Abstract
Abstract. A singular value decomposition (SVD) program on MATLAB platform was effectively used to handle gravity signals for the Tongshi gold field. Firstly, the gravity signals were decomposed into different eigenimages with the help of singular value decomposition method (SVD). Secondly, the thresholds between the eigenvalues reflecting different layers of ore-controlling factors were established by multi-fractal method. Finally images reflecting different layers of ore-controlling factors were rebuilt. This yielded two layers of two-dimensional singular value images that depict regional and local ore-controlling factors, respectively. 1. The regional ore-controlling factor is a saddle valley with the gravity anomaly values varying from −55 to 51 μm s−2 on the NW trending swell with the gravity anomaly values varying from −55 to 567 μm s−2 on the SW side of the Mesozoic volcanic sedimentary basin with the gravity anomaly values varying from −56 to −974 μm s−2. The saddle valley might be tectonically an extensional area where the Tongshi complex pluton and all gold deposits are located and thus this area is favorable for gold deposits. 2. The local ore-controlling factor is the Tongshi complex pluton with a negative circular gravity anomaly varying from −339 to −11 μm s−2 and the ring contact metasomatic mineralization zone around the Tongshi complex with the positive gravity anomaly varying from 37 to 345 μm s−2. The skarn and porphyry types of gold deposits are located within the complex pluton and the Carlin and cryptobreccia types of gold deposits are located within the contact metasomatic mineralization zone. Thus both of them are potential areas for gold deposits. 3. The Tongshi gold field exhibits a typical complexity with multi-layers of ore-controlling factors.
Highlights
Singularity is a property of different types of nonlinear natural processes, including cloud formation, rainfall, hurricanes, flooding, landslides, earthquakes, wildfires and mineralization (Cheng, 2008)
The skarn and porphyry types of gold deposits are located within the complex pluton and the Carlin and cryptobreccia types of gold deposits are Correspondence to: Y
The curve in log-log plot of λ−P of gravity signal in Tongshi gold field can be separated into three segments according to the break points between straight lines with different slopes (Fig. 3).The right segment is made of λ1 and λ2, and the percentage of its energy is about 90% of total energy
Summary
Singularity is a property of different types of nonlinear natural processes, including cloud formation, rainfall, hurricanes, flooding, landslides, earthquakes, wildfires and mineralization (Cheng, 2008). The results of singular geological process, for example, mineral deposits and ore-forming anomalies, represent fractal or multi-fractal distribution which can be described with power-law function (Cheng, 2009). SVD represent fractal or multi-fractal distribution described with power-law function. Anomalous amount of energy release or material accumulation which the singular geological process may result in within a narrow spatial-temporal interval might exist in some specific eigenimages. The energy of eigenimages or the squared eigenvalue (λ) perhaps represents multifractal distribution, and can be described with the power-low functions. The singular values obtained by SVD method have features as follows: (1) they are distributed in decreasing order along main diagonal; (2) they represent different weighting coefficients of eigenimages; (3) their squared values (i.e. λ) are equivalent to power spectral density values in Fourier space (Li, 2005).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
