DOI: 10.1016/j.earscirev.2021.103644
论文题名: The importance of tangential motion in the Central Alps: Kinematic analysis and Rb[sbnd]Sr dating of mylonitic rocks from the Pennine nappes in the eastern Central Alps
作者: Ring U. ; Glodny J.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2021
卷: 218 语种: 英语
中文关键词: Central Alps
; Kinematic analysis
; Normal faulting
; Out-of-plane deformation
; P-T conditions
; Rb-Sr geochronology
英文关键词: deformation
; geochronology
; kinematics
; metamorphism
; mylonite
; nappe
; normal fault
; P-T conditions
; rubidium-strontium dating
; thrust
; Alps
英文摘要: We discuss the important role of tangential stretching in the Central Alps highlighting that the Alps are a truly three-dimensional orogen. A review of pressure-temperature (P-T) conditions allows us to define three major breaks in metamorphic pressure (P-breaks) across the nappe pile. We constrain the kinematics of mylonites associated with these P-breaks and report eight new Rb[sbnd]Sr multi-mineral isochrons that define the age of the mylonites. Kinematic data and Rb[sbnd]Sr geochronology indicate that the timing of top-SE normal shearing in the Avers-Turba mylonite zone (≥45–34 Ma; P-break1) and in a zone of distributed top-E normal shearing (>35–30 Ma) above the (ultra)high-P Adula nappe of the distal, thinned European margin (P-breaks 2 and 3). The ages from both sets of mylonite are grading into each other at about 35–34 Ma. All ages appear to postdate high-P metamorphism in the Pennine nappes but are, in part, coeval with and predate (ultra)high-P metamorphism in the underlying Adula nappe of the distal European (Helvetic) margin. The oldest Rb[sbnd]Sr age of 42.3 ± 2.5 Ma (2σ uncertainties) dates the waning stage of mylonitization and indicates that the Avers-Turba mylonite zone started to operate ≥45 Ma, and predated the exhumation of the Adula nappe by ~10 Ma. We suggest that the motion in the Avers-Turba mylonite zone overlapped with backfolding of the Schams nappe in an extrusion wedge. When this process started, the Adula nappe was still being underthrust/underplated. The ages for distributed top-E normal shearing are contemporaneous with thrusting of the Adula nappe on top of distinctly lower-P Helvetic nappes. When the Adula nappe was being thrust onto non-high-P nappes the necessary reduction of its overburden was largely accomplished by distributed top-E normal faulting above the Adula nappe, and possibly still ongoing top-SE normal shearing. We discuss that major normal shearing occurred during lithospheric shortening. Our data indicate considerable tangential (out-of-plane) movements during overall top-N/NW thrust propagation in the Central Alps and have implications for current tectonic models of the Alps. © 2021 The Author(s) Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/166493
Appears in Collections: 气候变化与战略
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作者单位: Department of Geological Sciences, Stockholm University, Stockholm, 10691, Sweden; GFZ German Research Centre for Geosciences, Potsdam, 14473, Germany
Recommended Citation:
Ring U.,Glodny J.. The importance of tangential motion in the Central Alps: Kinematic analysis and Rb[sbnd]Sr dating of mylonitic rocks from the Pennine nappes in the eastern Central Alps[J]. Earth Science Reviews,2021-01-01,218