Geochemical and isotopic evidence for the age, orogenic setting and petrogenesis of the Nychum Volcanic association, North Queensland
作者:
J.C. Bailey,
W.R. Morgan,
L.P. Black,
期刊:
Journal of the Geological Society of Australia
(Taylor Available online 1982)
卷期:
Volume 29,
issue 3-4
页码: 375-393
ISSN:0016-7614
年代: 1982
DOI:10.1080/00167618208729221
出版商: Taylor & Francis Group
关键词: Rb/Sr;K/Ar age determinations;geochemistry;isotopes;calc‐alkaline volcanics;low‐pressure fractional crystallisation
数据来源: Taylor
摘要:
Rb‐Sr and K‐Ar age determinations agree with palaeobotanical evidence in assigning an age of 270 Ma (Lower Permian) to the Nychum Volcanics, North Queensland. Geological and geochemical evidence (moderate ‐REE, La/Yb, Th, Zr/Y, Hf/Yb, Sc/Ni) indicate that the volcanics were erupted on a thin, active continental margin. Five magma groups are present: high‐alumina basalts, andesite‐dacites, acid rocks, tholeiitic andesites, and pitchstone with a high La/Yb ratio. The high‐alumina basalts and calc‐alkaline andesites have a parent‐daughter (source rock‐partial melt) relationship. The acid rocks share high HREE, Zr, Hf, Zn, Sc, Fe/Mg and low Al with, and may be fractionated from, the tholeiitic subduction‐zone andesites. Low‐pressure fractional crystallisation is evident in all five magma groups.
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