Electromagnetic research in the ocean

The results of electromagnetic researches at sea and in the oceans are considered. Those in the U.S.S.R. are given particular attention.     

Electromagnetic studies in the central Arctic water basin

The results of the electromagnetic studies, obtained on the North Pole drifting stations, are reviewed. These results are still of current interest. The aspects of similar future works are discussed.     

Experimental study of Fe-Mg- and Ca-distribution between coexisting ortho- and clinopyroxenes at P=294 MPa,T=750 and 800° C

The Fe-Mg-Ca-distribution was investigated in synthesis experiments and with the mineral assemblage orthopyroxene+clinopyroxene+quartz. The phase compositions were identified by X-ray diffraction and, where possible, by electron microprobe. The attainment of equilibrium in the run products was signalled by the compositions from control runs (different solutions) becoming closely similar, by recycling runs, by the attainment of equilibrium from different directions (depending on the composition of starting phases), and by special kinetic experiments.The study produced the following results: (1) the Ca content of the clinopyroxenes decreases with increasing Fe (mol%) from 48.4 at X _Cpx ^Fe =5 to 39.8 at X _Cpx ^Fe =45 (800° C); from 47.6 at X _Cpx ^Fe = 10 to 41.7 at X _Cpx ^Fe =45 (750° C); increasing temperature expands the stability field of the less calcic clinopyroxenes. (2) The Ca content of orthopyroxenes increases slightly with Fe content from 1.8 at X _Opx ^Fe =20.5 to 3.2 at X _Opx ^Fe =75; the temperature effect on the Ca content under the T, P conditions of the experiment was not large. (3) Fe and Mg distribution between the coexisting ortho-and clinopyroxenes is largely temperature-dependent, particularly in the compositional range X _Opx ^Fe =15–75 mol%; as T increases, Fe redistributes from the rhombic to monoclinic mineral.Preliminary estimates of rock formation temperatures using the obtained data show that most of the known two-pyroxene geothermometers overstate the actual values by 50–150° C.     

The usage of the spatial-temporal magnetometry in the sea

The first successful experience of the spatial-temporal magnetometry application in the Caspian Sea has been described. The differential and integral curves have been obtained and the magnetic anomaly has been detected during low geomagnetic activity.     

Experimental study of Fe-Mg distribution between biotite and orthopyroxene at P=490 MPa

Partitioning of Mg and Fe between coexisting biotite and orthopyroxene has been experimentally determined at temperatures 700, 750 and 800° C and 490 MPa total pressure in the system KAlO₂-MgO-FeO-SiO₂-H₂O. Oxygen fugacity was controlled by the QFM buffer. Starting materials were synthetic minerals of differing Fe/(Fe+Mg) values. Run products were analyzed for partitioning of components by a microprobe. Orthopyroxene was established to be notably inhomogeneous, whereas biotite was essentially homogeneous. To establish equilibrium relations, statistical treatment of the results of each experiment in addition to the whole complex of experimental data was applied. The regression equations for isotherms of the Fe-Mg partitioning between the minerals studied have been obtained. As a result, the equation for a two-dimensional regression may be written as: $$\begin{gathered} Y = (A + A_1 t + A_2 t^2 )(X - X^4 ) + (B + B_1 t + B_1 t^2 )(X^2 - X^4 ) + \hfill \\ (C + C_1 t + C_1 t^2 )(X^3 - X^4 ) + X^4 {\text{ where }}Y = X_{{\text{Opx}}}^{{\text{Fe}}} ;{\text{ X}} = {\text{X}}_{{\text{Bi}}}^{{\text{Fe}}} ; \hfill \\ t = 1000/T,K, \hfill \\ \begin{array}{*{20}c} {A = {\text{ }}4.59398,} & {A_1 = - {\text{ }}8.29838,} & {A_2 = {\text{ }}4.97316,} \\ {B = - 11.13731,} & {B_1 = {\text{ }}28.19304,} & {B_2 = - 20.98240,} \\ {A = {\text{ }}8.25072,} & {C_1 = - 20.80485,} & {C_2 = {\text{ }}15.35967} \\ \end{array} \hfill \\ {\text{ }}\sigma = 0.0143{\text{ }} \hfill \\ \end{gathered}$$ . This equation enables extrapolation of partitioning isotherms over a wide range of temperatures.     

Fluid evolution and exhumation path of the Trivandrum Granulite Block,southern India

Contributions to Mineralogy and Petrology - In charnockites and host garnet-biotite gneisses of the Trivandrum Granulite Block (TGB), southern India, fluid inclusions are mainly represented by...