陳繼平，羅婷，王暉，廖群安，張雄華，陳恩科，王杰杰，孟秦宇，柳小明

(1．陜西省地質(zhì)調(diào)查中心，陜西 西安 710068；2.中國地質(zhì)大學(xué)(武漢)地球科學(xué)學(xué)院，湖北 武漢 430074 ；3.西北大學(xué)大陸動(dòng)力學(xué)國家重點(diǎn)實(shí)驗(yàn)室，陜西 西安 710069)

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新疆黃山鎂鐵-超鎂鐵巖帶鋯石Hf同位素特征及源區(qū)性質(zhì)探討

陳繼平1，羅婷1，王暉1，廖群安2，張雄華2，陳恩科1，王杰杰1，孟秦宇1，柳小明3

(1．陜西省地質(zhì)調(diào)查中心，陜西 西安 710068；2.中國地質(zhì)大學(xué)(武漢)地球科學(xué)學(xué)院，湖北 武漢 430074 ；3.西北大學(xué)大陸動(dòng)力學(xué)國家重點(diǎn)實(shí)驗(yàn)室，陜西 西安 710069)

黃山東、香山及土墩巖體均為多階段侵入的雜巖體，巖體與圍巖為侵入接觸關(guān)系，顯示熱侵位特征。巖石組成單元主要為超鎂鐵質(zhì)橄欖巖和鎂鐵質(zhì)輝長巖。巖石化學(xué)組成以拉斑玄武巖系列為主，存在部分鈣堿性系列和堿性系列。稀土元素具平坦的分配型式或輕稀土略富集的分配型式。鋯石Hf同位素指示巖石來源于虧損型地幔源區(qū)。黃山東、香山及土墩鎂鐵-超鎂鐵巖不是俯沖洋殼的殘余或者島弧環(huán)境的阿拉斯加型巖體，而是來源于虧損型地幔源區(qū)的巖漿底侵形成。

鎂鐵-超鎂鐵巖；鋯石；Hf同位素；源區(qū)性質(zhì)；東天山

產(chǎn)出于造山帶的鎂鐵-超鎂鐵質(zhì)巖能夠?yàn)槠溲莼瘹v史提供重要的信息，蛇綠巖帶中的鎂鐵-超鎂鐵質(zhì)巖是識(shí)別板塊縫合區(qū)的重要標(biāo)志(DILEK, 2003；SENG?R et al., 2004；ROBINSON et al., 2008；PEARCE et al., 2010)，且在許多蛇綠巖帶中鎂鐵-超鎂鐵質(zhì)巖賦存有豆莢狀鉻鐵礦床(NALDRETT et al.,1989；ZHOU et al.,1996；ZHANG et al., 2008；SHI et al., 2012)，但對(duì)于那些產(chǎn)于造山帶中與蛇綠巖無關(guān)的鎂鐵-超鎂鐵質(zhì)巖，它們?cè)从谏系蒯?HIMMELBERG et al., 1995；KUSKY et al., 2007；PIRAJNO et al., 2008；SANTOSH et al., 2009；AO et al., 2010；CAI et al., 2012)可以作為認(rèn)識(shí)深部地質(zhì)作用，地幔礦物組成的探針對(duì)于探討地幔演化過程、巖漿成因、殼幔巖漿作用以及大陸動(dòng)力學(xué)等方面具有重要的指示意義。

黃山-鏡爾泉巖帶位于康古爾斷裂與雅滿蘇斷裂之間(圖1)，受覺羅塔格造山帶-康古爾韌性剪切帶控制，該巖帶發(fā)現(xiàn)最早，研究程度最高，雜巖體數(shù)量最多，西起恰特卡爾塔格、東至鏡爾泉地區(qū)的圖拉爾根，大大小小約二十幾個(gè)，巖體規(guī)模均不大，露頭面積最大者不足10 km2，最小者只有幾平方米，地表形態(tài)呈近等軸狀或透鏡狀。由于該巖帶產(chǎn)有重要的銅鎳礦，因此吸引了許多地質(zhì)學(xué)家對(duì)其進(jìn)行研究，積累了豐富的資料，但仍存在爭議：部分被認(rèn)為是洋殼俯沖的殘余(白云來，1993；朱文斌等，1996)、部分被認(rèn)為產(chǎn)于碰撞后伸展環(huán)境(PIRAJNO et al., 2008；ZHOU et al., 2004)、或者是產(chǎn)于與俯沖有關(guān)的島弧環(huán)境(AO et al., 2010；郭繼春等，1992)。因此，弄清楚這些巖體的成因及構(gòu)造環(huán)境對(duì)于理解造山運(yùn)動(dòng)的機(jī)制以及增生造山帶的構(gòu)造演化具有重要意義。筆者選取了黃山東、香山、土墩3個(gè)代表性巖體作為研究對(duì)象，通過巖石地球化學(xué)及鋯石同位素?cái)?shù)據(jù)分析，討論巖漿源區(qū)及其形成的構(gòu)造背景，得出巖石成因。

①.康古爾斷裂；②.雅滿蘇斷裂；③.阿奇克庫都克斷裂；④.紅柳河斷裂；⑤.黃山-鏡爾泉鎂鐵-超鎂鐵質(zhì)巖帶；⑥.白石泉鎂鐵-超鎂鐵質(zhì)巖帶；⑦.城北鎂鐵-超鎂鐵質(zhì)巖帶圖1 東天山及北山裂谷帶鎂鐵-超鎂鐵質(zhì)雜巖體分布圖(據(jù)SU et al., 2011修改)Fig.1 The distribution of mafic-ultramafic complexes in the Eastern Tianshan and Beishan rift zone(After SU et al., 2011)

1 巖體地質(zhì)地球化學(xué)特征概述

黃山巖帶包含黃山東、黃山、香山、黃山南及西邊的土墩巖體，香山斷裂(F8)、黃山斷裂(F9)以及干洞斷裂(F12)從巖體附近穿過，由于其長期活動(dòng)，出現(xiàn)了一些派生小斷裂，控制了巖體的形態(tài)與產(chǎn)狀。巖體侵入的地層為上石炭統(tǒng)梧桐窩子組及下石炭統(tǒng)干墩組(圖2)，與圍巖接觸帶局部可見圍巖捕虜體和巖脈穿插圍巖的現(xiàn)象(王潤民等，1987)，而圍巖普遍受到熱接觸變質(zhì)而角巖化(張耀華，1987)，接觸帶可見石榴子石等熱接觸變質(zhì)礦物及重結(jié)晶礦物，顯示熱侵位特征(GU et al., 1995)。 梧桐窩子組為一套海相火山巖、火山碎屑巖-正常碎屑巖沉積*張興龍,李文鉛,李松齡,等.1∶25萬五堡幅區(qū)調(diào)報(bào)告， 2004.；干墩組為一套深灰色-灰黑色淺變質(zhì)的硅質(zhì)巖、凝灰?guī)r及少量的基性火山巖(蔡土賜，1999)。區(qū)內(nèi)華力西期不同侵入次閃長巖體和花崗巖體與鎂鐵-超鎂鐵質(zhì)巖體密切伴生，部分巖體直接侵入到鎂鐵-超鎂鐵質(zhì)巖中。

1.第四系；2.上石炭統(tǒng)梧桐窩子組；3.下石炭統(tǒng)干墩組；4.華力西期花崗巖；5.閃長巖；6.基性-超基性巖；7.銅鎳礦圖2 黃山一帶區(qū)域地質(zhì)圖(底圖引自董連慧等，2011*董連慧，等.覆蓋區(qū)礦產(chǎn)預(yù)測(cè)與示范驗(yàn)證天山區(qū)委托業(yè)務(wù)實(shí)施方案， 2010.)Fig.2 Geological map of the Huangshan area(After DONG et al., 2011)

黃山東、香山與土墩巖體巖石組合差異不大，超鎂鐵質(zhì)橄欖巖(堆晶二輝橄欖巖、單輝(方輝)橄欖巖)和鎂鐵質(zhì)輝長巖均有產(chǎn)出。鎂鐵質(zhì)巖為角閃輝長巖，但3個(gè)巖體角閃輝長巖的角閃石含量差異很大。香山角閃輝長巖中角閃石含量可達(dá)35%，黃山東與土墩巖體角閃輝長巖中角閃石含量均小于10%。角閃輝長巖中斜長石基本上為拉長石(An52～An60)，部分為中長石(An43～An44)，中長石出現(xiàn)在含礦輝綠巖或含礦角閃輝長巖中。巖體中輝石有斜方輝石和單斜輝石2類，以單斜輝石為主，產(chǎn)于超鎂鐵質(zhì)單輝橄欖巖中或鎂鐵質(zhì)角閃輝長巖中的為普通輝石或透輝石；斜方輝石多產(chǎn)于超鎂鐵質(zhì)巖中，為紫蘇輝石(黃山東、香山巖體)或古銅輝石、易變輝石(土墩巖體)。

在SiO2-(Na2O+K2O)圖解中，土墩鎂鐵-超鎂鐵質(zhì)巖均落入亞堿性系列范圍，樣品為橄欖巖成分或輝長巖成分，黃山東鎂鐵-超鎂鐵質(zhì)巖中輝長巖(D010)落入堿性系列，其余樣品為亞堿性系列，香山鎂鐵-超鎂鐵質(zhì)巖中有2個(gè)輝長巖和一個(gè)輝綠巖樣品為堿性系列，其余樣品為亞堿性系列。筆者將屬于亞堿性系列的黃山東、香山及土墩鎂鐵-超鎂鐵質(zhì)巖進(jìn)行AFM圖解和SiO2-TFeO/MgO圖解投點(diǎn)，黃山東、香山及土墩鎂鐵-超鎂鐵質(zhì)巖具有鈣堿性和拉斑系列之分，但以拉斑系列為主(圖3)。ACM圖解中超鎂鐵質(zhì)巖均屬于堆晶成因。

球粒隕石標(biāo)準(zhǔn)化稀土元素配分曲線為平坦型(土墩、香山巖體)或輕稀土略富集型(黃山東巖體)，原始地幔標(biāo)準(zhǔn)化微量元素特征表現(xiàn)為相對(duì)富集大離子親石元素(K、Sr、Ba、U)， 相對(duì)虧損高場強(qiáng)元素(Nb、Ta、P、Ti)及 Th，適度虧損Zr、Hf(陳繼平等，2013)。

2 鋯石樣品來源及測(cè)試方法

鋯石原位Lu-Hf同位素微區(qū)測(cè)定在中國地質(zhì)大學(xué)(武漢)地質(zhì)過程與礦產(chǎn)資源國家重點(diǎn)實(shí)驗(yàn)室中完成，采用Neptune Plus MC-ICP-MS系統(tǒng)在鋯石U-Pb定年分析的同一位置上進(jìn)行。測(cè)試的激光束直徑為44 μm，使用91500、GJ-1和Monastery作為鋯石標(biāo)樣檢測(cè)分析數(shù)據(jù)，每完成8個(gè)鋯石點(diǎn)的測(cè)定，加測(cè)GJ-1和Monastery一次，實(shí)驗(yàn)過程中，91500和GJ-1的176Hf/177Hf測(cè)定結(jié)果分別為0.282 294±0.000 008(1σ，n=6)、0.281 992±0.000 008(1σ，n=9)，詳細(xì)分析方法及參數(shù)參考YUAN et al(YUAN et al., 2008)。

MC.鎂鐵質(zhì)堆晶巖；UC.超鎂鐵質(zhì)堆晶巖；UMC.鎂鐵-超鎂鐵質(zhì)堆晶巖圖3 (a)SiO2-(Na2O+K2O)巖石分類圖解(據(jù)MIDDLEMOST et al., 1994)、(b)SiO2-TFeO/MgO圖解(據(jù)MIYASHIRO A.,1974)、(c)ACM圖解(據(jù)COLEMAN et al., 1977)和(d)AFM巖石系列判別圖解(據(jù)IRVINE et al.,1971 和COLEMAN.,1977)Fig.3 (a)Rock classification plots of SiO2 vs. (Na2O+K2O)(After MIDDLEMOST., 1994), (b)SiO2 vs. TFeO/MgO(After MIYASHIRO.,1974),(c)ACM diagram(After COLEMAN., 1977), (d)AFM diagram(After IRVINE et al.,1971 and COLEMAN.,1977)

3 測(cè)試結(jié)果

黃山東、香山及土墩角閃輝長巖鋯石用LA-ICP-MS進(jìn)行測(cè)試分析，測(cè)試樣品均新鮮，無蝕變。所測(cè)鋯石呈半自形-自形，短柱狀、 長柱狀居多，少數(shù)為不規(guī)則的粒狀，陰極發(fā)光圖像顯示多數(shù)鋯石具有較寬的結(jié)晶環(huán)帶，為典型的巖漿鋯石。測(cè)試結(jié)果顯示黃山東巖體結(jié)晶年齡為(276.9±1.3)Ma，香山巖體結(jié)晶年齡為(285.6±0.89)Ma，土墩巖體結(jié)晶年齡為(298.37±0.94)Ma(圖4)。

圖4 鋯石陰極發(fā)光圖像(實(shí)圈為鋯石年齡測(cè)試點(diǎn)，虛線圈為鋯石Hf同位素分析點(diǎn))及鋯石U-Pb諧和圖Fig.4 CL images of zircons and zircon U-Pb concordia diagrams

黃山東角閃輝長巖D003-1號(hào)樣品、香山角閃輝長巖XS1-1號(hào)樣品及土墩角閃輝長巖TD1-1號(hào)樣品鋯石原位Hf同位素分析結(jié)果如表1所示，D003-1樣品14顆鋯石的176Hf/177Hf初始值為0.282 970～0.283 029，加權(quán)平均值為0.283 003，εHf(t)變化于13.068 304～15.218 292；香山XS1-1中16顆鋯石初始值變化范圍較窄((176Hf/177Hf)i=0.282 921～0.282 988，Mean=0.282 962)，εHf(t)變化于11.540 684～13.910 124；土墩角閃輝長巖TD1-1樣品9顆鋯石的176Hf/177Hf初始值變化于0.282 969～0.283 022，均值為0.282 990，εHf(t)變化于13.541 364～15.418 109。

黃山東、香山及土墩輝長巖鋯石Hf同位素組成圖解中(圖5)，測(cè)點(diǎn)位于虧損地幔演化線附近，離球粒隕石演化線較遠(yuǎn)，暗示鋯石源于較球粒隕石的εHf(t)值強(qiáng)分異的虧損型地幔源區(qū)。

黃山東、香山及土墩輝長巖鋯石εHf(t)存在差異，黃山東及土墩εHf(t)變化區(qū)間較為一致，而香山εHf(t)則相對(duì)較小，說明三者巖漿源區(qū)虧損程度不一致，黃山東及土墩鋯石來源于比香山鋯石更虧損的地幔源區(qū)。

圖5 鋯石Hf同位素組成圖解Fig.5 Zircon Hf isotopic diagrams

筆者對(duì)黃山東、香山及土墩角閃輝長巖鋯石用LA-ICP-MS進(jìn)行分析，在鋯石原位進(jìn)行Lu-Hf同位素微區(qū)測(cè)定。三者εHf(t)值較高，均大于11，表明巖漿中幔源物質(zhì)貢獻(xiàn)巨大。黃山東巖體結(jié)晶年齡為276.9 Ma， TDM1變化于309～392 Ma，二者相差82～174 Ma；香山巖體結(jié)晶年齡為285 Ma，TDM1變化于367～458 Ma，二者相差30～116 Ma；土墩巖體結(jié)晶年齡為298.3 Ma， TDM1變化于319～395 Ma，二者相差20～97 Ma。其TDM1年齡均與巖體結(jié)晶年齡相近，稍大于巖漿結(jié)晶年齡，表明它們來源于虧損地幔，受到過地殼物質(zhì)的混染(吳福元等，2007)。香山、土墩及黃山東鋯石TDM1年齡峰值分別365 Ma、360 Ma、325 Ma，其巖漿從地幔熔融的時(shí)間均在早石炭世，暗示了早石炭世黃山地區(qū)存在重要的地質(zhì)事件，可能與天山洋的俯沖存在關(guān)聯(lián)，天山及鄰區(qū)下石炭統(tǒng)火山巖系與下伏地層之間呈不整合接觸，且呈區(qū)域性、分布廣泛(夏林圻等，2002)，暗示天山洋在早石炭世閉合，可能大于320 Ma。

4 源區(qū)性質(zhì)討論

黃山東、香山及土墩巖體巖石的鋯石Hf同位素指示其來源于虧損的地幔源區(qū)。稀土元素分配型式為平坦型(香山及土墩巖體)或輕稀土略富集的分配型式(黃山東巖體)，與由軟流圈產(chǎn)生的大陸玄武巖特征相似(夏林圻等，2007)，在εNd(t)-(87Sr/86Sr)i圖解中，樣品位于OIB和MORB區(qū)域(圖6)，指示其源區(qū)以軟流圈物質(zhì)為主導(dǎo)。黃山東、香山及土墩巖體鎂鐵質(zhì)巖各巖相中含有5%～35%的巖漿結(jié)晶角閃石，說明巖漿源區(qū)存在富水特征。巖石化學(xué)組成上以拉斑玄武巖系列為主，同時(shí)存在部分鈣堿性系列和堿性系列，樣品總體表現(xiàn)為相對(duì)富集大離子親石元素K、Sr、Ba，有較明顯的Nb、Ta虧損及弱Ti負(fù)異常，指示其地幔源區(qū)經(jīng)歷了俯沖事件的交代作用(IONOV et al.,1995)，交代流體主要富集大離子親石元素，而虧損高場強(qiáng)元素。洋殼俯沖過程中產(chǎn)生的流體相會(huì)將活動(dòng)性強(qiáng)的元素帶入上覆地幔楔，而虧損高場強(qiáng)元素(Nb、Ta、Ti)，從而使分配系數(shù)相近的一些不相容元素比值發(fā)生變化，La/Nb、Ba/Na值升高、Nb/Th降低等。在La/Nb-La/Ba圖解中，樣品點(diǎn)多數(shù)顯示此特征，位于受俯沖改造的巖石圈地幔區(qū)域。夏明哲等(2010)利用Sr-Nd同位素模擬黃山東巖體地幔源區(qū)特征，認(rèn)為存在約10%的EMII型富集地幔加入到了虧損型地幔源區(qū)(夏明哲等，2010)。因此，黃山東、香山及土墩巖體的巖漿源區(qū)以軟流圈為主導(dǎo)，存在部分受俯沖改造的巖石圈地幔組分。

圖6 鎂鐵質(zhì)-超鎂鐵質(zhì)雜巖巖漿源區(qū)判別圖解(Sr-Nd同位素：黃山東引自夏明哲等，2010，香山數(shù)據(jù)引自TANG et al., 2013)Fig.6 Discriminative diagrams of Magma source(Sr-Nd isotope：Huangshandong data from XIA et al., 2010，Xiangshan data from TANG et al., 2013)

5 結(jié)論

本次研究確定的黃山東巖體鋯石U-Pb年齡為(276.9±1.3) Ma，香山巖體U-Pb年齡為(285.6±0.89) Ma，土墩巖體U-Pb年齡(298.37±0.94) Ma，說明本區(qū)鎂鐵-超鎂鐵巖帶形成于二疊紀(jì)。結(jié)合鋯石Lu-Hf同位素測(cè)定數(shù)據(jù)計(jì)算，黃山東巖體鋯石εHf(t)值為13.06～15.21；香山巖體鋯石εHf(t)值為11.54～13.91；土墩巖體鋯石εHf(t)值為13.54～15.42。筆者認(rèn)為本區(qū)鎂鐵-超鎂鐵巖有關(guān)巖漿起源于虧損型地幔源區(qū)，與前人Sr-Nd同位素研究結(jié)果基本吻合。

白云來. 新疆哈密黃山-鏡兒泉鎳銅成礦系統(tǒng)的地質(zhì)構(gòu)造背景[J]. 甘肅地質(zhì)學(xué)報(bào), 2000, 9(2): 1-7.

BAI Yunlai. Geotectonic settings of Huangshan-Jingerquan Nickel-Copper metallogenic system in Hami, Xinjiang[J]. Acta Geologica Gansu, 2000, 9(2): 1-7.

朱文斌, 馬瑞士, 王賜銀. 論新疆東部黃山-鏡兒泉雜巖帶的構(gòu)造屬性[J]. 地質(zhì)科學(xué), 1996, 31(1): 22-32.

ZHU Wenbin, MA Ruishi, WANG Ciyin. Tectonic attribute of Huangshan-Jingerquan complex in Eastern Xinjiang, China[J]. Sceentia Geologica Sinica, 1996, 31(1): 22-32.

郭繼春, 胡受奚, 顧連興, 等. 東天山 (E85-90) 加里東溝-弧-盆褶皺系的地質(zhì)特征及其構(gòu)造演化[J]. 南京大學(xué)學(xué)報(bào) (自然科學(xué)版), 1992, 28(3): 431-438.

GUO Jichun, HU Shouxi, GU Lianxing, et al. Geological features and tectontc evolution East TianshanCaledonian trench-arc-basin foldbelt[J]. Journal of NanJing University(Natural Sciences Edition), 1992, 28(3): 431-438.

王潤民, 李楚思. 新疆哈密黃山東銅鎳硫化物礦床成巖成礦的物理化學(xué)條件[J]. 成都地質(zhì)學(xué)院學(xué)報(bào), 1987, 14(3): 1-9.

WANG Runmin, LI Chusi. Physicochemicalcondition of rock formation and mineralization of Huangshandong magmatogenic sulfide deposit HaMi, Xinjiang, China[J]. Journal of Chengdu College of Geology, 1987, 14(3): 1-9(in Chinese with English abstract).

張耀華. 新疆黃山東基性-超基性雜巖體地質(zhì)特征及其含礦性[J]. 西北地質(zhì), 1987, (4): 15-31.

蔡土賜. 新疆維吾爾自治區(qū)巖石地層[M]. 武漢: 中國地質(zhì)大學(xué)(武漢)出版社, 1999： 1-430.

陳繼平，廖群安，張雄華，等. 東天山地區(qū)黃山東與香山鎂鐵-超鎂鐵質(zhì)雜巖體對(duì)比[J]．地球科學(xué)，2013, 38(6)：1-14．

CHEN Jiping, LIAO Qunan, ZHANG Xionghua, et al. Contrast of Huangshandong and Xiangshan Mafic-Ultramafic complex, East Tianshan[J]. Earth Science-Journal of China University of Geosciences, 2013, 38(6)：1-14(in Chinese with English abstract)．

劉民武. 中國幾個(gè)鎳礦床的地球化學(xué)比較研究[D]. 西安：西北大學(xué), 2003.

LIU Minwu. Geochemical comparison of several nickel deposits in China[D]. Xi’an:Northwest University, 2003(in Chinese with English abstract).

張魁武, 沈步明, 李達(dá)周, 等. 阿拉斯加型超鎂鐵質(zhì)巖的巖石化學(xué)特征[J]. 地質(zhì)論評(píng), 1988, 34(3): 377-382.

顧連興, 諸建林, 郭繼春, 等. 造山帶環(huán)境中的東疆型鎂鐵-超鎂鐵雜巖[J]. 巖石學(xué)報(bào), 1994, 10(4): 356-399.

GU Lianxing, ZHU Jianlin, GUO Jichun, et al. The East Xinjiang-type Mafic-Ultramafic complexes in orogenic environments[J]. Acta Petrologica Sinica, 1994, 10(4): 356-399(in Chinese with English abstract).

吳福元, 李獻(xiàn)華, 鄭永飛, 等.Lu-Hf同位素體系及其巖石學(xué)應(yīng)用[J]. 巖石學(xué)報(bào), 2007, 23(2):185-220.

WU Fuyuan, LI Xianhua, ZHENG Yongfei, et al. Lu-Hf isotopic systematics and their applications in petrology [J]. Acta Petrologica Sinica, 2007, 23(2):185-220(in Chinese with English abstract).

夏林圻, 張國偉, 夏祖春, 等. 天山古生代洋盆開啟、閉合時(shí)限的巖石學(xué)約束-來自震旦紀(jì)、石炭紀(jì)火山巖的證據(jù)[J]. 地質(zhì)通報(bào), 2002, 21(2): 55-62.

XIA Linqi, ZHANG Guowei, XIA Zuchun, et al. Constraints on the timing of opening and closing of the Tianshan Paleozonic oceanic basin : ecvidence from Sinina and Carboniferous volcanic rocks[J]. Geological Bulietin of China, 2002, 21(2): 55-62(in Chinese with English abstract).

夏林圻, 夏祖春, 徐學(xué)義, 等. 利用地球化學(xué)方法判別大陸玄武巖和島弧玄武巖[J]. 巖石礦物學(xué)雜志, 2007, 26(1): 77-89.

XIA Linqi, XIA Zuchun, XU Xueyi, et al. The discrimination between continental basalt and islanf arc basalt based on geochemical method[J]. Acta Petroligical et Mineralogica, 2007, 26(1): 77-89(in Chinese with English abstract).

夏明哲, 姜常義, 錢壯志, 等. 新疆東天山黃山東巖體巖石地球化學(xué)特征與巖石成因[J]. 巖石學(xué)報(bào), 2010, 26(8): 2413-2430.

XIA Mingzhe, JIANG Changyi, QIAN Zhuangzhi, et al. Geochemistry and petrogenesis of Huangshandong intrusion, East Tianshan, Xinjiang[J]. Acta Petrologica Sinica, 2010, 26(8): 2413-2430(in Chinese with English abstract).

唐俊華, 顧連興, 張遵忠, 等. 東天山黃山-鏡兒泉過鋁花崗巖礦物學(xué), 地球化學(xué)及年代學(xué)研究[J]. 巖石學(xué)報(bào), 2008, 24(5): 921-946.

TANG Junhua, GU Lianxin, ZHANG Zunzhong, et al. Peralumious granite in Huangshan-Jingerquan area of eastern Tianshan : Geochemistry, mineralogy and geochronology[J]. Acta Petrologica Sinica, 2008, 24(5): 921-946(in Chinese with English abstract).

DILEK Y. Ophiolite concept and its evolution. In: Dilek Y, Newcomb S. (Eds.)[J]. Ophiolite concept and the evolution of geological thought: Geological Society of America Special Papers. 2003: 1-16.

SENG?R AC, NATAL’IN BA. Phanerozoic analogues of Archaean oceanic basement fragments: Altaid ophiolites and ophirags[J]. Developments in Precambrian Geology, 2004, 13(1): 675-726.

ROBINSON PT, ZHOU MF. The origin and tectonic setting of ophiolites in China[J]. Journal of Asian Earth Sciences, 2008, 32(5): 301-307.

PEARCE JA, ROBINSON PT. The Troodos ophiolitic complex probably formed in a subduction initiation, slab edge setting [J]. Gondwana Research, 2010, 18(1): 60-81.

NALDRETT AJ, VON Gruenewaldt G. Association of platinum-group elements with chromitite in layered intrusions and ophiolite complexes[J]. Economic Geology, 1989, 84(1): 180-187.

ZHOU MF, ROBINSON PT, MALPAS J, et al. Podiform chromitites in the Luobusa ophiolite (Southern Tibet): Implications for melt-rock interaction and chromite segregation in the upper mantle[J]. Journal of Petrology, 1996, 37(1): 3-21.

ZHANG Q, WANG CY, LIU DY, et al. A brief review of ophiolites in China[J]. Journal of Asian Earth Sciences, 2008, 32(5): 308-324.

SHI R, GRIFFIN W L, O’’REILLY S Y, et al. Melt/mantle mixing produces podiform chromite deposits in ophiolites: Implications of Re-Os systematics in the Dongqiao Neo-Tethyan ophiolite, northern Tibet[J]. Gondwana Research, 2012, 21(1): 194-206.

HIMMELBERG GR, LONEY RA. Characteristics and petrogenesis of Alaskan-type ultramafic-mafic intrusions, southeastern Alaska[M]. Washington: United States Government Printing Office, 1995：1-47.

KUSKY TM, GLASS A, TUCKER R. Structure, Cr-chemistry, and age of the Border Ranges Ultramafic-Mafic Complex: A suprasubduction zone ophiolite complex. In: Ridgway KD, Trop JM, Glen JM G, O’Neill JM.(Eds.), Tectonic growth of a collision continental margin: crustal evolution of Southern Alaska: Geological Society of America Special Papers, 2007, 431: 207-225.

PIRAJNO F, MAO JW, ZHANG ZH, et al. The association of mafic-ultramafic intrusions and A-type magmatism in the Tian Shan and Altay orogens, NW China: implications for geodynamic evolution and potential for the discovery of new ore deposits[J]. Journal of Asian Earth Sciences, 2008, 32(2): 165-183.

SANTOSH M, MARUYAMA S, YAMAMOTO S. The making and breaking of supercontinents: some speculations based on superplumes, super downwelling and the role of tectosphere[J]. Gondwana Research, 2009, 15(3): 324-341.

AO SJ, XIAO WJ, HAN CM, et al. Geochronology and geochemistry of Early Permian mafic-ultramafic complexes in the Beishan area, Xinjiang, NW China: implications for late Paleozoic tectonic evolution of the southern Altaids[J]. Gondwana Research, 2010, 18(2): 466-478.

CAI KD, SUN M, YUAN C, et al. Keketuohai mafic-ultramafic complex in the Chinese Altai, NW China: Petrogenesis and geodynamic significance[J]. Chemical Geology, 2012, 294(295): 26-41.

SU BX, QIN K Z, SAKYA P A, et al. U-Pb ages and Hf-O isotopes of zircons from Late Paleozoic mafic-ultramafic units in the southern Central Asian Orogenic Belt: Tectonic implications and evidence for an Early-Permian mantle plume[J]. Gondwana Research, 2011, 20(2): 516-531.

ZHOU MF, MICHAEL LESHER C, YANG ZX, et al. Geochemistry and petrogenesis of 270Ma Ni-Cu-(PGE) sulfide-bearing mafic intrusions in the Huangshan district, Eastern Xinjiang, Northwest China: implications for the tectonic evolution of the Central Asian orogenic belt[J]. Chemical Geology, 2004, 209(3): 233-257.

GU L X, ZHU JL, GUO JC, et al. Geology and genesis of the mafic-ultramafic complexes in the Huangshan-Jingerquan (HJ) belt, East Xinjiang[J]. Chinese Journal of Geochemistry, 1995, 14(2): 97-116.

YUAN HL, GAO S, DAI MN, et al. Simultaneous determinations of U-Pb age, Hf isotopes and trace element compositions of zircon by excimer laser-ablation quadrupole and multiple-collector ICP-MS[J]. Chemical Geology, 2008, 247(1): 100-118.

MCDONOUGH WF, SUN SS. The composition of the Earth[J]. Chemical Geology, 1995, 120(3): 223-253.

FREY FA, PRINZ M. Ultramafic inclusions from San Carlos, Arizona: petrologic and geochemical data bearing on their petrogenesis[J]. Earth and Planetary Science Letters, 1978, 38(1): 129-176.

MIDDLEMOST E AK. Naming materials in the magma/igneous rock system[J]. Earth-Science Reviews, 1994, 37(3): 215-224.

MIYASHIOR A. Volcanic rock series in island arcs and active continental margins[J]. American Journal of Science, 1974, 274(4): 321-355.

COLEMAN RG, Ophiolites: ancient oceanic lithosphere[M]. Berlin: Springer-Verlag Berlin, 1977： 1-230.

IRVINE T, BARAGAR W. A guide to the chemical classification of the common volcanic rocks[J]. Canadian Journal of Earth Sciences, 1971, 8(5): 523-548.

SUN SS, MCDONGOUGH WF. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes[J]. Geological Society, London, Special Publications, 1989, 42(1): 313-345.

SUN SS. Chemical composition and origin of the Earth’s primitive mantle[J]. Geochimica et Cosmochimica Acta, 1982, 46(2): 179-192.

BLICHERT-TOFT J, Albarède F. The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle-crust system[J]. Earth and Planetary Science Letters, 1997, 148(1): 243-258.

GRIFFIN WL, PEARSON NJ, BELOUSOVA E, et al. The Hf isotope composition of cratonic mantle: LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites[J]. Geochimica et Cosmochimica Acta, 2000, 64(1): 133-147.

AMELIN Y, LEE D, HALLIDAY AN, et al. Nature of the Earth’s earliest crust from hafnium isotopes in single detrital zircons[J]. Nature, 1999, 399(6733): 252-255.

S?DERLUND U, PATCHETT PJ, VERVOORT JD, et al. The 176Lu decay constant determined by Lu-Hf and U-Pb isotope systematics of Precambrian mafic intrusions[J]. Earth and Planetary Science Letters, 2004, 219(3): 311-324.

IONOV DA, HOFMANN AW. Nb-Ta-rich mantle amphiboles and micas: Implications for subduction-related metasomatic trace element fractionations[J]. Earth and Planetary Science Letters, 1995, 131(3): 341-356.

TANG DM, QIN KZ, SU BX, et al. Magma source and tectonics of the Xiangshanzhong mafic-ultramafic intrusion in the Central Asian Orogenic Belt, NW China, traced from geochemical and isotopic signatures[J]. Lithos, 2013, 2(13):144-163

SYLVESTER PJ. Post-collisional strongly peraluminous granites[J]. Lithos, 1998, 45(1): 29-44.

Zircon Hf Isotope Characteristics and Source of Mafic-ultramafic Intrusions in Huangshan Region, Xinjiang

CHEN Jiping1, LUO Ting1, WANG Hui1, LIAO Qun’an2, ZHANG Xionghua2,CHEN Enke1, WANG Jiejie1, MENG Qinyu1, LIU Xiaoming3

(1.Shaanxi Center of Geological Survey, Xi’an 710068, Shaanxi, China; 2.School of Earth Sciences,China University of Geosciences, Wuhan 430074, Hubei, China; 3.State Key Laboratory of Continental Dynamics, Northwest University,Xi’an 710069, Shaanxi, China)

Huangshandong, Xiangshan and Tudun plutons are multiple-phase intrusive complexs, which show clear intrusive contact boundaries with wall rock. These intrusions are mainly composed of peridotite and gabbro. Peridotite has orthopyroxene or plagioclase, while clinopyroxene is augite or diopside. The Huangshandong, Xiangshan and Tudun plutons are mainly tholeiitic in composition, and some of them show calc-alkaline and alkaline characteristics. Chondrite-normalized rare earth element patterns show flat feature or slight enrichment in LREE. Zircon Hf isotopic compositions indicate that the Huangshandong, Xiangshan and Tudun intrusive complexes are derived from the depleted mantle source.Huangshandong, Xiangshan and Tudun plutons are not the remnants of subducted oceanic crust or Alaska-type rocks, but they are formed by the underplating of depleted mantle source.

mafic-ultramafic rocks; zircon; Hf isotope; source characteristics;eastern Tianshan

2016-03-02；

2016-05-03

中國地質(zhì)調(diào)查局地質(zhì)調(diào)查工作項(xiàng)目(1212011085469)

陳繼平(1987-)，工程師，從事巖石地球化學(xué)方面的研究工作。E-mail: dddxycjp@163.com

P597.3

A

1009-6248(2016)04-0051-11