華北板塊北緣中段早石炭世構(gòu)造屬性:察哈爾右翼后旗高分異Ⅰ型花崗巖地球化學(xué)的制約

劉 群，王挽瓊，邱殿明，白新會，張金鳳，王 新

1.黑龍江省地球物理勘察院，哈爾濱 150036 2.西南石油大學(xué)地球科學(xué)與技術(shù)學(xué)院，成都 610500 3.吉林大學(xué)學(xué)報(bào)編輯部，長春 130026 4.吉林大學(xué)地球科學(xué)學(xué)院，長春 130061

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華北板塊北緣中段早石炭世構(gòu)造屬性:察哈爾右翼后旗高分異Ⅰ型花崗巖地球化學(xué)的制約

劉 群1，王挽瓊2，邱殿明3，白新會4，張金鳳4，王 新4

1.黑龍江省地球物理勘察院，哈爾濱 150036 2.西南石油大學(xué)地球科學(xué)與技術(shù)學(xué)院，成都 610500 3.吉林大學(xué)學(xué)報(bào)編輯部，長春 130026 4.吉林大學(xué)地球科學(xué)學(xué)院，長春 130061

察哈爾右翼后旗二長花崗巖巖體位于華北板塊北緣中段。巖體富SiO2、富K、富堿、低Ca和P、貧Fe和Mg，w(P2O5)與w(SiO2)呈負(fù)相關(guān)，鋁指數(shù)(A/CNK)為0.96～1.15，分異指數(shù)為90.36～92.96；主要造巖礦物為條紋長石、斜長石和石英，其鐵鎂礦物主要為黑云母，未出現(xiàn)堿性鐵鎂礦物和富鋁礦物，副礦物為鋯石、磁鐵礦、磷灰石、榍石和鈦鐵礦；可見察哈爾右翼后旗二長花崗巖屬高分異鈣堿性I型花崗巖類。結(jié)合較低的w(∑REE)((46.8～94.4)×10-6)、w(Th)((1.74～2.39)×10-6)、w(U)((0.27～0.39)×10-6)和微量元素判別圖解，二長花崗巖巖漿源區(qū)可能為下地殼，源巖可能為巖石圈地幔。巖石輕重稀土分餾較強(qiáng) ((La/Yb)N= 6.52～28.39)，δEu以正異常為主(0.83～3.51)，富集大離子親石元素(LILEs，Cs、Rb、Ba和K)，虧損高場強(qiáng)元素 (HFSEs，Nb、Ta、P和Ti)。地球化學(xué)特征反映了二長花崗巖具有火山弧巖石特征，且?guī)r體侵入新元古界埃迪卡拉系什那干群，表明巖體形成于活動大陸邊緣弧環(huán)境，其侵位反映了古亞洲洋的俯沖巖漿事件。

華北板塊北緣；內(nèi)蒙古；早石炭世；高分異I型花崗巖；活動大陸邊緣??；古亞洲洋

0 引言

中亞造山帶從哈薩克斯坦延伸至中國天山及華北板塊北緣[1]，其形成與古亞洲洋演化、相鄰板塊間相互作用密不可分[2-3]，即古亞洲洋閉合，西伯利亞板塊與塔里木--華北板塊碰撞造山，形成中亞造山帶[4]，與華北板塊北緣毗鄰的中亞造山帶即為興蒙造山帶[5]。中亞造山帶是全球顯生宙大陸增生最顯著的地區(qū)，同時(shí)也是全球最大的增生造山帶[6]，興蒙造山帶是中亞造山帶重要的一部分[7]。造山帶是巖漿活動最為顯著的地帶。在該造山帶及華北板塊北緣，發(fā)育大量近東西向的古生代巖漿巖帶[8]，其中以晚古生代火成巖最為顯著[9-14]。

華北板塊北邊界線為赤峰--白云鄂博斷裂[1，4，15]。察哈爾右翼后旗二長花崗巖巖體位于該斷裂以南，集寧--隆化斷裂以北(圖1)，主要由元山洼、察汗腦包和高木匠村巖體組成(圖1)。張臣等[10]2007年報(bào)道了該巖體的鋯石SHRIMP U-Pb 定年((342.5±4.9) Ma) 和其主量元素特征，但其痕量元素及巖漿源區(qū)特征等關(guān)鍵問題目前尚未被研究過。且目前報(bào)道的華北板塊北緣中段晚古生代巖漿巖時(shí)代集中在晚石炭世--二疊紀(jì)[5,19-20]，而早石炭世巖漿巖的報(bào)道較少。鑒于此，本文在1∶25萬集寧市幅*吉林大學(xué)地質(zhì)調(diào)查研究院. 1∶25萬集寧市幅地質(zhì)圖.長春：吉林大學(xué)，2012.區(qū)調(diào)修測基礎(chǔ)上，結(jié)合察哈爾右翼后旗二長花崗巖巖體的野外產(chǎn)狀、礦物特征、地球化學(xué)特征，進(jìn)一步探討了其成因及形成的構(gòu)造環(huán)境。

1 地質(zhì)背景及巖體特征

察哈爾右翼后旗二長花崗巖巖體出露面積約109.54 km2，整體呈北東向產(chǎn)出，侵入到新元古界埃迪卡拉系什那干群和早泥盆世石英二長巖之中，后被大面積新生界新近系上新統(tǒng)寶格達(dá)烏拉組砂礫黏土及少量中新統(tǒng)漢諾壩組玄武巖覆蓋，早白堊世花崗斑巖侵入其中(圖1)。見少量斜長角閃片麻巖捕擄體。

角圖據(jù)文獻(xiàn)[1]修改。圖1 研究區(qū)地質(zhì)簡圖Fig.1 Geological sketch map of research area

察哈爾右翼后旗二長花崗巖風(fēng)化面灰色，新鮮面肉紅色，大部分為斑狀結(jié)構(gòu)(圖2a、b)，少量為含斑結(jié)構(gòu)和細(xì)?；◢徑Y(jié)構(gòu)，塊狀構(gòu)造為主，局部石英拉長、黑云母不連續(xù)定向形成片麻理構(gòu)造(圖2c、d)。片麻理走向近東西向，可能受后期巖漿作用及區(qū)域擠壓作用形成。斑晶體積分?jǐn)?shù)為2%～10%，主要為條紋長石。基質(zhì)為中細(xì)粒結(jié)構(gòu)，主要礦物(體積分?jǐn)?shù))為：條紋長石(40%～45%，弱高嶺土化)、斜長石(30%～35%，絹云母化)、石英(25%)和黑云母(2%～5%，褪色析鐵)；副礦物為磁鐵礦，細(xì)雙錐狀、粒狀鋯石，柱狀、粒狀磷灰石，榍石和鈦鐵礦。高木匠村南1 km處為該巖體的中心相，中心相面積不大，巖性為淺肉紅色細(xì)粒含斑黑云母鉀長花崗巖，主要礦物為條紋長石(體積分?jǐn)?shù)小于60%)，石英(體積分?jǐn)?shù)25%)，斜長石(體積分?jǐn)?shù)大于10%)，黑云母(體積分?jǐn)?shù)5%)。張臣等[10]2007年報(bào)道的定年樣品采自該巖體的中心相。

2 樣品采集及實(shí)驗(yàn)方法

在高木匠村附近采集了5塊新鮮二長花崗巖樣品進(jìn)行全巖主量和痕量元素分析。巖石化學(xué)分析在國家地質(zhì)實(shí)驗(yàn)測試中心完成，主量元素采用ICP-AES(原子發(fā)射光譜)，燒失量為1 000 ℃燒失；稀土元素中La、Ce采用ICP-AES，其他元素采用ICP-MS；微量元素中Sc、Sr、Ba采用ICP-AES，Nb、Rb、Zr、Cr、V、Co、Th、Hf、Ta、U采用ICP-MS。

3 地球化學(xué)特征

3.1 主量元素

察哈爾右翼后旗二長花崗巖的主量元素和稀土微量元素分析結(jié)果見表1。從表1易見，花崗巖高SiO2(w(SiO2)=68.96%～71.25%)、富K、富堿(w(K2O)=4.31%～5.24%，w(K2O+Na2O)=9.13%～10.65%)，低Ca(w(CaO)=0.73%～1.12%)和P(w(P2O5)=0.028%～0.044%)，貧Fe(w(TFeO)=1.14%～2.02%)和Mg(w(MgO)=0.08%～0.16%)。在TAS侵入巖分類圖(圖3a)中主要落在花崗巖范圍內(nèi)，少量落在石英二長巖范圍內(nèi)；鋁指數(shù)(A/CNK)為0.96～1.15，屬準(zhǔn)鋁質(zhì)--弱過鋁質(zhì)花崗巖類(圖3b)。

樣品編號wB/%SiO2Al2O3Fe2O3FeOCaOMgOK2ONa2OTiO2P2O5MnO燒失量K2O+Na2OP32b6-171.0016.111.410.251.030.165.084.050.130.0440.0140.69.13P32b10-171.0916.031.390.120.730.135.244.560.120.0360.0260.429.80P32b15-168.9616.302.200.041.040.084.406.250.200.0430.0260.3610.65P32b16-169.6017.271.430.161.120.094.485.380.160.0340.0480.139.86P32b27-271.2516.211.200.060.950.084.315.280.120.0280.0310.389.59樣品編號Na2O/K2OA/CNKMg#wB/10-6CrNiCoRbCsSrBaVScNbP32b6-10.801.1515.813.022.541.7076.50.92632165024.00.331.60P32b10-10.871.1114.462.742.071.5267.30.99649120013.35.524.90P32b15-11.420.966.603.384.061.1455.90.4855488513.47.117.17P32b16-11.201.109.485.043.391.0686.61.96887159018.06.009.42P32b27-21.231.0811.003.433.921.1268.40.17683111012.04.724.64

表1(續(xù))

圖3 研究區(qū)二長花崗巖TAS圖解(a)和鋁飽指數(shù)圖解(b)Fig.3 TAS (a) and Shand's index (b) diagrams of the monzonite ranites in the study area

3.2 痕量元素

察哈爾右翼后旗二長花崗巖具相對富集輕稀土(w(∑LREE)=(42.70～82.80)×10-6)、虧損重稀土元素(w(∑HREE)=(2.31～11.61)×10-6)的右傾型稀土元素配分曲線(圖4a)。稀土元素總量低(w(∑REE)=(46.8～ 94.4)×10-6)，輕重稀土分餾程度強(qiáng)(∑LREE/∑HREE=7.13～22.16，(La/Yb)N=6.52～28.39)。輕稀土分餾強(qiáng)((La/Sm)N=2.77～13.24)，重稀土分餾較弱((Gd/Lu)N=0.98～1.56)。Eu以正異常為主(δEu=0.83～3.51)。相對位于巖體邊部的樣品P32b6-1(圖1)正Eu異常顯著(δEu=3.51)，重稀土總量低(w(∑HREE)=2.31×10-6)，輕稀土分餾強(qiáng)((La/Sm)N=13.24)，可能是受到了圍巖(早泥盆世石英二長巖)的混染。

微量元素原始地幔標(biāo)準(zhǔn)化蛛網(wǎng)圖(圖 4b)中，察哈爾右翼后旗二長花崗巖富集大離子親石元素(LILEs，Cs、Rb、Ba和K)，虧損高場強(qiáng)元素(HFSEs，Nb、Ta、P和Ti)，較明顯的Sr正異常。

球粒隕石標(biāo)準(zhǔn)化值據(jù)文獻(xiàn)[20]；原始地幔標(biāo)準(zhǔn)化值據(jù)文獻(xiàn)[21]。圖4 研究區(qū)二長花崗巖稀土元素球粒隕石標(biāo)準(zhǔn)化配分圖(a)和微量元素原始地幔標(biāo)準(zhǔn)化蛛網(wǎng)圖(b)Fig.4 Chondrite-normalized REE distribution patterns (a) and primitive mantle-normalized trace element patterns (b) of the monzonite granites in the study area

4 討論

4.1 成因類型

巖漿分異指數(shù)為90.36～92.96，固結(jié)指數(shù)為0.62～1.47，親鐵元素質(zhì)量分?jǐn)?shù)低(w(V)=(12.0～24.0)×10-6，w(Co)=(1.06～1.70)×10-6)，P2O5質(zhì)量分?jǐn)?shù)很低(w(P2O5)=0.028%～0.044%)，富硅貧鐵、鎂、鈣和鈦，反映了巖體經(jīng)歷了高度分異演化作用[22]。巖漿經(jīng)歷了高分異作用，為巖漿演化的晚期產(chǎn)物，礦物組成和化學(xué)成分都趨于低共結(jié)的花崗巖，因此很難區(qū)分花崗巖是I型、S型或A型，相對P2O5、Th和Rb等元素是判斷I、S型花崗巖較為可靠的標(biāo)志[23-24]。察哈爾右翼后旗二長花崗巖w(P2O5)隨w(SiO2)增高而降低(圖5a)，w(Th)隨w(Rb)升高而升高(圖5b)，顯示出I型花崗巖巖漿的演化趨勢；而S型花崗巖的w(P2O5)與w(SiO2)呈正相關(guān)，w(Th)與w(Rb)呈負(fù)相關(guān)[24-25]。在(Na2O+K2O)/CaO-w(Zr+Nb+Ce+Y)圖解(圖6a)中，樣品位于分異型花崗巖范圍內(nèi)；在主量元素判別圖解(圖6b)中，樣品落在高分異鈣堿性巖范圍內(nèi)。二長花崗巖不發(fā)育鐵鎂質(zhì)堿性礦物，較低質(zhì)量分?jǐn)?shù)的Zr、Nb、Y、La和Ce也反映了其為I型花崗巖并非A型[28]。

4.2 源區(qū)性質(zhì)

在微量元素蛛網(wǎng)圖(圖4b)上，察哈爾右翼后旗二長花崗巖明顯虧損高場強(qiáng)元素Nb、Ta、P和Ti，富集Eu，w(Th)和w(U)較低。若巖漿源區(qū)殘留金紅石，會致使巖漿虧損Nb、Ta、Ti、Zr、Hf等高場強(qiáng)元素[29]，但二長花崗巖只虧損Nb、Ta和Ti并不虧損Zr、Hf，因此二長花崗巖虧損Nb、Ta、Ti與巖漿源區(qū)是否殘留金紅石無關(guān)。巖漿源區(qū)或者巖漿演化中陸殼物質(zhì)的加入，也會使巖漿虧損Nb、Ta。二長花崗巖低的稀土總量和w(Th)、w(U)表明，巖漿演化早期可能不存在大規(guī)模的陸殼物質(zhì)混染。那么該巖體Nb、Ta虧損應(yīng)該是俯沖流體或者熔體交代作用所致[30]。Ti負(fù)異常主要是鈦鐵礦和角閃石分異所致。二長花崗巖經(jīng)歷了高程度的結(jié)晶分異作用，磷灰石一般在巖漿作用的早期結(jié)晶，磷灰石的結(jié)晶分異使熔體Eu富集，P虧損[31]。磷灰石富集REE、Th和U[25]，其結(jié)晶分異，可能也導(dǎo)致了二長花崗巖w(∑REE)、w(Th)和w(U)偏低。斜長石結(jié)晶分異會導(dǎo)致Sr、Eu虧損，鉀長石結(jié)晶分異致使Eu、Ba虧損[28]，但二長花崗巖的Sr、Eu和Ba富集，顯然巖漿演化過程中斜長石和鉀長石結(jié)晶分異不顯著。

圖5 研究區(qū)二長花崗巖哈克圖解Fig.5 Harker diagrams of the monzonite granites in the study area

A.A型花崗巖；FG.分異型M+I+S型花崗巖；OGT.非分異M+I+S型花崗巖。a底圖據(jù)文獻(xiàn)[26]，b底圖據(jù)文獻(xiàn)[27]。圖6 研究區(qū)二長花崗巖(Na2O+K2O)/CaO-w(Zr+Nb+Ce+Y)圖解(a)和主量元素判別圖解(b)Fig.6 (Na2O+K2O)/CaO-w(Zr+Nb+Ce+Y) diagram (a) and discrimanation diagram by major elements(b) of the monzonite granites in the study area

巖漿分異作用的晚期，稀土元素易保留在殘余液相中[31]。二長花崗巖經(jīng)歷了強(qiáng)烈的分異結(jié)晶，那么其稀土總量應(yīng)該比源區(qū)巖石的稀土總量更高。而二長花崗巖的w(∑REE)=(46.8～94.4)×10-6，部分樣品的稀土總量比下地殼(56.55×10-6[32])的還要低；w(Th)=(1.74～2.39)×10-6、w(U)=(0.27～0.39)×10-6，接近下地殼(w(Th)=1.2×10-6，w(U)=0.2×10-6[32])，暗示二長花崗巖源區(qū)可能為下地殼，源巖可能為巖石圈地幔，這與承德一帶晚石炭世花崗巖類具有類似的源區(qū)[11]。

4.3 地質(zhì)意義

在w(Nb)-w(Y)圖解(圖7a)中，察哈爾右翼后旗二長花崗巖落在火山弧+同碰撞范圍內(nèi)；w(Rb)-w(Y+Nb)圖解(圖7b)中，樣品落在火山弧范圍內(nèi)，據(jù)Pearce[33]對花崗巖源區(qū)和成巖途徑的分析，二長花崗巖源區(qū)可能是富集地幔和俯沖帶流體的混合；Rb/30-Hf-3Ta圖解(圖7c)中，樣品落在火山弧花崗巖范圍內(nèi)，反映了二長花崗巖形成于島弧或者活動大陸邊緣弧環(huán)境。二長花崗巖相對富集大離子親石元素(LILEs，Cs、Rb、Ba和K)，虧損高場強(qiáng)元素(HFSEs，Nb、Ta、P和Ti)，也反映了其類似俯沖帶巖漿巖的特征[34]。結(jié)合察哈爾右翼后旗二長花崗巖位于赤峰--白云鄂博斷裂以南(圖1)，侵入新元古界埃迪卡拉系什那干群中這種特征，表明二長花崗巖形成于活動大陸邊緣弧環(huán)境。

圖7 研究區(qū)二長花崗巖w(Nb)-w(Y)圖解(a), w(Rb)-w(Y+Nb)圖解(b)和Rb/30-Hf-3Ta圖解(c)Fig.7 w(Nb)-w(Y) (a), w(Rb)-w(Y+Nb) (b) and Rb/30-Hf-3Ta(c) diagrams of the monzonite granites in the study area

中亞造山帶作為古生代以來大陸地殼生長最重要的地帶[35]，80年代至今，眾多學(xué)者對其進(jìn)行了大量研究，最初的研究對象主要為古生物學(xué)、地層學(xué)和古地磁，近幾年報(bào)道了大量的侵入巖及地震剖面相關(guān)的證據(jù)。關(guān)于兩大板塊最終碰撞形成索倫縫合帶的時(shí)間目前主要有以下幾種觀點(diǎn)：晚志留世--泥盆紀(jì)[36]；中--晚泥盆世[3，37]；晚泥盆世--晚石炭世[38-40]；二疊紀(jì)--早三疊世[1-2，9，15-16，19，41-45]。察哈爾右翼后旗二長花崗巖的侵位表明華北板塊北緣中段在早石炭世為活動大陸邊緣弧環(huán)境，古亞洲洋處于俯沖狀態(tài)，顯然其閉合時(shí)間肯定在早石炭世之后。滿都拉南部推喇嘛廟一帶發(fā)育327、330 Ma的花崗閃長巖，其形成與洋殼俯沖有關(guān)[9]；固陽--滿都拉地區(qū)晚石炭世本巴圖組火山巖顯示島弧或活動大陸邊緣弧的特征[16]；四子王旗活佛灘閃長巖侵位年齡為(331±4)Ma，是古亞洲洋俯沖的產(chǎn)物[16]；蘇尼特右旗晚石炭世本巴圖組安山巖成巖時(shí)代為(300.9±1.6) Ma，其形成與古亞洲洋的俯沖作用有關(guān)[18]；Zhang[11]報(bào)道了大量灤平--承德--隆化地區(qū)晚石炭世閃長巖，形成于安第斯型活動大陸邊緣弧環(huán)境，侵位時(shí)代集中為(324±6)～(302±4) Ma；吉林省安圖縣海溝巖體于322～328 Ma侵位，其成因與古亞洲洋俯沖作用有關(guān)[46]；這些火成巖構(gòu)造構(gòu)成了華北板塊北緣早石炭世--晚石炭世火山弧。察哈爾右翼中旗具活動大陸邊緣弧特征的輝長巖于(297.2±1.7) Ma侵位(待發(fā)表數(shù)據(jù))；察哈爾右翼后旗北至溫都爾廟南地區(qū)，發(fā)育大面積早--中二疊世石英閃長巖和花崗閃長巖巖基，都具活動大陸邊緣弧特征[13]。童英[19]和張拴宏[5]總結(jié)了華北板塊北緣晚古生代弧巖漿巖時(shí)空展布等特征，其中巖漿活動的高峰期為二疊紀(jì)，分布在靠近索倫縫合帶的南側(cè)；石炭紀(jì)巖漿活動相對較弱，多分布在靠近華北板塊北緣內(nèi)陸一側(cè)。上述表明：早石炭世--晚石炭世古亞洲洋向華北板塊北緣俯沖，在靠近板塊內(nèi)側(cè)形成了早石炭世--晚石炭世火山??；二疊紀(jì)的俯沖作用形成了靠近索倫縫合帶的二疊紀(jì)弧巖漿巖帶。

5 結(jié)論

本文通過對察哈爾右翼后旗二長花崗巖的巖相學(xué)、主量、痕量元素研究，得出以下幾點(diǎn)結(jié)論：

1)二長花崗巖主要造巖礦物為條紋長石、斜長石和石英，鐵鎂礦物主要為黑云母，副礦物為鋯石、磁鐵礦、磷灰石、榍石和鈦鐵礦；富SiO2、K和(K2O+Na2O)，貧Ca、P、TFeO和Mg，鋁指數(shù)(A/CNK)為0.96～1.15，分異指數(shù)為90.36～92.96，屬高分異鈣堿性I型花崗巖。

2)經(jīng)歷高分異作用的二長花崗巖w(∑REE)、w(Th)和w(U)低，結(jié)合w(Rb)-w(Y+Nb)圖解，表明巖漿源區(qū)可能為下地殼，源巖為巖石圈地幔，俯沖帶流體作用顯著。Eu以正異常為主，Sr和Ba富集，表明巖漿結(jié)晶分異過程中斜長石和鉀長石分異不顯著。

3)巖體富集大離子親石元素(LILEs，Cs、Rb、Ba和K)，虧損高場強(qiáng)元素(HFSEs，Nb、Ta、P和Ti)，顯示火山弧巖漿巖特征；樣品在花崗巖構(gòu)造環(huán)境判別圖解中均落入火山弧范圍內(nèi)，且察哈爾右翼后旗二長花崗巖位于赤峰--集寧斷裂以南，侵入新元古界埃迪卡拉系什那干群,這種地質(zhì)特征表明巖體形成于活動大陸邊緣弧環(huán)境。

4)具有活動大陸邊緣弧特征的二長花崗巖的侵位，表明早石炭世((342.5±4.9) Ma)存在古亞洲洋向華北板塊北緣的俯沖事件。

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Early Carboniferous Tectonic Attribute of the Central-Northern Margin of North China Craton: Constraints from Geochemistry of Highly Fractionated Ⅰ-Type Granites in Cahayouhouqi Area

Liu Qun1，Wang Wanqiong2，Qiu Dianming3，Bai Xinhui4，Zhang Jinfeng4，Wang Xin4

1.HeilongjiangInstituteofGeophysicalExploration，Harbin150036，China2.SchoolofGeoscienceandTechnology,SouthwestPetroleumUniversity,Chengdu610500,China3.EditorialDepartmentofJournal,JilinUniversity,Changchun130026,China4.CollegeofEarthScience,JilinUniversity,Changchun130061,China

This study focuses on the petrology and geochemistry of the monzonitic granites from the Cahayouhouqi area in Inner Mongolia. Tectonically it is located in the central-northern margin of the North China craton. These rocks have high content of silica, kalium and alkalis, low abundance of calcium, phosphorus, iron, magnesium;w(P2O5) decreases with the increasing ofw(SiO2); A/CNK equals 0.96-1.15; and differentiation index DI is between 90.36-92.96. The granites consist mainly of perthite, plagioclase, quartz, minor biotite, no mafic alkaline minerals and Al-rich minerals; their accessory minerals are zircon, magnetite, apatite, sphene and ilmenite. Combined with the petrological and geochemical characteristics, the granites can be classified as a highly fractionated I-type granite. The low content of ∑REE ((46.8-94.4)×10-6), Th ((1.74-2.39)×10-6), and U ((0.27-0.39)×10-6), as well as their trace element discrimination diagrams indicate that the magma source derived from the lower crust， and their source-rock was lithosphere mantle. The chondrite normalized patterns are right declined with a serious positive Eu anomaly (δEu=0.83-3.51). They are enriched in the large ion lithophile elements (LILEs, e.g., Cs, Rb, Ba, and K), and depleted of the high field-strength elements (HFSEs, e.g., Nb, Ta, P, and Ti). Their geochemical characteristics indicates that the monzonitic granites emplaced in an active continental margin as a result of the Early Carboniferous subduction of Paleo-Asian Ocean towards the northern margin of the North China craton.

northern margin North China craton; Inner Mongolia; Early Carboniferous; highly fractionated I-type granites; active continental margin arc; Paleo-Asian Ocean

10.13278/j.cnki.jjuese.201504115.

2014-10-21

中國地質(zhì)調(diào)查局區(qū)域地質(zhì)大調(diào)查項(xiàng)目(1212011120709，1212011220459)

劉群(1962--)，男，高級工程師，主要從事地質(zhì)勘查工作和基礎(chǔ)地質(zhì)方面研究，E-mail:hrb-liuqun@sohu.com

王挽瓊(1986--)，女，講師，主要從事火成巖與區(qū)域地質(zhì)調(diào)查方面研究，E-mail:ww_q2006@126.com。

10.13278/j.cnki.jjuese.201504115

P588.12

A

劉群，王挽瓊，邱殿明，等.華北板塊北緣中段早石炭世構(gòu)造屬性: 察哈爾右翼后旗高分異Ⅰ型花崗巖地球化學(xué)的制約.吉林大學(xué)學(xué)報(bào):地球科學(xué)版,2015,45(4):1121-1131.

Liu Qun, Wang Wanqiong, Qiu Dianming, et al. Early Carboniferous Tectonic Attribute of the Central-Northern Margin of North China Craton: Constraints from Geochemistry of Highly Fractionated Ⅰ-Type Granites in Cahayouhouqi Area.Journal of Jilin University:Earth Science Edition,2015,45(4):1121-1131.doi:10.13278/j.cnki.jjuese.201504115.