Simultaneous cathodoluminescence hyperspectral imaging and X-ray microanalysis

A facility has been developed to acquire hyperspectral cathodoluminescence (CL) images simultaneously with X-ray composition data. Based around an electron microprobe, the system uses a built-in Cassegrain microscope to efficiently couple emitted light directly into the entrance slit of an optical spectrograph. A cooled array detector allows the parallel acquisition of CL spectra, which are then built up into a multidimensional data-cube containing the full set of spectrally- and spatially-resolved information for later analysis. This setup has the advantage of allowing wavelength-dispersive X-ray (WDX) data to be recorded concurrently, providing a powerful technique for the direct comparison of luminescent and compositional properties of materials. The combination of beam and sample scanning thus allows the correlation of composition and luminescence inhomogeneities on length scales ranging from a few cm to sub-micron

Adakite-like magmas and Cu-Au porphyry deposits derived from an inherited subduction component, Apuseni Mountains, Romania

ISSN:0016-7037ISSN:1872-953

Generation of normal and adakite-like calc-alkaline magmas in a non-subductional environment: An Sr-O-H isotopic study of the Apuseni Mountains neogene magmatic province, Romania

Neogene magmatism in the Apuseni Mountains of Romania was active between 15 and 7 Ma, with an isolated final eruption at 1.6 Ma. Several groups of magmatic rocks can be distinguished in the province on the basis of ages, trace elements and isotopic compositions. Most are of calc-alkaline affinity, despite the fact that the region is located 200 km from the postulated Carpathian subduction trench. However, adakite-like calc-alkaline magmas were also erupted and the youngest eruptions were of alkaline affinity. Magmatic rocks older than 13.5 Ma are characterised by the highest 87Sr/86Sr, δ18O and δD values in their phenocryst phases. This early magmatism is considered to be a result of crustal melting related to the fast rotation of small crustal blocks. Volcanic rocks younger than 13.5 Ma have lower 87Sr/86Sr and δ18O ratios, with a narrow range for pyroxene and amphibole mineral separates, indicating closed system fractional crystallization. A larger scatter of 87Sr/86Sr and δ18O values is found in plagioclase phenocrysts and groundmasses, indicating that a small amount of crustal assimilation also occurred. The δD values for hydrogen-bearing phases such as amphibole, biotite and groundmass indicate fractional crystallisation in a closed system and a trend of decreasing δD in the source with time. The magma source of normal calc-alkaline adakite-like magmas was not related to contemporaneous subduction, but was likely due to melting of delaminated eclogitic mafic lower crust. In contrast, the late-stage alkaline magmas were related to asthenospheric upwelling. Petrological analysis of the complex succession of magmas in the Apuseni Mountains province demonstrates that normal calc-alkaline and adakite-like magmatism can be generated in a non-subductional environment, in this case associated with an unusual extensional setting

Ph, Sr, and Nd isotopes and geochemistry of miocene magmas in the Apuseni mountains, Romania

ISSN:0016-7037ISSN:1872-953