A velocity model can have enduring and growing interpretive value, beyond its initial creation as a means to optimize the seismic image. The 3D velocity model is often built carefully with a combination of geophysical and geological input, because of the accuracy demands placed on it by the requirements of depth imaging. As such, this model becomes an increasingly effective interpretive tool.
This course addresses the ways in which the interpreter should participate in the development of the velocity model, and underscores its interpretive value with numerous case study examples. <...>

The Selwyn Line is the name adopted for an open arcuate zone of iron-copper-gold mineralisation, located ~150 km southeast of Mount Isa, in the Mount Isa Proterozoic inlier, northwest Queensland, Australia. Since the discovery of gold mineralisation in the Selwyn Hills in the 1970's, 5 small mines have been operated. These exploited high grade ironstone hosted gold-copper mineralisation, located within a zone of poly-aged shearing and complex alteration. The mines are located within the Starra Shear which has a history of ductile-brittle, brittle-ductile and brittle deformation. The structure is altered over widths of between 100 m and 500 m, and for over 10 km along strike. The alteration involved early albite +quartz +calcite +scapolite +actinolite replacement of the host sheared meta-sediments of the Staveley Formation. This was followed by a magnetite/hematite+biotite+quartz(+pyrite) overprint, and finally post tectonic oxidation of the magnetite, and chlorite-calcite alteration with associated chalcopyrite and gold mineralisation, and limited pyrite fonnation (Rotherham 1997). The high grade zones exhibit indications of strong structural controls. They typically plunge steeply to the north along magnetite bearing extensional duplex structures and shear planes which include portions of the hanging wall bounding shears and link structures to the footwall bounding shears. The dimensions of the mined and mineable resource (<8 mt) have always been regarded as small for typical Fe-Cu-Au systems. However resource work done on lower cut-off grades indicates that the system is more typical of the large systems of this sort found elsewhere in the district, with a pre-mining global resource of at least 29 mt at 2.5g/t Au and 1.4% Cu (at a 1.5% Cu Equivalent cutoff using a factor of- 0.8 depending on where the ore is from), 49 mt at 1.76 g/t Au and 1.05% Cu using a 1.0% cut off, or 95mt at 1. lg/t Au and 0.74%Cu at a 0.5% cutoff. These are embraced within a larger mineralised system with a global resource of 253 mt @ 0.48g/t Au and 0.34% Cu at measured, indicated and inferred categories, to a depth of ~300m below surface (using a 0.2% Cu Equivalent cut off).

The Sin Quyen deposit in northern Vietnam is an unusual example of the Fe oxide-Cu-Au-REE group of deposits. Magnetite-orthite-chalcopyrite-gold mineralisation is hosted by extremely altered amphibolite and biotite-gneiss lenses within highly defonned and metamorphosed sediments of the Proterozoic Sin Quyen Formation. The deposit fonned in a wide fault zone which acted as a channel for pre-mineralisation amphibolite and granitic dykes, mineralising fluids as well as post mineralisation granite, pegmatite and amphibolite. Metasomatic alteration produced a variety of assemblages predominantly composed of variable amounts of quartz, hastingsite and biotite but also including small zones of hedenbergite-garnet skarn. Alteration is closely associated with magnetite and orthite (allanite) development. Sulphide mineralisation, mainly chalcopyrite and pyrrhotite with lesser pyrite is a later and lower temperature hydrothermal phase, although the majority of the sulphides were deposited within the alteration zones.

A study of the Soviet state reserves system is important to the US intelligence comnqunity in two ways. First, the nature and extent of state reserves must be considered in assessing the war potential of the USSR. Second, state reserves serve as a "flywheel'' in the operation of the Soviet planned economy, and a better understanding of the working of the Soviet economy may be obtained by studying them.