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| THE EFFECTS OF USING HIGH-PRECISION GRAVITY AND MAGNETIC METHODS TO EXPLORE CHROMITE IN THE XIUGOU IRON DEPOSIT, LANGXIAN COUNTY, TIBET |
| LIU Tian-you1, YANG Yu-shan1, LIU Jian-xiong2, GOU Jin-chang2, SU Bao-hua3 |
1. Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China;
2. Northwest Geological Exploration Institute, China Bureau of Metallurgical Geology, Xi'an 710061, China;
3. Tibet Nyingchi Rongteng Mining Co., Ltd., Nyingchi 860400, China |
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Abstract The authors completed the assignment of 1:5 000 gravity and magnetic high-precision measurement in the Xiugou chromite deposit of Nangxian, Tibet, in 2010 and the total accuracy of gravity measurement was over 0.069 4 mGal. According to physical characteristics of rocks and minerals, both the geophysical models and the exploration indicators in search for chromite were established. The composite characteristics of gravity and magnetic anomalies seem to be indicators identifying chromite. The characteristics include the criteria that the amplitudes of local gravity anomalies range from 0.1 to 0.6 mGal, their widths range from tens of meters to 100 or 200 meters, the amplitudes of magnetic anomalies are moderate, and the magnetization direction is reversed. Moreover, the composite characteristics of local high gravity anomaly zones and braided rings with positive magnetic anomalies constitute indicators identifying ultrabasic rock zones. In addition, the authors utilized the approaches including the wavelet analysis method to extract the local gravity and magnetic anomalies generated by chromite and ultramafic rocks, employed the tilt-angle method to identify rock boundaries, applied Paker method to density mapping, and also used interactive 2.5D inversion method. The areas of serpentinized peridotite and 14 gravity and magnetic perspective anomalies of chromite and mineralized bodies were delineated, six of which were proved to be related to mineralization. It is also pointed out that the chromite exploration in Tibet requires not only high-precision field measurement but also careful indoor data processing and interpretation. Furthermore, making full use of new data processing techniques is essential for obtaining good geological effects.
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Received: 04 November 2011
Published: 10 June 2012
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