吉林大学学报(地球科学版)
吉林大學學報(地毬科學版)
길림대학학보(지구과학판)
JOURNAL OF JILIN UNIVERSITY(EARTH SCIENCE EDITION)
2014年
1期
186-197
,共12页
李承东%许雅雯%张庆红%周红英%彭树华%陈军强%张阔%赵利刚%李省印
李承東%許雅雯%張慶紅%週紅英%彭樹華%陳軍彊%張闊%趙利剛%李省印
리승동%허아문%장경홍%주홍영%팽수화%진군강%장활%조리강%리성인
新太古代%高镁安山岩%地球化学%张三沟岩组%金银别岩组%色洛河群
新太古代%高鎂安山巖%地毬化學%張三溝巖組%金銀彆巖組%色洛河群
신태고대%고미안산암%지구화학%장삼구암조%금은별암조%색락하군
Neoarchean%high-Mg andesite%geochemistry%Zhangsangou Formation-Complex%Jinyinbie Formation-Complex%Seluohe Group
吉南张三沟岩组和金银别岩组发育一套高镁安山岩类,S H RIM P锆石 U Pb定年为(2493±12)Ma ,形成于新太古代。高镁安山岩类属于钙碱性系列,w (SiO2)为53.93%~57.90%,富 MgO (w(MgO)为6.54%~8.82%),高Mg#值(0.68~0.71,平均0.69),高铬(w(Cr)为(270.66~1117.30)×10-6,平均443.62×10-6),高镍(w(Ni)为(141.74~542.98)×10-6,平均250.50×10-6),这种高MgO、Cr、Ni的特征表明其成因与地幔部分熔融有关。另一方面,该岩石富集大离子亲石元素(如Sr、Cs、K、Pb、Rb和Ba),亏损高场强元素(如Nb、Ta、Ti、P),富集LREE(w(Ce)为(38.34~59.34)×10-6),亏损 HREE (w(Yb)为(1.38~1.57)×10-6),显示弧火山岩的特点。上述地球化学特征表明,岩石可能是消减板片脱水流体或者消减板片部分熔融的熔体与地幔橄榄岩相互作用的结果,揭示它们形成于消减带的构造环境,表明新太古代已经存在现代类型的板块构造。
吉南張三溝巖組和金銀彆巖組髮育一套高鎂安山巖類,S H RIM P鋯石 U Pb定年為(2493±12)Ma ,形成于新太古代。高鎂安山巖類屬于鈣堿性繫列,w (SiO2)為53.93%~57.90%,富 MgO (w(MgO)為6.54%~8.82%),高Mg#值(0.68~0.71,平均0.69),高鉻(w(Cr)為(270.66~1117.30)×10-6,平均443.62×10-6),高鎳(w(Ni)為(141.74~542.98)×10-6,平均250.50×10-6),這種高MgO、Cr、Ni的特徵錶明其成因與地幔部分鎔融有關。另一方麵,該巖石富集大離子親石元素(如Sr、Cs、K、Pb、Rb和Ba),虧損高場彊元素(如Nb、Ta、Ti、P),富集LREE(w(Ce)為(38.34~59.34)×10-6),虧損 HREE (w(Yb)為(1.38~1.57)×10-6),顯示弧火山巖的特點。上述地毬化學特徵錶明,巖石可能是消減闆片脫水流體或者消減闆片部分鎔融的鎔體與地幔橄欖巖相互作用的結果,揭示它們形成于消減帶的構造環境,錶明新太古代已經存在現代類型的闆塊構造。
길남장삼구암조화금은별암조발육일투고미안산암류,S H RIM P고석 U Pb정년위(2493±12)Ma ,형성우신태고대。고미안산암류속우개감성계렬,w (SiO2)위53.93%~57.90%,부 MgO (w(MgO)위6.54%~8.82%),고Mg#치(0.68~0.71,평균0.69),고락(w(Cr)위(270.66~1117.30)×10-6,평균443.62×10-6),고얼(w(Ni)위(141.74~542.98)×10-6,평균250.50×10-6),저충고MgO、Cr、Ni적특정표명기성인여지만부분용융유관。령일방면,해암석부집대리자친석원소(여Sr、Cs、K、Pb、Rb화Ba),우손고장강원소(여Nb、Ta、Ti、P),부집LREE(w(Ce)위(38.34~59.34)×10-6),우손 HREE (w(Yb)위(1.38~1.57)×10-6),현시호화산암적특점。상술지구화학특정표명,암석가능시소감판편탈수류체혹자소감판편부분용융적용체여지만감람암상호작용적결과,게시타문형성우소감대적구조배경,표명신태고대이경존재현대류형적판괴구조。
The high-Mg andesite occurring in the Zhangsangou and Jinyinbie Formation-Complex in southern Jilin Province is dated at (2 493 ± 12) Ma by the SHRIMP zircon U Pb method ,which indicates that it was generated in the Neoarchean period . The high-Mg andesite belongs to the cal-calkaline series .It is geochemically characterized by SiO2 content of 53 .93% 57 .90% ,high MgO (6 .54% 8 .82 % ) and high Mg# (0 .68 0 .71 ,avg .0 .69) ,associated with enrichments of Cr (270 .66 × 10-6 1 117 .30 × 10 -6 ,avg .443 .62 × 10 -6 ) and Ni (141 .74 × 10 -6 542 .98 × 10 -6 ,avg .250 .50 × 10-6 ) .According to its high MgO ,Cr and Ni ,the high-Mg andesite is relate to the partial melting of mantle peridotites in genesis .On the other hand ,the andesite is strongly enriched in light rare earth elements (Ce:38 .34 × 10-6 59 .34 × 10-6 ) and large-ion-lithophile elements (such as Sr ,Cs ,K ,Pb ,Rb and Ba) ,and is also characterized by depletion of high-field-strength elements (such as Nb ,Ta ,Ti and P) and heavy rare earth elements (Yb:1 .38 × 10-6 1 .57 × 10 -6 ) ,which demonstrates geochemical characteristic of the arc volcanic rock .The high-Mg andesite was most likely derived from the products of interaction of slab-derived fluid or melt with mantle peridotites .It can thus be concluded that the high-Mg andesite was derived from the subduction zone and there occurred the modern plate tectonics in the Neoarchean period .