TY - JOUR
T1 - Derivation of A1-type granites by partial melting of newly underplated rocks related with the Tarim mantle plume
AU - Su, Yuping
AU - Zheng, Jianping
AU - Liang, Lili
AU - Dai, Hongkun
AU - Zhao, Junhong
AU - Chen, Ming
AU - Ping, Xianquan
AU - Liu, Ziqi
AU - Wang, Jian
PY - 2019/3
Y1 - 2019/3
N2 - The granitic rocks of the Tarim large igneous province (LIP) are
temporally and spatially related to mafic intrusions. However, their
tectonic setting and genetic relationship are debated. Here, we report
geochemical, and zircon U–Pb–Hf isotopic results for three alkali
feldspar granitic plutons in the Halajun area, western margin of the
Tarim Block. Zircon U–Pb ages suggest these plutons were emplaced at
268–275 Ma, coeval with the neighbouring mafic–ultramafic complexes and
syenitic rocks. These granitic rocks have high contents of SiO2,
alkalis, Rb, Th, Zr and REE (except Eu), and high ratios of FeO*/MgO
and Ga/Al, and show strong depletions in Ba, Sr, Eu, which are commonly
observed in the A1-type granites. Zircon Hf isotopes reveal a limited
range of εHf(t)
values from −1.0 to +3.5 for different samples from three granitic
plutons, obviously higher than those (mostly <0) of the mafic rocks.
This distinct difference, along with a Daly gap and small volume of
mafic rocks, argues against extreme fractionation of mafic magma as the
main origin of the A1-type granites. Instead the A1-type granites were
most likely derived from partial melting of newly underplated rocks
triggered by the upwelling asthenosphere, followed by extensive
fractionation. These A1-type granites were emplaced within an anorogenic
setting during the late stage of the Tarim LIP, which possibly lasts
for more than 30 Ma. The Piqiang mafic–ultramafic complex directly
stemmed from asthenospheric mantle and Halajun A1-type granites
represent two manners of vertical crustal growth.
AB - The granitic rocks of the Tarim large igneous province (LIP) are
temporally and spatially related to mafic intrusions. However, their
tectonic setting and genetic relationship are debated. Here, we report
geochemical, and zircon U–Pb–Hf isotopic results for three alkali
feldspar granitic plutons in the Halajun area, western margin of the
Tarim Block. Zircon U–Pb ages suggest these plutons were emplaced at
268–275 Ma, coeval with the neighbouring mafic–ultramafic complexes and
syenitic rocks. These granitic rocks have high contents of SiO2,
alkalis, Rb, Th, Zr and REE (except Eu), and high ratios of FeO*/MgO
and Ga/Al, and show strong depletions in Ba, Sr, Eu, which are commonly
observed in the A1-type granites. Zircon Hf isotopes reveal a limited
range of εHf(t)
values from −1.0 to +3.5 for different samples from three granitic
plutons, obviously higher than those (mostly <0) of the mafic rocks.
This distinct difference, along with a Daly gap and small volume of
mafic rocks, argues against extreme fractionation of mafic magma as the
main origin of the A1-type granites. Instead the A1-type granites were
most likely derived from partial melting of newly underplated rocks
triggered by the upwelling asthenosphere, followed by extensive
fractionation. These A1-type granites were emplaced within an anorogenic
setting during the late stage of the Tarim LIP, which possibly lasts
for more than 30 Ma. The Piqiang mafic–ultramafic complex directly
stemmed from asthenospheric mantle and Halajun A1-type granites
represent two manners of vertical crustal growth.
KW - A-type granites
KW - zircon U–Pb ages
KW - magma underplating
KW - crystal fractionation
KW - Permian
KW - Tarim mantle plume
UR - http://www.scopus.com/inward/record.url?scp=85061533135&partnerID=8YFLogxK
U2 - 10.1017/S0016756817000838
DO - 10.1017/S0016756817000838
M3 - Article
VL - 156
SP - 409
EP - 429
JO - Geological Magazine
JF - Geological Magazine
SN - 0016-7568
IS - 3
ER -