Geochemical and isotopic constraints on the role of juvenile crust and magma mixing in the UDMA magmatism, Iran: evidence from mafic microgranular enclaves and cogenetic granitoids in the Zafarghand igneous complex

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.

Download Full-text

Origin of mafic microgranular enclaves (MMEs) and their host quartz monzonites from the Muchen pluton in Zhejiang Province, Southeast China: Implications for magma mixing and crust–mantle interaction

Lithos ◽

10.1016/j.lithos.2012.12.005 ◽

2013 ◽

Vol 160-161 ◽

pp. 145-163 ◽

Cited By ~ 68

Author(s):

Liang Liu ◽

Jian-Sheng Qiu ◽

Zhen Li

Keyword(s):

Magma Mixing ◽

Zhejiang Province ◽

Southeast China ◽

Microgranular Enclaves ◽

Mafic Microgranular Enclaves

Download Full-text

Mineralogy, whole-rock and Sr–Nd isotope geochemistry of mafic microgranular enclaves in Cretaceous Dagbasi granitoids, Eastern Pontides, NE Turkey: Evidence of magma mixing, mingling and chemical equilibration

Geochemistry ◽

10.1016/j.chemer.2008.08.002 ◽

2009 ◽

Vol 69 (3) ◽

pp. 247-277 ◽

Cited By ~ 47

Author(s):

Abdullah Kaygusuz ◽

Emre Aydınçakır

Keyword(s):

Isotope Geochemistry ◽

Magma Mixing ◽

Nd Isotope ◽

Eastern Pontides ◽

Microgranular Enclaves ◽

Mafic Microgranular Enclaves ◽

Chemical Equilibration

Download Full-text

The structure and petrology of ultrabasic rocks in the southern part of the Cuillin Igneous Complex, Isle of Skye

Transactions of the Royal Society of Edinburgh Earth Sciences ◽

10.1017/s0263593300003345 ◽

1992 ◽

Vol 83 (4) ◽

pp. 635-653 ◽

Cited By ~ 7

Author(s):

R. V. Claydon ◽

B. R. Bell

Keyword(s):

Magma Mixing ◽

Structural Level ◽

Igneous Complex ◽

Melt Migration ◽

Early Tertiary ◽

Structural Levels ◽

Isle Of Skye

AbstractThe ultrabasic rocks of the southern portion of the Early Tertiary Cuillin Igneous Complex, Isle of Skye, are recognised as forming a Peridotite Series s.l. and have been separated into six distinct structural–lithological units. These units range from almost pure dunite (Unit 1, at the lowest structural level), through to feldspathic peridotites and allivalites (Units 5 and 6, at the highest structural levels). Detailed field and mineralogical studies indicate that both cumulus and postcumulus processes involving ultrabasic (picritic) magmas may be identified, and that the latter processes have significantly modified many of the primary features of these rocks.Layering, both modal and phase, is present within all six units, although it is more prominent within the higher units, especially Units 5 and 6. Differing orientations of fabrics defined by cumulus spinel and intercumulus plagioclase layers within Unit 3 indicate the important role of compaction and intercumulus melt migration. Unit 4 is extremely heterogeneous, involving material ranging in composition from peridotite to allivalite, and provides clear evidence for postcumulus melt movement, magma-mixing, disruption and brecciation. Units 5 and 6 developed with a more porous cumulus framework, giving rise to dendritic growths involving cumulus olivine and poikilitic plagioclase.It is concluded that postcumulus melt movement, injection and magma-mixing, involving ultrabasic magmas, were significant processes in the formation of the ultrabasic rocks of the Cuillin Igneous Complex.

Download Full-text