Magnetic mineralogy and fabric reliability constraints of Late Triassic Yanzhiba pluton in South Qinling Mountain

NIU Guangzhi; TAO Wei; LIANG Wentian; LI Yang; RAN Yazhou

2016 Vol. 35, No. 9

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NIU Guangzhi, TAO Wei, LIANG Wentian, LI Yang, RAN Yazhou. Magnetic mineralogy and fabric reliability constraints of Late Triassic Yanzhiba pluton in South Qinling Mountain[J]. Geological Bulletin of China, 2016, 35(9): 1522-1528.

Citation:

NIU Guangzhi, TAO Wei, LIANG Wentian, LI Yang, RAN Yazhou. Magnetic mineralogy and fabric reliability constraints of Late Triassic Yanzhiba pluton in South Qinling Mountain[J]. Geological Bulletin of China, 2016, 35(9): 1522-1528.

Magnetic mineralogy and fabric reliability constraints of Late Triassic Yanzhiba pluton in South Qinling Mountain

1. Academy of Regional Geological Survey and Mineral Resources Exploration of Shaanxi, Xianyang 712000, Shaanxi, China;
2. Department of Geology/State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, Shaanxi, China

Received Date: 09 December 2015

Revised Date: 01 June 2016

Publish Date: 15 September 2016

Abstract

Abstract

The Yanzhiba pluton is one of the typical Late Triassic granite plutons in Qinling Mountain, and lots of geochronological and geochemical work has been done for the Yanzhiba granite pluton in South Qinling Mountain recently. However, opinions of its tectonic settings are contradictory. Some recent studies have placed some new constraints on this problem based on the magnetic fabrics of these granite plutons. These studies have successfully elucidated the correlation between regional tectonics and granite emplacement. However, the reliability of the magnetic fabric method has not been specifically studied. In this paper, the authors present an elaborate magnetic mineralogy analysis, combined with previous petrographical data, to shed light on this problem. Mean susceptibility K_m and corrected anisotropy degree P_J of Yanzhiba pluton are low, which are consistent with data of paramagnetic granite. Hysteresis loops show that susceptibility of most samples originates from paramagnetic minerals, with a small portion of ferrimagnetic contribution, whose concentration, however, is very low. Isothermal remanent magnetization acquisition (IRM) and DC-Field demagnetization curves show that the ferrimagnetic component in pluton is mainly soft magnetic minerals, and χ-T curves confirm that it is magnetite. The hysteresis parameter ratios on Day plot further indicate multi-domain magnetite. The results obtained by the authors prove that the magnetic fabric result from Yanzhiba pluton is reliable and has recorded actual mica fabrics.
- AMS /
- IRM /
- hysteresis loops /
- thermomagnetic analyses /
- ferrimagnetic minerals /
- paramagnetic grantie

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References

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