Details
| Original language | English |
|---|---|
| Pages (from-to) | 415-434 |
| Number of pages | 20 |
| Journal | Lithos |
| Volume | 102 |
| Issue number | 3-4 |
| Early online date | 24 Aug 2007 |
| Publication status | Published - May 2008 |
Abstract
The Wangrah Suite granites (Lachlan Fold Belt, Australia) reflect different stages of differentiation in the magmatic history of an A-type plutonic suite. In this study we use experimentally determined phase equilibria of four natural A-type granitic compositions of the Wangrah Suite to constrain phases and phase compositions involved in fractionation processes. Each composition represents a distinct granite intrusion in the Wangrah Suite. The intrusions are the Danswell Creek (DCG), Wangrah (WG), Eastwood (EG) and Dunskeig Granite (DG), ordered from "most mafic" to "most felsic" by increasing SiO2 and decreasing FeOtotal. Experimental investigation show that the initial water content in melts from DCG is between 2-3 wt. % H2O. If the DCG is viewed as the parental magma for the Wangrah Suite, then (1) fractionation of magnetite, orthopyroxene and plagioclase (∼ 20 wt. %) of the DCG composition, leads to compositions similar to that of the EG; (2) further fractionation of plagioclase, quartz, K-feldspar and biotite (∼ 40 wt. %) from the EG composition, leads to the DG composition. These fractionation steps can occur nearly isobarically and are confirmed by bulk rock Ba, Sr, Rb and Zr concentrations. In contrast, the generation of the most abundant WG composition cannot be explained by fractional crystallisation from the DCG at isobaric conditions because of the high K2O content of this granite. Magma Mixing could be the process to explain the chemical distinctiveness of the Wangrah Granite from all the other granites of the Wangrah Suite.
Keywords
- A-type granite, Australia, Crystallisation, Experiments, Fractional crystallisation, Magma-mixing
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
Cite this
- Standard
- Harvard
- Apa
- Vancouver
- BibTeX
- RIS
In: Lithos, Vol. 102, No. 3-4, 05.2008, p. 415-434.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Fractionation vs. magma mixing in the Wangrah Suite A-type granites, Lachlan Fold Belt, Australia
T2 - Experimental constraints
AU - Klimm, Kevin
AU - Holtz, Francois
AU - King, Penelope L.
N1 - Funding Information: We thank B.W. Chappell for providing the natural samples from the Wangrah Suite and W. Johannes for the initiation of the project. The technical assistance of O. Dietrich and J. Koepke is gratefully appreciated. Helpful and constructive comments were provided by A.E. Patiño Douce and B. Landenberger on an earlier version of the manuscript. The reviews of B. Scaillet and O. Eklund are gratefully acknowledged. This study was supported by the German Science Foundation (DFG, project no.: Jo64/34). Copyright: Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2008/5
Y1 - 2008/5
N2 - The Wangrah Suite granites (Lachlan Fold Belt, Australia) reflect different stages of differentiation in the magmatic history of an A-type plutonic suite. In this study we use experimentally determined phase equilibria of four natural A-type granitic compositions of the Wangrah Suite to constrain phases and phase compositions involved in fractionation processes. Each composition represents a distinct granite intrusion in the Wangrah Suite. The intrusions are the Danswell Creek (DCG), Wangrah (WG), Eastwood (EG) and Dunskeig Granite (DG), ordered from "most mafic" to "most felsic" by increasing SiO2 and decreasing FeOtotal. Experimental investigation show that the initial water content in melts from DCG is between 2-3 wt. % H2O. If the DCG is viewed as the parental magma for the Wangrah Suite, then (1) fractionation of magnetite, orthopyroxene and plagioclase (∼ 20 wt. %) of the DCG composition, leads to compositions similar to that of the EG; (2) further fractionation of plagioclase, quartz, K-feldspar and biotite (∼ 40 wt. %) from the EG composition, leads to the DG composition. These fractionation steps can occur nearly isobarically and are confirmed by bulk rock Ba, Sr, Rb and Zr concentrations. In contrast, the generation of the most abundant WG composition cannot be explained by fractional crystallisation from the DCG at isobaric conditions because of the high K2O content of this granite. Magma Mixing could be the process to explain the chemical distinctiveness of the Wangrah Granite from all the other granites of the Wangrah Suite.
AB - The Wangrah Suite granites (Lachlan Fold Belt, Australia) reflect different stages of differentiation in the magmatic history of an A-type plutonic suite. In this study we use experimentally determined phase equilibria of four natural A-type granitic compositions of the Wangrah Suite to constrain phases and phase compositions involved in fractionation processes. Each composition represents a distinct granite intrusion in the Wangrah Suite. The intrusions are the Danswell Creek (DCG), Wangrah (WG), Eastwood (EG) and Dunskeig Granite (DG), ordered from "most mafic" to "most felsic" by increasing SiO2 and decreasing FeOtotal. Experimental investigation show that the initial water content in melts from DCG is between 2-3 wt. % H2O. If the DCG is viewed as the parental magma for the Wangrah Suite, then (1) fractionation of magnetite, orthopyroxene and plagioclase (∼ 20 wt. %) of the DCG composition, leads to compositions similar to that of the EG; (2) further fractionation of plagioclase, quartz, K-feldspar and biotite (∼ 40 wt. %) from the EG composition, leads to the DG composition. These fractionation steps can occur nearly isobarically and are confirmed by bulk rock Ba, Sr, Rb and Zr concentrations. In contrast, the generation of the most abundant WG composition cannot be explained by fractional crystallisation from the DCG at isobaric conditions because of the high K2O content of this granite. Magma Mixing could be the process to explain the chemical distinctiveness of the Wangrah Granite from all the other granites of the Wangrah Suite.
KW - A-type granite
KW - Australia
KW - Crystallisation
KW - Experiments
KW - Fractional crystallisation
KW - Magma-mixing
UR - http://www.scopus.com/inward/record.url?scp=42949170053&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2007.07.018
DO - 10.1016/j.lithos.2007.07.018
M3 - Article
AN - SCOPUS:42949170053
VL - 102
SP - 415
EP - 434
JO - Lithos
JF - Lithos
SN - 0024-4937
IS - 3-4
ER -