Successive magma mixing in deep-seated magma chambers recorded in zircon from mafic microgranular enclaves in the Triassic Mishuling granitic pluton, Western Qinling, Central China

2021 ◽  
Vol 207 ◽  
pp. 104656
Author(s):  
Jingzhao Dou ◽  
Xiguang Huang ◽  
Fukun Chen
Keyword(s):  
Magma Mixing ◽  
Central China ◽  
Magma Chambers ◽  
Western Qinling ◽  
Granitic Pluton ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves

Micro structural and mineralogical evidence for limited involvement of magma mixing in the petrogenesis of a Hercynian high-K calc-alkaline intrusion: the Kozárovice granodiorite, Central Bohemian Pluton, Czech Republic

2000 ◽  
Vol 91 (1-2) ◽  
pp. 15-26 ◽  
Author(s):  
Vojtěch Janoušek ◽  
D. R. Bowes ◽  
Colin J. R. Braithwaite ◽  
Graeme Rogers
Keyword(s):  
Magma Mixing ◽  
Fractional Crystallisation ◽  
Calc Alkaline ◽  
High K ◽  
Alkaline Intrusion ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Quartz Monzonite ◽  
Petrogenetic Process ◽  
Mineralogical Evidence

Textural and mineralogical features in the high-K calc-alkaline Kozárovice granodiorite (Hercynian Central Bohemian Pluton, Bohemian Massif) and associated small quartz monzonite masses imply that mixing between acid (granodioritic) and basic (monzonitic/monzogabbroic) magmas was locally petrogenetically significant.Net veining, with acicular apatite and numerous lath-shaped plagioclase crystals present in the quartz monzonite, and abundant mafic microgranular enclaves (MME) in the granodiorite, indicate that as the monzonitic magma was injected into the granodioritic magma chamber, it rapidly cooled and was partly disintegrated by the melt already present. Evidence from cathodoluminescence suggests that the two magmas exchanged early-formed plagioclase crystals. In the quartz monzonite, granodiorite-derived crystals were overgrown by narrow calcic zones, followed by broad, normally zoned sodic rims. In the granodiorite, plagioclase crystals with calcic cores overgrown by normally zoned sodic rims are interpreted as xenocrysts from the monzonite. After thermal adjustment, crystallisation of the monzonitic magma ceased relatively slowly, forming quartz and K-feldspar oikocrysts.Although the whole-rock geochemistry of the quartz monzonite and the MME support magma mixing, major- and trace-element based modelling of the host granodiorite has previously indicated an origin dominated by assimilation and fractional crystallisation. Magma mixing therefore seems to represent a local modifying influence rather than the primary petrogenetic process.

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.

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