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The deposit is in the recently discovered Cerro Vanguardia epithermal gold field. Mineralisation occurs in quartz veins with free gold and scarce sulphides/sulphosalts, in stockworks and in silicified and replaced bodies related to silica sinters and breccias. Fluid inclusions and isotopic data indicate that mineralising fluids were of meteoric-hydrothermal origin related to volcanic-sedimentary episodes of Middle to Upper Jurassic age. Ore mineralogy, gangue phases and hydrothermal alteration are consistent with the low-sulphidation epithermal model., The deposit is in the recently discovered Cerro Vanguardia epithermal gold field. Mineralisation occurs in quartz veins with free gold and scarce sulphides/sulphosalts, in stockworks and in silicified and replaced bodies related to silica sinters and breccias. Fluid inclusions and isotopic data indicate that mineralising fluids were of meteoric-hydrothermal origin related to volcanic-sedimentary episodes of Middle to Upper Jurassic age. Ore mineralogy, gangue phases and hydrothermal alteration are consistent with the low-sulphidation epithermal model.

A millimeter wave measurement apparatus utilizing a phase-locked transmitter to generate a millimeter wave signal and a phase-locked local oscillator receiver to receive the transmitted millimeter wave signal. A conventional microwave receiver unit receives the IF signal from the millimeter wave receiver and downconverts the IF signal for detectiona and measurement., Supersedes PAT-APPL-388 327-82, AD-D009 697.

An experiment designed to measure wavefront statistics in 3.2-mm wavelength horizontal transmission over an 18.95-km path is described. A frequency-stabilized signal is transmitted over the path and is received in two spaced antennas having variable separation. The receivers are instrumented to measure phase difference and amplitude fluctuations. A simultaneous beam-swinging experiment using a precision-controlled 4.57-m antenna colocated with the phase difference receivers provides data on wavefront tilt fluctuations. Preliminary results indicate that the random wavefront tilt is the predominant atmosphere-induced wavefront phase disturbance. They further suggest that spatial coherence of wavefronts is of sufficient extent that apertures in excess of 7 m in diam are feasible at the 3.2-mm wavelength. (Author)

Mineralogical, chemical and granulometric analyses were carried out on a talc sample from the Tupungato District, Mendoza province, Argentina. Granulometric fractions were obtained using a beneficiation method involving crushing, dry sieving and dry magnetic separation. The concentrate obtained showed a reduced content of abrasive minerals such as quartz, tremolite, diopside and serpentine and of opaque Fe-containing minerals. The colour of the treated samples was also improved, making them suitable for industrial applications such as white fillers for plastics, paper and paints., Mineralogical, chemical and granulometric analyses were carried out on a talc sample from the Tupungato District, Mendoza province, Argentina. Granulometric fractions were obtained using a beneficiation method involving crushing, dry sieving and dry magnetic separation. The concentrate obtained showed a reduced content of abrasive minerals such as quartz, tremolite, diopside and serpentine and of opaque Fe-containing minerals. The colour of the treated samples was also improved, making them suitable for industrial applications such as white fillers for plastics, paper and paints.

Barite is present in this area as nodules, small lenses, massive beds and small crystals disseminated through certain shale beds. The barite-bearing levels are 0.5 to several metres thick and are scattered throughout the sequence, alternating with barren levels. The barite is dark grey to black in colour and has densities from 3.8 to 4.15. It is proposed that the deposition of the barite layers and nodules were syn- to early diagenetic and the growth of the barite crystals occurred in a late diagenetic stage., Barite is present in this area as nodules, small lenses, massive beds and small crystals disseminated through certain shale beds. The barite-bearing levels are 0.5 to several metres thick and are scattered throughout the sequence, alternating with barren levels. The barite is dark grey to black in colour and has densities from 3.8 to 4.15. It is proposed that the deposition of the barite layers and nodules were syn- to early diagenetic and the growth of the barite crystals occurred in a late diagenetic stage.

The Andean belt southwest of Mendoza, Argentina, hosts 23 Fe, Fe-Cu, and Cu (Ag) deposits classified variously in the literature as skarn, iron oxide-copper-gold (IOCG), and manto-type Cu deposits. The Vegas Peladas deposit is one of the best exposed Fe skarns with mineral assemblages and hydrothermal features similar to many other calcic Fe skarns of the world. The plutonic rocks of Vegas Peladas consist of a series of diorite to granite stocks, dikes, and sills. The major, trace and rare earth element geochemistry of these igneous rocks indicates they were derived from subarc mantle sources. The Vegas Peladas deposit formed by the overprinting of an earlier diorite-related skarn with a later granite-related skarn. On the evidence of fluid inclusion, stable isotope, and REE data, the prograde skarn formed at depths of c.3.5 km under lithostatic pressure of c.1 kbar, from high-temperature (670-400 degrees C), saline and iron-rich magmatic fluids with intermediate oxygen fugacity. Iron ore and retrograde exoskarn assemblages formed under hydrostatic condition after the fracturing of early skarn, from fluids of lower temperature (up to 320 degrees C) and salinity.The mineralogy and positive Eu anomaly of the retrograde assemblage indicate an environment with high oxygen fugacity. Mixing and dilution of early magmatic fluids with external fluids such as meteoric waters caused a decrease in fluid temperature, salinity, and total REE concentration in latest stage of the skarn formation., The Andean belt southwest of Mendoza, Argentina, hosts 23 Fe, Fe-Cu, and Cu (Ag) deposits classified variously in the literature as skarn, iron oxide-copper-gold (IOCG), and manto-type Cu deposits. The Vegas Peladas deposit is one of the best exposed Fe skarns with mineral assemblages and hydrothermal features similar to many other calcic Fe skarns of the world. The plutonic rocks of Vegas Peladas consist of a series of diorite to granite stocks, dikes, and sills. The major, trace and rare earth element geochemistry of these igneous rocks indicates they were derived from subarc mantle sources. The Vegas Peladas deposit formed by the overprinting of an earlier diorite-related skarn with a later granite-related skarn. On the evidence of fluid inclusion, stable isotope, and REE data, the prograde skarn formed at depths of c.3.5 km under lithostatic pressure of c.1 kbar, from high-temperature (670-400 degrees C), saline and iron-rich magmatic fluids with intermediate oxygen fugacity. Iron ore and retrograde exoskarn assemblages formed under hydrostatic condition after the fracturing of early skarn, from fluids of lower temperature (up to 320 degrees C) and salinity.The mineralogy and positive Eu anomaly of the retrograde assemblage indicate an environment with high oxygen fugacity. Mixing and dilution of early magmatic fluids with external fluids such as meteoric waters caused a decrease in fluid temperature, salinity, and total REE concentration in latest stage of the skarn formation.