Petrogenesis Mount Melbourne

The origin of the volcanic rocks of the Melbourne volcanic field was investigated by Worner and Viereck (1989) and by Worner et al. (1989) by mapping the rocks in the field and by study in the laboratory. Worner and Viereck (1989, p. 369) reported that the rocks consists of  

Lava lows that were erupted subaqueously formed pillows and pillow breccias, while scoria cones and pahoehoe flows are typical of subaerial eruptions. An older sequence of subaerially erupted flows is discon-formably overlain by thick subglacial hyaloclastic deposits topped by subaerial tuff rings, scoria cones, and lava flows. These rock formations in turn are over-lain by Holocene deposits formed by plinian, strom-bolian, and vulcanian eruptions. 

Worner et al. (1989) reported chemical analyses for 92 samples of volcanic rocks from ten subdivisions of the Melbourne volcanic field. The analyses included major and trace elements and the resulting normative mineral compositions. Without classifying each one of these specimens, it is sufficient to record that their chemical compositions range widely just as they do in the Erebus volcanic province of southern Victoria Land (Fig. 16.4). Worner et al. (1989) also reported isotope 

The data array in Fig. 16.30 is collinear with EM 2 (87Sr/86Sr = 0.7075, = 0.51265,206pb/204pb 

Worner et al. (1989) observed that the Sr/ Sr ratios of the volcanic rocks cluster into three groups in Fig. 16.31 depending on their chemical compositions. Alkali basalt and basanite have the lowest Sr/ Sr ratios (0.7025-0.7040), mugearites, benmoreites, and trachyandesites have higher Sr/ Sr ratios (0.7035-0.7050), and trachytes have the highest Sr/ Sr ratios 

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