Singularity Analysis of Volcanic Ages and Implications for Tectonic Setting in the Mesozoic, Great Xing’an Range, Northeast China

Zhu Zhu,Cheng Cheng

doi:10.3390/min9070419

Abstract

Frequency distribution of zircon U–Pb ages has been commonly utilized to interpret the age of a magmatic event. Anomalies in age peaks are related to plate movement caused by mantle convection during the formation of supercontinents and continent crust growth. In this paper, a singularity analysis method (frequency anomalies) is used to analyze a dataset (n = 823, discordance lower than 10%) of zircon U–Pb ages from the Great Xing’an Range (GXR), in order to characterize the causal relationship between age transitions and Pacific Plate subduction. The numberage plot result shows that there is a peak around at 125 Ma, and the log–log plot reveals that there are two transitional ages (knee points) at 125 Ma and 145 Ma. The age densities of the peak at 125 Ma and the transition at 145 Ma can both be fitted by power law functions, which indicate transitional ages have the characteristic of singularity. Combined with the subduction geological background in the late Mesozoic, the possible singularity mechanisms corresponding to the age peak at 125 Ma and the transition at 145 Ma are slab rollback and slab breakoff of the Pacific Plate, which is consistent with conclusions from geology and geochemistry. This result suggests that singularity analysis can be used as a new method to quantitatively characterize volcanic activities and tectonic setting in geological processes.

Highlights

The Great Xing’an Range (GXR, Figure 1), east of the Central Asian Orogenic Belt (CAOB or Altaid), is dominated by Mesozoic volcanic rocks and other associated igneous rocks [1,2,3,4]
We present a singularity analysis method to analyze a dataset (n = 823) of volcanic zircon U–Pb ages in the Mesozoic from the GXR in order to characterize the relationship between transitional ages and Paleo-Pacific Plate subduction
The singularity analysis results for volcanic zircon U–Pb ages of the GXR from 98 to 515 Ma are shown in Figures 2 and 3

Summary

Introduction

The Great Xing’an Range (GXR, Figure 1), east of the Central Asian Orogenic Belt (CAOB or Altaid), is dominated by Mesozoic volcanic rocks and other associated igneous rocks [1,2,3,4]. There has been much debate concerning the tectonic setting in which these rocks formed, and two main proposals have been put forward: (1) subduction of the Mongol–Okhotsk Ocean from the north [5,6], and (2). Previous studies suggested that the exact eruption ages and spatial distribution of the volcanic rocks and granites are the key factors for understanding the tectonic setting [4,7,8,9,10,11]. This study attempts to address this issue from a new view point, using a singularity analysis method on the basis of a dataset (n = 823) of volcanic zircon U–Pb ages. The concept of singularity for a geological application point of view was originally introduced by. The singularity model was applied to the Minerals 2019, 9, 419; doi:10.3390/min9070419 www.mdpi.com/journal/minerals

Results

Discussion

Conclusion