HR: 1340h
AN: G33A-0902    [Abstracts]
TI: Igneous Rock and Paleogravity
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., Beijing, 100029, China
AB: Due to the Earth has evolved for 4.5 billion years since its birth, it is not reasonable to let scientists to believe that gravity field has never changed. Paleogravity, the ancient gravity field, will become a very important parameter to study Earth's evolution, even the evolution of the solar system, if people can find some rational and feasible way to measure paleogravity. A. D. Steward had made great efforts on that and tried to use the temperature of inclusions and geothermal temperature in mantle to estimate the limits of paleogravity. Unfortunately, in his approach, there are no enough parameters of covering materials above the inclusion, such as density and elastic module, therefore, the physics for measuring paleogravity is not solid, and the result from that is not acceptable. So far as I know, has yet a rational and feasible way to find out the paleogravity. In my approach, without any strong assumption, a feasible way has been derived. We drill out a vertical lava core cylinder from a typical ancient igneous rock mass, from the top part of the core cylinder; we cut out one piece of sample sector 0, and cut out two pieces of samples sectors 1 and 2 from the rest parts, from higher position to lower position. All samples must be unbroken and un-decayed. By measuring their densities d0, d1 and d2 and elastic deformation modulus E1 and E2, respectively, we can find the paleogravity. g=A(B+C), where A=1/(dh), B=E2-E1, C=(E1/d1-E2/d2)d0; And where d is the average density from sector 1 to sector 2, h is the distance between sector 1 to sector 2. Considering the influence on densities and elastic deformation modules caused at different layers by not only the paleogravity, but also the different composition of sectors at different layers£¬we must take a composition normalization on the ratios E2/E1 and d2/d1, by mass spectrum or melting method.
DE: 0920 Gravity methods (1219)
SC: Geodesy [G]
MN: 2007 Fall Meeting