Movement of melt during synchronous regional deformation and granulite-facies anatexis, an example from the Wuluma Hills, central Australia
Published:January 01, 1999
E. W. Sawyer, C. Dombrowski, W. J. Collins, 1999. "Movement of melt during synchronous regional deformation and granulite-facies anatexis, an example from the Wuluma Hills, central Australia", Understanding Granites: Integrating New and Classical Techniques, Antonio Castro, Carlos Fernández, Jean Louis Vigneresse
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Granulite facies anatexis (T ≈ 900 °C) in the Wuluma Hills region of the Arunta Inlier was synchronous with deformation. During D3 contractional deformation strain was partitioned into S3 shear zones, which alternate with lower strain domains containing F3 fold hinges. Subsequent D4 deformation was minor and in part extensional.
Leucosomes in the S3 shear zones are principally veins oriented parallel, or subparallel, to the pervasive S3 foliation. Leucosomes in the F3 hinge domains are more complex, and occur parallel to anisotropy due to lithological layering, the pre-existing S1/2 foliation, S3 and fold axial planes (F3 and F4). Some leucosomes (generally high Na2O, low K2O and Rb/Sr) record melt migration paths, and other sites of melt accumulation.
All the migmatites are residual and lost melt when deformation forced melt from matrix grain boundaries, through a network of small lensoid channelways to accumulation sites in fold hinges, there larger batches of magma developed. Leucosomes in accumulation sites develop a schlieric or diatexitic appearance because inflowing melt eroded the host rocks. Later increments of D3 contractional strain overpressured the accumulated granitic magma and it migrated again to other (more stable) low pressure sites through veins generally oriented parallel to S3. Magma/melt movement stopped when the solidus was reached, or the magma reached a structurally stable site (e.g. pluton).
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Understanding Granites: Integrating New and Classical Techniques
Granite magmatism represents a major contribution to crustal growth and recycling and, consequently, is one of the most important mechanisms to have contributed to the geochemical differentiation of the Earth’s crust since Archaean time. Granites are also often associated with ore bodies, and their study therefore has direct commercial relevance.
The modern view of the granite problems requires the application of many different theoretical, experimental and empirical resources provided by geophysics, geochemistry, experimental petrology, structural geology, scale modelling and field geology. Because of the complexity of the granite problem, it is necessary to integrate a variety of techniques and corroborate the findings with field observations.This is the philosophy of this book.
Many chapters are review papers dealing with the development and achievements of a particular technique, whilst other chapters deal with the application of a number of techniques to a specific problem. This volume brings together papers that would otherwise be dispersed in different publications.
The book will be of interest to igneous petrologists, geophysicists, structural geologists and geochemists.