内蒙古卫境地区查干哈达岩体地球化学特征及其成因探讨
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摘要
对位于中亚造山带东南部,紧邻华北板块北缘的查干哈达花岗岩体进行了岩石地球化学研究。主量元素研究显示查干哈达花岗岩具有SiO_2含量变化较大、准铝质-弱过铝质、碱性-碱钙性、偏铁质等特征;微量元素显示其具有K,Rb,Th,U,Pb和Nd等相对富集,Sr,Ba,Ti,Nb和Ta等相对亏损,稀土总量较高且变化大(96. 7×10~(-6)～373×10~(-6),平均276×10~(-6)),具有高的La_N/Yb_N值(4. 42～33. 0),轻稀土富集,具有较强的Eu亏损(δEu=0. 28～0. 67)等特征。绝大多数样品的ACNK均<1. 1、P_2O_5含量均随着SiO_2含量的升高而降低,表明了查干哈达岩体花岗岩应属于Ⅰ型花岗岩。
Chaganhada pluton is located in the southeast of the Central Asian Orogenic Belt( CAOB) and adjacent to the north margin of the North China Craton( NCC). The SiO_2 of Chaganhada granites contents show variety,and the Chaganhada Pluton belongs to metaluminous to weakly peraluminous,alkali-calcic to alkali,ferroan granites. Chaganhada granites are all enriched in K,Rb,Th,U,Pb,Nd,LREE and depleted in Sr,Ba,Ti,Nb,Ta,HREE. All samples display high and variety total REE contents( 96. 7 × 10~(-6)～ 373 × 10~(-6),average 276× 10~(-6)),and strong negative Eu anomalies. The chondrite-normalized REE patterns of Chaganhada granite are characterized by light REE enrichments relative to heavy REE with high,high La_N/Yb_N ratios( 4. 42 ～ 33. 0)Most samples characterized as ACNK < 1. 1,and negative correlation between P_2O_5 contents and SiO_2 contents. It indicate that Chaganhada granites belong to Ⅰ-type granites.
Chaganhada pluton is located in the southeast of the Central Asian Orogenic Belt( CAOB) and adjacent to the north margin of the North China Craton( NCC). The SiO_2 of Chaganhada granites contents show variety,and the Chaganhada Pluton belongs to metaluminous to weakly peraluminous,alkali-calcic to alkali,ferroan granites. Chaganhada granites are all enriched in K,Rb,Th,U,Pb,Nd,LREE and depleted in Sr,Ba,Ti,Nb,Ta,HREE. All samples display high and variety total REE contents( 96. 7 × 10~(-6)～ 373 × 10~(-6),average 276× 10~(-6)),and strong negative Eu anomalies. The chondrite-normalized REE patterns of Chaganhada granite are characterized by light REE enrichments relative to heavy REE with high,high La_N/Yb_N ratios( 4. 42 ～ 33. 0)Most samples characterized as ACNK < 1. 1,and negative correlation between P_2O_5 contents and SiO_2 contents. It indicate that Chaganhada granites belong to Ⅰ-type granites.
引文
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何国奇.1994.海拉尔盆地乌尔逊凹陷构造样式分析及动力学分析[D].成都:成都理工大学硕士学位论文:12-22.
洪大卫,王试光,谢锡林,等.2000.兴蒙造山带正ε(Nd,t)值花岗岩的成因和大陆地壳生长[J].地学前缘,7(2):441-456.
胡鉴,聂逢君,高爽,等.2016.内蒙古卫境岩体查干哈达地段碱交代蚀变岩特征与铀成矿作用研究[J].东华理工大学学报:自然科学版,39(4):301-309.
朱洛婷.2014.二连浩特-镶黄旗中生代花岗岩年代学及地球化学[D].北京:中国地质大学(北京)硕士学位论文:52-59.
Chappell B W.1999.Aluminium saturation in I-and S-type granites and the characterization of fractionated haplogranites[J].Lithos:535-551.
Chappell B W,White AJR.2001.Two contrasting granite types:25years later[J].Australian Journal of Earth Sciences,48:489-499.
Dahlquist J A,Alasino P H,Bello C.2014.Devonian F-rich peraluminous A-type magmatism in the proto-Andean foreland(Sierras Pampeanas,Argentina):geochemical constraints and petrogenesis from the western-central region of the Achala batholith[J].Mineralogy and Petrology,108:391-417.
Frost B R,Barnes C G,Collins W J,et al.2001.A geochemical classification for granitic rocks[J].Journal of Petrology,42:2033-2048.
Frost B R,Frost C D.2008.A Geochemical Classification for Feldspathic Igneous Rocks[J].Journal of Petrology,49:1955-1969.
Irvine T,Baragar W.1971.A guide to the chemical classification of the common volcanic rocks[J].Canadian Journal of Earth Sciences,8:523-548.
Loiselle M C,Wones D R.1979.Characteristics and origin of anorogenic granites[C]//Abstracts of papers to be presented at the Annual Meeting of the Geological Society of America and Associated Societies,San Diego,California:468.
Maniar P D,Piccoli P M.1989.Tectonic discrimination of granitoids[J].Geological Society of America Bulletin,101:635-643.
Watson E B,Harrison T M.1983.Zircon saturation revisited:temperature and composition effects in a variety of crustal magma types[J].Earth and Planetary Science Letters,64(2):295-304.
Whalen J B,Currie K L,Chappell B W.1987.A-type granites:geochemical characteristics,discrimination and petrogenesis[J].Contributions to Mineralogy and Petrology,95(4):407-419.
Yu J H,O'Reilly S Y,Zhao L,et al.2007.Origin and evolution of topaz-bearing granites from the Nanling Range,South China:a geochemical and Sr-Nd-Hf isotopic study[J].Mineralogy and Petrology,90(3):271-300.