Acheron River, Coalgate, Selwyn District, Canterbury Region, South Island, New Zealand
|Latitude & Longitude (WGS84):||43° 22' 58'' South , 171° 36' 37'' East|
|Latitude & Longitude (decimal):||-43.38305,171.61039|
|Köppen climate type:||Cfb : Temperate oceanic climate|
A group of three lacco-liths and three sills varying in composition from dolerite to picroteschenite, outcropping in the Acheron River area of Mid-Canterbury. They are emplaced in coal- measures of Upper Cretaceous age (Coombs, 1960)
The locations of the material is described as in the largest sill on a south facing bank of the river a little downstream from the old coal mine, within the river bed at the mine entrance, and 200-300 yards further north.
It is the first known occurrence of xonolite reported in New Zealand.
It is found in joints, and shatter zones as aggregates of sub-parallel, or radiating asbestiform fibres, forming masses of almost pure xonolite up to 1.5 inches thick, often perpendicular to the vein walls. Weathered xonolite is white, while unweathered material is a delicate pink colour. Small amounts of intergrown calcite is found with it.
Wollastonite listed on Mindat appears to be assumed from the formation of the material, rather than present in hand specimens.
3 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Eocene - Late Cretaceous|
33.9 - 100.5 Ma
|Eyre Group and Broken River Formation Late Cretaceous-Eocene terrestrial sedimentary rocks|
Age: Phanerozoic (33.9 - 100.5 Ma)
Stratigraphic Name: Eyre Group; Broken River Formation
Reference: Edbrooke, S.W., Heron, D.W., Forsyth, P.J., Jongens, R. (compilers). Geology Map of New Zealand 1:1 000 000. GNS Science Geological Map 2. 
|Lutetian - Santonian|
41.3 - 86.3 Ma
|Broken River Formation Late Cretaceous - Eocene mudstone (Eyre Group)|
Age: Phanerozoic (41.3 - 86.3 Ma)
Stratigraphic Name: Broken River Formation
Reference: Heron, D.W. . Geology Map of New Zealand 1:250 000. GNS Science Geological Map 1. 
|Jurassic - Triassic|
145 - 252.17 Ma
|Mesozoic sedimentary and volcanic rocks|
Age: Mesozoic (145 - 252.17 Ma)
Stratigraphic Name: Torlesse Supergroup
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529.