气候变化领域集成服务门户(CCPortal): 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

CCPortal

DOI	10.1016/j.earscirev.2021.103644
	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
	Ring U.; Glodny J.
发表日期	2021
ISSN	00128252
卷号	218
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)
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
语种	英语
来源期刊	Earth Science Reviews
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/204124
作者单位	Department of Geological Sciences, Stockholm University, Stockholm, 10691, Sweden; GFZ German Research Centre for Geosciences, Potsdam, 14473, Germany
推荐引用方式 GB/T 7714	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],2021,218.
APA	Ring U.,&Glodny J..(2021).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.Earth Science Reviews,218.
MLA	Ring U.,et al."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".Earth Science Reviews 218(2021).