The Physical And Chemical Response To Deformation Structure In High Temperature And High Pressure Dynamic Experiment

The task of this article is as below: With the abservation,testing and stress–strain analysis to the samles after experiment, we study the deformation structureand deformation behavior. And then explain the melting nature of minerals andstudy the mechanism of migration and aggregation of components.The experimental samles include gabbro, granite, granulite and plagioclaseamphibolite, which are massive structure.The rock samles are made into massive cylinder with the diameter of 25mm.The gabbro is cut into two samles, one is G3, the other G5. G3 samle is studied bythe experiment with the conditions that the constant confining pressure andtemperature is 50 Mpa and 800℃, designed strain 10%, constant strain velocity 1×10^-5/s. The experiment of G5 samle is conducted by the adding grads of50Mpa/20min and 130℃/20min of confining pressure and temperature and final ofthat is 780℃ and 300Mpa . The strain velocity is 1×10^-5/s and the total strain7%. Granite, granulite and plagioclase amphibolite has the same experimental conditionsthat the constant confining pressure and temperature is 600 Mpa and 600℃, designedstrain 10%, constant strain velocity 1×10^-5/s. The differential stresses of all aboveexperiment are contralled automatically by experimental system.After experiment, several conclusions are revealed such as below:1 Different deformation structure of different crust lithosphere in compressiveenvironmentThe brittle fracture, ductile deformation and substance flow all indicate that thedeformation of gabbro is controlled by compressive–tensile stress field. While the granite,granulite and plagioclase amphibolite is controlled by compressive–shearing stress field.Gabbro has two kinds of cleavages that one is the tensile axial fracture, the other cross thesample. The granite, granulite and plagioclase amphibolite has also two kinds of cleavages.But except the cross ones, the other is a couple of shearing cleavages.Besides the brittle fracture, ductile deformation and substance flow also indicate thesimilar characteristics. The flowing plagioclases was oriented along compressionalstretching. The ductile deformation of granite concentrates in shearing position.Calcite veins of granulite distribute along compressional stretching orientation andshearing orientation. Many magnetite veins, melt veins or mixing veins along conjugateshearing nets are discovered in plagioclase amphibolite.Compared with the deformation of shearing belt, extrusion belt and tensile area,the deformation of compressive areas is not so obvious that all samples show amacroscopic deformation structure. Gabbro indicates a Dispersing band Structure.Butthere is a conjugate fan structure in the granite, granulite and plagioclase amphibolitesamples. According to the confining pressure of experiments, we know that thedeformation structure of gabbro represent upper crust′s or near the earth surface′sdeformation.And the granite, granulite and plagioclase amphibolite represent mid–lowercrust′s.2 Typical dynamic meltingThe dispersing band structure of gabbro and the conjugate fan structure in granite,granulite and plagioclase amphibolite samples not only control the distribution ofdeformation, but also control the occurring and distribution of melting in samples.In order to describe the melting phenomenon controlled by deformation structure,we set up the concept of dynamic melting. The shearing and pressing meltingterms are used when we analyze the mechanism of dynamic melting. Because ofinfluence of ground temperature, the conjugate fan deformation–melting model isthought to be more possible and logical in natural geology conditions.The establishing of dynamic melting largely expand the origin area of magma.The heat origin also include ground temperature and mechanical heat newly. Thedelaminating melting model we established is what lithosphere in different depthcan be melted separately. On the base of all above theories, the delaminatingmelting–magma mixing genesis of island arc calc-alkaline andesite and thedynamic melting genesis of Ⅰ-type adakite and syntectonic granite wereadvanced. The possibility of delaminating melting existing in rift environmentand the typology of the delaminating melting were thought of.3 The rheological dynamics mechanism of crustal rocks in brittle–ductiletransition fieldWith analysis of the deformation structure of experimental samples, we knowthat components can aggregate follow the occurring of orientational deformation,such as the formation of bunchiness and stratification of plagioclase and the vein′sformation of caltite and magnetite. At the same time, the active or easily rheologic substanceis the initiative component in deforming process. For example, plagioclase is the maindeforming component in gabbro. Calcite is the main one in granulite. Magnetite andhornblende are the main ones in plagioclase amphibolite. The other minerals in all abovesamples are passively adjustive components.4 The stability of petrochemistry or mineral chemistry in dynamic conditionsThe major elements of main minerals in granite which experience ductileshearing are analyzed. The conclusion indicates that the increasing of SiO2 isrelative which is caused by the decreasing of other compositions, especially ofAl2O3. The variation of major elements in orthoclase is not so obvious as otherminerals. From above all, we can know that deformation can cause variation ofcompositions in minerals. SiO2 is the most stable component in dynamicconditions. Former weakness plane or structure disfigurement can influence thestability of minerals′ components greatly.5 The study of melting characteristics and melting dynamics of gabbroBesides the dynamic melting, the melting of gabbro has some characteristicsas below:(1) Orthopyroxene is melted more easily than clinopyroxene. The meltingsequence of main minerals is Bi→Hy→Di→Pl→Ol.(2) The melting phenomenon in G3 and G5 is different. In G3 sample, themelting phenomenon of orthopyroxene is similar to GOD model described byRong jiashu. And the melting of clinopyroxene indicate a sponge phenomenon.But in G5 sample, both orthopyroxene and clinopyroxene produce melt directly.All above the melting phenomenons are explained on the base of meltingdynamics:①Dynamic factor.②The influence of compositionsAccording to the study of Tao Yuxiang, in anhydrous system, the meltingpoint of deforming metamorphic rock increases with the increasing ofFeO+MgO+CaO+TiO2,Al2O3 and decreases with the decreasing of SiO2,K2O+Na2O. According to the quantity of above compositions or compositionassemblages, the calculated melting sequence is given out which is on the wholeconsistent with the experimental sequence.③Different melting mechanism with different melting stage or velocityOn the base of experimental conditions and melting phenomenons, we knowthat the melting natures of orthopyroxene and clinopyroxene in G3 samplerepresent the state of low melting degree, low melting velocity and stable meltingconditions. But the G5 sample represent the state of high melting degree andlarge melting velocity. In high melting velocity, the phenomenon in low velocitymay not exist or be covered.From the above analysis, we can conclude that certain melting phenomenon ormelting sequence can be influenced by many kinds of melting conditions. Onlywhen we do analysis and comparison completely, can we determine the nature ofmelting which can help us understand the process of geology.