Geology and genesis of the Toongi rare metal (Zr,Hf, Nb,Ta, Y and REE) deposit,NSW, Australia,and implications for rare metal mineralization in peralkaline igneous rocks

The Toongi Deposit, located in central NSW, Australia, hosts significant resources of Zr, Hf, Nb, Ta, Y and REE within a small (ca. 0.3 km²), rapidly cooled trachyte laccolith. Toongi is part of regional Late Triassic to Jurassic alkaline magmatic field, but is distinguished from the other igneous bodies by its peralkaline composition and economically significant rare metal content that is homogenously distributed throughout the trachyte body. The primary ore minerals are evenly dispersed throughout the rock and include lueshite/natroniobite and complex Na–Fe–Zr–Nb–Y–REE silicate minerals dominated by a eudialyte group mineral (EGM). The EGM occurs in a unique textural setting in the rock, commonly forming spheroidal or irregular-shaped globules, herein called “snowballs”, within the rock matrix. The snowballs are often protruded by aegirine and feldspar phenocrysts and contain swarms of fine aegirine and feldspar grains that often form spiral or swirling patterns within the snowball. Secondary ore minerals include REE carbonates, Y milarite, catapleiite and gaidonnayite that fill fractures and vesicles in the rock. Based on bulk-rock geochemical and Nd isotope data, and thermodynamic modelling of magma fractionation, the alkaline rocks of the region are interpreted to represent extrusive to hyperbyssal products of mantle-derived magma that ponded at mid-crustal levels (ca. 0.3 GPa) and underwent extensive fractionation under low-oxygen fugacity conditions. The high Na₂O, peralkaline nature of the Toongi Deposit trachyte developed via extensive fractionation of an alkali olivine basalt parental magma initially in the mid-crust and subsequently at shallow levels (ca. 0.1 GPa). This extended fractionation under low fO₂ and relatively low H₂O-activity conditions limited volatile release and allowed build-up of rare metal contents to ore grades. We speculate that the ore minerals may have originally formed from rare metal-rich sodic-silicate melt that formed immiscible globules (subsequently crystallized to EGM) in the magma shortly before emplacement and rapid cooling. Subsequent hydrothermal alteration caused relatively limited and localized remobilization of some ore metals into fractures and vesicles in the rock.     

Variable features on Mars III: Comparison of Mariner 1969 and Mariner 1971 photography

Mariner 9 (M9) and Mariner 6 and 7 photography of common regions of Mars are compared, with appropriate attention to the photometric properties of the camera systems. The comparison provides a 2.5yr time baseline for study of variable albedo features. We find the development of bright streaks and patches, a phenomenon unobserved through the entire M9 mission; the evolution of dark crater splotches into dark streaks; and a planetwide increase in splotchiness. Yet, a large number of splotches and albedo boundaries remain fixed over the same period. Many of the observations are interpreted in terms of a global fallout and subsequent local redistribution of bright fine particulates raised by global dust storms.     

Variable features on Mars. IV. Pavonis Mons

A remarkable set of albedo changes has been uncovered by Mariner 9 photography of the upper slopes of the shield volcano Pavonis Mons, near its summit caldera. The most likely explanation of the event is aeolian transport of fine-grained particles. Since the atmospheric pressure in this locality is ～ 1.5 mb, minimum wind velocities above the surface boundary layer of about 110 m/s are necessary, corresponding to 0.51 of the speed of sound. Slope winds in this velocity range are expected near the upper flanks of major Martian volcanic constructs.     

Differential transmission of sunlight on Mars: Biological implications

A euphotic zone seems to exist at about 1 cm subsurface in the Martian epilith. At this depth visible light is still intense enough to be utilized by conceivable photosynthetic organisms; but the germicidal ultraviolet intensities at the Martian surface have been reduced to values manageable by terrestrial life. Such euphotic zone organisms would experience moderately high Martian temperatures at equatorial latitudes and can be dispersed readily during global dust stroms. During such storms the Martian euphotic zone may reach the surface. The aerosol content of the Martian atmosphere can be monitored by multiband single line scans of the sun at large zenith angles by the Viking lander camera; and the postulated euphotic zone organisms can be searched for with the Viking lander sample arm and biology experiments.     

Evidence for a small,high-Z,iron-like solar core

The high-Z core (HZC) model of the Sun, supported in Rouse (1985) by superior agreements of nonradial g-mode periods of oscillation with long period observations, is used to calculate frequencies of oscillation in the five-minute band (5MB). Allowing for the fact that the present HZC model profile does not include an upper photosphere and self-consistent chromosphere, the HZC model of the Sun is also supported by the very good agreements of the 5MB nonradial frequencies of oscillation with observations for HZC l degrees 0 to 19 and orders n 20, and the good agreement of the HZC purely radial frequencies of oscillation with about the same n-orders with observations previously identified as l = 0 oscillations. Two important aspects of these agreements are (1) the nonradial frequencies were calculated with the equations that neglect the gravitational perturbation (the Cowling approximation), and (2) the radial frequencies were calculated with the equation that includes the gravitational perturbation. The present agreements suggest that for solar-type stars, the gravitational perturbation may not affect the nonradial p-modes of oscillation as much as it affects the radial modes and the nonradial g-modes. More research will be performed.     

Planetary engineering on Mars

Some 10⁹ to 10¹⁰ metric tons of low albedo material, transported during the course of a century to the permanent Martian polar caps, may be capable of rapidly transforming Mars to much more Earth-like conditions. Alternatively the introduction to Mars of a dark plant which grows on the polar snows might accomplish the same objective. Fortunately neither program is a practical engineering venture for the near future.     

Strukturböden,Solifluktion und Frostklimate der Erde

Ohne Zusammenfassung