变质温度压力计.ppt

 变质作用中，许多进变质作用中的反应都是脱水或脱碳酸反应。与固--固反应不同，脱挥发分反应在温压图上表现为曲线。 A = B + H2O. 对于这个反应，可以写出： △S = SB + SH2O - SA =? △S固体 + SH2O △V = VB + VH2O - VA =? △V固体 + VH2O 温度升高时，一般 △S 为正。尤其在这种有气体或液体相产生的反应中，因为气体的熵要高于固体。在低压的情况下， △V固体 通常为负。但在低压情况下 VH2O 却会很大，因为气体或水会膨胀，填充可能的空间。这样 dP/dT 为正。当压力升高时，气体和液体比固体容易压缩，所以总的 △V 将逐渐变小，dP/dT 会升高。最终由于气体和液体的可压缩性△V固体与 VH2O 相等，反应的△V 变为0，使得dP/dT为无穷。压力高于这一点，水的体积会越来越小，使得反应中的 △V 变为负增长，因此 dP/dT 也为负增长。 变质岩温压条件的确定 2. 应用各种地质温度计及压力计 a. 成份温度计、压力计 Pl－Am Am中Al压力计 b. 元素分配温度计、压力计 Gt－Bi（Mg） 能斯特分配原理： LnKd=-?Gr/RT ?Gr= ?H-?ST+?V(P-1) From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept From 3rd equation can extract DH from slope (know P and DV) and DS from intercept * Figure 27-10. P-T diagram showing the results of garnet-biotite geothermometry (steep lines) and GASP barometry (shallow lines) for sample 90A of Mt. Moosilauke (Table 27-4). Each curve represents a different calibration, calculated using the program THERMOBAROMETRY, by Spear and Kohn (1999). The shad