Copper inclusions in sheet silicates from porphyry Cu deposits
Economic geologists have studied the Cu contents of biotite for at least a quarter of a century as potential guides for exploration and as clues to the genesis of porphyry copper deposits1–12. These earlier studies used bulk analytical techniques, and a common, although cautious, assumption was that Cu substituted for Fe in the octahedral sites of the biotite. Here we report data from high-resolution and X-ray analytical transmission electron microscopy which demonstrate that anomalous Cu in biotite is present primarily as submicrometre inclusions of pure native Cu in the interlayer regions of the mica. The inclusions occur with greatest density and size in mixed-layer sheet silicate domains which form by alteration of biotite and chlorite. Less abundant and smaller Cu inclusions are associated with biotites that show subtle alteration only on the high-resolution transmission electron microscopy scale. The association of Cu inclusions with alteration domains, coupled with mass-balance considerations, suggests that these sheet silicates act as Cu sinks, and not as sources for primary mineralization.
Geochemical evidence for magmatic fluids in porphyry copper mineralization
The Cu contents of biotites (av. 880 ppm), amphiboles (16 ppm) and magnetites (160 ppm) from barren intrusions of the Koloula Igneous Complex are significantly greater than the Cu contents of the same minerals from unaltered mineralizing intrusions (av. 23, 6, and 20 ppm respectively). The Cu content of amphiboles from mineralizing intrusions is strongly domain-dependent, with Cu (and chlorine) being depleted in compositional domains that formed during intermittent boiling of hydrothermal fluids. The conversion of pyroxene to amphibole is an unlikely process for the release of Cu.Owing to the differences in Cu contents of biotite, amphibole, and magnetite, mineralizing rock types from the Koloula Igneous Complex are depleted in Cu compared to barren intrusions by 60 ppm, of which 57 ppm is attributable to biotite, 0.5 ppm to amphibole, and 2 ppm to magnetite. Partitioning of the amount of Cu measured here into the fluid phase during boiling is potentially large enough to produce porphyry copper orebodies. The high Cu-contents of minerals from barren rocks suggest that igneous complexes that are hosts for porphyry copper deposits may be anomalously enriched in that metal.
Testing digital circuits using a Mixed-Signal Automatic Test Equipment
This paper presents the results of parametric testing of digital ICs using a dedicated Mixed Signal Automatic Testing Equipment. Due to the prohibitive price of the ATE equipment and dedicated Device Interface Board (DIB) for digital Integrated Circuits (ICs), a DIB for analog circuits was used to perform the testing. Despite the challenges presented by the experiments, the results prove to be accurate for the performed tests, according to the data sheet of the digital ICs and production test data provided by the manufacturer.