Identifier: geologyofcoroman00fras (find matches)
Title: The geology of the Coromandel subdivision, Hauraki, Auckland
Year: 1907 (1900s)
Authors: Fraser, Colin, 1875-1944 Adams, James Henry New Zealand Geological Survey
Subjects: Geology
Publisher: Wellington, N.Z. : by authority John Mackay, Govt. Printer
Contributing Library: University of Connecticut Libraries
Digitizing Sponsor: LYRASIS Members and Sloan Foundation

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he Tertiaryvolcanic rocks of the First Period, but are also found in the Jurassic and Pre-Jurassic sedimentaries.These veins occurring in the mining-areas of Coromandel Township, Waikoromiko, and elsewhere donot extend into the younger andesites (Beesons Island Series), which in these localities flank the oldervolcanics ; hence they were evidently formed before the eruption of the younger andesites.fjSflf. To this period of mineralisation may be ascribed the veins of all the mining-areas lying to thewest of the main mountain divide ; those of the Tokatea Hill, Success Hill (Kaipawa), and otherlocalities on the main divide ; and those occurring within the belt of First Period volcanics, extendingfrom Matamataharakeke to the Upper Mahakirau Valley on the eastern side of the mountain divide. W,Veins formed during the second period of mineralisation are apparently confined to certain areason the eastern side of the main range. They occur in the andesites of the Beesons Island Series at r^
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d <3 99 Materangi. .Murphys Hill, Owera. and Moewai, all situated on the inner portion of the KuaotunuPeninsula, and in the basement sedimentaries at the main Kuaotunu mining centre. With these shouldpossibly be correlated the Silver Lode of Tangiaro Creek, Port Charles, occurring near the contactof the First and Second Period volcanies. The veins of both the first and second periods ofmineralisation, whether occurring in the basement sedimentaries or in the neighbouring volcanies, aredue to similar causes. It is evident that they were formed by the ascent of heated mineral-bearingwaters during the solfataric periods succeeding and connected with the extrusions of the volcanies.Since the andesites of the First Period were the results of several eruptions separated in certaincases bv relatively long intervals of quiescence, the time-range of the earlier period of mineralisationwas probably considerable, and therefore the veins may not all be contemporaneous. This appearsto be exempl

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