HR: 0800h
AN: NS31A-07    [Abstracts]
TI: Airborne Gravity and Geomagnetism Survey
AU: * Tang, K
EM: kytang@mail.igcas.ac.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, No.19, North Tucheng West Road,Chaoyang Dist. POBox 9825, Beijing, 100029, China
AU: Qian, J
EM: qianjin@nim.ac.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, No.19, North Tucheng West Road,Chaoyang Dist. POBox 9825, Beijing, 100029, China
AB: The State Development and Reform Commission is setting a national project to push the development, the project of airborne remote sensing has been started since last winter, leading by the Chinese Academy of Sciences. To complete a geo-scientific observation system, our dynamic gravimeter and tree-axis magnetometer are included. Our team will run the gravimeter and magnetometer, to obtain the gravity and 3-components geomagnetic data. As a pre-study of this project, we are conducting some land observation. Meanwhile, Tang is taking efforts on the study of paleogravity. Actually igneous rock and sedimentary rock are keeping solid evidence for paleogravity. During the consolidation of the igneous rock, rock's structures were formed under the original pressure and temperature. The physical parameters, such as density, elastic modulus and porosity were determined. After that the structure were disturbed by later stresses. But if the later stresses were eliminated, rock's structure as well as the physical parameter will almost return to the original statues. Base on this physical consideration, we can drill a vertical well from a large rock body with old age and take the rock core out, then the additional stress will be eliminated, the rock's structure will almost reflect the original environment when the igneous rock were formed. From the core cylinder, we cut three pieces of unbroken sample sections 1,2 and 3 from higher position to lower position, and measure their density d1, d2 and d3, elastic modulus E1, E2, E3 and porosity K1, K2, K3, we have the relation connecting the pressure difference and section deformation between sections, i.e., following two equations: dj1hj1g = EjBj - E1B1, j=2,3, where dj1, j=2,3 are the average densities from section j to section 1, hj1, j=2,3 are the heights from section j to section 1 respectively, Bi=(K0 - Ki)/(1- Ki), i=1,2,3 are the relative deformations along cylinder axis for each sections, K0 is the ideal porosity with zero pressure while igneous magma were consolidated. We can find there are only two variables g and K0 unknown in the two equations, so the paleogravity g can be solved out. Preliminary results of paleogravity from Beijing Area's igneous rocks could be presented. This approach can also be applied to sedimentary rock.
DE: 0480 Remote sensing
DE: 0920 Gravity methods (1219)
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly