Silicate liquid immiscibility in lunar magmas, evidenced by melt inclusions in lunar rocks

Examination of multiphase melt inclusions in 91 sections of 26 lunar rocks revealed abundant evidence of late-stage immiscibility in all crystalline rock sections and in soil fragments and most breccias. The two individual immiscible silicate melts (now glasses) vary in composition, but are essentially potassic granite and pyroxenite. This immiscibility may be important in the formation of the lunar highlands and tektites. Other inclusions yield the following temperatures at which the several minerals first appear on cooling the original magma: ilmenite (?) liquidus, 1210 degrees C; pyroxene, 1140 degrees C; plagioclase, 1105 degrees C; solidus, 1075 degrees C. The glasses also place some limitations on maximum and minimum cooling rates.     

Field-based evidence for devolatilization in subduction zones: implications for arc magmatism

Metamorphic rocks on Santa Catalina Island, California, afford examination of fluid-related processes at depths of 15 to 45 kilometers in an Early Cretaceous subduction zone. A combination of field, stable isotope, and volatile content data for the Catalina Schist indicates kilometer-scale transport of large amounts of water-rich fluid with uniform oxygen and hydrogen isotope compositions. The fluids were liberated in devolatilizing, relatively low-temperature (400 degrees to 600 degrees C) parts of the subduction zone, primarily by chlorite-breakdown reactions. An evaluation of pertinent phase equilibria indicates that chlorite in mafic and sedimentary rocks and melange may stabilize a large volatile component to great depths (perhaps >100 kilometers), depending on the thermal structure of the subduction zone. This evidence for deep volatile subduction and large-scale flow of slab-derived, water-rich fluids lends credence to models that invoke fluid addition to sites of arc magma genesis.     

Serpentine stability to mantle depths and subduction-related magmatism

Results of high-pressure experiments on samples of hydrated mantle rocks show that the serpentine mineral antigorite is stable to approximately 720 degrees C at 2 gigapascals, to approximately 690 degrees C at 3 gigapascals, and to approximately 620 degrees C at 5 gigapascals. The breakdown of antigorite to forsterite plus enstatite under these conditions produces 13 percent H(2)O by weight to depths of 150 to 200 kilometers in subduction zones. This H(2)O is in an ideal position for ascent into the hotter, overlying mantle where it can cause partial melting in the source region for calc-alkaline magmas at a depth of 100 to 130 kilometers and a temperature of approximately 1300 degrees C. The breakdown of antigorite in hydrated mantle produces an order of magnitude more H(2)O than does the dehydration of altered oceanic crust.     

High-pressure reactions and shear strength of serpentinized dunite

The recently reported Pronounced decrease in shear strength of serpentine-bearing rocks at 30 to 40 kilobars in the temperature range 300 degrees to 520 degrees C may be attributed to the transformation of serpentine to a Pressure-dependent, 10-angstrom,2: 1 layer silicate plus brucite and periclase. This reaction increases density by about 8.5 percent.     

Hot and dry deep crustal xenoliths from tibet

Anhydrous metasedimentary and mafic xenoliths entrained in 3-million-year-old shoshonitic lavas of the central Tibetan Plateau record a thermal gradient reaching about 800 degrees to 1000 degrees C at a depth of 30 to 50 kilometers; just before extraction, these same xenoliths were heated as much as 200 degrees C. Although these rocks show that the central Tibetan crust is hot enough to cause even dehydration melting of mica, the absence of hydrous minerals, and the match of our calculated P-wave speeds and Poisson's ratios with seismological observations, argue against the presence of widespread crustal melting.     

The 25-km Discontinuity: Implications for Lunar History

The lunar velocity profile and laboratory data on terrestrial and lunar rocks are constraints on models of lunar history. They show that shock-induced microcracks are absent from the rocks present in the moon today at depths of 25 to 60 kilometers. All possible causes of this observation are examined, and the most likely explanations are that either the rocks at depths of 25 to 60 kilometers formed after the major impacts ceased or the microcracks have annealed at temperatures of about 600 degrees C over geologically long times.     

Hydrocarbons in hydrothermal vent fluids: the role of chromium-bearing catalysts

Fischer-Tropsch type (FTT) synthesis has long been proposed to account for the existence of hydrocarbons in hydrothermal fluids. We show that iron- and chromium-bearing minerals catalyze the abiotic formation of hydrocarbons. In addition to production of methane (CH4aq), we report abiotic generation of ethane (C2H6aq) and propane (C3H8aq) by mineral-catalyzed hydrothermal reactions at 390 degrees C and 400 bars. Results suggest that the chromium component in ultramafic rocks could be an important factor for FTT synthesis during water-rock interaction in mid-ocean ridge hydrothermal systems. This in turn could help to support microbial communities now recognized in the subsurface at deep-sea vents.     

Freeze avoidance in a mammal: body temperatures below 0 degree C in an Arctic hibernator

Hibernating arctic ground squirrels, Spermophilus parryii, were able to adopt and spontaneously arouse from core body temperatures as low as -2.9 degrees C without freezing. Abdominal body temperatures of ground squirrels hibernating in outdoor burrows were recorded with temperature-sensitive radiotransmitter implants. Body temperatures and soil temperatures at hibernaculum depth reached average minima during February of -1.9 degrees and -6 degrees C, respectively. Laboratory-housed ground squirrels hibernating in ambient temperatures of -4.3 degrees C maintained above 0 degree C thoracic temperatures but decreased colonic temperatures to as low as -1.3 degrees C. Plasma sampled from animals with below 0 degree C body temperatures had normal solute concentrations and showed no evidence of containing antifreeze molecules.     

Water and carbon in rusty lunar rock 66095

Lunar rock 66095 contains a hydrated iron oxide and has an unusual amount of water for a lunar rock (140 to 750 parts per million), 90 percent of which is released below 690 degrees C. The deltaof water released at these low temperatures varies from -75 to -140 per mil relative to standard mean ocean water (SMOW). The small amount of water released between 690 degrees and 1300 degrees C has a delta of about -175 +/-25 per mil SMOW. These delta values are not unusual for terrestrial water. The delta(18)O of water extracted from 110 degrees to 400 degrees C has a value of +5+/- I per mil SMOW, similar to the value for lunar silicates from rock 66095 and different from the value of -4 to -22 per mil found for samples of terrestrial rust including samples of rusted meteoritic iron. The amount of carbon varies from 11 to 59 parts per million with a delta(13)C from -20 to -30 per mil relative to Pee Dee belemnite. Only very small amounts of reduced species (such as hydrogen, carbon monoxide, and methane) were found, in contrast to the analyses of other lunar rocks. Although it is possible that most of the water in the iron oxide (goethite) may be terrestrial in origin or may have exchanged with terrestrial water during sample return and handling, evidence presented herein suggests that this did not happen and that some lunar water may have a deltaD that is indistinguishable from that of terrestrial water.     

Kyanite-Andalusite Equilibrium from 700{degrees} to 800{degrees}C

The metastable kyaniteandalusite equilibrium in the Al(2)SiO(5) system has been reversed at 700 degrees , 750 degrees , and 800 degrees C at elevated water pressures, with a variety of natural and synthetic kyanites and andalusites as starting materials. Sillimanite, the stable form of Al(2)SiO(5) under these conditions, did not appear. The value of the transition pressure at 750 degrees C is 6.6 +/- 0.4 kilobars, several kilobars below pressures given by several convergent previous determinations. The Al(2)SiO(5) pressure-temperature triple point now indicated lies far from the points found by others. The revised aluminum silicate phase diagram indicates that many rocks crystallized at lower pressures than formerly thought possible.     

Nanometer-size alpha-PbO(2)-type TiO(2) in garnet: A thermobarometer for ultrahigh-pressure metamorphism

A high-pressure phase of titanium dioxide (TiO(2)) with an alpha-PbO(2)-type structure has been identified in garnet of diamondiferous quartzofeldspathic rocks from the Saxonian Erzgebirge, Germany. Analytical electron microscopy indicates that this alpha-PbO(2)-type TiO(2) occurred as an epitaxial nanometer-thick slab between twinned rutile bicrystals. Given a V-shaped curve for the equilibrium phase boundary of alpha-PbO(2)-type TiO(2) to rutile, the stabilization pressure of alpha-PbO(2)-type TiO(2) should be 4 to 5 gigapascals at 900 degrees to 1000 degrees C. This suggests a burial of continental crustal rocks to depths of at least 130 kilometers. The alpha-PbO(2)-type TiO(2) may be a useful pressure and temperature indicator in the diamond stability field.     

Cooling history of orthopyroxenes

Order-disorder transitions between ferrous iron and magnesium in orthopyroxenes [minerals close to the composition (Fe, Mg) SiO(3)] occur rapidly between approximately 480 degrees and 1000 degrees C. Disordering and ordering have been studied experimentally. The determination of the metastable ferrous iron site occupancy in orthopyroxenes from rapidly cooled volcanic rocks provides information on the cooling rates, especially from 600 degrees to 480 degrees C.     

High crystallization temperatures indicated for igneous rocks from tranquillity base

Complex intergrowths of troilite (FeS) and iron in the igneous rocks from Tranquillity Base contain 8.4 percent native iron by volume. The intergrowths were derived from an initially homogeneous sulfide liquid that separated immiscibly from the magma at 1140 degrees C or above. Textures show that the sulfide liquid formed late in the crystallization and cooling history of the igneous rocks and after the major ilmenite and pyroxene had formed.     

冷藏对石蒜鳞茎休眠生理及开花的影响

为掌握冷藏对石蒜(Lycoris radiata)鳞茎休眠生理及开花的影响,研究了石蒜球根在6和9℃低温下分别冷藏4、7、9周后,鳞茎尖内的生理变化,并观察其开花时间.结果表明:在6℃冷藏4周花期推迟19d;9℃冷藏4周花期推迟12d;6、9℃条件下冷藏7和9周均未开花.在6℃冷藏4周条件下,蛋白质和核酸质量分数均保持着较低的水平;同时对内源激素质量摩尔浓度测定表明内源激素IAA极显著对花期具有影响作用,ABA、ZR也具有影响花期的作用,而内源激素GA3质量摩尔浓度变化对开花无显著影响.     

Diamond from the dabie shan metamorphic rocks and its implication for tectonic setting

Diamond occurs in ultrahigh pressure metamorphic rocks from Dabie Shan, Anhui Province, eastern China. Diamond-bearing rocks include eclogite, gamet-pyroxenite, and jadeitite. Diamond occurs in a mineral assemblage with coesite and jadeite. The diamonds and diamondiferous rocks of Dabie Shan are interpreted to be the products of ultrahigh pressure metamorphism in the undérthrust basement of the Yangtze continental plate during the early Mesozoic, at greater than 4.0 gigapascals and 900 degrees C. This interpretation is based on the distribution of rock units, the stability field of diamond, and isotopic data indicating a crustal origin for the rocks. Most diamonds occur as euhedral inclusions in garnets and are 10 to 60 micrometers across, although some are up to 700 micrometers across.     

Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

The water content of the breccia is 150 to 455 ppm, with a deltaD from-580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a deltaD of -830 to -970 per mil. The CO(2) is 290 to 418 ppm with delta (13)C = + 2.3 to + 5.1 per mil and delta(18)O = 14.2 to 19.1 per mil. Non-CO(2) carbon is 22 to 100 ppm, delta(13)C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H(2)O (D = 80 ppm) and 188 ppm total carbon(delta(13)C = -17.6 per mil). The (18)O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100 degrees to 1300 degrees C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.     

Rare gases, hydrogen, and nitrogen: concentrations and isotopic composition in lunar material

The concentrations and isotopic abundances of the rare gases have been investigated in fines and three types of rocks. The results obtained from different grain-size fractions and from samples etched to different degrees with nitric and hydrofluoric acids demonstrate the strong concentrations of the solar-wind component in the surface layers of the grains. Exposure ages as well as gas retention ages have been determined in different types of Apollo 11 material. Hydrogen, nitrogen, and other gases have been analyzed by a high-resolution mass spectrometer. As compared with that in terrestrial water, deuterium is depleted by at least a factor of 3 in the investigated type C rocks.     

Abiogenic hydrocarbon production at lost city hydrothermal field

Low-molecular-weight hydrocarbons in natural hydrothermal fluids have been attributed to abiogenic production by Fischer-Tropsch type (FTT) reactions, although clear evidence for such a process has been elusive. Here, we present concentration, and stable and radiocarbon isotope, data from hydrocarbons dissolved in hydrogen-rich fluids venting at the ultramafic-hosted Lost City Hydrothermal Field. A distinct "inverse" trend in the stable carbon and hydrogen isotopic composition of C1 to C4 hydrocarbons is compatible with FTT genesis. Radiocarbon evidence rules out seawater bicarbonate as the carbon source for FTT reactions, suggesting that a mantle-derived inorganic carbon source is leached from the host rocks. Our findings illustrate that the abiotic synthesis of hydrocarbons in nature may occur in the presence of ultramafic rocks, water, and moderate amounts of heat.     

Generation and migration of light hydrocarbons

Light hydrocarbons (containing from 1 to 14 carbon atoms) are formed from disseminated organic matter in sediments at the parts-per-billion level by biological and low-temperature (< 50 degrees C) chemical reactions and at the parts-permillion level by high-temperature (> 50 degrees C) cracking reactions. The cooler reactions produce mainly branched hydrocarbons, whereas the hotter reactions yield more straight chains. Hydrocarbon generation zones in the subsurface can be recognized on the basis of hydrocarbon distribution patterns. Hydrocarbons with tertiary carbon atoms form at lower temperatures than those with quaternary carbons. Methane and ethane migrate vertically through fine-grained shales by diffusion and solution, whereas many of the C(3+) hydrocarbons show little or no vertical migration. Concentrations of light hydrocarbons, including methane, in fine-grained source rocks decrease to low values in deep, high-temperature (>200 degrees C) sediments. This decrease may be one reason why no economic accumulation of gas has been found to date deeper than 8.2 kilometers (27,000 feet).     

Activation volume for creep in the upper mantle

The activation volume for creep, V*, of olivine-rich rocks has been determined in pressure-differential creep experiments on dunite at temperatures from 1100 degrees to 1350 degrees C and confining pressures from 5 to 15 kilobars. Values of V* range from 10.6 to 15.4 cubic centimeters per mole with a mean value of 13.4 cubic centimeters per mole, near that expected for oxygen ion self-diffusion. The quantity V* is incorporated into existing flow equations; in combination with observations on naturally deformed mantle xenoliths, estimates are given of the variation with depth of stress, strain rate, and viscosity.