto.2020.228455
	Pure shear-dominated transpression and vertical extrusion in a strike-slip fault splay from the Itapirapuã Shear Zone, Ribeira Belt, Brazil
	Forero-Ortega A.J.; Campanha G.A.C.; Faleiros F.M.; Yogi M.T.A.G.
发表日期	2020
ISSN	00401951
卷号	786
英文摘要	The Itapirapuã Shear Zone is a major NE-trending dextral transcurrent zone from the southern Ribeira Belt (Brazil), which was active during the Neoproterozoic Brasiliano-Pan African Orogeny, related with West Gondwana assembly. Macroscopic sigmoid-shaped blocks in its northernmost splay termination present a NE-trending subvertical tectonic foliation and subvertical stretching lineation suggesting a transpressional tectonics. This paper investigates this splay termination using integration of data from geological mapping, thermodynamic modeling, microtectonics, quartz c-axis fabrics, kinematic vorticity and finite strain analysis. Distinct rock assemblages are placed in tectonic contacts along the splay termination, including Statherian sillimanite-biotite paragneiss and granitic orthogneiss (Apiaí-Mirim Complex), Statherian phyllites (Bairro dos Prestes Formation), Calymmian chlorite-epidote-actinolite metabasites (Fazenda Velha Suite), Ediacaran phyllites, metalimestone and quartzite (Itaiacoca Group) and Ediacaran granite (Três Córregos Suite). Isochemical phase diagrams constrain synkinematic metamorphic conditions of 490–510 °C and 11–12.5 kbar (chlorite-biotite-phengite phyllite), 520–560 °C and 9–10 kbar (biotite-phengite phyllite) and 680–690 °C and 5–6 kbar (sillimanite-biotite paragneiss), with isothermal decompression paths. Microstructural evidence suggests that increase in metamorphic temperatures were accompanied by changes in the dominant deformation mechanism in quartz aggregates from subgrain rotation to grain boundary migration recrystallization. Significant contribution of dissolution-precipitation creep indicates water-abundant deformational conditions. Strain ellipsoids are oblate-shaped and present NE-trending subvertical XY planes and subvertical X-axes in agreement with field tectonic fabric. Quartz c-axis fabrics in XZ sections of the strain ellipsoid are dominated by symmetrical crossed girdles, while the fabrics present dextral asymmetry in horizontal YZ sections, consistent with macroscopic structural deflection, indicating a subvertical vorticity axis. Vorticity results indicate 48–59% of pure shear contribution. The data indicate that strain in the Itapirapuã Shear Zone northern termination was accommodated by a pure shear-dominated transpression with vertical extrusion at mid-crustal conditions, which contrasts with a transtensional deformation in the southeastern block. © 2020 Elsevier B.V.
英文关键词	Belts; Biotite; Deformation; Extrusion; Grain boundaries; Metamorphic rocks; Quartz; Strike-slip faults; Structural geology; Vorticity; Dissolution precipitations; Dominant deformation mechanism; Finite strain analysis; Grain boundary migrations; Isothermal decompression; Metamorphic conditions; Transpressional tectonics; Transtensional deformation; Mica; decompression; deformation mechanism; foliation; geological mapping; Gondwana; microearthquake; microstructure; quartz; recrystallization; shear zone; strike-slip fault; tectonic setting; thermodynamics; transpression; transtension; Brazil; Ribeira Belt
语种	英语
来源期刊	Tectonophysics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/207752
作者单位	Instituto de Geociências, Universidade de São Paulo, Rua do Lago 562, São Paulo, SP CEP 05508-080, Brazil; Tectonic - Geodynamics Research Group, Colombian Geological Service (SGC), Diagonal 53 No. 34-53, Bogotá, postal code 110231, Colombia
推荐引用方式 GB/T 7714	Forero-Ortega A.J.,Campanha G.A.C.,Faleiros F.M.,et al. Pure shear-dominated transpression and vertical extrusion in a strike-slip fault splay from the Itapirapuã Shear Zone, Ribeira Belt, Brazil[J],2020,786.
APA	Forero-Ortega A.J.,Campanha G.A.C.,Faleiros F.M.,&Yogi M.T.A.G..(2020).Pure shear-dominated transpression and vertical extrusion in a strike-slip fault splay from the Itapirapuã Shear Zone, Ribeira Belt, Brazil.Tectonophysics,786.
MLA	Forero-Ortega A.J.,et al."Pure shear-dominated transpression and vertical extrusion in a strike-slip fault splay from the Itapirapuã Shear Zone, Ribeira Belt, Brazil".Tectonophysics 786(2020).