岩石学报  2016, Vol. 32 Issue (6): 1770-1794   PDF    
西天山巴音布鲁克地区早古生代成矿地质环境:岩浆岩及其时代和元素同位素约束
邢浩, 赵晓波, 张招崇, 叶锦超, 冯博    
地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083
摘要: 西天山位于中亚造山带(CAOB)西南部,是其重要组成部分。CAOB晚古生代金属成矿环境和过程尤为典型,但早古生代成矿地质环境还不甚清楚。新疆巴音布鲁克地区出露(原定时代晚志留世)巴音布鲁克组火山岩夹浅海相碎屑岩和灰岩,是认识西天山早古生代成矿地质环境的难得对象。巴音布鲁克组出露于Nikolaev-那拉提山北缘断裂与Atbash-Inylchek-那拉提山南缘断裂之间的中天山,在巴音布鲁克地区典型发育,火山岩包括玄武岩、玄武安山岩、英安岩、流纹岩及相应的火山碎屑岩,其中侵入岩有正长斑岩和花岗闪长岩。LA-ICP-MS测得玄武安山岩、英安岩、正长斑岩、花岗闪长岩、流纹岩锆石U-Pb年龄分别为455.6±8.1Ma、444.5±1.9Ma、441.4±1.6Ma、455.4±5.3Ma、424±1.9Ma,岩浆活动于晚奥陶-早志留世,喷出和侵入时代接近,原定巴音布鲁克组地层时代晚志留世应改为晚奥陶-早志留世。这些岩浆岩具有相似的稀土元素地球化学特征,微量元素相比原始地幔均亏损Nb、Ta、P、Ti。玄武岩正的εNd(t)=+1.6~+6.7,低的(87Sr/86Sr)i=0.70377~0.70489,指示岩浆源区具有亏损地幔特征,弱的Zr-Hf负异常,低的Th/Nb比值,较窄的同位素变化范围暗示地壳混染并不显著,微量元素及铅同位素特征(206Pb/204Pb=18.26~18.77,207Pb/204Pb=15.63~15.69,208Pb/204Pb=38.21~38.34)表明岩浆源区可能是俯冲流体及洋底沉积物交代的地幔楔橄榄岩部分熔融成因。西天山巴音布鲁克地区早古生代岩浆岩应是南天山洋晚奥陶-早志留世向北向中天山陆块之下俯冲在中天山-伊犁板块南缘活动大陆边缘的岩浆产物,指示了陆缘岩浆弧环境。这种陆缘弧环境有利于斑岩铜金成矿系统发育,值得高度关注相关铜金矿的地质找矿。
关键词: 岩浆岩     锆石U-Pb测年     元素和同位素     早古生代     巴音布鲁克组     西天山    
Early Paleozoic geological environment of metallogeny in Bayinbuluk region, western Tien Shan: Igneous rocks and their dating, elementary and isotopic constraints
XING Hao, ZHAO XiaoBo, ZHANG ZhaoChong, YE JinChao, FENG Bo    
State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
Abstract: The western Tien Shan is an important metallogenic belt that situated along the southwest margin of the Central Asian Orogenic Belt (CAOB). The geological environment and metallogeny of the CAOB during Late Paleozoic are well concerned, however, the geodynamic setting of the CAOB during Early Paleozoic remains unclear and the metallogenic potential of this period is also poorly documented. Volcanic rocks and interlayered neritic clastic and limestone of the Upper Silurian Bayinbuluke Formation offer a rare opportunity for understanding these issues. The Bayinbuluke Formation is typically exposed in the Bayinbuluke area of the Xinjiang Central Tien Shan, which is generally sandwiched between the Nikolaev-North Nalati Fault and the Atbash-Inylchek-South Nalati Fault. The rocks in the Bayinbuluke area comprise of basalt, basaltic andesite, dacite, rhyolite and volcanic clastics that intruded by syenite porphyry and granodiorite. Zircon LA-ICP-MS U-Pb dating of the basaltic andesite, dacite, syenite porphyry, granodiorite, rhyolite yield ages of 455.6±8.1Ma, 444.5±1.9Ma, 441.4±1.6Ma, 455.4±5.3Ma and 424±1.9Ma, respectively, confirming that the magmatism in this area occurred during Late Ordovician to Early Silurian rather than Late Silurian as previously suggested. The element and isotopic geochemical characteristics of volcanic and intrusive rock show clear similarities, e.g., all the igneous rocks have the same chondrite-normalized rare earth element patterns and prominent negative Nb-Ta and P-Ti anomalies on mantle-normalized trace element diagrams. Basalts have positive εNd(t) values (+1.6~+6.7), and low (87Sr/86Sr)i ratios (0.70377~0.70489). Sr-Nd isotopic compositions of these rocks indicated that the primitive magma was possibly originated from a depleted mantle source. The rocks all have low Th/Nb ratios, narrow isotopic variations, and slightly negative Zr-Hf anomalies, suggesting insignificant crustal contamination. They are enriched in large ion lithophile elements (LILE), depleted in high field strength elements (HFSE) and the radiogenic Pb isotopic ratios of 206Pb/204Pb=18.26~18.77, 207Pb/204Pb=15.63~15.69, 208Pb/204Pb=38.21~38.34, consistent with the involvement of subduction-related fluids and sediments in the magma source region. Based on our new data and previously published results, we suggest that the Early Paleozoic magmatic rocks in the Bayinbuluke area was formed in a continental arc setting that related to the northward subduction of the South Tien Shan Ocean beneath the Central Tien Shan Block during Late Ordivician-Early Silurian. Considering the continental arc setting is favorable for giant porphyry Cu-Au systems, it is proposed that major porphyry Cu-Au deposits may have been developed in the Bayinbuluke area.
Key words: Igneous rock     Zircon U-Pb dating     Element and isotope     Early Palaeozoic era     Bayinbuluk Formation     Western Tien Shan    
1 引言

西天山是中亚造山带(CAOB)重要组成部分(Şengör et al.,1993; Jahn et al.,2000; Xiao et al.,2008; 高俊等,2009),蕴育出金铜多金属巨型成矿带(薛春纪等,2014a; Goldfarb et al.,2014; Seltmann et al.,2014),特别是其核心地带东西向延伸约2500km的“亚洲金腰带”备受世人瞩目(薛春纪等,2014b),产有世界最大的Muruntau造山型金矿床(Frimmel,2008)和亚洲最大的Kalmakyr斑岩金矿床(Cooke et al.,2005; 薛春纪等,2013),成矿和找矿潜力巨大(薛春纪等,2015)。CAOB晚古生代金属成矿环境和过程已被普遍认知和肯定(薛春纪等,2014ab2015; Goldfarb et al.,2014; Seltmann et al.,2014),但早古生代成矿地质环境还不甚清楚(Zhao et al.,2015)。新疆巴音布鲁克地区出露巴音布鲁克组火山岩夹浅海相碎屑岩和灰岩,原定时代为晚志留世,是认识西天山早古生代成矿地质环境的难得对象。我国新疆西天山巴音布鲁克地区处在“亚洲金腰带”内(薛春纪等,2014b),原定上志留统巴音布鲁克组基性、中基性和少量酸性火山岩夹浅海相碎屑岩和灰岩,其中侵入了酸性小岩体。但笔者最近针对这些岩浆岩的一组年代学研究结果表明,巴音布鲁克组时代应属晚奥陶-早志留世,而非原定晚志留世;前人研究认为,这些火山岩属弧火山岩,但尚存在大洋岛弧(朱志新等,2006a; 马中平等,2008)、陆缘弧(Gao et al.,1998)等不同认识。巴音布鲁克组所在区域其他地段也发现早古生代花岗岩类(韩宝福等,2004; Gao et al.,2009; 徐学义等,2010),有研究认为它们与Terskey洋向南向中天山之下俯冲有关(车自成,1994; 郭召杰和张志诚,1993; Gao et al.,2009),有研究认为它们与早古生代碰撞造山晚期伸展事件有关(韩宝福等,2004),也有研究认为它们与南天山洋向北向中天山之下俯冲相关(Gao et al.,2009; Zhou et al.,2001; 杨天南等,2006; 龙灵利等,2007; 朱志新等,2006b2011)。西天山巴音布鲁克地区成矿地质环境认识分歧显著。

本文针对西天山巴音布鲁克组火山岩及其中酸性侵入岩开展年代学、元素和Sr-Nd-Pb同位素地球化学研究,约束岩浆起源,揭示板块构造背景,认识成岩成矿地质环境,旨在明确本区域针对下古生界分布区的地质找矿方向。

2 区域背景

巴音布鲁克地区位于西天山成矿带的东部(图 1a)。西天山成矿带从西到东跨乌兹别克斯坦、吉尔吉斯斯坦、哈萨克斯坦和我国新疆西北部。巴音布鲁克地区早古生代岩浆岩出露于中天山中部(图 1b)。中天山北以Nikolaev-那拉提山北缘断裂为界与北天山相邻,南以中天山南缘断裂为界与南天山相望(图 1b)。北天山是哈萨克斯坦-伊犁板块及其南北缘活动大陆边缘褶皱带,Nikolaev-那拉提山北缘断裂是Terskey洋关闭后形成的早古生代缝合带(Biske and Seltmann,2010; Gao et al.,2009; Bazhenov et al.,2003; 薛春纪等,2014a)。南天山主体是塔里木板块北部被动大陆边缘褶皱冲断带,中天山南缘断裂是南天山洋关闭后形成晚古生代缝合带(Gao et al.,2009; 薛春纪等,2014a)。中天山呈狭长条带状处在北天山与南天山之间(图 1b)。

图 1 西天山成矿带(a)和新疆西天山地质矿产简图(b)据(高俊等,2009修编) Fig. 1 Location of western Tien Shan metallogenic belt(a)and map of geology and mineral resources in Xinjiang,western Tien Shan(b)(modified after Gao et al.,2009)

在新疆西部,中天山是近东西走向的隆起带,前寒武纪变质结晶基底多有出露(薛春纪等,2014a),中元古界长城系特克斯岩群为变碎屑岩-碳酸盐岩夹酸性-基性火山岩,主要在特克斯河与巴克提萨依之间出露;蓟县系科克苏群为浅海相富硅碳酸盐岩夹碎屑岩,主要分布在库尔代河以北的喀拉卓恩一带(朱志新,2007);中上元古界那拉提群以片麻岩、混合岩为主,夹少量角闪片岩和大理岩,沿那拉提山呈带状分布。拉尔墩达坂北坡玄武岩中锆石U-Pb法测得2567Ma、2546Ma年龄(朱永峰等,2006),巴伦台北部乌拉斯台地区的糜棱岩化花岗岩中锆石U-Pb法测得2515Ma年龄(杨天南等,2006),拉尔墩达坂阳起石片岩Sm-Nd法测得1128±125Ma年龄(王宝瑜等,1994),指示中天山具晚太古代至中新元古代变质结晶基底。中天山盖层多为下古生界中基性火山熔岩夹碳酸岩-火山碎屑岩建造(薛春纪等,2014a),下古生界以巴音布鲁克组为主,其岩性为海相中基性火山岩夹碳酸盐岩-碎屑岩建造,分布在巴音布鲁克以北地区。

巴音布鲁克区域中天山侵入岩大面积出露,主要为晚古生代花岗岩、花岗斑岩和闪长岩,构成近东西走向的侵入岩带(图 2)。早古生代侵入岩也有出露,那拉提森木塔斯地区石英闪长岩锆石U-Pb法测得426.7±9.4Ma年龄,巴音布鲁克北部石英闪长岩TIMS锆石U-Pb法测得446.8±1.2Ma年龄(徐学义等,20102006),阿克牙兹河与比开河交汇处花岗闪长岩锆石U-Pb法测得479±2Ma年龄(Gao et al.,2009),拉尔墩达坂钾长花岗岩锆石U-Pb法测得457±27Ma年龄,戈伦唐古什地区片麻状花岗岩锆石U-Pb法测得421±11Ma年龄,巴伦台黑云母花岗岩锆石U-Pb法测得456.2±0.6Ma年龄(韩宝福等,2004)。

图 2 西天山巴音布鲁克地区地质矿产图(据中国地质大学(北京),2012) Fig. 2 Map of Geology and mineral resources in Bayinbuluk region,western Tien Shan

中国地质大学(北京). 2012. 新疆和静乔霍特铜矿定位预测研究课题成果报告修编

在巴音布鲁克区域中天山,产有巴音布鲁克乔霍特铜矿,近年发现新源县卡特巴阿苏大型金铜矿床(杨维忠等,2013; 薛春纪等,2014b; 冯博等,2014; 张祺等,2015)以及众多铜矿点(图 2)。

3 岩浆岩岩石学3.1 火山岩

巴音布鲁克地区下古生界火山岩主要产在巴音布鲁克组(图 2图 3)。巴音布鲁克组之上不整合覆盖下石炭统雅满苏组(C1y)灰岩和下二叠统砾岩、砂砾岩构成的磨拉石(图 3)。巴音布鲁克组地层走向近东西向,倾角较大,主体向北倾,分两个亚组,下亚组(O3-S1b1)为灰绿色至黄褐色砂质、粉砂质板岩,分布在巴音布鲁克组出露区的北部,厚度约816m;上亚组(O3-S1b2)为玄武岩、玄武安山岩和少量英安岩、流纹岩夹生物碎屑灰岩及砂岩、凝灰岩、凝灰质砂岩,分布在巴音布鲁克组出露区的南部;上、下亚组之间以逆断层接触,下亚组推覆到上亚组之上(图 3)。上亚组中赋存有巴音布鲁克铜矿床。

图 3 西天山巴音布鲁克地区地质矿产图(据中国地质大学(北京),2012修编) Fig. 3 Map of geology and mineral resources in Bayinbuluk area, western Tien Shan

巴音布鲁克组上亚组从老到新分5个岩性段,彼此多整合(部分断层)接触(图 3图 4)。第一岩性段(O3-S1b2-1)为灰绿色、深灰色玄武岩(图 4),厚度约163m,其中侵入了花岗闪长岩(图 3);第二岩性段(O3-S1b2-2)以玄武安山岩类为主,顶部见钙质粉砂岩、砂岩;第三岩性段(O3-S1b2-3)以灰绿色块状玄武岩、气孔-杏仁状玄武岩、紫色富铁玄武岩为主,夹少量英安岩、流纹岩;第四岩性段(O3-S1b2-4)为生物碎屑灰岩、砂岩;第五岩性段(O3-S1b2-5)为凝灰质砂岩、长石岩屑砂岩,厚度231m。以下描述主要类型火山岩的岩石学特征。

图 4 西天山巴音布鲁克地区巴音布鲁克组及其中侵入岩地质剖面 Fig. 4 Geological section of Bayinbuluk Formation and intusions in Bayinbuluk area, western Tien Shan

玄武岩呈暗灰色、灰黑色,斑状结构,块状构造(图 5a)。斑晶约30%,主要为斜长石(图 5bc),少量辉石。斜长石斑晶长200~500μm,宽50~100μm,半自形板状,辉石大多已蚀变,蚀变矿物为绿泥石(图 5b)。

图 5 西天山巴音布鲁克地区岩浆岩及其显微岩相学
(a)玄武岩;(b)玄武岩,斑状结构,斑晶为斜长石和辉石,辉石已绿泥石化(单偏光);(c)玄武岩,斑状结构,斑晶主要为斜长石(正交偏光);(d)玄武安山岩;(e)玄武安山岩,斑状结构,斑晶为斜长石(单偏光);(f)玄武安山岩,斑状结构,斑晶为斜长石(正交偏光);(g)流纹岩;(h)流纹岩,斑状结构,斑晶为斜长石和石英,基质中雏晶石英和长石略显流纹构造(正交偏光);(i)流纹岩,斑状结构,斑晶为斜长石和石英(正交偏光);(j)正长斑岩;(k)正长斑岩,斑状结构,斑晶为正长石,基质雏晶结构(单偏光);(l)正长斑岩,斑状结构,斑晶为正长石,基质雏晶结构(正交偏光);(m)花岗闪长岩;(n)花岗闪长岩,中粒花岗结构,由石英、钾长石、斜长石、角闪石组成(单偏光);(o)花岗闪长岩,中粒花岗结构,由石英、钾长石、斜长石、角闪石组成(正交偏光).Qtz-石英,Pl-斜长石,Or-正长石,Kfs-钾长石,Chl-绿泥石
Fig. 5 Igneous rocks and their petrography in Bayinbuluk area, western Tien Shan
(a) basalt; (b) basalt, porphyritic texture, the phenocryst is plagioclase and pyroxene, the pyroxene had been replaced by chlorite (PPL); (c) basalt, porphyritic texture, the phenocryst is mainly plagioclase (CPL); (d) basaltic andesite; (e) basaltic andesite, porphyritic texture, the phenocryst is plagioclase (PPL); (f) basaltic andesite, porphyritic texture, the phenocryst is mainly plagioclase (CPL); (g) rhyolite; (h) rhyolite, porphyritic texture, the phenocryst is plagioclase and quartz, crystallitic quartz and plgioclase in the groundmass possess fluxion structure (CPL); (i) rhyolite, porphyritic texture, the phenocryst is mainly plagioclase and quartz (CPL); (j) syenite porphyry; (k) syenite porphyry, porphyritic texture, the phenocryst is orthoclase, groundmass is crystallitic structure (PPL); (l) syenite porphyry, porphyritic texture, the phenocryst is mainly orthoclase,groundmass is crystallitic texture (CPL); (m) granodiorite; (n) granodiorite, porphyritic texture, medium- to coarse-grained granitic texture, granodiorite consists of quartz (20%), K-feldspar (15%), plagioclase (30%), hornblende (5%) (under single polarized light); (o) granodiorite, medium-grained granitic texture, granodiorite consists of quartz (20%), K-feldspar (15%), plagioclase (30%), hornblende (5%) (under cross polarized light). Mineral abbreviations: Qtz-quartz, Pl-plagiocase, Or-orthoclase, Kfs-K-feldspar, Chl-chlorite

玄武安山岩暗灰色、暗灰绿色,常块状、杏仁状构造(图 5d),斑状结构,部分岩石的斑晶少于5%而呈少斑结构。斑晶含量10%~20%,以斜长石为主(图 5ef),少量单斜辉石,斜长石斑晶半自形板状。基质中斜长石大小为(10~30)×(100~200)μm,交织结构,约含40%。

流纹岩呈淡紫色、紫灰色(图 5g),流纹构造,局部见块状构造,斑状结构(图 5h)。斑晶为斜长石(图 5hi),宽85~100μm,长300~500μm,呈半自形板状。基质为微晶结构,微晶石英和长石呈不规则粒状,流动状定向排列,石英和长石含量相近。副矿物主要为锆石等。

3.2 侵入岩

巴音布鲁克地区侵入于巴音布鲁克组中的岩体包括正长斑岩、花岗闪长岩、花岗岩和辉绿岩(图 3)。正长斑岩呈岩脉、岩枝产出,走向近东西,长约200m,宽约30m,见冷凝边,侵入于巴音布鲁克组上亚组或沿上、下亚组之间的断层出露(图 3)。花岗闪长岩呈岩枝、岩株产出,在研究区内走向近东西向,长约700m,宽约100m,侵入于巴音布鲁克组上亚组(图 3),其中见巴音布鲁克组玄武安山岩捕掳体。花岗岩呈岩脉、岩枝产出,走向近东西,侵入于巴音布鲁克组上亚组或沿上、下亚组之间的断层出露(图 3)。辉绿岩呈岩脉侵入于巴音布鲁克组上亚组,规模较小(图 3)。这些侵入体均呈近东西走向的岩脉、岩枝产出,与西天山区域构造线及巴音布鲁克地区主要断裂构造走向一致(图 3)。以下描述主要类型侵入岩的岩石学特征。

正长斑岩呈淡红色,块状构造,斑状结构(图 5j)。斑晶为半自形晶正长石(图 5kl)含量10%~20%。基质为霏细结构或玻基交织结构(图 5kl),可能由雏晶状钾长石、石英组成,少量玻璃质。

花岗闪长岩呈淡红色,中粒花岗结构,块状构造(图 5m),主要由钾长石、斜长石、石英、角闪石组成(图 5no)。钾长石呈他形粒状,粒度1~1.5mm,含量15%~20%;斜长石呈半自形-他形粒状,大小多为0.4×0.2mm~3×1.5mm,有时可见聚片双晶,含量30%~40%;石英为他形粒状,粒径多在0.5~1.5mm,含量约25%;角闪石自形-半自形晶结构(图 5n),含量10%~15%。岩石中副矿物以锆石、榍石为主,少量细粒针状磷灰石。

4 样品及分析

本次对西天山巴音布鲁克地区火山岩和侵入岩开展了主量和微量元素及锆石U-Pb法测年、Sr-Nd-Pb同位素组成分析。样品采自地表,未明显风化。

在河北省地质矿产局区域地质矿产调查大队实验室先将岩石样品在金刚石切割机上切去风化表皮和可能影响成分分析的其他脉体,蒸馏水洗净晾干,然后将样品机械破碎成细小块(20目),用蒸馏水清洗4次晾干后,用玛瑙碾钵粉碎至200目以备主量和微量元素组成分析。全岩样品主量和微量元素组成分析在国家地质实验测试中心完成。主量元素组成分析依据《GB/T 14506.28—93硅酸盐岩石化学分析方法》,在Philips PW2404型XRF上完成,FeO采用湿化学法分析确定,岩石中SiO2、TiO2、Al2O3、FeO、Fe2O3、MnO、MgO、CaO、Na2O、K2O、P2O5和LOI的分析精度优于1%,分析结果见(表 1)。微量元素组成分析依据《DZ/T 0223-2001电感耦合等离子体质谱方法通则》在Element-I型ICP-MS上完成,首先用高精度电子天平秤称取100mg样品,在高纯度HNO3-HF混合溶液中恒温200℃下48h溶样;冷却后,加入HClO4两次并分别将溶液蒸干;然后将溶样瓶密封好,在200℃电热板上恒温12h以上;冷却至室温并将固体样品称重,然后使用干净的聚酯瓶盛装样品,滴入1mL浓度为11×10-6的In作为内标;再将样品溶液稀释到40g摇匀,最后进行ICP-MS分析。分析结果见(表 2)。

表 1 西天山巴音布鲁克地区岩浆岩主量元素组成(wt%) Table 1 Major element compositions (wt%) of igneous rocks in Bayinbuluk area, western Tien Shan

表 2 西天山巴音布鲁克地区岩浆岩微量元素组成(×10-6) Table 2 Trace element compositions of igneous rocks in Bayinbuluk area, western Tien Shan (×10-6)

在河北省地质矿产局区域地质矿产调查大队实验室常规物理方法完成锆石矿物分离和挑选。先将样品破碎至80~100目,然后用水清洗晾干;再用磁铁去除其中磁铁矿等磁性矿物,用重液分选锆石,除去磷灰石等杂物;最后在实体显微镜下逐粒挑选获得锆石单矿物样品,以备制作样品靶。将锆石样品和标样逐粒粘贴在靶托上,用环氧树胶浇铸,磨去锆石颗粒一半后抛光,制成锆石测年用靶,在反射、透射、背散射和阴极发光下观察、拍照(图 6)并选择无内部裂隙和包裹体的锆石样品备U-Pb法测年。测年工作在中国地质科学院成矿作用和资源评价重点实验室La-ICP-MS实验室完成,所用仪器为Finnigan Neptune型MC-ICP-MS,激光器为Newwave UP 213型,用锆石标样GJ-1调试仪器,U、Th含量以锆石标样M127(U=923×10-6;Th=439×10-6;Th/U=0.475)(Nasdala et al.,2008)为外标进行校正,每分析样品10个点,重复测定锆石标样以精确控制分析质量。所用衰变常数:235U=0.98485×10-9/a和238U=0.15513×10-9/a,数据处理使用CommPbCorr软件(Andersen,2002),U-Pb谐和曲线绘制采用Isoplot 3.0程序(Ludwig et al.,2003),针对巴音布鲁克地区3组火山岩、2组侵入岩中锆石的测年结果分别见表 3表 4图 7图 8

图 6 西天山巴音布鲁克地区岩浆岩中锆石CL图像及206Pb/238U视年龄 Fig. 6 Zircon CL images and 206Pb/238U apparent ages of igneous rocks in Bayinbuluk area, western Tien Shan

表 3 西天山巴音布鲁克地区火山岩锆石U-Pb法测年结果 Table 3 Zircon U-Pb dating results of volcanic rocks in Bayinbuluk area, western Tien Shan

表 4 西天山巴音布鲁克地区侵入岩锆石U-Pb法测年结果 Table 4 Zircon U-Pb dating results of intrusive rocks in Bayinbuluk area, western Tien Shan

图 7 西天山巴音布鲁克地区火山岩锆石U-Pb测年结果 Fig. 7 Zircon U-Pb dating results of volcanic rocks in Bayinmuluk area, western Tien Shan

图 8 西天山巴音布鲁克地区侵入岩锆石U-Pb测年结果 Fig. 8 Zircon U-Pb dating results of intrusive rocks in Bayinmuluk area, western Tien Shan

全岩Sr-Nd同位素组成分析的前处理工作在北京大学造山带与地壳演化教育部重点实验室完成,首先准确称取样品50~100mg,用纯化HF-HClO4溶样,120℃蒸干样品溶液,然后加入纯化HCl,用Rb-Sr、Sm-Nd交换柱(AG50W*12,200~400目)进行分离提纯和元素提取;在中国地质大学地质过程与矿产资源国家重点实验室完成同位素比值分析。所用仪器为Triton Plus型TIMS,数据以86Sr/88Sr=0.1194和146Nd/144Nd=0.7219内校正作为分馏修正,国际标样NBS987的实测值为87Sr/86Sr=0.710250±2(2σ),分析结果见表 5

表 5 西天山巴音布鲁克地区岩浆岩Sr-Nd-Pb同位素组成 Table 5 Sr-Nd-Pb isotopic compositions of igneous rocks in Bayinbuluk area, western Tien Shan

Pb同位素组成分析的前处理工作在北京大学造山带与地壳演化教育部重点实验室完成,称取样品约50~100mg,加入HNO3溶液0.5mL分解样品。通过AG-1×8(200~400目)阴离子树脂交换柱,最后用HCl解析Pb。Pb同位素分析在中国科学技术大学放射性成因同位素地球化学实验室完成。在MAT262型MC-ICP-MS仪器上完成测试,Pb同位素比值测试采用单Re金属带并以硅胶为发射剂,Pb标准溶液NBS981的测量结果用于Pb同位素的质量分馏校正,多次测量结果显示,在1300℃测量温度条件下,Pb同位素分馏系数为0.1%每原子质量单位(p.a.m.u.),Pb同位素比值测量精度好于0.01%。全岩Pb同位素分析的全流程本底<200pg。详细的同位素分析流程可以参见(Chen et al.,200020022007),分析结果见表 5

5 讨论5.1 岩浆岩和地层时代

将玄武安山岩、英安岩、流纹岩、正长斑岩、花岗闪长岩分选出的锆石分别编号为BXX-2、XXP-1、QX-7、XXP-5、BXX-1。样品BXX-2锆石半自形柱状,长40~135μm,宽20~100μm,长宽比为1.5:1~3.5:1,岩浆结晶环带清晰(图 6),锆石232Th/238U比为0.46~0.66(表 3),显示岩浆锆石成因,这与其形态特点一致;样品XXP-1锆石粒径偏小,呈自形半自形结构,长40~70μm,宽20~50μm,长宽比为1.2:1~2:1,锆石232Th/238U比为1.18~2.87(表 3),显示岩浆锆石成因;样品QX-7锆石颗粒粒径小,但锆石数量多,锆石呈无色长柱状晶体,长50~200μm,宽30~100μm,长宽比为2:1~4:1,岩浆结晶环带清晰(图 6),232Th/238U比为0.51~1.82(表 3),显示岩浆锆石成因;样品XXP-5锆石数目较多但粒度偏小,晶形呈板状、磨圆状,长50~100μm,宽30~80μm,长宽比为1.4:1~1.6:1,有熔蚀、浑圆化迹象(图 6),232Th/238U比值为0.64~1.05(表 4),反映岩浆成因特征;样品BXX-1锆石颗粒数目多且粒度较大,自形半自形结构,长70~150μm,宽40~90μm,长宽比为1.4:1~3:1,岩浆结晶环带清晰(图 6),232Th/238U比为0.40~0.73(表 4),岩浆成因锆石特征明显(吴元保和郑永飞,2004; Schulz et al.,2006)。

锆石年龄测定中用标样M127进行分析质量的精确控制,所用La-ICP-MS U-Pb测年方法可靠,岩浆锆石年龄结果可信。

玄武安山岩5个分析点在谐和曲线上且较集中,加权平均年龄为455.6±8.1Ma(MSWD=0.14,n=5),可信度94%(图 7),表明该火山岩形成于晚奥陶世;英安岩加权平均年龄为444.5±1.9Ma(MSWD=1.00,n=5)(图 7),表明其形成于晚奥陶世;流纹岩18个分析点在误差范围内有一致的U-Pb年龄,构成单一的正态分布形式,加权平均年龄为424.2±1.9Ma(MSWD=0.66,n=18)(图 7),可信度85%,属于早志留世;正长斑岩206Pb/238U年龄在437.4±3.5Ma~466.7±3.6Ma之间(表 4),加权平均年龄为441.4±1.6Ma(MSWD=1.4,n=13)(图 8),指示该岩体侵入时代为晚奥陶世;花岗闪长岩206Pb/238U年龄介于451~459Ma之间(图 6),加权平均年龄455.4±5.3Ma(MSWD=0.069,n=12)(图 8),可信度100%,表明该岩体侵入时代为晚奥陶世。

多组岩浆岩的测年结果表明,巴音布鲁克地区下古生界火山岩地层形成年龄为晚奥陶至早志留世,而不是前人认为的晚志留世,岩浆岩成岩时代反映巴音布鲁克地区岩浆喷发和侵入主要集中在晚奥陶-早志留世,这套岩浆岩年龄接近,是同一岩浆系统的产物吗?

5.2 岩石组合和岩浆系列

巴音布鲁克组火山岩岩石组合为玄武岩-玄武安山岩-安山岩-英安岩-流纹岩。基性岩Mg#(0.43~0.67)较高,Fe2O3/FeO比值高(多数>1),表现为氧化岩浆的特点。火山岩全碱质量分数为4.51%~8.06%,FeOT质量分数为2.87%~11.35%,MgO质量分数为0.09%~9.00%,AFM和Th/Yb-Ta/Yb图解反映火山岩主体属钙碱性岩浆系列(图 9)。

图 9 西天山巴音布鲁克地区铜矿区火山岩主微量元素选择性地球化学图解
(a)玄武岩岩石系列AFM图解(Kuno,1968; Irvine and Baragar,1971);(b)微量元素Th/Yb-Ta/Yb岩浆系列判别图解
Fig. 9 Element geochemistry diagram from Bayinbuluk volcanic rocks,western Tien Shan
(a)AFM diagram(Kuno,1968; Irvine and Baragar,1971);(b)trace element Th/Yb-Ta/Yb diagram

流纹岩SiO2为70.86%~74%、Al2O3为12.77%~13.50%,铝饱和指数介于A/CNK=0.9~1.11之间,岩石具准铝质至弱过铝质特征;正长斑岩SiO2为71.23%~73.72%,全碱(K2O+Na2O)为8.08%~9.77%,Al2O3为12.33%~14.53%,铝饱和指数A/CNK=1.05~1.18,岩石具弱过铝质特征,总体与准铝质至弱过铝质花岗岩类似。流纹岩、正长斑岩分异指数(DI)介于89~94之间,表明结晶分异程度较高;花岗闪长岩SiO2为60.83%~71.34%,全碱(K2O+Na2O)为5.22%~7.32%,分异指数(DI)63.85~82.25。Al2O3为11.92%~15.33%,铝饱和指数A/CNK=0.84~1.24,岩石具弱过铝质特征。侵入岩里特曼组合指数δ介于0.96~3.11 < 3.3,反映它们均为钙碱性岩浆系列;

弱过铝质熔浆中,I型花岗岩中磷灰石溶解度与SiO2含量呈负相关,而S型花岗岩中则相反(朱弟成等,2009);正长斑岩、花岗闪长岩、流纹岩P2O5分别为0.06%~0.09%、0.11%~0.18%、0.03%~0.13%,它们与SiO2含量呈明显的负相关(图 10),并且三者铝饱和度A/CNK均接近或小于1.1,而长英质S型花岗岩一般显示出强过铝质特征(A/CNK>1.1),这与S型花岗岩明显不同(Chappell,1999),三者CIPW标准矿物中出现刚玉分子(S型花岗岩,A/CNK>1.1,刚玉>1%),但镜下未发现明显的富铝矿物白云母等,其整体仍表现I型花岗岩特征。

图 10 西天山巴音布鲁克地区岩浆岩地球化学图解 Fig. 10 Characteristics of major elements from Bayinbuluke intrusive rock,western Tien Shan

微量元素原始地幔标准化蛛网图显示岩浆岩具有相似的富集大离子亲石元素(Cs、Rb、Ba、Th、U)、亏损高场强元素(Nb、Ta、Ti)的特征(图 11ab),酸性岩P、Ti亏损程度逐渐增强。球粒陨石标准化的稀土元素配分曲线图中,玄武岩轻重稀土分布较平缓(图 11c),稀土总量较低(∑REE=47×10-6~108×10-6,平均为82×10-6(表 2));酸性岩稀土总量变化范围较大,轻重稀土分馏明显,三者稀土总量均低于地壳平均值165.35×10-6(黎彤,1976),显示出岩浆的深源性(花岗闪长岩∑REE=29.5×10-6~114×10-6,平均为63×10-6,正长斑岩∑REE=66.9×10-6~174×10-6,平均为119×10-6,流纹岩∑REE=92.0×10-6~208×10-6,平均为132×10-6(表 2));玄武岩铕异常不明显,花岗闪长岩Eu负异常,表明存在斜长石的分离结晶,后者镜下也能观察到斜长石晶体排列紧密,条板状斜长石晶体裂隙间夹着石英和角闪石呈一定的堆晶结构(图 5o);正长斑岩、流纹岩具明显Eu负异常(图 11d),说明岩浆演化过程中斜长石的分离结晶作用较强烈(孙鼐和彭亚鸣,1985),镜下基性火山岩中斜长石斑晶细小而正长斑岩、流纹岩斜长石斑晶多较粗大(图 5klhi);基性岩至酸性岩,Eu的负异常逐渐加大,轻稀土逐渐富集,轻重稀土分馏作用增强,显示演化岩浆的特征(图 11)(李昌年,1992)。

图 11 西天山巴音布鲁克地区火山-侵入岩原始地幔标准化微量元素蛛网图(a、b)和球粒陨石标准化稀土元素配分图(c、d)(标准化值据Sun and MacDonough,1989)
Southern Andean arc basalt数据源自GEOROC数据库(http://georoc.mpchmainz.gwdg.de/georoc)
Fig. 11 Primitive mantle-normalized trace element spider diagrams(a, b)and chondrite-normalized REE patterns(c, d)of Bayinbuluk volcanic-intrusive rocks,western Tien Shan(normalization values after Sun and MacDonough,1989)
Data of the Southern Andean arc basalt are from GEOROC database(http://georoc.mpchmainz.gwdg.de/georoc)

Harker图解显示巴音布鲁克组岩浆岩具有密切的关联性,CaO、Fe2O3T与MgO含量呈正相关,暗示辉石的分离结晶,Al2O3、TiO2、P2O5与MgO呈正相关(图 12),表明长石类、钛铁矿、磷灰石的分离结晶,薄片中可观察到部分矿物结晶分异后的斑晶(图 5);同时,它们Nd同位素初始值和εNd(t)相近暗示三者可能具有共同的岩浆源区(Rollinson,2000),在微量元素Tb/Yb-Yb图中(图 13a),岩浆岩的Tb含量近乎相同,并且酸性岩样品点沿着基性火山岩结晶分异的方向移动。

图 12 西天山巴音布鲁克地区火山-侵入岩MgO与主量元素Harker图解 Fig. 12 MgO versus major oxides Harker variation diagrams from Bayinbuluk volcanic-intrusive rocks, western Tien Shan

图 13 西天山巴音布鲁克地区岩浆岩微量元素协变图解(a,底图据Fan et al.,2004)及Zr/Y-Zr双变量构造环境判别图(b,底图据Li et al.,2015)
CAB、IOAB、OIB、MORB数据源自GEOROC数据库(http://georoc.mpchmainz.gwdg.de/georoc)
Fig. 13 The trace element diagram(a, after Fan et al., 2004)and Zr/Y vs. Zr binary diagram discrimination fields(b, after Li et al., 2015)for basalts from Bayinbuluk volcanic-intrusive rocks, western Tien Shan
Data of the CAB, IOAB, OIB, MORB discrimination fields are from GEOROC database(http://georoc.mpchmainz.gwdg.de/georoc)

可见,巴音布鲁克组岩浆岩基性至酸性均有发育,它们具有相似的微量元素地球化学特征、一致的岩浆系列和密切的关联性,表明这套岩浆岩不仅时代接近,而且是同一岩浆过程演化不同阶段、不同相的产物。那么,这套岩浆岩形成于什么类型的地质环境?

5.3 岩浆岩形成的地质环境

前人研究认为,巴音布鲁克组火山岩属弧火山岩,但尚存在洋内岛弧(朱志新等,2006a;马中平等,2008)、陆缘弧(Gao et al.,1998)等不同认识。巴音布鲁克所在区域其他地段发现的早古生代花岗岩类形成背景亦存在明显的分歧,有研究认为它们与Terskey洋南向俯冲有关(车自成等,1994; 郭召杰和张志诚,1993; Gao et al.,2009),有研究认为它们与早古生代碰撞造山晚期伸展事件有关(韩宝福等,2004),也有研究认为它们与南天山洋北向俯冲有关(Gao et al.,2009; Zhou et al.,2001; 杨天南等,2006; Yang and Zhou,2009; 龙灵利等,2007; 朱志新等,2006b2011)。

现有资料表明,洋内岛弧系统中,岛弧发育初期一般以拉斑玄武岩为主,而安山岩和英安岩则出现在岛弧成熟阶段以及活动大陆边缘环境(Baker,1982)。大洋盆地内部玄武岩典型发育洋岛玄武岩,由碱性玄武岩和拉斑玄武岩组成。活动大陆边缘环境以南美Andes山为代表,其岩石组合多为玄武安山岩-安山岩-英安岩-流纹岩,岩石属钙碱性-碱性系列(Calvache and Williams,1997);

巴音布鲁克地区下古生界火山岩岩石组合为玄武岩-玄武安山岩-安山岩-英安岩-流纹岩,火山岩富集大离子亲石元素(LILE)、亏损高场强元素(HFSE),高的LREE/HFSE及 LILE/HFSE比值(图 11),反映它们的形成环境可能为与俯冲有关的洋内岛弧或活动大陆边缘(Pearce and Peate,1995)。活动大陆边缘环境中英安岩、流纹岩以及火山碎屑岩相比洋内岛弧显著增多,岩浆系列以钙碱性和高钾钙碱性为主,基性岩类Al2O3含量高,岩石中常见斜长石斑晶(茹艳娇,2012)。与之相比,巴音布鲁克组火山岩Al2O3质量分数介于12.35%~19.01%之间,镜下基性、中基性岩石中斜长石斑晶较常见,岩浆属钙碱性系列,火山岩夹层中发育英安岩、流纹岩、火山碎屑岩和浅海相灰岩;此外,玄武岩微量元素及稀土元素特征均与Andeans玄武岩相似(图 11ac),而Andeans玄武岩形成于典型的活动大陆边缘,同时在高场强元素Zr-Zr/Y图解中巴音布鲁克组玄武岩(MgO>5%)落点(图 13b)基本位于大陆弧玄武岩区域。据此推测巴音布鲁克组岩浆岩形成环境属于活动大陆边缘环境。

志留纪中天山干沟地区前陆盆地碎屑岩中陆源碎屑锆石最新年龄为461Ma,说明Terskey洋最终于460Ma左右消亡,Terskey古洋此时可能已经闭合(Biske and Seltmann,2010; Gao et al.,2009)。区域上中天山西段科克苏河和比开河地区识别出两个花岗岩带,其中早期花岗岩(>470Ma)被认为与Terskey洋俯冲相关,晚期花岗岩(460~398Ma)与南天山洋俯冲相关(Gao et al.,2009);夏林圻等(2002)认为南天山洋于早寒武后已经开启,而后经历了向北的俯冲消减至早石炭世初期完成最终闭合;朱志新(2007)认为古生代时期是南天山洋洋盆形成与演化重要时期,奥陶世时期南天山洋已经开始向中天山下俯冲;巴音布鲁克地区南侧毗邻南天山蛇绿混杂岩带-米斯布拉克、库勒湖、黑英山、榆树沟,其中榆树沟蛇绿混杂岩中麻粒岩锆石核部U-Pb法测得452~640Ma年龄(周鼎武等,2004),表明南天山洋盆在晚前寒武-早古生代已经形成。中天山陆缘弧环境有可能始于480Ma之前,在433~398Ma及352~349Ma发展至顶峰(Gao et al.,2009),杨天南等(2006)朱志新等(2006b)对中天山南缘花岗岩研究表明区内发育有436~366Ma的火山弧,其形成与南天山洋北向俯冲有关。巴音布鲁克区域其他地段同期岩体亦被研究证明形成于南天山洋俯冲于中天山下的活动大陆边缘环境,如:那拉提山锆石U-Pb法测得436Ma年龄的二长花岗岩(朱志新等,2006b),菁布拉克锆石U-Pb法测得431±6Ma年龄的辉石闪长岩(Yang and Zhou,2009),以及乔霍特铜矿区锆石U-Pb法测得450.4±1.1Ma年龄的I型花岗闪长岩(张喜等,2011)。

可见,巴音布鲁克组火山岩应是奥陶世晚期南天山洋向北向中天山下俯冲形成于活动大陆边缘岩浆带。那么,巴音布鲁克组岩浆岩其岩浆源区是什么性质?

5.4 岩浆起源

巴音布鲁克组玄武岩与原始地幔相比具有明显的Nb-Ta负异常和轻微Ti异常(图 11a),地壳物质亏损Nb、Ta、Ti(Rollinson,1993),地壳混染(AFC)过程的确可以引起微量元素的这种特征(Condie,2005),但大量地壳物质混染会导致Zr-Hf的正异常以及高的Th/Nb比值(Taylor and McLennan,1985)。然而,巴音布鲁克组玄武岩显示轻微Zr-Hf的负异常,较低的Th/Nb比值(0.51~1.25),并且岩浆上涌过程中若混染了大量地壳物质,εNd(t)数值随之降低,(如:壳幔混合源εNd(t)范围-9~-4,幔源εNd(t)>0),随着幔源物质成分增加,εNd(t)逐渐表现为正值,本文玄武岩低的(87Sr/86Sr)i=0.70377~0.70489及正的εNd(t)(+1.6~+6.7)并未反映显著的壳源物质成份(Barbarin,1990; 倪守斌等,1995),在143Nd/144Ndi vs. 147Sm/144Nd图解中(图 14),地壳混染的特征亦并不显著,同时其εNd(t)、铅同位素组成(206Pb/204Pb=18.26~18.77,207Pb/204Pb=15.63~15.69,208Pb/204Pb=38.21~38.34)相比区域上菁布拉克岩体具有相似的演化趋势,并不显示受控于AFC作用(图 15)。地壳混染可能并不是巴音布鲁克组玄武岩形成的主要过程。因此,玄武岩所表现的同位素、高场强元素的地球化学特征可能指示了岩浆源区的性质,因为它们在岩浆的分离结晶和部分熔融过程中保持稳定(McCulloch and Gamble,1991)。

图 14 岩浆岩147Sm/144Nd-(147Nd/144Nd)i图解(底图据Ge et al.,2015) Fig. 14 147Sm/144Nd vs.(147Nd/144Nd)i for the studied igneous rocks(after Ge et al.,2015)

图 15 西天山巴音布鲁克地区玄武岩εNd(t)、铅同位素与SiO2协变图解(底图据Yang and Zhou,2009) Fig. 15 Plot of εNd(t)and Pb isotope ratios versus SiO2 for rocks of the Bayinbuluke basalts,western Tien Shan(after Yang and Zhou,2009)

Yang and Zhou(2009)通过对中天山西段菁布拉克基性-超基性侵入岩的微量元素、锶钕同位素及铅同位素分析,认为其岩浆源区具有MORB型亏损地幔特征,同时受洋底沉积物影响,推测其具有与EMⅡ储库成分相似的地幔组成,与之相比,巴音布鲁克玄武岩落点在εNd(t)vs.(87Sr/86Sr)i图解中位于MORB与EMⅡ储库之间(图 16a),且具有更高的放射性铅同位素比值(图 16b),可能暗示了其岩浆源区受到洋底沉积物的交代作用,因EMⅡ储库同位素特征一般归因于存在洋底沉积物组分(Hofmann,1997);与此同时,俯冲环境下地幔楔橄榄岩部分熔融后经结晶分异作用所产生的玄武质岩浆上涌至陆缘弧系统,会导致陆壳增生过程中存在新生幔源成份的加入(Long et al.,2011),这说明巴音布鲁克地区陆缘弧环境亦存在新生幔源物质成份。而酸性岩εNd(t)及(87Sr/86Sr)i介于(-2.1~+5.1)及(0.70432~0.70473)之间,说明幔源物质在酸性岩形成过程中起了主要作用,但酸性岩不会直接来源于地幔(邓晋福等,2004),所以酸性岩可能是早期或同期俯冲背景下地幔楔形区玄武质熔体上涌至陆缘弧系统中,诱发陆缘弧地壳物质发生部分熔融成因,因此酸性岩具有幔源物质与陆缘弧地壳物质混合的特征,同时代中天山其它地段分布众多中酸性侵入岩,其εNd(t)变化于(-6.5~+4.22)之间(表 6),它们均被证明是由幔源物质与陆壳物质重熔后混合形成。

图 16 西天山巴音布鲁克地区火山-侵入岩εNd(t)-(87Sr/86Sr)i (a)及(207Pb/204Pb)i-(206Pb/204Pb)i (b)图解(a)MORB数据范围据Zimmer et al.,1995; OIB数据范围据White and Duncan,1996; EMⅠ和EMⅡ数据据Hart,1988;(b)DMM、EMⅠ和EMⅡ数据据Zindler and Hart,1986;现代太平洋MORB数据据White et al.,1987;北半球参考线(NHRL)数据据Hart,1984 Fig. 16 Plot of εNd(t)versus(87Sr/86Sr)i(a)and(207Pb/204Pb)i-(206Pb/204Pb)i(b)for the Bayinbuluk volcanic-intrusive rocks,western Tien ShanData sources:(a)MORB field is from Zimmer et al.,1995; OIB field is from White and Duncan,1996; EMⅠand EMⅡ from Hart,1988;(b)the field for modern DMM,EM1 and EM2 are from Zindler and Hart,1986; The field for modern Pacific MORB is from White et al.,1987; Northern Hemisphere Reference Line(NHRL)is from Hart,1984

表 6 西天山巴音布鲁克地区其他地段岩浆岩地质年龄、Sr-Nd同位素组成 Table 6 Geochronology and Sr-Nd isotopic compositions of igneous rocks of other districts near to Bayinbuluk area, western Tien Shan

俯冲背景下,原始母岩浆源区物质一般包括:(1)地幔楔橄榄岩;(2)俯冲板片脱水释放的流体;(3)洋壳沉积物;(4)俯冲板片熔融(Tatsumi and Takahashi,2006)。然而俯冲板片熔融形成的母岩浆多以安山质为主,具有Adakite岩石的特征。Adakite岩石具有低Y(Y≤18×10-6,Yb≤1.9×10-6)、高Sr(≥400×10-6)、亏损HREE以及(87Sr/86Sr)i与MORB相似(< 0.7040)的特征(Defant and Drummond,1990),巴音布鲁克组火山岩具较低的Sr含量(38×10-6~561×10-6,平均220×10-6),较高Y、Yb含量(Y=15×10-6~49×10-6,平均29×10-6,Yb=1.82×10-6~5.99×10-6,平均3.4×10-6),(87Sr/86Sr)i基本大于0.7040,这与Adakite质岩石明显不同。

玄武岩微量元素相比原始地幔富集大离子亲石元素(Cs、 Rb、 Ba、 Th、 U)、 亏损高场强元素(Nb、 Ta、Ti)、 高的LREE/HREE比值(L/H=2.5~5.2),说明岩浆源区是俯冲流体交代后的地幔楔橄榄岩部分熔融形成。事实上地幔楔部分熔融过程中俯冲流体扮演关键角色,众多情况下,正是流体的加入诱发地幔楔橄榄岩部分熔融(Gill,1981; Tatsumi et al.,1986; Zindler and Hart,1986)。热液体系中高场强元素(如:Zr)活动性远低于大离子亲石元素(如:Ba、Sr、Rb)(Pearce and Norry,1979),高的Ba/Zr、Sr/Zr、Ba/Th比值是源区中流体参与的最佳指示剂。巴音布鲁克组玄武岩Ba/Zr=0.55~6.84、Sr/Zr=0.83~5.75、Ba/Th=12.9~491(平均202),与典型的俯冲带流体参与形成的岛弧岩浆(如:格林纳达C系列玄武岩,Sr/Zr>10)相比流体作用并不显著,相反与源区中洋壳沉积物贡献显著的岛弧岩浆(如:圣文森特玄武岩、格林纳达M系列玄武岩)具有较高的重叠(图 17ab)(Devine,1995; Macdonald et al.,2000)。

图 17 西天山巴音布鲁克地区玄武岩和玄武安山岩(MgO>5%)Sr/Zr、Ba/Zr和MgO图解(底图据Devine,1995)
格林纳达岛C系列玄武岩数据来自文献(Thirlwall and Graham,1984),圣文森特岛玄武岩数据来自文献(Brown et al.,1977; Rowley,1978)
Fig. 17 Sr/Zr,Ba/Zr versus MgO diagrams from Bayinbuluk basalts and basaltic andesite(MgO>5%),western Tien Shan
Data of Grenada C series basalts is from Thirlwall and Graham,1984; St. Vincent basalts is from Brown et al.,1977; Rowley,1978

我们利用Nd及其同位素的特征进一步阐述岩浆源区中沉积物的作用,因为Nd在热液体系中活动性较弱,却能随沉积物运移(You et al.,1996),沉积岩中143Nd/144Nd同位素比值一般较低,如:晚太古代澳洲页岩均值 < 0.512(Taylor and McLennan,1985);此外,Th在洋底沉积物中高度富集(Plank and Langmuir,1993; Ben Othman et al.,1989)、Ce在热液体系中比Th更容易从体系中迁移出来(You et al.,1996)。所以,岛弧系统中,低的143Nd/144Nd及高的Th/Ce比值指示源区存在沉积物组份(Macdonald et al.,2000)。与源区沉积物作用显著的格林纳达M系列玄武岩相比,巴音布鲁克组玄武岩源区中洋底沉积物组份的作用较为突出(图 18);同时对比同区域菁布拉克基性岩体,巴音布鲁克玄武岩铅同位素落点位于全球洋壳沉积物均值附近(图 16b),也反映源区富集洋壳沉积物的典型特征(Yang and Zhou,2009)。因此,巴音布鲁克组岩浆岩原始岩浆是流体诱发地幔楔橄榄岩部分熔融,但是洋底沉积物对岩浆源区的影响较大。

图 18 西天山巴音布鲁克地区玄武岩Th/Ce-143Nd/144Nd图解(底图据Macdonald et al.,2000)
PAAS太古代后澳洲页岩平均含量数据来自Taylor and McLennan,1985; MORB和OIB平均值据Macdonald et al.,2000
Fig. 18 Th/Ce vs. 143Nd/144Nd diagrams from Bayinbuluk basalts,western Tien Shan(after Macdonald et al.,2000)
PAAS is Post-Archaean average Australian Shale from Taylor and McLennan,1985; average MORB and OIB compositions are also shown by Macdonald et al.,2000

存在于中天山南缘断裂南侧的南天山蛇绿混杂岩带-米斯布拉克、库勒湖、黑英山、榆树沟代表南天山洋大洋壳(郝杰和刘小汉,1993; 刘本培等,1996; 龙灵利等,2006; 周鼎武等,2004),在456Ma时期南天山洋向中天山陆块之下俯冲,形成晚奥陶巴音布鲁克组玄武岩,到424Ma时期,已经发展为较成熟的陆缘弧环境,南天山洋俯冲时限可能远大于456~424Ma,但有一点值得相信,至少在此期间是南天山洋俯冲至中天山陆块之下时期。

随着南天山洋俯冲至中天山陆块之下,在中天山活动大陆边缘形成众多火山-侵入岩(Yang and Zhou,2009; 杨天南等,2006; 徐学义等,2006; 龙灵利等,2007; 朱志新等,2006b)。巴音布鲁克地区早古生代岩浆事件主要是由俯冲相关玄武质熔体与少量地壳物质重熔两者混合形成,玄武质岩浆由洋底沉积物及洋壳板片富水矿物相脱水交代地幔楔橄榄岩部分熔融形成,富含挥发份的原始母岩浆上涌,在压力骤降的情况下,原始母岩浆直接喷发至地表(如:巴音布鲁克、菁布拉克、苏鲁、乔勒铁可西),随着玄武质熔体不断在地表堆积,导致晚期岩浆无法直接喷出地表,因此在浅部岩浆房经历了结晶分异和一定程度的同化混染地壳物质后,侵入至早期同源喷发岩之中(图 19)。

图 19 西天山巴音布鲁克地区早古生代岩浆岩成因模式 Fig. 19 A magma generation model of Early Palaeozoic era in Bayinbuluk region, western Tien Shan

活动大陆边缘是世界级斑岩铜矿产出的典型环境(如:南美Andes山),古生代时期中天山具有与此相似的构造背景。巴音布鲁克地区岩浆形成深度大,因此金属元素可以来源于地幔或者富含铜金属元素的洋壳沉积物,在与地幔楔交代过程中产生富含挥发分(H2S、CO2、H2O)、卤化物的流体,金属物质随流体和岩浆共同喷发至地表,形成富含金属元素的火山岩,晚期酸性岩体的多期次侵入,为晚阶段次生岩浆的萃取提供了有利的先决条件。值得注意的是,与巴音布鲁克同处中天山岛弧环境产有世界级的Almalyk矿集区,包含 Kalmakyr、Dal’neye、Sari-Cheku、Kyzada和Kulqiular大型-超大型斑岩金铜矿床(Cooke et al.,2005; 薛春纪等,2013)。因此,巴音布鲁克地区具有斑岩型铜金找矿潜力。

6 结论

西天山巴音布鲁克地区发育玄武岩-玄武安山岩-安山岩-英安岩-流纹岩火山-侵入岩石组合,属钙碱性岩浆系列,LA-ICP-MS锆石U-Pb法分别测得玄武安山岩、英安岩、正长斑岩、花岗闪长岩、流纹岩455.6±8.1Ma、444.5±1.9Ma、441.4±1.6Ma、455.4±5.3Ma、424±1.9Ma成岩时代;传统认为西天山上志留统巴音布鲁克组的地层时代应改为晚奥陶-早志留世。

西天山巴音布鲁克地区火山-侵入岩石组合是晚奥陶-早志留世南天山洋北向俯冲过程中在中天山-伊犁板块南缘活动大陆边缘的岩浆产物,岩浆起源于俯冲洋壳流体和沉积物交代地幔楔橄榄岩部分熔融;典型的陆缘弧环境有利于斑岩型铜金矿形成,巴音布鲁克地区值得高度关注斑岩型铜金矿地质找矿。

致谢    野外调查中得到和静招金有色矿业公司支持;实验测试在地质过程与矿产资源国家重点实验室、国家地质实验测试中心、北京大学造山带与地壳演化教育部重点实验室完成;论文撰写中得到莫宣学院士、翟裕生院士指导;评审人给予十分有益的意见和具体建议;作者一同表示诚挚感谢。
参考文献
[1] Andersen T. 2002. Correction of common lead in U-Pb analyses that do not report 204Pb. Chemical Geology, 192(1-2): 59-79
[2] Baker PE. 1982. Evolution and classification of orogenic volcanic rocks. In: Thorpe RS (ed.). Andesites, Orogenic Andesites and Related Rocks. London: Wiley, 12-23
[3] Barbarin B. 1990. Granitoids: Main petrogenetic classifications in relation to origin and tectonic setting. Geological Journal, 25(3-4): 227-238
[4] Bazhenov ML, Collins AQ, Degtyarev KE, Levashova NM, Mikolaichuk AV, Pavlov VE and Van der voo R. 2003. Paleozoic northward drift of the North Tien Shan (Central Asia) as revealed by Ordovician and Carboniferous paleomagnetism. Tectonophysics, 366(1-2): 113-141
[5] Ben Othman D, White WM and Patchett J. 1989. The geochemistry of marine sediments, island arc magma genesis, and crust-mantle recycling. Earth and Planetary Science Letters, 94(1-2): 1-21
[6] Biske YS and Seltmann R. 2010. Paleozoic Tian-Shan as a transitional region between the Rheic and Urals-Turkestan oceans. Gondwana Research, 17(2-3): 602-613
[7] Brown GM, Holland JG, Sigurdsson H, Tomblin JF and Arculus RJ. 1977. Geochemistry of the Lesser Antilles volcanic island arc. Geochimca et Cosmochimica Acta, 41(6): 785-801
[8] Calvache VML and Williams SN. 1997. Geochemistry and petrology of the Galeras Volcanic Complex, Colombia. Journal of Volcanology and Geothermal Research, 77(1-4): 21-38
[9] Chappell BW. 1999. Aluminium saturation in I- and S-type granites and the characterization of fractionated haplo granites. Lithos, 46(3): 535-551
[10] Che ZC, Liu HF and Liu L. 1994. Formation and Evolution of the Central Tianshan Orogenic Belt. Beijing: Geological Publishing House, 1-135 (in Chinese)
[11] Chen F, Hegner E and Todt W. 2000. Zircon ages and Nd isotopic and chemical compositions of orthogneisses from the Black Forest, Germany: Evidence for a Cambrian magmatic arc. International Journal of Earth Sciences, 88(4): 791-802
[12] Chen F, Siebel W, Satir M, Terzioğlu N and Saka K. 2002. Geochronology of the Karadere basement (NW Turkey) and implications for the geological evolution of the Istanbul zone. International Journal of Earth Sciences, 91(3): 469-481
[13] Chen FK, Li XH, Wang XL, Li QL and Siebel W. 2007. Zircon age and Nd-Hf isotopic composition of the Yunnan Tethyan belt, southwestern China. International Journal of Earth Sciences, 96(6): 1179-1194
[14] Chen JF, Man FS and Ni SB. 1995. Neodymium and Strontium isotopic geochemistry of mafic-ultramafic intrusions from Qinbulake rock belt, West Tianshan Mountain, Xinjiang. Geochimica, 24(2): 121-127 (in Chinese with English abstract)
[15] Condie KC. 2005. High field strength element ratios in archean basalts: A window to evolving sources of mantle plumes? Lithos, 79(3-4): 491-504
[16] Cooke DR, Hollings R and Walshe JL. 2005. Giant porphyry deposits: Characteristics, distuibution, and tectonic controls. Economic Geology, 100(5): 801-818
[17] Defant MJ and Drummond MS. 1990. Derivation of some modern arc magmas by melting of young subducted lithosphere. Nature, 347(6294): 662-665
[18] Deng JF, Luo ZH, Su SG, Mo XX, Yu BS, Lai XY and Shen HW. 2004. Petrogenesis, Tectonic Setting and Mineralization. Beijing: Geological Publishing House, 1-381 (in Chinese)
[19] Devine JD. 1995. Petrogenesis of the basalt-andesite-dacite association of Grenada, Lesser Antilles island arc, revisited. Journal of Volcanology and Geothermal Research, 69(1-2): 1-33
[20] Fan WM, Guo F, Wang YJ and Zhang M. 2004. Late Mesozoic volcanism in the northern Huaiyang tectono-magmatic belt, central China: Partial melts from a lithospheric mantle with subducted continental crust relicts beneath the Dabie orogen? Chemical Geology, 209(1-2): 27-48
[21] Feng B, Xue CJ, Zhao XB, Ding ZX, Zhang Q, Zu B, Yang WZ, Lin ZH and Chen W. 2014. Petrology, geochemistry and zircon U-Pb isotope chronology of monzogranite of the Katbasu Au-Cu deposit, western Tianshan, Xinjiang Province. Earth Science Frontiers, 21(5): 187-195 (in Chinese with English abstract)
[22] Frimmel HE. 2008. Earth's continental crustal gold endowment. Earth and Planetary Science Letters, 267(1-2): 45-55
[23] Gao J, Li MS, Xiao XC, Tang YQ and He GQ. 1998. Paleozoic tectonic evolution of the Tianshan Orogen, Northwestern China. Tectonophysics, 287(1-4): 213-231
[24] Gao J, Long LL, Klemd R, Qian Q, Liu DY, Xiong XM, Su W, Liu W, Wang YT and Yang FQ. 2009. Tectonic evolution of the South Tianshan orogen and adjacent regions, NW China: Geochemical and age constraints of granitoid rocks. International Journal of Earth Sciences, 98(6): 1221-1238
[25] Gao J, Qian Q, Long LL, Zhang X, LI JL and Su W. 2009. Accretionary orogenic process of western Tianshan, China. Geological Bulletin of China, 28(12): 1804-1816 (in Chinese with English abstract)
[26] Ge SS, Zhai MG, Safonova Inna, Li DP, Zhu XY, Zuo PF and Shan HX. 2015. Whole-rock geochemistry and Sr-Nd-Pb isotope systematics of the late Carboniferous volcanic rocks of the Awulale metallogenic belt in the western Tianshan Mountains (NW China): Petrogenesis and geodynamical implications. Lithos, 228-229: 62-77
[27] Gill JB. 1981. Orogenic Andesites and Plate Tectonics. Berlin, Heidelberg: Springer
[28] Goldfarb RJ, Taylor RD, Collins GS, Goryachev NA and Orlandini OF. 2014. Phanerozoic continental growth and gold metallogeny of Asia. Gondwana Research, 25(1): 48-102
[29] Guo ZJ and Zhang ZC. 1993. On the Early Paleozoic island arc belt of Mid-Tianshan. Journal of Hebei College of Geology, 16(2): 132-139 (in Chinese with English abstract)
[30] Han BF, He GQ, Wu TR and Li HM. 2004. Zircon U-Pb dating and geochemical features of Early Paleozoic granites from Tianshan, Xinjiang: Implications for tectonic evolution. Xinjiang Geology, 22(1): 4-11 (in Chinese with English abstract)
[31] Hao J and Liu XH. 1993. Ophiolite melange time and tectonic evolutional model in South Tianshan area. Scientia Geologica Sinica, 28(1): 93-95 (in Chinese with English abstract)
[32] Hart SR. 1984. A large-scale isotope anomaly in the Southern Hemisphere mantle. Nature, 309(5971): 753-757
[33] Hart SR. 1988. Heterogeneous mantle domains: Signatures, genesis and mixing chronologies. Earth and Planetary Science Letters, 90(3): 273-296
[34] Hofmann AW. 1997. Mantle geochemistry: The message from oceanic volcanism. Nature, 385(6613): 219-229
[35] Irvine TN and Baragar WRA. 1971. A guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences, 8(5): 523-548
[36] Jahn BM, Griffin WL and Windley B. 2000. Continental growth in the Phanerozoic: Evidence from Central Asia. Tectonophysics, 328(1-2): ⅶ-ⅹ
[37] Kuno H. 1968. Differentiation of basalt magmas. In: Hess HH and Poldervaart A (eds.). Basalts: The Poldervaart Treatise on Rocks of Basaltic Composition. New York: Interscience, 623-688
[38] Li CN. 1992. Petrology of Trace Element in Volcanic Rocks. Wuhan: China University of Geosciences Press, 1-195 (in Chinese)
[39] Li CS, Arndt NT, Tang QY and Ripley EM. 2015. Trace element indiscrimination diagrams. Lithos, 232: 76-83
[40] Li T. 1976. Chemical element abundances in the earth and it's major shells. Geochimica, (3): 167-174 (in Chinese with English abstract)
[41] Liu BP, Wang ZQ, Zhang CH, Ma HW, Zhou HR, Zhu H, Gong YM and Jia WM. 1996. The Tectonic Framework and Evolution of in Southwest Tienshan Mountains, China. Wuhan: China University of Geosciences Press, 1-120 (in Chinese)
[42] Long LL, Gao J, Xiong XM and Qian Q. 2006. The geochemical characteristics and the age of the Kule Lake ophiolite in the southern Tianshan. Acta Petrologica Sinica, 22(1): 65-73 (in Chinese with English abstract)
[43] Long LL, Gao J, Xiong XM and Qian Q. 2007. Geochemistry and geochronology of granitoids in Bikai region, southern Central-Tianshan mountains, Xinjiang. Acta Petrologica Sinica, 23(4): 719-732 (in Chinese with Engl ish abstract)
[44] Long LL, Gao J, Klemd R, Beier C, Qian Q, Zhang X, Wang JB and Jiang T. 2011. Geochemical and geochronological studies of granitoid rocks from the Western Tianshan Orogen: Implications for continental growth in the southwestern Central Asian Orogenic Belt. Lithos, 126(3-4): 321-340
[45] Ludwig KR. 2003. ISOPLOT 3.0: A Geochronological Toolkit for Microsoft Excel. Berkeley: Berkeley Geochronology Center
[46] Ma ZP, Xia LQ, Xu XY, Xia ZC, Li XM and Wang LS. 2008. Geochemical characteristics and petrogenesis of the Early Paleozoic igneous rocks from Bayinbuluke, southern Tianshan. Acta Petrologica Sinica, 24(10): 2289-2300 (in Chinese with English abstract)
[47] Macdonald R, Hawkesworth CJ and Heath E. 2000. The Lesser Antilles volcanic chain: A study in arc magmatism. Earth-Science Reviews, 49(1-4): 1-76
[48] McCulloch MT and Gamble JA. 1991. Geochemical and geodynamical constraints on subduction zone magmatism. Earth and Planetary Science Letters, 102(3-4): 358-374
[49] Nasdala L, Hofmeister W, Norberg N, Martinson JM, Corfu F, Dörr W, Kamo SL, Kennedy AK, Kronz A, Reiners PW, Frei D, Kosler J, Wan YS, Götze J, Häger T, Kröner A and Valley JW. 2008. Zircon M257: A homogeneous natural reference material for the ion microprobe U-Pb analysis of zircon. Geostandards and Geoanalytical Research, 32(3): 247-265
[50] Ni SB, Man FS and Chen JF. 1995. REE and Sr-Nd isotopic study of Qiongawuzi ultramafic intrusion, western Tianshan. Acta Petrologica Sinica, 11(1): 65-70 (in Chinese with English abstract)
[51] Pearce JA and Norry MJ. 1979. Petrogenetic implications of Ti, Zr, Y, and Nb variations in volcanic rocks. Contributions to Mineralogy and Petrology, 69(1): 33-47
[52] Pearce JA and Peate DW. 1995. Tectonic implications of the composition of volcanic arc magmas. Annual Review of Earth and Planetary Sciences, 23(1): 251-285
[53] Plank T and Langmuir CH. 1993. Tracing trace elements from sediment input to volcanic output at subduction zones. Nature, 362(6422): 739-743
[54] Rollinson H. 1993. Using Geochemical Data: Evaluation, Presentation, Interpretation. Singapore: Longman, 1-352
[55] Rollinson HR. 2000. Petrology Geochemistry. Yang XM and Chen SX (trans.). Beijing: Chinese Science and Technology University Publishing Press, 1-275 (in Chinese)
[56] Rowley K. 1978. Stratigraphy and geochemistry of the Soufriere volcano, St. Vincent, W. I. Ph. D. Dissertation. St. Augustine, Trinidad: University of the West Indies
[57] Ru YJ. 2012. The Stratigraphic sequanence, petrogenesis and tectonic setting of the volcanic rocks of the dahalajunshan formation, western Tianshan Mountain, China. Master Degree Thesis. Xi'an: Chang'an University, 1-113 (in Chinese with English summary)
[58] Schulz B, Klemd R and Brätz H. 2006. Host rock compositional controls on zircon trace element signatures in metabasites from the Austroalpine basement. Geochimica et Cosmochimica Acta, 70(3): 697-710
[59] Seltmann R, Porter TM and Pirajno F. 2014. Geodynamics and metallogeny of the central Eurasian porphyry and related epithermal mineral systems: A review. Journal of Asian Earth Sciences, 79: 810-841
[60] Şengör AMC, Natal'In BA and Burtman VS. 1993. Evolution of the Altaid tectonic collage and Palaeozoic crustal growth in Eurasia. Nature, 364(6435): 299-307
[61] Sun N and Peng YM. 1985. Ingenious Petrology. Beijing: Geologic Publishing House, 1-324 (in Chinese)
[62] Sun SS and McDonough WF. 1989. Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes. In: Saunders AD and Norry MJ (eds.). Magmatism in the Ocean Basins. Geological Society, London, Special Publications, 42(1): 313-345
[63] Tatsumi Y, Hamilton DL and Nesbitt RW. 1986. Chemical characteristics of fluid phase released from a subducted lithosphere and origin of arc magmas: Evidence from high-pressure experiments and natural rocks. Journal of Volcanology and Geothermal Research, 29(1-4): 293-309
[64] Tatsumi Y and Takahashi T. 2006. Operation of subduction factory and production of andesite. Journal of Mineralogical and Petrological Sciences, 101(3): 145-153
[65] Taylor SR and McLennan SM. 1985. The Continental Crust: Its Composition and Evolution. Oxford: Blackwell, 1-312
[66] Thirlwall MF and Graham AM. 1984. Evolution of high-Ca, high-Sr C-series basalts from Grenada, Lesser Antilles: the effects of intra-crustal contamination. Journal of the Geological Society, 141(3): 427-445
[67] Wang BY, Lang ZJ, Li XD et al. 1994. The Comprehensive Study of Geologic Profile in West Tianshan. Beijing: Science Press, 1-202 (in Chinese)
[68] White WM, Hofmann AW and Puchelt H. 1987. Isotope geochemistry of Pacific mid-ocean ridge basalt. Journal of Geophysical Research, 92(B6): 4881-4893
[69] White WM and Duncan RA. 1996. Geochemistry and geochronology of the Society islands: New evidence for deep mantle recycling. In: Basu A and Hart S (eds.). Earth Processes: Reading the Isotopic Code. Washington, DC: Geophysical Monograph, AGU, 183-206
[70] Wu YB and Zheng YF. 2004. Genesis of zircon and its constraints on interpretation of U-Pb age. Chinese Science Bulletin, 49(15): 1554-1569
[71] Xia LQ, Zhang GW, Xia ZC, Xu XY, Dong YP and Li XM. 2002. Constraints on the timing of opening and closing of the Tianshan Paleozoic oceanic basin: Evidence from Sinian and Carboniferous volcanic rocks. Geological Bulletin of China, 21(2): 55-62 (in Chinese with English abstract)
[72] Xiao WJ, Han CM, Yuan C, Sun M, Lin SF, Chen HL, Li ZL, Li JL and Sun S. 2008. Middle Cambrian to Permian subduction-related accretionary orogenesis of Northern Xinjiang, NW China: Implications for the tectonic evolution of Central Asia. Journal of Asian Earth Sciences, 32(2-4): 102-117
[73] Xu XY, Ma ZP, Xia ZC, Xia LQ, Li XM and Wang LS. 2006. TIMS U-Pb isotopic dating and geochemical characteristics of Paleozoic granitic rocks from the middle-western section of Tianshan. Northwestern Geology, 39(1): 50-75 (in Chinese with English abstract)
[74] Xu XY, Wang HL, Ma GL, Li P, Chen JL and Li T. 2010. Geochronology and Hf isotope characteristics of the Paleozoic granite in Nalati area, West Tianshan Mountains. Acta Petrologica et Mineralogica, 29(6): 691-706 (in Chinese with English abstract)
[75] Xue CJ, Duan SG, Chai FM, Maimaiti M, Typeceóeκοв AX and Qu WJ. 2013. Metallogenetic epoch of the Almalyk porphyry copper ore field, Uzbekistan and its geological significance. Earth Science Frontiers, 20(2): 197-204 (in Chinese with English abstract)
[76] Xue CJ, Zhao XB, Mo XX, Chen YC, Dong LH, Gu XX, Zhang ZC, Nurtaev B, Pak N, Li ZD, Wang XL, Zhang GZ, Yalikun Y, Feng B, Zu B and Liu JY. 2014a. Tectonic-metallogenic evolution of western Tianshan giant Au-Cu-Zn-Pb metallogenic belt and prospecting orietation. Acta Geologica Sinica, 88(12): 2490-2531 (in Chinese with English abstract)
[77] Xue CJ, Zhao XB, Mo XX, Dong LH, Gu XX, Nurtaev B, Pak N, Zhang ZC, Wang XL, Zu B, Zhang GZ, Feng B and Liu JY. 2014b. Asia Gold Belt in western Tianshan and its dynamic setting, metallogenic control and exploration. Earth Science Frontiers, 21(5): 128-155 (in Chinese with English abstract)
[78] Xue CJ, Zhao XB, Zhang GZ, Mo XX, Gu XX, Dong LH, Zhao SM, Mi DJ, Nurtaev B, Pak N, Li ZD, Wang XL, Zu B, Yaxiaer YLK and Feng B. 2015. Metallogenic environments, ore-forming types and prospecting potential of Au-Cu-Zn-Pb resources in western Tianshan Mountains. Geology in China, 42(3): 381-410 (in Chinese with English abstract)
[79] Yang SH and Zhou MF. 2009. Geochemistry of the-430-Ma Jingbulake mafic-ultramafic intrusion in western Xinjiang, NW China: Implications for subduction related magmatism in the South Tianshan orogenic belt. Lithos, 113(1-2): 259-273
[80] Yang TN, Li JY, Sun GH and Wang YB. 2006. Earlier Devonian active continental arc in Central Tianshan: Evidence of geochemical analyses and Zircon SHRIMP dating on mylonitized granitic rock. Acta Petrologica Sinica, 22(1): 41-48 (in Chinese with English abstract)
[81] Yang WZ, Xue CJ, Zhao XB, Zhao SM, Wei J, Feng B, Zhou H, Lin ZH, Zheng H, Liu JW, Zhang Q and Zu B. 2013. The discovery of the Kateba'asu large Au-Cu deposit in Xinyuan County, western Tianshan, Xinjiang. Geological Bulletin of China, 32(10): 1613-1620 (in Chinese with English abstract)
[82] You CF, Castillo PR, Gieskes JM, Chan LH and Spivack AJ. 1996. Trace element behavior in hydrothermal experiments: Implications for fluid processes at shallow depths in subduction zones. Earth and Planetary Science Letters, 140(1-4): 41-52
[83] Zhang Q, Xue CJ, Zhao XB, Feng B, Xing H, Mo XX, Zhao SM, Yang WZ and Xing L. 2015. Geology, geochemistry and metallogenic epoch of the Katebasu large-sized gold deposit, western Tianshan Mountains, Xinjiang. Geology in China, 42(3): 411-437 (in Chinese with English abstract)
[84] Zhang X, Gao J, Dong LH, Li JL, Jiang T, Qian Q and Su W. 2011. Zircon LA-ICP-MS U-Pb age of I-type granitoids from Qiaohuote copper deposit in Central Tianshan of Xinjiang and its geological implications. Acta Petrologica Sinica, 27(6): 1637-1648 (in Chinese with English abstract)
[85] Zhao XB, Xue CJ, Chi GX, Pak N and Zu B. 2015. Re-Os pyrite and U-Pb zircon geochronology from the Taldybulak Levoberezhny gold deposit: Insight for Cambrian metallogeny of the Kyrgyz northern Tien Shan. Ore Geology Reviews, 67: 78-89
[86] Zhou D, Graham SA, Chang EZ, Wang BY and Hacker B. 2001. Paleozoic tectonic amalgamation of the Chinese Tian Shan: Evidence from a transect along the Dushanzi-Kuqa Highway. Memoir of the Geological Society of American, 194: 23-46
[87] Zhou DW, Su L, Jian P, Wang RS, Liu XM, Lu GX and Wang JL. 2004. Zircon U-Pb SHRIMP ages of high-pressure granulite in Yushugou ophiolitic terrane in southern Tianshan and their tectonic implications. Chinese Science Bulletin, 49(13): 1415-1419
[88] Zhu DC, Mo XX, Wang LQ, Zhao ZD, Niu YL, Zhou CY and Yang YH. 2009. Petrogenesis of highly fractionated I-type granites in the Zayu area of eastern Gangdese, Tibet: Constraints from zircon U-Pb geochronology, geochemistry and Sr-Nd-Hf isotopes. Science in China (Series D), 52(9): 1223-1239
[89] Zhu YF, Zhou J, Song B, Zhang LF and Guo X. 2006. Age of the "Dahalajunshan" Formation in Xinjiang and its disintegration. Geology in China, 33(3): 487-497 (in Chinese with English abstract)
[90] Zhu ZX, Wang KZ, Li JY, Wang XK, Guo L, Zhang C and Song Y. 2006a. The igneous rock petrochemisty character of bayinbuluke formation in the western Tianshan, Xinjiang and the geological implication. Xinjiang Geology, 24(1): 9-12 (in Chinese with English abstract)
[91] Zhu ZX, Wang KZ, Zheng YJ, Sun GH, Zhang C and Li YP. 2006b. Zircon SHRIMP dating of Silurian and Devonian granitic intrusions in the southern Yili block, Xinjiang and preliminary discussion on their tectonic setting. Acta Petrologica Sinica, 22(5): 1193-1200 (in Chinese with English abstract)
[92] Zhu ZX. 2007. The geological components and tectonic evolution of South Tainshan, Xinjiang. Ph. D. Dissertation. Beijing: Chinese Science Academy, 1-221 (in Chinese with English summary)
[93] Zhu ZX, Li JY, Dong LH, Wang KZ, Zhang XF and Xu SQ. 2011. Geological characteristics and tectonic significance of Paleozoic intrusive rocks in western Tianshan of Xinjiang Province. Earth Science Frontiers, 18(2): 170-179 (in Chinese with English abstract)
[94] Zimmer M, Kröner A, Jochum KP, Reischmann T and Todt W. 1995. The Gabal Gerf complex: A Precambrian N-MORB ophiolite in the Nubian Shield, NE Africa. Chemical Geology, 123(1-4): 29-51
[95] Zindler A and Hart SR. 1986. Chemical geodynamics. Annual Review of Earth and Planetary Sciences, 14: 493-571
[96] 车自成, 刘洪福, 刘良. 1994. 中天山造山带的形成与演化. 北京: 地质出版社, 1-135
[97] 陈江峰, 满发胜, 倪守斌. 1995. 西天山菁布拉克岩带基性-超基性岩的Nd、Sr同位素地球化学. 地球化学, 24(2): 121-127
[98] 邓晋福, 罗照华, 苏尚国, 莫宣学, 于炳松, 赖兴运, 谌宏伟. 2004. 岩石成因、构造环境与成矿作用. 北京: 地质出版社, 1-381
[99] 冯博, 薛春纪, 赵晓波, 丁振信, 张祺, 俎波, 杨维忠, 林泽华, 陈威. 2014. 西天山卡特巴阿苏大型金铜矿赋矿二长花岗岩岩石学、元素组成和时代. 地学前缘, 21(5): 187-195
[100] 高俊, 钱青, 龙灵利, 张喜, 李继磊, 苏文. 2009. 西天山的增生造山过程. 地质通报, 28(12): 1804-1816
[101] 郭召杰, 张志诚. 1993. 中天山早古生代岛弧构造带研究. 河北地质学院学报, 16(2): 132-139
[102] 韩宝福, 何国琦, 吴泰然, 李惠民. 2004. 天山早古生代花岗岩锆石U-Pb定年、岩石地球化学特征及其大地构造意义. 新疆地质, 22(1): 4-11
[103] 郝杰, 刘小汉. 1993. 南天山蛇绿混杂岩形成时代及大地构造意义. 地质科学, 28(1): 93-95
[104] 李昌年. 1992. 火成岩微量元素岩石学. 武汉: 中国地质大学出版社, 1-195
[105] 黎彤. 1976. 化学元素的地球丰度. 地球化学, (3): 167-174
[106] 刘本培, 王自强, 张传恒, 马鸿文, 周洪瑞, 朱鸿, 龚一鸣, 贾维民. 1996. 西南天山构造格局与演化. 武汉: 中国地质大学出版社, 1-120
[107] 龙灵利, 高俊, 熊贤明, 钱青. 2006. 南天山库勒湖蛇绿岩地球化学特征及其年龄. 岩石学报, 22(1): 65-73
[108] 龙灵利, 高俊, 熊贤明, 钱青. 2007. 新疆中天山南缘比开(地区)花岗岩地球化学特征及年代学研究. 岩石学报, 23(4): 719-732
[109] 马中平, 夏林圻, 徐学义, 夏祖春, 李向民, 王立社. 2008. 南天山北部巴音布鲁克早古生代火成岩的地球化学特征与岩石成因. 岩石学报, 24(10): 2289-2300
[110] 倪守斌, 满发胜, 陈江峰. 1995. 西天山琼阿乌孜超基性岩体的稀土元素和Sr、Nd同位素研究. 岩石学报, 11(1): 65-70
[111] Rollinson HR. 2000. 岩石地球化学. 杨晓勇, 陈双喜译. 北京: 中国科学技术大学出版社, 1-275
[112] 茹艳娇. 2012. 西天山大哈拉军山组火山岩地层序列、岩石成因与构造环境. 硕士学位论文. 西安: 长安大学, 1-113
[113] 孙鼐, 彭亚鸣. 1985. 火成岩石学. 北京: 地质出版社, 1-324
[114] 王宝瑜, 郎智君, 李向东等. 1994. 中国天山西段地质剖面综合研究. 北京: 科学出版社, 1-202
[115] 吴元保, 郑永飞. 2004. 锆石成因矿物学研究及其对U-Pb年龄解释的制约. 科学通报, 49(16): 1589-1604
[116] 夏林圻, 张国伟, 夏祖春, 徐学义, 董云鹏, 李向民. 2002. 天山古生代洋盆开启、闭合时限的岩石学约束——来自震旦纪、石炭纪火山岩的证据. 地质通报, 21(2): 55-62
[117] 徐学义, 马中平, 夏祖春, 夏林圻, 李向民, 王立社. 2006. 天山中西段古生代花岗岩TIMS法锆石U-Pb同位素定年及岩石地球化学特征研究. 西北地质, 39(1): 50-75
[118] 徐学义, 王洪亮, 马国林, 李平, 陈隽璐, 李婷. 2010. 西天山那拉提地区古生代花岗岩的年代学和锆石Hf同位素研究. 岩石矿物学杂志, 29(6): 691-706
[119] 薛春纪, 段士刚, 柴凤梅, 木合塔尔·买买提, Typeceóeκοв AX, 屈文俊. 2013. 乌兹别克斯坦Almalyk斑岩铜矿田成矿时代及其地质意义. 地学前缘, 20(2): 197-204
[120] 薛春纪, 赵晓波, 莫宣学, 陈毓川, 董连慧, 顾雪祥, 张招崇, Nurtaev B, Pak N, 李志丹, 王新利, 张国震, 亚夏尔亚力坤, 冯博, 俎波, 刘家瑛. 2014a. 西天山巨型金铜铅锌成矿带构造成矿演化和找矿方向. 地质学报, 88(12): 2490-2531
[121] 薛春纪, 赵晓波, 莫宣学, 董连慧, 顾雪祥, Nurtaev B, Pak N, 张招崇, 王新利, 俎波, 张国震, 冯博, 刘家瑛. 2014b. 西天山"亚洲金腰带"及其动力背景和成矿控制与找矿. 地学前缘, 21(5): 128-155
[122] 薛春纪, 赵晓波, 张国震, 莫宣学, 顾雪祥, 董连慧, 赵树铭, 米登江, Nurtaev B, Pak N, 李志丹, 王新利, 俎波, 亚夏尔亚力坤, 冯博. 2015. 西天山金铜多金属重要成矿类型、成矿环境及找矿潜力. 中国地质, 42(3): 381-410
[123] 杨天南, 李锦轶, 孙桂华, 王彦斌. 2006. 中天山早泥盆世陆弧: 来自花岗质糜棱岩地球化学及SHRIMP-U/Pb定年的证据. 岩石学报, 22(1): 41-48
[124] 杨维忠, 薛春纪, 赵晓波, 赵树铭, 魏俊, 冯博, 周华, 林泽华, 郑鸿, 刘家伟, 张祺, 俎波. 2013. 新疆西天山新发现新源县卡特巴阿苏大型金铜矿床. 地质通报, 32(10): 1613-1620
[125] 张祺, 薛春纪, 赵晓波, 冯博, 邢浩, 莫宣学, 赵树铭, 杨维忠, 邢令. 2015. 新疆西天山卡特巴阿苏大型金矿床地质地球化学和成岩成矿年代. 中国地质, 42(3): 411-437
[126] 张喜, 高俊, 董连慧, 李继磊, 江拓, 钱青, 苏文. 2011. 新疆中天山乔霍特铜矿区Ⅰ型花岗岩锆石LA-ICP-MS U-Pb年龄及其地质意义. 岩石学报, 27(6): 1637-1648
[127] 周鼎武, 苏梨, 简平, 王润三, 柳小明, 陆关祥, 王居里. 2004. 南天山榆树沟蛇绿岩地体中高压麻粒岩SHRIMP锆石U-Pb年龄及构造意义. 科学通报, 49(14): 1411-1415
[128] 朱弟成, 莫宣学, 王立全, 赵志丹, 牛耀龄, 周长勇, 杨岳衡. 2009. 西藏冈底斯东部察隅高分异I型花岗岩的成因: 锆石U-Pb年代学、地球化学和Sr-Nd-Hf同位素约束. 中国科学(D辑), 39(7): 833-848
[129] 朱永峰, 周晶, 宋彪, 张立飞, 郭璇. 2006. 新疆"大哈拉军山组"火山岩的形成时代问题及其解体方案. 中国地质, 33(3): 487-497
[130] 朱志新, 王克卓, 李锦轶, 王新昆, 郭利, 张超, 宋杨. 2006a. 新疆西天山巴音布鲁克组火山岩地质特征及构造意义. 新疆地质, 24(1): 9-12
[131] 朱志新, 王克卓, 郑玉洁, 孙桂华, 张超, 李亚萍. 2006b. 新疆伊犁地块南缘志留纪和泥盆纪花岗质侵入体锆石SHRIMP定年及其形成时构造背景的初步探讨. 岩石学报, 22(5): 1193-1200
[132] 朱志新. 2007. 新疆南天山地质组成和构造演化. 博士学位论文. 北京: 中国地质科学院, 1-221
[133] 朱志新, 李锦轶, 董连慧, 王克卓, 张晓帆, 徐仕琪. 2011. 新疆西天山古生代侵入岩的地质特征及构造意义. 地学前缘, 18(2): 170-179