The fluid dynamics of a basaltic magma chamber replenished by influx of hot,dense ultrabasic magma     

Herbert E. Huppert  R. Stephen J. Sparks 《Contributions to Mineralogy and Petrology》1981,75(3):279-289

This paper describes a fluid dynamical investigation of the influx of hot, dense ultrabasic magma into a reservoir containing lighter, fractionated basaltic magma. This situation is compared with that which develops when hot salty water is introduced under cold fresh water. Theoretical and empirical models for salt/water systems are adapted to develop a model for magmatic systems. A feature of the model is that the ultrabasic melt does not immediately mix with the basalt, but spreads out over the floor of the chamber, forming an independent layer. A non-turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion. Both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock. The convection continues until the two layers have almost the same temperature. The compositions of the layers remain distinct due to the low diffusivity of mass compared to heat. The temperatures of the layers as functions of time and their cooling rate depend on their viscosities, their thermal properties, the density difference between the layers and their thicknesses. For a layer of ultrabasic melt (18% MgO) a few tens of metres thick at the base of a basaltic (10% MgO) magma chamber a few kilometres thick, the temperature of the layers will become nearly identical over a period of between a few months and a few years. During this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling. Olivines only settle after the two layers have nearly reached thermal equilibrium. At this stage residual basaltic melt segregates as the olivines sediment in the lower layer. Depending on its density, the released basalt can either mix convectively with the overlying basalt layer, or can continue as a separate layer. The model provides an explanation for large-scale cyclic layering in basic and ultrabasic intrusions. The model also suggests reasons for the restriction of erupted basaltic liquids to compositions with MgO<10% and the formation of some quench textures in layered igneous rocks.  相似文献   

Determination of Aquifer Parameters from Large-Diameter Dug Well Pumping Tests   总被引：1，自引：0，他引：1  

R. Herbert  R. Kitching 《Ground water》1981,19(6):593-599

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A laboratory model of a replenished magma chamber     

Herbert E. Huppert  J. Stewart Turner 《Earth and Planetary Science Letters》1981,54(1):144-152

It has recently been suggested that periodic influxes of hot but heavy magma into the base of a basaltic magma chamber can remain isolated from the rest of the chamber while the new magma cools and crystallization proceeds. When thermal equilibrium is almost complete, the suspended crystals settle out and the residual, less dense liquid can then mix with the fluid above. In the present paper the basic fluid-dynamical processes underlying this model have been investigated in laboratory experiments using aqueous solutions. The lower layer was hot KNO₃ solution, for which saturated solutions become less dense as the temperature decreases. With a cold, deeper layer of less dense NaNO₃ or K₂CO₃ above the lower layer, there was strong convective transfer of heat through a sharp interface separating the layers, at a rate which is predicted here drawing on previous studies carried out with oceanographic applications in mind. Once crystallization began, non-equilibrium effects became important and the observed temperatures differ somewhat from those predicted. In the experiments crystals grew mainly from the bottom rather than while in suspension, but this is not an essential aspect of the model. The important fact is that the density of the residual liquid in the lower layer decreased until it became equal to that of the upper layer, and then the interface broke down so that the two layers mixed thoroughly together, leaving a layer of KNO₃ crystals at the base. No crystallization at all occurred when the hot input liquid was forced to mix initially with the cold solution already in the chamber.  相似文献   

The cosmic abundance of molybdenum     

Herbert Palme  Werner Rammensee 《Earth and Planetary Science Letters》1981,55(3):356-362

Fifteen carbonaceous chondrites were analysed for Mo and Ir by neutron activation analysis combined with a metal extraction method. The results of two Orgueil analyses gave a mean concentration of 915 ppb Mo. This corresponds to 2.51 atoms Mo/10⁶ atoms Si, which is 50% lower than data reported by Case et al. [3]. The lower Mo concentration for Orgueil was predicted by Suess and Zeh [4] from semi-empirical abundance rules. A constant Mo/Ir ratio is found for C1, C2, and C3V chondrites; C3Os have variable Mo/Ir ratios. These variations are due to variable Ir concentrations. Micron-sized grains enriched in Ir but not in Mo are presumably responsible for these variations. The Mo content of Karoonda is nearly a factor of four lower than that of C3V chondrites.  相似文献   

Cores of soft lake sediments   总被引：5，自引：0，他引：5  

Herbert E. Wright Jr. 《Boreas: An International Journal of Quaternary Research》1980,9(2):107-114

Short cores of soft sediment, used in studying the pollution history of lakes, can be obtained with a plastic tube fitted with a piston and piston wire. If the sediments of deep water are annually laminated (and thus difficult to sample without disturbance) or contain excess gas (which can disrupt the stratigraphy during its escape), a short 'core' can be acquired by producing a frozen crust on a tube filled with dry ice and butanol.
A continuous core of soft lake sediment at least 7 m long can be obtained in a single drive beneath deep water with a hand-driven piston corer. Such a core assures the complete continuity necessary for counting annual laminations or for making close-interval analyses without fear of gaps, and it provides the uniform orientation required for measurements of paleomagnetic directions.  相似文献   

On the age of KREEP     

Herbert Palme 《Geochimica et cosmochimica acta》1977,41(12):1791-1801

Many lunar highland rocks have been extensively metamorphosed during the late heavy bombardment of the Moon 3.9–4.0 AE ago. Rubidium and other, more volatile elements were preferentially mobilized during this event, which resulted in a considerable scatter of RbSr model ages. This scatter can be considerably reduced by estimating the original Rb content on the basis of Sm or other, less mobile, incompatible elements. The principal uncertainty on the corrected model ages of 4.25–4.45 AE comes from the original Sm/Rb ratio.Highland rocks enriched in incompatible elements in most cases are mixtures between KREEP-basalt and other highland rock types. After corrections for Rb mobilization 3.9–4.0 AE ago, slight isotopic differences among KREEP-enriched rocks from different landing sites becomes noticeable. These differences correspond to different meteoritic groups as defined by Morgan et al. (1974). Apparently there existed slightly different KREEP basalt reservoirs, with formation ages ranging from 4.25 to 4.45 AE. These reservoirs were partly exposed through impacts of basin-forming planetesimals 3.9–4.0 AE ago. The resulting impact melts were contaminated with meteoritic material from the bombarding planetesimals.The $\text{4.63 ± 0.1}$ AE RbSr isochron of trace element poor highland rocks (Schonfeld, 1976) is determined by a K,Rb- and Ba-rich component, which formed earlier and independently of KREEP basalts.  相似文献   

Fallout radionuclides in the Pacific Ocean: Vertical and horizontal distributions,largely from GEOSECS stations     

Vaughan T. Bowen  Victor E. Noshkin  Hugh D. Livingston  Herbert L. Volchok 《Earth and Planetary Science Letters》1980,49(2):411-434

From GEOSECS stations, largely, the 1974 distributions of Pu and of¹³⁷Cs are described in the Pacific Ocean north of about 20°S latitude. Changes in some of these distributions are described from 1978 cruises by the authors.The Pacific exhibited, everywhere, a shallow subsurface layer of Pu-rich water with its concentration maximum at about 465 m in 1974; over a large portion of the central North Pacific a second layer of Pu-labelled water, less concentrated than the shallow layer, lay just above the bottom. Similar features were not observed in the case of¹³⁷Cs.The inventories of both Pu and¹³⁷Cs in the water column at most 1974 stations are substantially greater than those to be expected from world-wide fallout alone; these inventory excesses appear to be attributable to close-in fallout, but only if the ratio Pu/¹³⁷Cs in this source was much higher than in world-wide fallout. The North Pacific mean ratio of the inventories is 2.2 times that observed in world-wide fallout.Resolubilization of Pu both from sinking particles and from sediments explains peculiarities of its depth distributions.There is little evidence for tracer movement by sliding downward along density surfaces;¹³⁷Cs appears to have moved to depth by downmixing at the edge of the Kuroshio, and then moved horizontally and upward alongσ_t contours. The shallow Pu-rich layer shows no coordination with density, salinity or O₂ isopleths. The deep Pu-rich layer is restricted to a narrow range of O₂ concentrations that confirm its origin in the Aleutian Trench and rapid spread southward and laterally. Near-bottom circulation processes have been much more active than here-to-fore described.  相似文献   

Theoretical studies of the parameterization of the non-neutral surface boundary layer     

Walter-Georg Panhans  Fritz Herbert 《Boundary-Layer Meteorology》1979,16(2):155-167

The parameterization of the non-neutral atmospheric surface layer has been reexamined using the basic principles of small-scale energetics and thermodynamics. On the basis of this more complete treatment, theK-parameterization has been reformulated. It is found that the linear regression laws between fluxes and driving gradient forces of the turbulent heat and humidity exchanges in the surface layer can be derived in a much more comprehensive manner than by using the commonly used K-theory. With respect to stationary conditions and in the context of similarity concepts, a system of algebraic equations has been formulated which provides reasonable estimates of the distributions of the dimension less rates of viscous energy dissipation as well as turbulent kinetic and thermal-diffusive energy transport as functions of the variablez/L. Quantitative calculations have been performed using the scaling height formulations of Takeuchi and Yokoyama, Prandtl, and von Karman as closure conditions of the equations.  相似文献   

Computing a design flood in the absence of historical records     

Herbert Riehl  Horace R. Byers 《Pure and Applied Geophysics》1960,45(1):215-226

Summary A design flood for a Venezuelan river is computed in the absence of rainfall and stream-flow data of more than a few years. From synoptic studies of an area embracing northern South America and the Caribbean, the type of disturbance producing the abundant rains of the area is determined. A disturbance of this type is maximized on the basis of the ratio of energy dissipated through friction to released latent energy represented by rainfall — in other words, theefficiency of the system is given its highest reasonable value. The synthetic disturbance is moved over the river basin in a manner most favorable for heavy rain. Certain data available from other rivers are used as a cross-check on the resultant flood values.  相似文献   

Liquidus karrooite stability and composition at reducing conditions     

Alexander?BorisovEmail author  Frank?Brenker  Herbert?Palme 《Contributions to Mineralogy and Petrology》2004,148(1):69-78

We have determined the stability of rutile and karrooite on the liquidus of pseudobinary silicate melts of anorthite–diopside eutectic composition with, in addition, of up to 32 wt% TiO₂ at one atm total pressure and at wide range of oxygen fugacities. At 1,300°C and at an fO₂ below 10^–11.2 atm rutile (TiO₂) is replaced as liquidus phase by the pseudobrookite-type MgTi₂O₅–Ti₃O₅ solid solution with some Al in the crystal structure. The composition of karrooite was found to be strongly dependent on oxygen fugacity. Crystalline phases were identified by transmission electron microscopy (TEM). The results obtained in this study are relevant for understanding the chemistry of lunar armalcolites. Using excess rutile solubility at reducing conditions, we estimated the Ti⁴⁺ /Ti³⁺ ratio in silicate melts at 1,300°C as function of fO₂.  相似文献