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高盐度,高温和高成矿金属的岩浆成矿流体—以格拉斯伯格Cu—Au矿为例 总被引:29,自引:12,他引:17
印度尼西北格拉斯伯格Cu-Au矿是与斑状的石英二长岩体有关的斑岩矿床,石英二长岩遭受了钾化为主的们随有绢云图和磁铁矿化的蚀变,Cu-Au矿化可分为网脉型和浸染型,以前者为主,含金的黄铜矿石英脉切穿了岩体和钾化蚀变带。本次研究见到四类包裹体,即岩民裹体、含子矿物包裹体、所体包裹体和液体包裹体,与矿化有关的是含子矿物包裹体和气体裹体,这两类包裹体的均一温度从400℃到〉700℃,含子包裹体和液体包裹体 相似文献
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High-resolution X-ray computed tomography (HRXCT) provides unique information of the geological and metallurgical significance
for gold and related ore minerals in the supergiant Grasberg porphyry Cu–Au deposit. Digital radiographs have proved to be
an effective means of screening samples for the presence of gold for HRXCT studies. Digital radiograph effectiveness is limited
by the thickness of samples (typically to ≤2 cm), as well as the associated minerals. Thus, preselecting samples for gold
studies using HRXCT is most effective using digital radiographs combined with assay information. Differentiating between metallic
mineral grains with relatively small differences in density, e.g., bornite (5.1 g/cm3) from chalcopyrite (4.2 g/cm3), is relatively straightforward for isolated monominerallic grains or composites in a similar lower-density matrix, but difficulties
are encountered with the interpretation of typical intergrown ore minerals. X-ray beam-hardening artifacts lead to inconsistency
in attenuation determination, both within and among slice images, complicating quantitative processing. However, differentiation
of chalcopyrite and bornite has been successful in smaller-diameter (≤22-mm) cores of Grasberg ores. Small-diameter (≤10 mm)
cores of the Grasberg stockwork Cu–Au ore were analyzed using HRXCT methods scanned at the minimum spacing currently available
(7.5 μm), and data reduction protocols using the Blob3D program were modified to improve the quantification of grain sizes
and shapes. Grains as small as 6.5 μm have been identified. All of these grains are in direct contact with chalcopyrite, providing
support for gold distribution in porphyry copper systems being a result of exsolution from copper sulfides. HRXCT scanning
(±digital radiography) precisely defines the in situ location of mineral grains of interest within a sample, which then can
be studied in conventional petrographic sections, and other types of analytical studies conducted, e.g., gold trace element
geochemistry. 相似文献
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