TY  - JOUR
A1  - Bartoli, Omar
A1  - Acosta-Vigil, Antonio
A1  - Ferrero, Silvio
A1  - Cesare, Bernardo
T1  - Granitoid magmas preserved as melt inclusions in high-grade metamorphic rocks
JF  - American mineralogist : an international journal of earth and planetary materials
N2  - This review presents a compositional database of primary anatectic granitoid magmas, entirely based on melt inclusions (MI) in high-grade metamorphic rocks. Although MI are well known to igneous petrologists and have been extensively studied in intrusive and extrusive rocks, MI in crustal rocks that have undergone anatexis (migmatites and granulites) are a novel subject of research. They are generally trapped along the heating path by peritectic phases produced by incongruent melting reactions. Primary MI in high-grade metamorphic rocks are small, commonly 5-10 pm in diameter, and their most common mineral host is peritectic garnet. In most cases inclusions have crystallized into a cryptocrystalline aggregate and contain a granitoid phase assemblage (nanogranitoid inclusions) with quartz, K-feldspar, plagioclase, and one or two mica depending on the particular circumstances. After their experimental remelting under high-confining pressure, nanogranitoid MI can be analyzed combining several techniques (EMP, LA-ICP-MS, NanoSIMS, Raman). The trapped melt is granitic and metaluminous to peraluminous, and sometimes granodioritic, tonalitic, and trondhjemitic in composition, in agreement with the different P-T-a(H2o) conditions of melting and protolith composition, and overlap the composition of experimental glasses produced at similar conditions. Being trapped along the up-temperature trajectory as opposed to classic MI in igneous rocks formed during down-temperature magma crystallization fundamental information provided by nanogranitoid MI is the pristine composition of the natural primary anatectic melt for the specific rock under investigation. So far similar to 600 nanogranitoid MI, coming from several occurrences from different geologic and geodynamic settings and ages, have been characterized. Although the compiled MI database should be expanded to other potential sources of crustal magmas, MI data collected so far can be already used as natural "starting-point" compositions to track the processes involved in formation and evolution of granitoid magmas.
KW  - Granitoid magmas
KW  - melt inclusions
KW  - nanogranite
KW  - crustal anatexis
KW  - peritectic phase
Y1  - 2016
U6  - https://doi.org/10.2138/am-2016-5541CCBYNCND
SN  - 0003-004X
SN  - 1945-3027
VL  - 101
SP  - 1543
EP  - 1559
PB  - Mineralogical Society of America
CY  - Chantilly
ER  -