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Experiments were performed determining the distribution of chromium between olivine, pyroxenes, and melt at oxygen fugacity values near those of lunar rocks for a wide range of bulk compositions. The range of values of D-Cr (wt% of Cr2O3 in crystals/Cr2O3 in melt) is 0.6-1.3 for olivine and 1.6-3.5 for pyroxene; this ratio shows no obvious dependence on any experimental parameter.
The early intense bombardment of the moon has not necessarily gardened most of the crust to more than a few kilometers depth. Deep crustal material sampled by the largest impacts is most likely to be preserved as melt-rock deposits on or near the rims of mare basins. The Apollo 17 melt-rock boulders and the matrices of the Apollo 15 'black-and-white' rocks (15445, 15455) are considered the most likely of all lunar samples to represent deep crustal material. These samples have the composition of low-K Fra Mauro (LKFM) basalt. A two- or three-layer crustal model is proposed, in which a layer of anorthositic gabbro, which forms most of the exposed surface of the lunar highlands, is underlain by a layer of LKFM basalt. If the Apollo 15 and 17 heat-flow measurements are representative of the mean lunar heat flow, they constrain the LKFM layer to be no more than 20 km thick.
The reported investigation was conducted in connection with the desirability to obtain information regarding the response of a solidified planetary surface to the primary impact of a meteoroid whose dimensions are small compared to that of the planet. The investigation is an extension of studies conducted by Ahrens and O'Keefe (1977) concerned with a calculation via finite-difference techniques of the entire flow field, the energy partitioning, and the quantity of melt and vapor produced upon impact of an iron object on a gabbroic anorthosite half-space at 15 km/sec. The assumptions used in these calculations are summarized. Calculations based on an equation of state for the low- and high-pressure mineral assemblage of gabbroic anorthosite, initial density 2.94 g/cu cm are considered. An algorithm is formulated for the description of the phase transformation upon shock loading. It is shown that the relative volume of melt and the equivalent volume of shock-induced vapor is proportional to the meteoroid kinetic energy (at high speeds) using the similarity scaling of projectile and target properties as suggested by Dienes and Walsh (1970).
Primary silicate melt inclusions in ilmenite crystals in seven mare basalt samples were analyzed by electron microprobe, and analyses were made of their host and associated phases. Two distinct and restricted chemical composition ranges are drawn: high-K and low-K. The high-K samples are nearly identical with the granitic residual liquid, averaging a weight percentage of 6.27% K20, 76.3% SiO2, plus 82% normative quartz and orthoclase. It is noted that no low-K melt was found as a re-entrant or interstitial inclusion in any sample; only as isolated inclusions in illmenite.
Equilibrium crystallization sequences are determined in melting experiments in vacuum at Fe saturation on synthetic mare basalt compositions 70215 and 15318 Red Glass (both high-Ti) as well as 15555-15016 (low-Ti). The experiments confirm that much of the chemical variation within both the high- and low-Ti suites is controlled by near-surface fractionation processes, although the two suites cannot be related by such mechanisms. The components and crystallization products of the liquidus at various temperatures and pressures are reported. Mare basalt petrogenesis is interpreted in terms of high-pressure equilibria at Fe saturation; it is suggested that low-Ti basalts represent partial melts of a differentiated olivine-pyroxenite lunar mantle at 240 km or deeper, while cumulus clinopyroxene in the source is responsible for their REE characteristics. The formation of high-Ti basalts is considered.
The Chassigny meteorite, an iron-rich dunite (Fo 68), is a moderately shocked olivine achondrite or chassignite with features indicative of a cumulate origin with some subsolidus annealing. The evidence that the meteorite experienced shock pressures of approximately 150-200 kbar is described. Kaersutitic amphibole, found only in melt inclusions, represents the first extraterrestrial occurence of hydrous amphibole and the first meteoritic amphibole type other than fluorichterite. Fractionation data indicate that Chassigny formed under relatively more oxidizing conditions than most other achondrites, which implies that its parental melt could not have been directly derived from a chondritic composition in a simple single-stage process. Similarities and differences with the Brachina meteorite, the only other meteorite of the Chassigny type, are considered.
A saturated solution of silicon and an element such as carbon having a segregation coefficient less than unity is formed by placing a solid piece of carbon in a body of molten silicon having a temperature differential decreasing toward the surface. A silicon carbide seed crystal is disposed on a holder beneath the surface of the molten silicon. As a rod or ribbon of silicon is slowly pulled from the melt, a supersaturated solution of carbon in silicon is formed in the vicinity of the seed crystal. Excess carbon is emitted from the solution in the form of silicon carbide which crystallizes on the seed crystal held in the cool region of the melt.
An evaluation of a crystal-fractionation model for Apollo 12 ilmenite basalts with melting experiments under controlled oxygen fugacities is reported. The crystallization sequence including olivine, chromium spinel, and pigeonite phases was determined, showing that the changes in melt composition are dominated by olivine crystallization and the decrease in MgO with a corresponding increase in CaO, Al2O3, and TiO2. It is concluded that the bulk composition of the ilmenite basalts was established by crystallization of olivine and minor spinel prior to the onset of pyroxene and plagioclase.
The melting relations and distribution of K and Cs in portions of the system was determined at high pressures. Ferrosilite is stable as a primary phase at high pressures because of the incongruent melting of ferrosilite to quartz plus liquid and the boundary between the one and two liquid fields on the joint Fe(1-x) O-FeS-SiO2 shifts away from silica with increasing pressures. Potassium K was found to have limited solubility in metal sulfide liquids at pressures up to 45 kb. The speculation that K may dissolve significantly in metal-metal sulfide liquids after undergoing first order isomorphic transition was tested by determining the distribution of Cs between sulfide and silicate liquids as an analogy to K. At 45 kb, 1400 C and 27 kb, 1300 C only limited amounts of Cs were detected in quench sulfide liquids even at pressures beyond the isomorphic transition of Cs.
A susceptor for facilitating induction heating of silicon melt is described. The susceptor comprises a pair of susceptor halves of a thickness less than two skin depths, each being the mirror image of the other, disposed in mutually opposed, electrically insulated relation. The crucible comprises a quartz body supported by the graphite susceptor, whereby the R-F coil is electrically coupled with the melt.
A heat transport analysis which considers forced convective fluid flow induced by the motion of a continuous solid ribbon over a melt has been done for horizontal ribbon growth. A model has been developed which treats both 'active' and 'passive' cooling at the ribbon surface. The results show that heat flow from the melt requires active cooling in the region of the leading growth edge or growth tip. Steady-state liquid-solid interface shape is analyzed and numerical results are given for steady-state pulling of silicon ribbon.
Technique for recharging surface with "hot-melt" film makes use of one sided, high-temperature, pressure-sensitive adhesive tape. Purpose of the one-sided tape is to hold hot-melt charge in place until fused to surface. After adhesive has fused to surface and cooled, tape is removed, leaving adhesive on surface.
Seed substrate pulled under InGaAsP wipe melt at temperature of 650 degrees C for approximately 15 to 60 seconds. After pullthrough and meltback, surface has high smoothness and luster without meniscus lines, exaggerated erosion, pits, and pearls characteristic of other wipe melts. Layer-to-substrate interface structure is more planar and of better quality. New combination of elements leaves smooth high luster surface.
Undercooling and structural refinements in droplets of molten metal levitated in an induction field and/or by dispersion in a fluid carrier were studied. Nickel base and lower melting point alloys levitated in molten carrier fluids are considered. The dispersion of molten alloy droplets in a high temperature fluid following the procedures developed by Perepezko and co-workers for lower melting point alloys; obtaining a similar dispersion by room temperature mechanical mixing of particles of the metal and solidified liquid carrier; and solidification of single relatively large droplets in a transparent fluid carrier, enabling high-speed temperature measurement of the recalescence and subsequent cooling behavior are described.
The application of finite element computer analyses to polymer flows of the type encountered in melt processing operations is described. A code capable of predicting values of fluid veleocity, pressure, shear stress, and temperature at any point within the flow field was developed. As such, is is of value in diagnosing such processing problems as regions of fluid stagnation at which thermal degradation may occur, or regions of excessive shear deformation which lead to thermomechanical damage. It is further able to generate predictions of the forces which must be applied to the melt to achieve the desired flow, and this information is of value in designing processing equipment of optimal efficiency and minimum energy consumption.
A melt processable polyimide which contains sulfur and oxygen bridges between the aromatic rings (BDSDA/APB) was synthesized and characterized. Its physical, mechanical, thermal and flow properties were determined as was its resistance to some of the more commonly used solvents. The melt flow properties were measured for the temperature range 250 C - 350 C and under the conditions (stress/strain) encountered in commercial processes.
The capabilities of and potential problems with ion microprobe analysis are illustrated in the determination of Ni distribution between silicate melt and diopside as a function of concentration. Samples of diopside and a melt in the albite-anorthite-diopside system were doped with Ni to levels of 5.22 and 1.08 wt % and 1060, 138, 42 and 30 ppm, and with 3 ppm of Ni-63, and characterized by both electron and ion microprobe techniques. Measurements of Ni-62 distribution by the ion probe method give a ratio of 1.87 for the ratio of count rates in the diopsides with the glass, which is slightly lower than the value of 2.05 obtained from beta-track mapping. The measurements required the secondary ion signal to be linear with concentration in the range measured, and a calibration to correct for differential secondary ion yields from different phases. It is found, however, that partition coefficients measured for Ni-58 and Ni-60 are not constant with Ni concentration, probably due to Ni migration during crystallization. The results thus show ion microprobe analyses to be feasible for simultaneous measurements of distributions of more than one element, and of elements inappropriate for beta-track mapping or electron probe analysis.
Attention is given to all the mechanisms currently known which might have been responsible for the melting of the moon. A comparison is conducted of the terrestrial planets and the moon, taking into account the conditions in the early solar system as a function of time. The assumption is made that the terrestrial planets and the moon all reached sizes comparable to their present sizes at the same time, so that the same heating mechanisms were operating on all of the bodies when their early crusts were formed. A chronology of the early solar system is established in order to evaluate the time periods during which each of the mechanisms might have been active. If the moon and planets formed within 2,000,000 years after the formation of the protosun, the conclusion appears inescapable that all of the terrestrial planets melted.