A geochemical investigation of the alkalic rocks of the Seacliff district, East Otago, New Zealand.
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Abstract:
A suite of alkaline rocks, geochemically similar to those of the Dunedin Volcano are described and implications arising from their study are discussed.
Rock types studied include basanites, basalts, hawaiites, benmoreites and trachyandesites. A summary of Benson's work on Landslide features in the Seacliff district is also included, with present day observations.
Major and trace element whole rock analyses are presented. Three possible geochemical trends are suggested:
Two sodic series :
(a) basalt-hawaiite-(mugearite)-trachyandesite-benmoreite.
(b) basanite-nepheline hawaiite-(nepheline mugearite)-nepheline benmoreite.
A more potassic undersaturated series
(c) basanite-nepheline hawaiite-nepheline trachyandesite-nepheline benmoreite.
An electron microprobe study of the mineralogy of a trachyandesite from the pyroclastic breccia unit at Green Point, which contains an unnamed mineral, has been done.
A detailed study of the Green Point to Brinns Point coastal section has been carried out and a possible eruption mechanism proposed.
The rocks from the Seacliff area are geochemically similar to the more potassian members of the Dunedin Volcanic Complex.
Rock types studied include basanites, basalts, hawaiites, benmoreites and trachyandesites. A summary of Benson's work on Landslide features in the Seacliff district is also included, with present day observations.
Major and trace element whole rock analyses are presented. Three possible geochemical trends are suggested:
Two sodic series :
(a) basalt-hawaiite-(mugearite)-trachyandesite-benmoreite.
(b) basanite-nepheline hawaiite-(nepheline mugearite)-nepheline benmoreite.
A more potassic undersaturated series
(c) basanite-nepheline hawaiite-nepheline trachyandesite-nepheline benmoreite.
An electron microprobe study of the mineralogy of a trachyandesite from the pyroclastic breccia unit at Green Point, which contains an unnamed mineral, has been done.
A detailed study of the Green Point to Brinns Point coastal section has been carried out and a possible eruption mechanism proposed.
The rocks from the Seacliff area are geochemically similar to the more potassian members of the Dunedin Volcanic Complex.
Thesis description:
xii. 137 p. Diagms, photos, map (folded in pocket); 30 cm.
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1986Reddy
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Citation
Reddy, DP, “A geochemical investigation of the alkalic rocks of the Seacliff district, East Otago, New Zealand.,” Otago Geology Theses, accessed June 12, 2025, https://theses.otagogeology.org.nz/items/show/204.