The Beginning: Mafic Magmas Invading Felsic Magma Chambers

2021 ◽  
pp. 77-86
Author(s):  
Diego Perugini
Keyword(s):  
Felsic Magma ◽  
Magma Chambers ◽  
Mafic Magmas

Mafic-silicic layered intrusions: the role of basaltic injections on magmatic processes and the evolution of silicic magma chambers

1996 ◽  
Vol 87 (1-2) ◽  
pp. 233-242 ◽  
Author(s):  
R. A. Wiebe
Keyword(s):  
Basaltic Magma ◽  
Mafic Magma ◽  
Silicic Magma ◽  
Granitic Magma ◽  
Magma Chambers ◽  
Mechanical Mixing ◽  
Diffusive Convection ◽  
Type Granite ◽  
Mafic Magmas ◽  
Silicic Magmas

ABSTRACT:Plutonic complexes with interlayered mafic and silicic rocks commonly contain layers (1–50 m thick) with a chilled gabbroic base that grades upwards to dioritic or silicic cumulates. Each chilled base records the infusion of new basaltic magma into the chamber. Some layers preserve a record of double-diffusive convection with hotter, denser mafic magma beneath silicic magma. Processes of hybridisation include mechanical mixing of crystals and selective exchange of H2O, alkalis and isotopes. These effects are convected away from the boundary into the interiors of both magmas. Fractional crystallisation aad replenishment of the mafic magma can also generate intermediate magma layers highly enriched in incompatible elements.Basaltic infusions into silicic magma chambers can significantly affect the thermal and chemical character of resident granitic magmas in shallow level chambers. In one Maine pluton, they converted resident I-type granitic magma into A-type granite and, in another, they produced a low-K (trondhjemitic) magma layer beneath normal granitic magma. If comparable interactions occur at deeper crustal levels, selective thermal, chemical and isotopic exchange should probably be even more effective. Because the mafic magmas crystallise first and relatively rapidly, silicic magmas that rise away from deep composite chambers may show little direct evidence (e.g. enclaves) of their prior involvement with mafic magma.

Genesis and evolution of mafic microgranular enclaves through various types of interaction between coexisting felsic and mafic magmas

1992 ◽  
Vol 83 (1-2) ◽  
pp. 145-153 ◽  
Author(s):  
Bernard Barbarin ◽  
Jean Didier
Keyword(s):  
Chemical Exchange ◽  
Magma Chambers ◽  
Mixing Processes ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Mass Fractions ◽  
Long Time ◽  
Mafic Magmas ◽  
The Many ◽  
Structural Levels

ABSTRACTThermal, mechanical and chemical exchange occurs between felsic and mafic magmas in dynamic magma systems. The occurrence and efficiency of such exchanges are constrained mainly by the intensive parameters, the compositions, and the mass fractions of the coexisting magmas. As these interacting parameters do not change simultaneously during the evolution of the granite systems, the exchanges appear sequentially, and affect magmatic systems at different structural levels, i.e. in magma chambers at depth, in the conduits, or after emplacement. Hybridisation processes are especially effective in the plutonic environment because contrasting magmas can interact over a long time-span before cooling. The different exchanges are complementary and tend to reduce the contrasts between the coexisting magmas. They can be extensive or limited in space and time; they are either combined into mixing processes which produce homogeneous rocks, or only into mingling processes which produce rocks with heterogeneities of various size-scales. Mafic microgranular enclaves represent the most common heterogeneities present in the granite plutons. The composite enclaves and the many types of mafic microgranular enclaves commonly associated in a single pluton, or in polygenic enclave swarms, are produced by the sequential occurrence of various exchanges between coexisting magmas with constantly changing intensive parameters and mass fractions. The complex succession and repetition of exchanges, and the resulting partial chemical and complete isotopic equilibration, mask the original identities of the initial components.

Isotopic evidence for multiple contributions to felsic magma chambers: Gouldsboro Granite, Coastal Maine

Lithos ◽  
2007 ◽  
Vol 93 (3-4) ◽  
pp. 234-247 ◽  
Author(s):  
Tod E. Waight ◽  
Robert A. Wiebe ◽  
Eirik J. Krogstad
Keyword(s):  
Felsic Magma ◽  
Magma Chambers ◽  
Isotopic Evidence

scholarly journals Atlantic Geology Special Issue Processes in felsic magma chambers: Foreword

10.4138/1173 ◽  
2003 ◽  
Vol 39 (2) ◽  
Author(s):  
David Gibson ◽  
Dan Lux ◽  
Sanda Barr
Keyword(s):  
Felsic Magma ◽  
Special Issue ◽  
Magma Chambers

VARIATIONS IN MANTLE COMPOSITION AND SUBDUCTION CONTRIBUTIONS TO MAFIC MAGMAS IN THE SOUTHERN CASCADE ARC

2019 ◽  
Author(s):  
Emily R. Johnson ◽  
◽  
Jamie Shaffer ◽  
Meredith A. Cole ◽  
Frank C. Ramos ◽  
...  
Keyword(s):  
Cascade Arc ◽  
Mantle Composition ◽  
Mafic Magmas
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