The Bainiuchang deposit in Yunnan Province, China, is located geographically between the Gejiu ore field and the Dulong ore
field. In addition to >7000 t Ag reserves, the deposit possesses large-scale Pb, Zn, Sn reserves and a mass of dispersed elements
(i.e., In, Cd, Ge, Ga, etc.). Based on systematic studies of sulfur isotopic composition, the authors conclude: The Bainiuchang
deposit experienced two epochs of metallogenesis, i.e., the Middle-Cambrian sea-floor exhalative sedimentary metallogenic
epoch and the Yanshanian magmatic hydrothermal superimposition metallogenic epoch. In the two metallogenic epochs, the δ34S values of sulfides were all near 0, showing a tendency of being enriched slightly in heavy sulfur. The δ34S values of sulfides in the early metallogenic epoch are within the range of 2‰–5‰ with a peak value range of 2‰–3‰ and an
average of 3.0‰, and those of sulfides in the late metallogenic epoch are within the range of 2‰–6‰ with a peak value of 3‰–4‰
and an average of 3.9‰. For the single metallogenic epoch, sulfur in the ore-forming fluids in the early epoch already reached
isotopic equilibrium and was derived mainly from underneath the magma chamber or basement metamorphic igneous rocks. Sulfur
in the sulfides in the late epoch was derived mainly from magmatic hydrothermal fluids formed in the process of remelting
of the basement metamorphic igneous rocks. 相似文献
A diagonal or lumped mass matrix is of great value for time-domain analysis of structural dynamic and wave propagation problems, as the computational efforts can be greatly reduced in the process of mass matrix inversion. In this study, the nodal quadrature method is employed to construct a lumped mass matrix for the Chebyshev spectral element method (CSEM). A Gauss-Lobatto type quadrature, based on Gauss-Lobatto-Chebyshev points with a weighting function of unity, is thus derived. With the aid of this quadrature, the CSEM can take advantage of explicit time-marching schemes and provide an efficient new tool for solving structural dynamic problems. Several types of lumped mass Chebyshev spectral elements are designed, including rod, beam and plate elements. The performance of the developed method is examined via some numerical examples of natural vibration and elastic wave propagation, accompanied by their comparison to that of traditional consistent-mass CSEM or the classical finite element method (FEM). Numerical results indicate that the proposed method displays comparable accuracy as its consistent-mass counterpart, and is more accurate than classical FEM. For the simulation of elastic wave propagation in structures induced by high-frequency loading, this method achieves satisfactory performance in accuracy and efficiency.