The Effect Of Differential Stresses On Rocks' Partial Melting And Mechanisms

Differential stresses is always a research hotspot on geology,and what's theinfluences about the differential stresses for rocks' partial melting and which aspects itmanifest?In order to discuss and resolve these scientific problems this paperinvestigate and analysis the effects and mechnisms of differential stresses on rocks'partial melting by the method of HTHP.It mainly contains two kinds of types which are static and dynamic meltingexperiments. After the experiments we firstly count the melt content and make sureimportant experimental parameters, secondly we respectively depict the micrographiccharacteristics of static and dynamic experiments. Researches mainly contain threeparts:the effects of differential stresses on rocks melting;distribution characteristics ofmelt in static and dynamic experiments;melt component's migration anddifferentiation.The first part static and dynamic experiments are made up of samples ofbiotite-plagioclase gneiss,hornblende granulite and gabbro.We can gain the effects ofdifferential stresses on rocks melting by contrasting the same melting degreecorresponding to differential stresses and tem-perature.In part two,we try to find whatrole the differential stresses will play in the process of melt migration throughdescribing and contrasting melt characteristics of fine-grain diorite in static anddynamic experiments.In part three,we have finished static and dynamic experimentsof fine-grain diorite and granite and dynamic experiments of gabbro and static experiments of leptite,I do some electron probe tests and mainly analyze majorelements and contrast the variation of SiO₂contents to explore migration anddifferentiation of melt components.Finally, we obtain some conclusions:(1).In acid and neutral rocks their meltingdegrees both show positive correlation with differential stresses andtemperatures.(2).Different stresses can decline the melting points.(3).The effect of20℃is equal to5MPa to biotite plagioclase gneiss and the effect of40℃is equal to5MPa to hornblende granulite and the effect of50℃is equal to5MPa togabbro.Basic rock is the most sensitive to different stresses,mesite is less and acidrock is the least.(4).The distribution characteristics of fine-grain diorites' static anddynamic experiments suggest it is accordance with other results such ascharacteristics of gabbro dynamic and biotite plagioclase gneiss static meltingexperiments which show that in medium rock differential stresses also are regarded asthe main driven-stress for migration of melt and forming joined3D networktexture.(5).The differential stresses greatly increase the rate of melt migration and therates in rocks mainly composed by hydrous minerals are much faster thanothers.(6).In the fine-grain diorite partial melting experiments hornblende as hydrousminerals firstly begin to melt under the effect of differential stresses but plagioclasesmelt later,so differential stresses control the melt components changing from basalticrock to andesite.(7).In the gabbro's dynamic melting experiments because of meltcomponents continuously assembling it will form olivine whose component is morebasaltic,also magnetite crystalline nucleus can be formed which suggest thatdifferential stresses promote rocks' composition differentiation and provide favorableconditions for separation of rocks' composition.