Middle-crust accumulation of hornblendite and pyroxenes from slab- and mantle wedge-derived magmas and recharge of high-O-18 felsic magma collectively generated the Hadanxun arc magmas, northern East Junggar
Middle-crust accumulation of hornblendite and pyroxenes from slab- and mantle wedge-derived magmas and recharge of high-O-18 felsic magma collectively generated the Hadanxun arc magmas, northern East Junggar
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板片和地幔楔衍生岩浆中角闪石和辉石在中地壳的堆积和高 O-18 长英质岩浆的补给共同形成了东准噶尔北部的哈丹逊岛弧岩浆
DOI：
10.1016/j.lithos.2021.105986
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发表时间：
2021
期刊：
影响因子：
3.5
通讯作者：
Liu Xiujin
中科院分区：
文献类型：
--
作者：
Liu Wei;Si Cuiqin;Liu Xiujin
Secondary-ion mass spectrometric U-Pb age and δ18O and laser-ablation multi-collector ICP-MS εHf(t) of zircons, mineral chemistry and whole-rock geochemistry and Nd-Sr isotopes of the Hadanxun intrusive complexes and Bieli'atun pluton, northern East Junggar were analyzed in this study. The Hadanxun intrusive complexes were intruded during Carboniferous (324.8–323.1 Ma) and Early Permian (290.0–281.3 Ma). The Carboniferous intrusive complex varies from diorite (with entrained block of hornblendite cumulate), monzodiorite through quartz monzonite/monzonite to monzogranite. The Early-Permian intrusive rocks include gabbro/dioritic rock, quartz monzonite/monzonite with anorthosite, entrained block of feldspathic pyroxenite and alkali-feldspar granite. The Carboniferous intrusive rocks exhibit decreasing MgO, TFe2O3, TiO2, CaO, Sr and V with increasing SiO2. Their rare earth element (REE) distribution patterns are concave-up and steeply-dipping with decreasing Dy/Yb and primitive-mantle normalized NbN/TaN. These characteristics can be modeled with two stage fractional crystallization early of hornblendite and late of feldspar-dominated minerals. These rocks all plot within adakite field in the Sr/Y vs. Y diagram, suggesting derivation from subducting oceanic-slab.The Early-Permian intrusive rocks with pronounced Nb, Ta and Ti negative anomalies and depleted isotopic compositions manifest arc affinity with derivation from slab fluid-metasomatized mantle wedge. The feldspathic pyroxenites exhibit negative Eu anomaly (Eu/Eu* = 0.57–0.78), flat HREE distribution pattern with relative enrichment of HREE, significant negative Sr, P anomalies and REE = 157.8–186.7 ppm and Zr = 97.9–177. Just the opposite, the anorthosite and quartz monzonite/monzonite manifest remarkable positive Eu anomalies (Eu/Eu* = 1.27–1.47), steep REE distribution pattern with depleted HREE, positive Sr, P anomalies and REE = 167–189.8 and Zr = 92.9–141. The complementarity of the two categories of rock with high REE and Zr suggests that they have equilibrated via a crustal melt-buffered liquid. In the quartz monzonite/monzonite, extensive K-, Na-metasomatism of plagioclase and metasomatism of hornblende into biotite suggest mixing of K-, Na- and Si-rich felsic magma into Al-, Ca-rich magma. Quantitative modeling can reproduce the complementarity of the two categories of rock with alkali-feldspar granite as Stage 2 residual melt. Underplating coupled with interaction of high-18O fluid caused hydrogen metasomatism and partial melting of juvenile lower-crust generating K-, Na- and Si-rich felsic magma. The latter was replenished to magma plumbing system and drove the preceding magma to ascend together. Meanwhile, the felsic magma mixed with pyroxene crystal mush in the upper stream and Al-, Ca-rich derivative magma in the down stream. This eventually formed lower cumulate beneath upper cumulate at emplacement, i.e. feldspathic pyroxenite (cumulus pyroxenes cemented by mesoperthite) beneath quartz monzonite/monzonite plus anorthosite of the Hadanxun main pluton. Al-in-hornblende barometry and two-pyroxene thermobarometry reveal that hornblendite (population 1 hornblendes: 26–22 km depth; population 2: 20–18 km) and pyroxenite (23–16 km) cumulates constitute high P-wave velocity body (27 to 15 km depth) in the middle crust of northern East Junggar, whereas fragment of hornblendite and symplectitic pyroxenes (18–8 km) record decompression when they were brought through magma plumbing system. The Hadanxun intrusive rocks including mixed product i.e. quartz monzonite/monzonite exhibit clustered εNd(t …
