TY - JOUR
T1 - Physical and chemical interactions between coeval magmas
T2 - a case study of mixing and mingling from the Urumieh plutonic complex, NW Iran
AU - Jafari, Amin
AU - Williams, Ian S.
AU - Moayyed, Mohsen
AU - Jamei, Susan
N1 - Publisher Copyright:
© 2021 Informa UK Limited, trading as Taylor & Francis Group.
PY - 2022
Y1 - 2022
N2 - Field observations, whole-rock geochemistry, mineral chemistry and zircon U-Pb dating results from microgranular mafic enclaves and their host syenite, Urumieh plutonic complex, NW Iran, show that the enclaves and host are coeval, genetically related and evolved by synchronous magma mixing–fractionation. Geochemically all belong to the shoshonitic series and probably originated from the same enriched subcontinental mantle-derived magma in a subduction setting. SHRIMPU-Pb dating of zircon from representative samples of host rocks and enclaves yields mutually indistinguishable late Cretaceous crystallization ages, 90.7 (Formula presented.) 1.3 and 91.3 (Formula presented.) 1.1 Ma (host syenite), and 90.2 (Formula presented.) 0.7 and 91.6 (Formula presented.) 0.7 Ma (enclaves). Pressure and temperature estimates from Al-in-amphibole and amphibole-plagioclase pairs from both host and enclaves suggest that the interacting magmas mixed and crystallized under similar P-T conditions at middle crustal levels (average 662–716°C and 2.2–2.8 kbar). The occurrence of hybrid to mafic enclaves along with disrupted mafic dikes indicates a long-lived mafic source with multiple replenishments throughout the crystallization history of the complex, and large variability in viscosity within the magmatic system. The transition from mixing to mingling depends on the different crystalline states of the interacting magmas, especially the host magma, which strongly influence rheological properties. In the liquid-liquid state, mixing typically will continue until complete hybridization. With increasing polymerization and crystal load in the host magma, magmatic relationships change progressively from chemical mixing to more mechanical mixing (mingling), producing distributed mafic enclaves, then disrupted mafic dikes, then syn-plutonic mafic dikes as a continuum given sufficient time.
AB - Field observations, whole-rock geochemistry, mineral chemistry and zircon U-Pb dating results from microgranular mafic enclaves and their host syenite, Urumieh plutonic complex, NW Iran, show that the enclaves and host are coeval, genetically related and evolved by synchronous magma mixing–fractionation. Geochemically all belong to the shoshonitic series and probably originated from the same enriched subcontinental mantle-derived magma in a subduction setting. SHRIMPU-Pb dating of zircon from representative samples of host rocks and enclaves yields mutually indistinguishable late Cretaceous crystallization ages, 90.7 (Formula presented.) 1.3 and 91.3 (Formula presented.) 1.1 Ma (host syenite), and 90.2 (Formula presented.) 0.7 and 91.6 (Formula presented.) 0.7 Ma (enclaves). Pressure and temperature estimates from Al-in-amphibole and amphibole-plagioclase pairs from both host and enclaves suggest that the interacting magmas mixed and crystallized under similar P-T conditions at middle crustal levels (average 662–716°C and 2.2–2.8 kbar). The occurrence of hybrid to mafic enclaves along with disrupted mafic dikes indicates a long-lived mafic source with multiple replenishments throughout the crystallization history of the complex, and large variability in viscosity within the magmatic system. The transition from mixing to mingling depends on the different crystalline states of the interacting magmas, especially the host magma, which strongly influence rheological properties. In the liquid-liquid state, mixing typically will continue until complete hybridization. With increasing polymerization and crystal load in the host magma, magmatic relationships change progressively from chemical mixing to more mechanical mixing (mingling), producing distributed mafic enclaves, then disrupted mafic dikes, then syn-plutonic mafic dikes as a continuum given sufficient time.
KW - Syenite
KW - U–Pb dating
KW - geochemistry
KW - mafic enclave
KW - magma mingling
KW - magma mixing
UR - http://www.scopus.com/inward/record.url?scp=85098543098&partnerID=8YFLogxK
U2 - 10.1080/00206814.2020.1858454
DO - 10.1080/00206814.2020.1858454
M3 - Review article
SN - 0020-6814
VL - 64
SP - 489
EP - 508
JO - International Geology Review
JF - International Geology Review
IS - 4
ER -