Application of Singular Value Decomposition (SVD) to the Extraction of Gravity Anomalies Associated with Ag-Pb-Zn-W Polymetallic Mineralization in the Bozhushan Ore Field, Southwestern China

Abstract

The Bozhushan Ore Field, located at the western margin of the South China Block, is an important area for Ag-Pb-Zn-W polymetallic mineralization which may be associated with the Late Cretaceous granitic magmaism. In this paper, the singular value decomposition (SVD) was effectively applied to decompose gravity data at scale of 1: 50 000 within the Bozhushan Ore Field to extract deep ore-finding information. Two gravity anomaly images displaying different scales of the ore-controlling factors were obtained. (1) The low-pass filtered image may reflect the deeply buried geological structures, hidden intrusions and concealed ore bodies. The negative gravity anomaly may reflect the overall distribution of granite bodies in the Bozhushan Ore Field. One negative gravity anomaly area may correspond to the exposed part of the Baozhushan granitic intrusion and the other corresponds to the concealed part of the granitic intrusion. The granitic intrusions are the main ore-controlling factors in this ore district. (2) The band-pass filtered image depicts the shallow concealed geological structures and geological bodies within this study area. There are two obvious negative gravity anomalies, which may be created by the hidden granites at different depths at both northwestern and southeastern sides of the exposed granitic intrusion. Thus the two negative gravity anomalies are favorable prospecting areas for various type of polymetallic ore deposits at depth. The gravity anomalies extracted by using the SVD exactly reflect the distribution of the ore deposits, structures and intrusions, which will give new insights for further mineral exploration in the study area.

Keywords

singular value decomposition (SVD) / gravity anomaly / Ag-Pb-Zn-W polymetallic deposits / Bozhushan granitic complex / southwestern China

References

Agterberg F P. Multifractal Modeling of the Sizes and Grades of Giant and Supergiant Deposits. International Geology Review, 1995, 37(1): 1-8.

Chen X C, Hu R Z, Bi X W, . Zircon U-Pb Ages and Hf-O Isotopes, and Whole-Rock Sr-Nd Isotopes of the Bozhushan Granite, Yunnan Province, SW China: Constraints on Petrogenesis and Tectonic Setting. Journal of Asian Earth Sciences, 2015, 99: 57-71.

Chen, Y. Q., Huang, J. N., Zhang, S. Y., et al., 2007. Application of Multi-Fractal Filtering in Geochemistry Data Decomposing: A Case Study from the South Region of “Sanjiang Ore-Forming Belt”, South-Western China. In: Bernd, M., Ed., Proceedings of Fifth Decennial International Conference on Mineral Exploration, Exploration 07, Volume 2, Totronto. 985–988

Chen Y Q, Zhang L N, Zhao B B. Application of Singular Value Decomposition (SVD) in Extraction of Gravity Components Indicating the Deeply and Shallowly Buried Granitic Complex Associated with Tin Polymetallic Mineralization in the Gejiu Tin Ore Field, Southwestern China. Journal of Applied Geophysics, 2015, 123: 63-70.

Chen Y Q, Zhang L N, Zhao B B. Application of Bi-Dimensional Empirical Mode Decomposition (BEMD) Modeling for Extracting Gravity Anomaly Indicating the Ore-Controlling Geological Architectures and Granites in the Gejiu Tin-Copper Polymetallic Ore Field, Southwestern China. Ore Geology Reviews, 2017, 88: 832-840.

Chen Y Q, Zhang S Y, Xia Q L, . Application of Multifractal Filtering to Extraction of Geochemical Anomalies from Multi-Geochemical Backgrounds: A Case Study of the South Section of “Sanjiang Ore-Forming Zone”, Southwestern China. Earth Science, 2006, 31(6): 861-866. (in Chinese with English Abstract)

Chen Y Q, Zhao B B. Extraction of Gravity Anomalies Associated with Gold Mineralization: A Comparison of Singular Value Decomposition and Bi-Dimensional Empirical Mode Decomposition. Advanced Materials Research, 2012, 455/456: 1567-1577.

Cheng Q M, Agterberg F P. Singularity Analysis of Ore-Mineral and Toxic Trace Elements in Stream Sediments. Computers & Geosciences, 2009, 35(2): 234-244.

Cheng Q M, Zhao P D. Singularity Theories and Methods for Characterizing Mineralization Processes and Mapping Geo-Anomalies for Mineral Deposit Prediction. Geoscience Frontiers, 2011, 2(1): 67-79.

Cheng Q M. Singularity Theory and Methods for Mapping Geochemical Anomalies Caused by Buried Sources and for Predicting Undiscovered Mineral Deposits in Covered Areas. Journal of Geochemical Exploration, 2012, 122: 55-70.

Cheng Q M. Non-Linear Theory and Power-Law Models for Information Integration and Mineral Resources Quantitative Assessments. Mathematical Geosciences, 2008, 40(5): 503-532.

Cheng Q M. Mapping Singularities with Stream Sediment Geochemical Data for Prediction of Undiscovered Mineral Deposits in Gejiu, Yunnan Province, China. Ore Geology Reviews, 2007, 32(1/2): 314-324.

Clifford, G. D., 2005. Singular Value Decomposition & Independent Component Analysis for Blind Source Separation. Signal Image Process, Biomed

Freire S L M, Ulrych T J. Application of Singular Value Decomposition to Vertical Seismic Profiling. Geophysics, 1988, 53(6): 778-785.

Huang J N, Zhao P. Application of a Multi-Fractal Model for Identification of Cu, Au and Zn Anomalies in Western Yunnan, Southwestern China. Geochemistry: Exploration, Environment, Analysis, 2015, 15(1): 54-61

Li Q M. GIS-Based Multifractal/Inversion Methods for Feature Extraction and Applications in Anomaly Iidentification for Mineral Exploration: [Dissertation], 2005, Toronto: York University

Li Q M, Cheng Q M. Fractal Singular-Value (Egin-Value) Decomposition Method for Geophysical and Geochemical Anomaly Reconstruction. Earth Science, 2004, 29(1): 109-118. (in Chinese with English Abstract)

Li Q M, Liu S H. Geophysical Signal Decomposition by Singular Method and Application in GIS. Progress in Geophysics, 2003, 18(1): 97-102. (in Chinese with English Abstract)

Liu J S, Zhang H P, Ouyang Y F, . Bainiuchang Super-Large Silver-Polymetallic Ore Deposit Related to Granitic Magmatism in Mengzi, Yunnan. Journal of Central South University of Technology, 2007, 14(4): 568-574.

Mandelbrot B B. Multifractal Measures, Especially for the Geophysicist. PAGEOPH, 1989, 131(1/2): 5-42.

Pan G C, Harris D P. Information Synthesis for Mineral Exploration, 2000, Oxford: Oxford University Press, 461

Turcotte D L. Fractals and Chaos in Geology and Geophysics, 1997, Cambridge: Cambridge University Press, 398

Vrabie V D, Mars J I, Lacoume J L. Modified Singular Value Decomposition by Means of Independent Component Analysis. Signal Processing, 2004, 84(3): 645-652.

Zhang Y H, Zhang S T, Tan S C, . The Genetic Relationship between the Large Guanfang W Deposit and Granitic Intrusions, in Yunnan Province, Southwest China: Evidence from U-Pb and Re-Os Geochronology and Pb and Sr Isotopic Characteristics. Ore Geology Reviews, 2016, 79: 332-345.

Zhao B B, Chen Y Q. Singular Value Decomposition (SVD) for Extraction of Gravity Anomaly Associated with Gold Mineralization in Tongshi Gold Field, Western Shandong Uplifted Block, Eastern China. Nonlinear Processes in Geophysics, 2011, 18(1): 103-109.

Zhong S H. Effect of 1: 50 000 Gravity Measurement on Identify in Concealed Granite in Mengzi Country, Yunan, China. Yunnan Geology, 1992, 11(1): 101-103. (in Chinese)