Late Mesozoic compressional to extensional tectonics in the Yiwulüshan massif, NE China and their bearing on the Yinshan–Yanshan orogenic belt

Abstract

Granitoids play an important role in deciphering both crustal growth and tectonic evolution of Earth. In the eastern end of the Yinshan-Yanshan belt of North China Craton, the Yiwulüshan massif is a typical region that presents the tectonic evolution features of this belt. Our field work on the host rocks has demonstrated two phases of opposite tectonics: compressional and extensional, however, the deformation is almost invisible in the intrusive rocks. To improve the understanding of the tectonic evolution of the Yiwulüshan massif and the Late Mesozoic tectonics of East Asia, a multidisciplinary study has been carried out. In this study, anisotropy of magnetic susceptibility (AMS) and gravity modeling have been applied on these Jurassic plutons (Lüshan, Jishilazi and Guanyindong), which intrude into the Yiwulüshan massif. According to laboratory measurements and microscopic observations on thin sections, the AMS of the Yiwulüshan massif is characterized by secondary fabrics, indicating that the intensive post solidus deformation has reset the (primary) magmatic magnetic fabrics. A relatively gentle NW dipping magnetic foliation has been identified with two distinct groups of magnetic lineations of N34°E and N335°E orientations, namely L M1 and L M2 , relatively. Gravity modeling reveals a southward thinning of the massif with a possible feeding zone rooted in the northern part of the massif. Integrating all results from structural observation, geochronological investigation, AMS measurement and gravity modeling, two tectonic phases have been identified in the Yiwulüshan massif, posterior to the Jurassic (180-160 Ma) magmatism in the Yinshan-Yanshan area. The early one concerns a Late Jurassic-Early Cretaceous (~141 Ma) compressional event with a top-to-the-south to southwest sense of shear. The second one shows an Early Cretaceous (~126 Ma) NW-SE ductile extensional shearing. At that time, sedimentary basins widened and Jurassic plutons started to be deformed under post solidus conditions. In fact, the NW-SE trend of the maximum stretching direction is a general feature of East Asian continent during Late Mesozoic.

Late Mesozoic compressional to extensional tectonics in the Yiwulüshan massif, NE China and its bearing on the evolution of the Yinshan–Yanshan orogenic belt

“…14). Our AMS work also documents a NE-SW magnetic lineation (L M1 , Lin et al, 2013). The D 1 event can be observed in every unit, except in the Cretaceous Fuxin-Yixian basin, and in the late intrusive tonalitic and adamellitic Shishan pluton.…”

“…However, several decacentimeter-scale shear zone with NW-SE trending mineral and stretching lineation are recognized (Fig. 2), and our AMS work in the NE of the Lüshan pluton reveals a NW-SE magnetic lineation L M2 due to a secondary magnetic fabric related to a solid-state deformation (Lin et al, 2013). These structures indicate that even the main detachment fault is not arched in the eastern part of massif, as a subbranch, several splays related to this D 2 deformation had marked at this part (Fig.…”

“…Several approaches have been applied, such as structural geology, 40 Ar/ 39 Ar geochronology on different potassium rich minerals, U-Pb geochronology on zircon, Anisotropy of Magnetic Susceptibility (AMS) on granite massif and gravity modeling on granite. The AMS and gravity data will be presented in the companion paper (Lin et al, 2013).…”

A multidisciplinary study on the emplacement mechanism of the Qingyang–Jiuhua Massif in Southeast China and its tectonic bearings. Part I: Structural geology, AMS and paleomagnetism

“…As illustrated by numerous case studies during past decades, AMS fabric pattern of a pluton may reflect the tectonic regime during its emplacement while the paleomagnetic records are easily to be influenced by the tectonic event after the crystallization of the pluton (Bouchez and Gleizes, 1995;Talbot et al, 2005a;Joly et al, 2007;Charles et al, 2011;Lin et al, 2013). These two methods are applied to investigate different scaled deformation and tectonic characteristics of the study area.…”

Continental dynamics of Eastern China: Insights from tectonic history and receiver function analysis

“…Continental-scale compressional and extensional tectonics have been identified from the Late Mesozoic-Cenozoic geology of East Asia (Davis et al, 2001;Ritts et al, 2001;Zhao et al, 2004a;Lin et al, 2013).…”