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The Boziguoer A-type granitoids in Baicheng County,Xinjiang,belong to the northern margin of the Tarim platform as well as the neighboring EW-oriented alkaline intrusive rocks.The rocks comprise an aegirine or arfvedsonite quartz alkali feldspar syenite,an aegirine or arfvedsonite alkali feldspar granite,and a biotite alkali feldspar syenite.The major rock-forming minerals are albite,K-feldspar,quartz,arfvedsonite,aegirine,and siderophyllite.The accessory minerals are mainly zircon,pyrochlore,thorite,fluorite,monazite,bastnaesite,xenotime,and astrophyllite.The chemical composition of the alkaline granitoids show that SiO2varies from 64.55%to 72.29%with a mean value of 67.32%,Na2O+K2O is high(9.85%–11.87%)with a mean of 11.14%,K2O is 2.39%–5.47%(mean=4.73%),the K2O/Na2O ratios are 0.31–0.96,Al2O3ranges from 12.58%to 15.44%,and total FeO T is between 2.35%and 5.65%.CaO,MgO,MnO,and TiO2are low.The REE content is high and the total SREE is(263–1219)ppm(mean=776 ppm),showing LREE enrichment and HREE depletion with strong negative Eu anomalies.In addition,the chondrite-normalized REE patterns of the alkaline granitoids belong to the“seagull”pattern of the right-type.The Zr content is(113–1246)ppm(mean=594 ppm),Zr+Nb+Ce+Y is between(478–2203)ppm with a mean of 1362 ppm.Furthermore,the alkaline granitoids have high HFSE(Ga,Nb,Ta,Zr,and Hf)content and low LILE(Ba,K,and Sr)content.The Nb/Ta ratio varies from 7.23 to 32.59(mean=16.59)and the Zr/Hf ratio is 16.69–58.04(mean=36.80).The zircons are depleted in LREE and enriched in HREE.The chondrite-normalized REE patterns of the zircons are of the“seagull”pattern of the left-inclined type with strong negative Eu anomaly and without a Ce anomaly.The Boziguoer A-type granitoids share similar features with A1-type granites.The average temperature of the granitic magma was estimated at 832–839°C.The Boziguoer A-type granitoids show crust–mantle mixing and may have formed in an anorogenic intraplate tectonic setting under high-temperature,anhydrous,and low oxygen fugacity conditions.
The Boziguoer A-type granitoids in Baicheng County, Xinjiang, belong to the northern margin of the Tarim platform as well as the nearby EW-oriented alkaline intrusive rocks.The rocks comprise an aegirine or arfvedsonite quartz alkali feldspar syenite, an aegirine or arfvedsonite alkali feldspar granite, and a biotite alkali feldspar syenite. the major rock-forming minerals are albite, K-feldspar, quartz, arfvedsonite, aegirine, and siderophyllite.The accessory minerals are mainly zircon, pyrochlore, thorite, fluorite, monazite, bastnaesite, xenotime , and astrophyllite. The chemical composition of the alkaline granitoids that that SiO2 varies from 64.55% to 72.29% with a mean value of 67.32%, Na2O + K2O is high (9.85% -11.87%) with a mean of 11.14%, K2O is 2.39 % -5.47% (mean = 4.73%), the K2O / Na2O ratios are 0.31-0.96, Al2O3ranges 12.58% to 15.44%, and total FeO T is between 2.35% and 5.65% .CaO, MgO, MnO, and TiO2are low The REE content is high and the total SREE is (263-1219) ppm (mean = 776 ppm), showing LREE en rich and HREE depletion with strong negative Eu anomalies. In addition, the chondrite-normalized REE patterns of the alkaline granitoids belong to the “seagull” pattern of the right-type. The Zr content is (113-1246) ppm = 594 ppm), Zr + Nb + Ce + Y is between (478-2203) ppm with a mean of 1362 ppm.Furthermore, the alkaline granitoids have high HFSE (Ga, Nb, Ta, Zr, and Hf) content and low LILE (Ba, K, and Sr) content.The Nb / Ta ratio varies from 7.23 to 32.59 (mean = 16.59) and the Zr / Hf ratio is 16.69-58.04 (mean = 36.80). The zircons are depleted in LREE and enriched in HREE. The chondrite-normalized REE patterns of the zircons are of the “seagull” pattern of the left-inclined type with strong negative Eu anomaly and without a Ce anomaly. The Boziguoer A-type granitoids share similar features with A1- type granites. The average temperature of the granitic magma was estimated at 832-839 ° C. The Boziguoer A-type granitoids show crust-mantle mixing and may have formed in an anogenic intraplate tectonic se tting under high-temperature, anhydrous, and low oxygen fugacity conditions.