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Determination of trace elements in analyzed mineral phase by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a new in situ technique for mineral phase analyses. As an important mineral in porphyry copper deposits, the major and trace elements of pyrite can provide important information for the ore-forming process. A method for determination of the trace elements in pyrite by LA-ICP-MS and major elements by Electron Microprobe was developed and has been applied to the Baishantang porphyry copper ore district. For the LA-ICP-MS experiment, the laser beam is 60 μm, the carrier gas is helium, the repetition frequency is 5 Hz, the laser energy is 6 J/cm2, and the analysis time of single point is 60 s. Iron was used as an internal standard and MASS-1 was used to calibrate the data. Analysis precision of most elements is better than 10%. For the similar optical properties of pyrite and arsenopyrite, the differences of physical properties can be used to distinguish them. Pyrite in the Baishantang porphyry copper deposit is depleted in sulfur but rich in iron, indicating a hydrothermal origin. The trace element composition of pyrite indicates that pyrite was formed at a medium depth and belongs to the medium-low temperature hydrothermal type related to volcanism. This conclusion has provided important evidence for the ore genesis and the source of ore-forming fluids of the Baishantang porphyry copper deposit, which can also guide the next-step exploration.

The phyllic alteration zone is regarded as one of the most important near-surface markers in mineral exploration of porphyry deposits. The Gongpoquan and Baishantang copper deposits are two typical porphyry deposits in the Beishan metallogenic belt. A comprehensive structural and chemical study for white micas from sericitolites of these two deposits, utilizing polarized microscope, Scanning Electron Microscope (SEM), powder X-ray Diffractometer (XRD) and Electron Microprobe Analyzer (EMPA) is reported in this paper. It was discovered that both 1M polytype common sericites/muscovites and 2M1 polytype phengites co-exist in the samples. The micas occur as irregular petals, kinked platelets or straight platelets during SEM observation. According to XRD analyses, both 1M and 2M1 polytypes co-exist with different b0 values in micas, indicating their different forming conditions. The SiⅣ atoms in micas range from 3.04 to 3.37 and from 3.03 to 3.35 for Gongpoquan and Baishantang deposits, respectively, indicating the co-existence of sericites/muscovites and hydrothermal phengites. The co-existence of two types of white micas in porphyry copper deposits of the Beishan area indicate the rapid changes of ore-forming fluids from higher temperature and acidity to lower temperature and less acidity during mineralization.

Asub-micron uranium-bearing mineral in pomegranate amphibolite in the Altyn area was identified by Electron Microprobe(EPMA) and Scanning Electron Microscopy(SEM).Optical Microscope, Raman Spectroscopy and Electron Back Scattering Diffraction(EBSD) were used to study the chemical composition, occurrence state, physical and optical properties and crystal structure.Results show that this mineral is an opaque mineral closely associated with ilmenite and occurs at the edge of ilmenite.The mineral is composed of TiO2, ZrO2 and UO2 and the crystallochemical formula is(Zr, U)Ti2O6 with isomorphous substitution of U and Zr.It has a unique Raman spectrum characteristic and possibly belongs to orthorhombic system with a fersmite structure.EPMA Th-U-Pb dating of Ti-Zr-U oxide mineral yields an isochron age of 451±49 Ma, which represents the retrograde age of the host rock.Compared to the crystals which have a similar chemical composition to Ti-Zr-U oxide, the crystal structure of Ti-Zr-U oxide was found to be different from that of Srilankite, but similar to a synthetic crystal(Zr5Ti7O24) in chemical composition and crystal structure.Therefore, it is inferred that the Ti-Zr-U oxide is previously undiscovered mineral.