1887

oa South African Journal of Geology - Geochemical variations in a long Karoo dyke, Eastern Cape

Volume 101 Number 2
  • ISSN : 1012-0750
  • E-ISSN: 1996-8590

 

Abstract

A prominent vertical dolerite dyke, up to 30 m wide and which can be traced for over 100 km, is compositionally homogeneous along much of its length and shows no evidence of flow differentiation. Associated parallel dykes are compositionally distinct and are unrelated by closed-system processes. The main dyke has geochemical characteristics of the Maloti or Senqu Units in the upper part of the main Lesotho basalt sequence, whereas the parallel dykes are geochemically similar to the lower Mafika Lisiu Unit. On the basis of size and composition the main dyke may well represent a fissure which once fed effusions of Karoo basalt.


'n Opvallende vertikale dolerietgang, tot 30 m wyd en wat vir meer as 100 km ver gevolg kan word, het 'n homogene sames telling langs 'n groot gedeelte van sy lengte en toon geen tekens van vloeidifferensiasie nie. Geassosieerde ewewydige gange verskil in samestelling en is nie verwant a.g.v. prosesse in 'n geslote stelsel nie. Die hoofgang het geochemiese eienskappe van die Maloti of Senqu Eenhede in die boonste deel van die hoofopeenvolging van Lesothobasalt, terwyl die ewewydige gange geuchemies soortgelyk aan die laer Mafika Lisiu Eenheid. Op die grondslag van grootte en samestelling kan die hoofgang 'n spleet verteenwoordig wat eens uitvloeiings van Karoobasalt gevoed het.

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1998-06-01
2020-09-22

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