2017, Vol. 33
2. 中国海洋大学海洋地球科学学院, 海底科学与探测技术教育部重点实验室, 青岛 266100;
3. 青岛海洋科学与技术国家实验室海洋地质功能实验室, 青岛 266061;
4. 吉林大学地球科学学院, 长春 130061;
5. 同位素地球化学国家重点实验室, 中国科学院广州地球化学研究所, 广州 510640
2. MOE Key Laboratory of Submarine Geosciences and Prospecting Technique, College of Marine Geosciences, Ocean University of China, Qingdao 266100, China;
3. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China;
4. College of Earth Sciences, Jilin University, Changchun 130061, China;
5. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
弧岩浆作用和伴随的变质作用是增生型造山带的典型特征，对于大陆生长和再造具有重要意义。弧岩浆作用通常被认为是太古代之后大陆地壳生长和活化的主要过程(Rudnick, 1995; Andersson et al., 2006; Bahlburg et al., 2009; Cawood et al., 2009; Kemp et al., 2009; Jagoutz et al., 2011; Jagoutz and Schmidt, 2012; Johnson et al., 2014; Niu, 2016)，弧岩浆就位为变质作用的进行提供了重要的热源(Hollis et al., 2003, 2004)，岩浆弧的侵位导致地壳加厚阶段也常常伴随高温变质作用(Wells, 1980; Barton and Hanson, 1989; De Yoreo et al., 1989; Brown and Solar, 1998; Corona-Chávez et al., 2006)。深成岩体和高级变质岩记录了岛弧岩浆作用，弧陆碰撞作用和岩浆伸展作用的历史(Mattinson et al., 1986; Brown, 1996; Daczko et al., 2001; Hollis et al., 2003)。因此，弧岩浆作用和变质作用研究为增生造山带的构造演化过程提供了重要线索。
北祁连造山带位于青藏高原北部的祁连地块和阿拉善地块之间，包含一系列的岛弧、增生楔、蛇绿岩、高压低温变质岩等，被认为是典型的早古生代板块缝合带(Xu et al., 1994; Wu et al., 1993; Gehrels et al., 2003a, b; Smith et al., 1997; Smith, 2006; Smith and Yang, 2006; Song, 1997; Song et al., 2006, 2009, 2013; 张建新等, 1997, 1998; Zhang et al., 2007, 2017; Li et al., 2017a, b)。前人已经对这条缝合带内的高压/低温(HP/LT)变质岩(Liou et al., 1989; Wu et al., 1993; Xu et al., 1994; Liu et al., 2006; Zhang and Meng, 2006; Song et al., 2004, 2006, 2007, 2013; 张建新等, 1997, 1998; Zhang et al., 2007, 2012, 2017; Ker et al., 2015)，广泛出露的花岗岩(Wang et al., 2005; 王金荣等, 2006; Tseng et al., 2009; 吴才来等, 2004, 2006, 2010; Wu et al., 2011; 熊子良等, 2012; Song et al., 2013; Chen et al., 2012, 2014; Huang et al., 2015; Yu et al., 2015)进行了大量研究，并取得了一系列重要研究成果。北祁连造山带中部百经寺一带发育的HP/LT变质岩的峰期温压条件为420~580℃和19~24kbar (Wei and Song, 2008; Zhang et al., 2007, 2012)，变质时代为440~512Ma (Liou et al., 1989; Wu et al., 1993; Liu et al., 2006; Song et al., 2004, 2006; 张建新等, 1997; Zhang et al., 2007)。根据岩石成因和年代学的差异，花岗岩被进一步分为弧花岗岩(520~460Ma)、同碰撞花岗岩(440~420Ma)和碰撞后花岗岩(≤420Ma) (Song et al., 2013)。但是关于北祁连造山带南部发育的弧岩浆岩和高级变质岩的研究还很薄弱，制约了对于北祁连造山带构造演化的认识。最近几年在北祁连南部报道的一些500Ma左右的阿拉斯加型基性岩体和“Ⅰ”型花岗岩体暗示了北祁连洋可能存在向南俯冲的极性(Gehrels et al., 2003a, b; Xiao et al., 2009; 吴才来等, 2010; Zhang et al., 2012; Huang et al., 2015)。本文选取北祁连造山带南部门源-柯柯里地区新发现的高温低压变质岩和弧岩浆岩为研究对象，采用岩相学观察、PT视剖面模拟和锆石U-Pb定年分析相结合的综合研究方法，阐明弧岩浆作用与变质作用事件的关系，约束北祁连洋早古生代的俯冲极性。
2 区域地质背景北西-南东向展布的阿尔金-祁连造山带位于中国三大克拉通(华北克拉通、华南克拉通、塔里木克拉通)的结合部位，地理位置独特(图 1a)。其西侧被左行的新生代阿尔金断裂所切割，走滑大约400km (许志琴等, 1999; 葛肖虹和刘俊来, 1999; Yang et al., 2001; Zhang et al., 2001, 2005, 2017)，一些研究证实北祁连与北阿尔金具有类似的古构造单元属性(Zhang et al., 2001; 许志琴等, 1999)。北祁连造山带自南向北可以分为：(1)俯冲-增生杂岩带；(2)走廊南山古火山弧；(3)走廊南山北坡弧后盆地；(4)早古生代被动大陆边缘带。构成了典型的“沟-弧-盆”体系(Xu et al., 1994; 张建新等, 1997, 1998; Xia et al., 2003; 夏林圻等, 2016; Zhang et al., 2012, 2017)。北祁连造山带以发育典型的HP/LT变质岩(蓝片岩和低温榴辉岩)、蛇绿岩、弧火山岩和弧后杂岩为特征(Xu et al., 1994)，特别是保存完好的含硬柱石蓝片岩和榴辉岩以及含纤柱石的高压变沉积岩指示了冷的洋壳俯冲(Zhang and Meng, 2006; Song et al., 2007; Wei and Song, 2008; Zhang et al., 2007, 2009, 2017)。
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图 1 阿尔金-祁连造山带构造格架简图(a，据Zhang et al., 2012修改)和门源地区区域地质简图及采样点位置(b) NQL-北祁连俯冲增生杂岩; NAT-北阿尔金俯冲增生杂岩; DHB-敦煌地块; QLB-祁连地块; CAB-中阿尔金地块; NQD-柴北缘俯冲碰撞杂岩; SAT-南阿尔金俯冲碰撞杂岩; TRB-塔里木地块; QL-祁连山; QDB-柴达木盆地; WKL-西昆仑; EKL-东昆仑; HMLY-喜马拉雅山; INP-印度板块 Fig. 1 Schematic map showing major tectonic units of the Altyn Tagh-Qilian orogenic system (a, after Zhang et al., 2012) and geological sketch map of Menyuan area showing geological setting and sample locations (b) NQL-North Qilian subduction-accretion complex; NAT-North Altun subduction-accretion complex; DHB-Dunhuang Block; QLB-Qilian Block; CAB-central Altun Block; NQD-North Qaidam subduction-collision complex; SAT-South Altun subduction-collision complex; TRB-Tarim Basin; QL-Qilian Mountains; QDB-Qaidam Basin; WKL-Western Kunlun Mountains; EKL-Eastern Kunlun Mountains; HMLY-Himalaya Mountains; INP-Indian plate |
本文的研究区位于门源-柯柯里一带(图 1b)，主要由一套高级变质岩、早古生代侵入岩、中生代和新生代沉积岩组成，这套高级变质岩被认为是祁连地块的基底，也被称作“湟源群”。这套高级变质岩包括副片麻岩、花岗片麻岩、角闪岩、泥质片麻岩和大理岩等组成。最近相关的年代学研究结果证明其中的花岗片麻岩原岩年龄为870~950Ma (Wan et al., 2001; Xu et al., 2007; Tung et al., 2007, 2012, 2013; Yu et al., 2013)。
3 岩石学特征本次研究的样品包括花岗闪长岩、石榴角闪岩、片麻岩和斜长角闪岩。花岗闪长岩(AQ15-2-4.1)在野外呈灰白色、细粒至中粒结构，块状构造，主要由长石、石英和角闪石等矿物组成，其中长石+石英含量约占80%(图 2a)。石榴角闪岩(AQ14-2-2.1)主要由石榴子石、角闪石、长石、石英及少量金红石、钛铁矿等组成(图 2b、图 3e)，石榴子石和角闪石变斑晶内部可见长石、石英包体，石榴子石边部呈港湾状，角闪石边部发生部分分解，在石榴子石的边部可见熔体假象(图 3e)。研究区的片麻岩主要有两种类型，其中石榴黑云斜长片麻岩(AQ14-1-1.4)主要由石榴子石、黑云母、斜长石、角闪石、石英及少量金红石、钛铁矿组成。石榴子石斑晶为自形粒状，发育明显裂纹，但包体很少，石榴子石边部部分呈港湾状，黑云母呈碎片状，石英呈他形并被拉长；石英、云母、长石显示特征的片麻状构造(图 2a, b)。在岩相学观察的基础上，石榴黑云斜长片麻岩可以分为至少两期，峰期矿物组合为Bt+Pl+Kfs+Grt+Rt+Ilm+Qz，此阶段的矿物组合中黑云母，斜长石，钾长石均经历了后期的变形改造，呈一定程度定向排列。晚期矿物组合为Bt+Pl+Kfs+Grt+Rt+Qz+Ms，以白云母的出现为特征。角闪石的出现可能代表了更晚期的矿物组合，部分角闪石中可见石榴子石、黑云母、长石、石英等包体，说明角闪石与石榴子石等矿物不是同一期矿物，不平衡共生。夕线石榴黑云片麻岩(QL11-22-3.2)主要矿物包括石榴子石、黑云母、白云母、夕线石、斜长石和石英等(图 2c、图 3c, d)，其石榴子石核部和幔部发育较多的包体，夕线石呈针簇状与云母呈定向排列，显示该岩石遭受了更为强烈的构造变形。斜长角闪岩(AQ14-5-3.3)野外露头呈灰绿色(图 2d、图 3f)，主要由角闪石和细粒他形粒状长石和石英组成，矿物分布均匀，角闪石边缘呈不规则锯齿状，斜长石部分蚀变退化。矿物名称缩写参考Whitney and Evans (2010)。
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图 2 门源-柯柯里地区火成岩和变质岩野外露头照片 (a)门源花岗闪长岩(AQ15-2-4.1)包裹变基性岩；(b)门源石榴角闪岩(AQ14-2-2.1)；(c)门源石榴黑云斜长片麻岩(AQ14-1-1.4)；(d)柯柯里斜长角闪岩(AQ14-5-3.3) Fig. 2 Photographs of outcrops of plutons and metamorphic rocks (a) granodiorite(AQ15-2-4.1) and metabasite xenoliths in Menyuan; (b) garnet-amphibolites(AQ14-2-2.1) in Menyuan; (c) garnet-biotite-gneiss(AQ14-1-1.4)in Menyuan; (d) amphibolites(AQ14-5-3.3)in Kekeli |
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图 3 门源-柯柯里地区火成岩和变质岩镜下显微结构特征 (a、b)石榴黑云斜长片麻岩(AQ14-1-1.4)，主要由石榴子石、黑云母、斜长石、角闪石、石英及少量金红石、磁铁矿组成，石英、云母呈拉长状显示特征的片麻状构造; (c、d)夕线石榴黑云片麻岩(QL11-22-3.2)，主要矿物有石榴子石、黑云母、白云母、夕线石、斜长石、石英，石榴石核部和幔部发育较多的包体，夕线石呈针簇状与云母呈定向排列；(e)石榴角闪岩(AQ14-2-2.1)，石榴石和角闪石中可见较大的长石、石英包体，石榴石边部呈港湾状，角闪石部分分解，可见熔体假象；(f)斜长角闪岩(AQ14-5-3.3)，角闪石边缘呈不规则锯齿状，斜长石部分蚀变退化 Fig. 3 Photomicrographs of representative igneous and metamorphic rocks in Menyuan-Kekeli (a, b) garnet-biotite-plagioclase gneiss (AQ14-1-1.4), consisting of garnet, biotite, plagioclase, quartz and minor opaque minerals, showing distinct foliation, which is defined by the elongated quartz mica and layers of mica; (c, d) sillimanite-garnet-biotite-plagioclase gneiss(QL11-22-3.2), consisting of garnet, biotite, muscovite, plagioclase, sillimanite and quartz, with many inclusions in the garnet. Sillimanite is needle-like and parallel symbiotic with mica; (e) garnet-amphibolites (AQ14-2-2.1) with big inclusions in garnet and amphibole, garnet has a harbor-like edge, amphibole is partial resolved; (f) amphibolites (AQ14-5-3.3), the edge of the amphibole is irregularly serrated, and the plagioclase is partially altered |
样品的矿物化学成分分析是在中国地质科学院地质研究所的JEOL JXA 8900电子探针仪进行分析的。运行条件是15kV加速电压，5nA电子束电流，5mm的电子束斑，少数的矿物包裹体采用2mm的电子束斑，数据检测时间为10s。为了观察石榴子石的成分变化，选取一条线穿越石榴子石中心的线做石榴子石成分剖面线，在沿线选点时在保证避开包体的前提下，尽量保证等间距选点分析。
锆石U-Pb定年测试分析在中国地质科学院矿产资源研究所MC-ICP-MS实验室完成，锆石定年分析所用仪器为Finnigan Neptune型MC-ICP-MS及与之配套的Newwave UP 213激光剥蚀系统。激光剥蚀所用斑束直径为25μm，频率为10Hz，能量密度约为2.5J/cm2，以He为载气。LA-MC-ICP-MS激光剥蚀采样采用单点剥蚀的方式，样品测试前用锆石GJ-1进行调试仪器，使之达到最优状态, 锆石U-Pb定年以锆石GJ-1为外标，U、Th含量以锆石M127 (U: 923×10-6; Th: 439×10-6; Th/U: 0.475)为外标进行校正。测试过程中在每测定5~7个样品前后重复测定两个锆石GJ-1对样品进行校正，并测量一个锆石Plesovice，观察仪器的状态以保证测试的精确度。数据处理采用ICPMSDataCal程序(Liu et al., 2010), 锆石年龄谐和图用Isoplot 3.0程序获得。详细实验测试过程可参见侯可军等(2007)。
5 测试结果 5.1 矿物成分结果代表性的矿物的化学成分数据见表 1、表 2，矿物中Fe2O3的含量通过电价平衡方法计算获得。
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表 1 石榴黑云斜长片麻岩中代表性的石榴子石电子探针分析结果(wt%) Table 1 The compositions of the representative garnets from the garnet-biotite-plagioclase gneiss (wt%) |
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表 2 石榴黑云片麻岩和石榴角闪岩中代表性的矿物成分电子探针分析结果(wt%) Table 2 The compositions of the representative mineral from the garnet-biotite-plagioclase gneiss and garnet-amphibolites (wt%) |
石榴子石 石榴子石主要由铁铝榴石(Alm)、镁铝榴石(Prp)、钙铝榴石(Grs)的固溶体组成，另外还有少量的锰铝榴石组分。本次研究选择石榴黑云斜长片麻岩中的石榴子石变斑晶进行成分剖面分析。石榴黑云斜长片麻岩(AQ14-1-1.4)中的石榴子石斑晶颗粒较大，沿石榴子石中心做了一条成分剖面线，从石榴子石核部到边部，镁铝榴石(Prp)逐渐减少，钙铝榴石(Grs)逐渐增多，显示了明显的扩散环带(图 4b)，表明石榴子石核部成分保留了峰期变质阶段的成分特征(表 1)。
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图 4 石榴黑云斜长片麻岩的石榴石背散射图(a)和石榴子石成分剖面(b) Alm-铁铝榴石；Sps-锰铝榴石；Prp-镁铝榴石；Grs-钙铝榴石 Fig. 4 Back-scattered electron (BSE) images (a) and compositional profile (b) of garnet Alm-almandite; Sps-spessarite; Prp-pyrope; Grs-grossularite |
黑云母 在石榴黑云斜长片麻岩(AQ14-1-1.4)中，黑云母的FeO、MgO、TiO2含量分别为19.22%~19.40%、10.81%~10.90%、3.71%~3.94%(表 2)。较高的TiO2含量显示黑云母形成于较高的温度条件(Schreurs, 1985)，黑云母成分差异不大，说明它们在降温过程中遭受了不同程度的均一化改造。
斜长石 电子探针结果显示斜长石主要由钙长石(An)和钠长石(Ab)组成，含有极少量的正长石(Or)。石榴黑云斜长片麻岩和石榴角闪岩中的钙长石含量分别为40.14%~42.64%，77.48%~79.42%，钠长石含量分别为56.57%~59.25%，20.22%~22.27%(表 2)。
角闪石 在石榴黑云斜长片麻岩和石榴角闪岩中，角闪石的Si原子数分别在6.50~6.57和6.48~6.55之间变动，而XMg(XMg=Fe/(Fe+Mg))值分别在0.43~0.50和0.38~0.40之间变化，Ti原子数在0.10~0.15和0.14~0.16之间变化(表 2)，主要落在铁浅闪石和铁钙镁质角闪石的区域(图 5)。
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图 5 角闪石分类图解(据Leake et al., 1997修改) Fig. 5 Classification of the representative amphiboles from the gneiss and garnet-amphibolites (modified after Leake et al., 1997) |
选取了门源-柯柯里地区2个代表性的变质岩和1个侵入岩样品进行锆石U-Pb定年。详细的数据结果见表 3所示。花岗闪长岩AQ15-2-4.1的锆石形态呈长柱状，其长、宽分别为100~200μm和50μm，阴极发光图像显示锆石具有核-幔-边结构，核部为不规则的具不清晰环带的继承性碎屑锆石，幔部较宽，具有岩浆锆石典型的震荡环带特征(吴元保和郑永飞, 2004)，边部出现较窄的增生边，阴极发光较强，无明显分带，锆石的Th/U比值明显大于0.4，同样指示锆石为岩浆成因(表 3、图 6)，对锆石的幔部进行锆石测年，得到32个测点的加权平均值为495±3Ma (MSWD=2.2)(图 7a)；样品AQ14-5-3.3为斜长角闪岩，样品AQ14-1-1.4为石榴黑云斜长片麻岩，样品AQ14-5-3.3的锆石具有等轴状、浑圆状，弱CL强度和冷杉叶状分带或面状分带特征(图 6)，24个测点获得的变质锆石的变质作用年龄加权平均值为495±2Ma (MSWD=1.9)(图 7b)，其Th/U比值在0.30~0.51之间(表 3)。样品AQ14-1-1.4的锆石具有他形到等轴状、浑圆状的特征，长宽比约为1.2：1，长度约为50~100μm，锆石内部无分带或者弱分带(图 6)，Th/U比值介于0.02~0.52之间，且主要位于0.02~0.40之间(表 3)，属典型变质成因锆石(吴元保和郑永飞, 2004)。样品AQ14-1-1.4中47个测点获得的加权平均年龄为493±3Ma (MSWD=2.9)(图 7c)，可能代表了其峰期变质年龄。
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表 3 门源地区花岗闪长岩、石榴黑云斜长片麻岩及柯柯里地区斜长角闪岩的锆石LA-ICP-MS U-Pb定年结果 Table 3 LA-ICP-MS U-Pb analytical data for zircons from granodiorite, garnet-biotite-gneiss in Menyuan and amphibolite in Kekeli |
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图 6 花岗闪长岩和变质岩中锆石的阴极发光特征 Fig. 6 Cathodoluminescene images (CL) showing internal texture of zircons from granodiorite, amphibolite and gneiss |
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图 7 花岗闪长岩(a)、斜长角闪岩(b)及片麻岩(c)的锆石LA-ICP-MS U-Pb年龄谐和图 Fig. 7 Zircon U-Pb concordia diagrams for granodiorite (a), amphibolite (b) and gneiss (c) from the Menyuan-Kekeli |
根据研究区广泛出露不同类型变质岩的特点，本文选取门源地区的石榴黑云斜长片麻岩(AQ14-1-1.4)进行PT视剖面模拟，结合石榴石等值线温压计进行变质PT条件的定量估计。视剖面模拟采用Perple_X计算程序(Connolly, 2005, version of December of 2016; http://www.perplex.ethz.ch/)及内置的热力学数据库(Holland and Powell 1998, updated 2002)。相平衡模拟选择的化学体系为Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3(NCKFSMASHTO)。假定变质过程中流体为纯水，样品中的H2O含量被认为是饱和的，MnO因为含量较少且几乎不影响镁铁矿物的稳定性而被忽略(Wei et al., 2004)。
视剖面模拟过程中岩石的有效成分采用结合体系中各矿物相丰度进行综合计算的方法(White et al., 2003; Wei and Powell, 2003; Wei et al., 2007)。根据详细的薄片观察，样品AQ14-1-1.4中各矿物成分的摩尔体积分别为石榴子石18%，黑云母25%，白云母3%，斜长石20%，石英28%，钾长石4%，钛铁矿1%，金红石1%。结合相应的电子探针分析数据计算出有效全岩成分为SiO2=58.46%, Al2O3=10.44%, CaO=4.13%, MgO=5.62%, FeO=12.11%, K2O=1.70%, Na2O=1.01%, TiO2=3.15%, H2O=3.31%, Fe3+的含量根据电价平衡的原则从含铁矿物进行恢复。
石榴子石中的镁、钙等值线(XMg=[Mg/(Fe+Ca+Mg)]和XCa=[Ca/(Fe+Ca+Mg+Mn)])被当做两个独立的热力学变量用来描绘石榴子石P-T区间的成分变化。样品AQ14-1-1.4的相平衡模拟结果如图 8所示，其中石榴子石、斜长石和透长石稳定存在于600~900℃和3.0~12.0kbar的PT范围内。黑云母稳定存在于小于750℃的条件下，金红石出现于6.6kbar之上。固相线位于720~760℃之间，视剖面模拟表明片麻岩通过白云母脱水熔融产生熔体，对应的反应式为Ms+Pl+Qz+H2O=Melt (Fornelli et al., 2002)。由薄片观测可知样品AQ14-1-1.4的峰期矿物组合为Bt+Pl+Kfs+Grt+Rt+Ilm+Qz，该峰期矿物组合落在视剖面图中的一个较大稳定区间720~840℃和6.5~10kbar。推测的峰期后矿物组合Bt+Pl+Kfs+Grt+Ms+Rt+Qz在视剖面图中对应的区间P-T范围为700~750℃和8.4~12kbar (图 8a)。石榴子石等值线轮廓被用来进一步限定P-T范围图 8b。已知钙等值线值随着压力的增加而增加，镁等值线值随着温度的增加而增加(Zhang et al., 2013; Cai et al., 2014)。如前所述，样品AQ14-1-1.4的石榴子石具有明显的扩散环带，石榴子石核部的XMg=0.23、XCa=0.13 (表 1)，交点表征峰期变质条件为795℃、8.9kbar(图 8b)。石榴子石的边部XMg=0.16、XCa=0.17，交于730℃、9.9kbar，落在峰期后矿物组合所在的稳定域内(图 8b)。样品AQ14-2-2.1采用角闪石-斜长石温度计(Holland and Blundy, 1994)和石榴石-角闪石-斜长石-石英压力计(Dale et al., 2000)估算出峰期变质温压条件790℃、8.4kbar。
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图 8 石榴黑云斜长片麻岩的P-T视剖面图(a)和石榴子石成分等值线(b) 红色和蓝色线条分别代表XMg[=Mg/(Fe+Ca+Mg)]和XCa[=Ca/(Fe+Ca+Mg+Mn)], 红色圆圈和绿色圆圈分别代表峰期变质和退变质温压条件范围 Fig. 8 P-T pseudosection of the gneiss (AQ14-1-1.4) (a) and garnet composition isopleths superimposed on the P-T pseudosection (b) The red lines and blue lines represent isopleths of XMg[=Mg/(Fe+Ca+Mg)] and XCa[=Ca/(Fe+Ca+Mg+Mn)], respectively. The red circle and green circle refer to the P-T condition calculated from the composition isopleths of garnet core and rim, respectively |
门源-柯柯里地区的石榴黑云斜长片麻岩(AQ14-1-1.4)可以至少识别出两期变质阶段。相平衡模拟构建的变质温压条件显示样品AQ14-1-1.4经历了一个从峰期温压795℃, 8.9kbar到峰期后730℃, 9.9kbar的近等压降温的逆时针轨迹(图 8b)。通常认为俯冲带或大陆碰撞环境(Brown, 1993; Zhao et al., 1998)的变质P-T轨迹可分为西阿尔卑斯型(Western Alpine type)和弗朗西斯科型(Franciscan type)。前者具有热松弛过程，退变质阶段为近等温降压(ITD), 通常与地体快速隆升有关。后者表现为退变质P-T轨迹沿原路折返，表现为“发卡”状。本区石榴黑云斜长片麻岩的P-T演化轨迹与经典的俯冲带的P-T轨迹不一致，表现为逆时针方向近等压降温(IBC)过程。考虑到门源-柯柯里地区广泛出现的弧岩浆岩和弧火山岩，本区的变质岩可能产生于俯冲带外侧弧岩浆岩增生的区域，洋壳俯冲诱导产生了大量的弧火山岩和弧岩浆岩，带来了大量的热使得门源-大通地区发生了高温变质作用，洋壳俯冲过程伴随的构造挤压及岩浆增生带来的地壳加厚使得中地壳岩石经历了近等压或升压的过程，随后的热松弛产生了近等压降温的过程。
7.2 大通-门源地区混杂岩的早古生代岩浆作用与变质作用北祁连造山带门源-柯柯里地区出露广泛的弧岩浆岩。弧侵入岩主要包括柯柯里Ⅰ型花岗闪长岩、柴达诺S型二长花岗岩、牛心山Ⅰ型石英闪长岩以及湟源斜长花岗岩。锆石U-Pb定年和元素地化特征揭示这些侵入体都形成于460~520Ma的大陆弧环境(吴才来等, 2004, 2006, 2010; Song et al., 2004, 2013; Huang et al., 2015)。弧火山岩呈带状与北祁连造山带的高压变质岩和蛇绿岩呈平行分布，主要分布于祁连、门源、白银一带，绵延1000多千米(Wang et al., 2005; Song et al., 2013)，对清水沟长英质火山岩的定年结果为479~511Ma(Song et al., 2013)。本文获得的花岗闪长岩(AQ15-2-4.1)的结晶年龄为495±3Ma与作者之前在同一地区获得的3个弧岩浆岩的年龄在误差范围内一致，都接近于500Ma，并且后者正的εHf(t)值显示了幔源物质来源的特征(Peng et al., 2017)。考虑到区域上祁连地块北缘广泛出露的500Ma左右的弧岩浆岩，充分说明了门源-柯柯里一带经历了一期500Ma左右的弧岩浆作用事件。
本文对门源-柯柯里一带的石榴黑云片麻岩和斜长角山岩进行了锆石U-Pb定年，阴极发光图像结果显示锆石无分带或弱分带的特征，属典型变质特征(吴元保和郑永飞, 2004)，其加强平均结果495±2Ma和493±3Ma应代表岩石变质时代。而锆石较高的Th/U比值(0.30~0.51)可能由于较高的温度下，富Th矿物(独居石或者帘石类矿物)的分解，从而造成熔体中富Th(Hermann, 2002)，并最终在熔体中生长出具有较高Th和Th/U比值的变质锆石。或者由于变质增生锆石较快的生长速率，使得锆石具有较低的U含量和较高的Th/U比值(Vavra et al., 1999; 吴元保和郑永飞, 2004)。Vavra et al.(1999)对于角闪岩相、角闪岩到麻粒岩过渡相样品及麻粒岩相样品进行系统对比研究后发现生长速度最快的麻粒岩样品中等轴状变质增生锆石具有最高的Th/U比值(均大于0.1，最大值为0.73)，结合变质温压条件可以判定这两个变质岩中的锆石年龄代表了麻粒岩相变质年龄。这与作者之前在门源地区获得的3个500Ma左右的变质年龄在误差范围内近乎一致(Peng et al., 2017)。同时前人的的研究也表明北祁连造山带在早古生代时期经历了多期的变质作用，相关的变质年龄介于440~512Ma (Liu et al., 2006; Song et al., 2004, 2006; 张建新等, 1997; Zhang et al., 2007)。也进一步反映了区域上门源-柯柯里地区确实存在一期500Ma左右的变质事件。相平衡模拟表明石榴黑云斜长片麻岩和石榴角闪岩都经历了峰期角闪岩相-麻粒岩相变质作用，可能代表了幔源岩浆增生及大陆地壳生长的位置，因为麻粒岩相变质作用和高的热流是活动大陆边缘的两个判别特征(Collins, 2002a, b; Scott et al., 2009)。另外有研究者认为具峰期后近等压降温的反时针P-T轨迹特征的麻粒岩相岩石的形成最可能与幔源岩浆的底垫有关(Bohlen, 1991; Zhao and Zhai, 2013)。因此门源地区的麻粒岩相变质作用与幔源岩浆的侵入密切相关。将门源-柯柯里地区的多个500Ma左右的变质年龄和500Ma左右的弧岩浆作用年龄结合起来，以及高角闪岩相-麻粒岩相变质作用事件与幔源弧岩浆作用的关系，还有这些变质岩和弧岩浆岩在空间上的密切关系，有理由相信500Ma这一期变质事件与同一时间北祁连洋俯冲导致的500Ma这一期弧岩浆作用密切相关。
7.3 构造意义早古生代时期北祁连洋的俯冲极性一直存在争议。一部分学者支持向北俯冲的模式依据发育的典型的沟弧盆体系(Xu et al., 1994; 张建新等, 1997, 1998; Xia et al., 2003; Song et al., 2013)，一部分学者支持向南俯冲的模式(Song, 1997; Sobel and Arnaud, 1999; Gehrels et al., 2003a; Yin et al., 2007)，还有一部分学者支持南北双向俯冲的模式(左国朝和刘寄陈, 1987; 吴才来等, 2010; Zhang et al., 2012)。最近越来越多的早古生代(516~477Ma)花岗岩类在祁连地块的北缘被发现，暗示了北祁连洋存在向南俯冲的极性。例如几个500Ma左右的阿拉斯加基性杂岩在北祁连造山带的南部被报道(张建新等, 1997; 吴才来等, 2010; Huang et al., 2015)；另外同时代的弧岩浆作用广泛存在于北祁连造山带的南部，如柯柯里和牛心山花岗岩，也暗示了为北祁连洋南向俯冲形成的大陆弧(Gehrels et al., 2003a, 2011; Yin et al., 2007; Xiao et al., 2009; Zhang et al., 2012)。
洋壳俯冲可以形成一条沿海沟俯冲带分布的高压低温变质内带和沿火山岛链分布的高温低压变质外带(Miyashiro, 1961, 1973)。为了证明北祁连双变质带的存在，将门源-柯柯里地区高级变质岩的峰期P-T值和清水沟-百经寺地区高压低温变质岩的峰期P-T值投在变质相系图和热力学梯度模式图上(Brown, 2010)(图 9)。本文的2个变质岩的峰期PT值落在麻粒岩相区域和750℃/GPa的热力学梯度线以下区域。与之相对的清水沟-百经寺高级变质岩则经历了榴辉岩相变质作用和小于350℃/GPa的热力学梯度叠加。前者是典型的HT/LP变质岩，后者是典型的HP/LT变质岩。结合作者之前在门源地区获得的四个样品峰期PT值也经历了麻粒岩相变质作用和大于750℃/GPa热力学梯度叠加。说明门源-柯柯里地区确实经受了高温低压变质作用，清水沟-百经寺地区则经受了高压低温变质作用。同时，前人的研究证实清水沟-百经寺地区HP/LT变质岩的峰期变质年龄也在500Ma左右(Wei and Song, 2008; Zhang et al., 2007, 2012)。考虑到门源-柯柯里HT/LP变质岩和清水沟-百经寺HP/LT变质岩的空间展布关系，两者成平行展布，且均与北祁连洋的俯冲有关。这两条准同期的HT/LP变质岩和HP/LT变质岩可以很好的用双变质带(Brown, 2009, 2010)模型进行解释。双变质带中洋壳俯冲一般沿着HP/LT变质带向HT/LP变质带的方向进行(Frisch, 2014)，因此北祁连洋经历了沿清水沟-百经寺一带向门源-柯柯里一带的南向俯冲。另外许多学者认为北祁连洋初始向北俯冲的时间早于510Ma(Zhang et al., 2017; Song et al., 2013; Xia et al., 2016)。综合考虑门源-柯柯里地区500Ma左右的弧岩浆作用和变质作用，推断北祁连洋初始向南俯冲的可能略早于500Ma，洋壳俯冲随后导致了相应的弧岩浆作用和变质作用事件的发生。
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图 9 变质相系PT图(a)和热力学梯度模式图(b) BS=蓝片岩相; AEE=绿帘角闪榴辉岩相; ALE=硬柱石角闪榴辉岩相; LE=硬柱石榴辉岩相; AE=角闪榴辉岩相. UHPM=超高压变质作用; E-HPG=中温榴辉岩相-高温麻粒岩相变质作用; G=麻粒岩相变质作用; UHTM=麻粒岩相的超高温变质作用部分 Fig. 9 P-T diagram to show the metamorphic facies location of selected samples (a) and metamorphic patterns show the thermal gradient of representative samples in NQL based on the peak metamorphic P-T conditions (b) HPM-UHPM includes the following: BS=blueschist facies; AEE=amphibole-epidote eclogite facies; ALE=amphibole-lawsonite eclogite facies; LE=lawsonite eclogite facies; AE=amphibole eclogite facies. UHPM=ultrahigh pressure metamorphism; E-HPG=medium temperature eclogite-high pressure granulite metamorphism; G=granulite facies metamorphism; UHTM=the ultrahigh temperature metamorphic part of the granulite facies |
本文呈现了青藏高原北部门源-柯柯里地区代表性岩石的岩石学、相平衡模拟、锆石U-Pb定年分析的综合结果。主要的结论总结如下：
(1) 相平衡模拟和传统地质温压计估算的结果显示门源地区石榴黑云斜长片麻岩和石榴角闪岩的的峰期变质作用的温压条件分别为780℃、9.0kbar和790℃、8.4kbar。表明门源地区经历了早古生代高角闪岩相-麻粒岩相的变质作用。
(2) 本文在门源地区新获得的1个变质年龄和1个闪长岩岩浆结晶年龄分别为493±3Ma和495±3Ma。在柯柯里地区获得的1个变质年龄为495±2Ma，结合柯柯里地区出露的多个500Ma左右的弧岩浆年龄及门源地区多个500Ma左右的弧岩浆作用年龄和变质作用年龄，推测门源-柯柯里一带共同经历了500Ma左右的变质作用和弧岩浆作用事件。
(3) 门源-柯柯里地区的HP/LT变质岩和北祁连造山带中部百经寺-清水沟一带的HP/LT变质岩组成了双变质带，并指示了北祁连洋早古生代时期向南俯冲的极性。
致谢 感谢中国地质科学院地质研究所董昕副研究员和中国地质调查局南京地质调查中心赵希林副研究员提出的建设性修改意见与建议，在此深表感谢。
Andersson UB, Högdahl K, Sjöström H and Bergman S. 2006. Multistage growth and reworking of the Palaeoproterozoic crust in the Bergslagen area, southern Sweden:Evidence from U-Pb geochronology. Geological Magazine, 143(5): 679-697. DOI:10.1017/S0016756806002494 |
Bahlburg H, Vervoort JD, Du Frane SA, Bock B, Augustsson C and Reimann C. 2009. Timing of crust formation and recycling in accretionary orogens:Insights learned from the western margin of South America. Earth-Science Reviews, 97(1-4): 215-241. DOI:10.1016/j.earscirev.2009.10.006 |
Barton MD and Hanson RB. 1989. Magmatism and the development of low-pressure metamorphic belts:Implications from the western United States and thermal modeling. Geological Society of America Bulletin, 101(8): 1051-1065. DOI:10.1130/0016-7606(1989)101<1051:MATDOL>2.3.CO;2 |
Bohlen SR. 1991. On the formation of granulites. Journal of Metamorphic Geology, 9(3): 223-229. DOI:10.1111/jmg.1991.9.issue-3 |
Brown EH. 1996. High-pressure metamorphism caused by magma loading in Fiordland, New Zealand. Journal of Metamorphic Geology, 14(4): 441-452. DOI:10.1046/j.1525-1314.1996.06024.x |
Brown M. 1993. P-T-t evolution of orogenic belts and the causes of regional metamorphism. Journal of the Geological Society, 150(2): 227-241. DOI:10.1144/gsjgs.150.2.0227 |
Brown M and Solar GS. 1998. Granite ascent and emplacement during contractional deformation in convergent orogens. Journal of Structural Geology, 20(9-10): 1365-1393. DOI:10.1016/S0191-8141(98)00074-1 |
Brown M. 2009. Metamorphic patterns in orogenic systems and the geological record. In:Cawood PA and Kröner A (eds.). Earth Accretionary Systems in Space and Time. The Geological Society, London, Special Publications, 318:37-74
|
Brown M. 2010. Paired metamorphic belts revisited. Gondwana Research, 18(1): 46-59. DOI:10.1016/j.gr.2009.11.004 |
Cai J, Liu FL, Liu PH, Liu CH, Wang F and Shi JR. 2014. Metamorphic P-T path and tectonic implications of pelitic granulites from the Daqingshan Complex of the Khondalite Belt, North China Craton. Precambrian Research, 241: 161-184. DOI:10.1016/j.precamres.2013.11.012 |
Cawood PA, Kröner A, Collins WJ, Kusky TM, Mooney WD and Windley BF. 2009. Accretionary orogens through earth history. Geological Society, London, Special Publications, 318(1): 1-36. DOI:10.1144/SP318 |
Chen YX, Xia XH and Song SG. 2012. Petrogenesis of Aoyougou high-silica adakite in the North Qilian orogen, NW China:Evidence for decompression melting of oceanic slab. Chinese Science Bulletin, 57(18): 2289-2301. DOI:10.1007/s11434-012-5069-3 |
Chen YX, Song SG, Niu YL and Wei CJ. 2014. Melting of continental crust during subduction initiation:A case study from the Chaidanuo peraluminous granite in the North Qilian suture zone. Geochimica et Cosmochimica Acta, 132: 311-336. DOI:10.1016/j.gca.2014.02.011 |
Collins WJ. 2002a. Hot orogens, tectonic switching, and creation of continental crust. Geology, 30(6): 535-538. DOI:10.1130/0091-7613(2002)030<0535:HOTSAC>2.0.CO;2 |
Collins WJ. 2002b. Nature of extensional accretionary orogens. Tectonics, 21(4): 6-1. DOI:10.1029/2000TC001272 |
Connolly JAD. 2005. Computation of phase equilibria by linear programming:A tool for geodynamic modeling and its application to subduction zone decarbonation. Earth and Planetary Science Letters, 236(1-2): 524-541. DOI:10.1016/j.epsl.2005.04.033 |
Corona-Chávez P, Poli S and Bigioggero B. 2006. Syn-deformational migmatites and magmatic-arc metamorphism in the Xolapa Complex, southern Mexico. Journal of Metamorphic Geology, 24(3): 169-191. DOI:10.1111/jmg.2006.24.issue-3 |
Daczko NR, Klepeis KA and Clarke GL. 2001. Evidence of Early Cretaceous collisional-style orogenesis in northern Fiordland, New Zealand and its effects on the evolution of the lower crust. Journal of Structural Geology, 23(4): 693-713. DOI:10.1016/S0191-8141(00)00130-9 |
Dale J, Holland T and Powell R. 2000. Hornblende-garnet-plagioclase thermobarometry:A natural assemblage calibration of the thermodynamics of hornblende. Contributions to Mineralogy and Petrology, 140(3): 353-362. DOI:10.1007/s004100000187 |
De Yoreo JJ, Lux DR and Guidotti CV. 1989. The role of crustal anatexis and magma migration in the thermal evolution of regions of thickened continental crust. Geological Society London Special Publications, 43(1): 187-202. DOI:10.1144/GSL.SP.1989.043.01.12 |
Fornelli A, Piccarreta G, Moro AD and Acquafredda P. 2002. Multi-stage melting in the lower crust of the Serre (southern Italy). Journal of Petrology, 43(12): 2191-2217. DOI:10.1093/petrology/43.12.2191 |
Frisch W. 2014. Paired metamorphic belt. In:Encyclopedia of Marine Geosciences. Netherlands:Springer, 1-4
|
Ge XH and Liu JL. 1999. Formation and tectonic background of the northern Qilian orogenic belt. Earth Science Frontiers, 6(4): 223-230. |
Gehrels GE, Yin A and Wang XF. 2003a. Magmatic history of the northeastern Tibetan Plateau. Journal of Geophysical Research, 108(B9): 2423. DOI:10.1029/2002JB001876 |
Gehrels GE, Yin A and Wang XF. 2003b. Detrital-zircon geochronology of the northeastern Tibetan Plateau. Geological Society of America Bulletin, 115(7): 881-896. DOI:10.1130/0016-7606(2003)115<0881:DGOTNT>2.0.CO;2 |
Gehrels GE, Kapp P, DeCelles P, Pullen A, Blakey R, Weislogel A, Ding L, Guynn J, Martin A, McQuarrie N and Yin A. 2011. Detrital zircon geochronology of pre-Tertiary strata in the Tibetan-Himalayan orogen. Tectonics, 30(5): TC5016. |
Hermann J. 2002. Allanite:Thorium and light rare earth element carrier in subducted crust. Chemical Geology, 192(3): 289-306. |
Holland T and Blundy J. 1994. Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry. Contributions to Mineralogy and Petrology, 116(4): 433-447. DOI:10.1007/BF00310910 |
Holland TJB and Powell R. 1998. An internally consistent thermodynamic data set for phases of petrological interest. Journal of Metamorphic Geology, 16(3): 309-343. |
Hollis JA, Clarke GL, Klepeis KA, Daczko NR and Ireland TR. 2003. Geochronology and geochemistry of high-pressure granulites of the Arthur River Complex, Fiordland, New Zealand:Cretaceous magmatism and metamorphism on the palaeo-Pacific margin. Journal of Metamorphic Geology, 21(3): 299-313. DOI:10.1046/j.1525-1314.2003.00443.x |
Hollis JA, Clarke GL, Klepeis KA, Daczko NR and Ireland TR. 2004. The regional significance of Cretaceous magmatism and metamorphism in Fiordland, New Zealand, from U-Pb zircon geochronology. Journal of Metamorphic Geology, 22(7): 607-627. DOI:10.1111/jmg.2004.22.issue-7 |
Hou KJ, Li YH, Zou TR, Qu XM, Shi YR and Xie GQ. 2007. Laser ablation-MC-ICP-MS technique for Hf isotope microanalysis of zircon and its geological applications. Acta Petrologica Sinica, 23(10): 2595-2604. |
Huang H, Niu YL, Nowell G, Zhao ZD, Yu XH and Mo XX. 2015. The nature and history of the Qilian Block in the context of the development of the Greater Tibetan Plateau. Gondwana Research, 28(1): 209-224. DOI:10.1016/j.gr.2014.02.010 |
Jagoutz O, Müntener O, Schmidt MW and Burg JP. 2011. The roles of flux-and decompression melting and their respective fractionation lines for continental crust formation:Evidence from the Kohistan arc. Earth and Planetary Science Letters, 303(1-2): 25-36. DOI:10.1016/j.epsl.2010.12.017 |
Jagoutz O and Schmidt MW. 2012. The formation and bulk composition of modern juvenile continental crust:The Kohistan arc. Chemical Geology, 298-299: 79-96. DOI:10.1016/j.chemgeo.2011.10.022 |
Johnson TE, Brown M, Kaus BJP and Van Tongeren JA. 2014. Delamination and recycling of Archaean crust caused by gravitational instabilities. Nature Geoscience, 7: 47-52. |
Kemp AIS, Hawkesworth CJ, Collins WJ, Gray CM and Blevin PL. 2009. Isotopic evidence for rapid continental growth in an extensional accretionary orogen:The Tasmanides, eastern Australia. Earth and Planetary Science Letters, 284(3-4): 455-466. DOI:10.1016/j.epsl.2009.05.011 |
Ker CM, Yang HJ, Zhang JX, Shau YH, Chieh CJ, Meng FC, Takazawa E and You CF. 2015. Compositional and S-Nd-Hf isotopic variations of Baijingsi eclogites from the North Qilian orogen, China:Causes, protolith origins, and tectonic implications. Gondwana Research, 28(2): 721-734. DOI:10.1016/j.gr.2014.06.006 |
Leake BE, Wooley AR, Arps CES, Birch WD, Gilbert MC, Grice JD, Hawthorne FC, Kato A, Kisch HJ, Krivovichev VG, Linthout K, Laird J, Mandarino JA, Maresch WV, Nickel EH, Rock NMS, Schumacher JC, Smith DC, Stephenson NCN, Ungaretti L, Whittaker EJW and Guo YZ. 1997. Nomenclature of amphiboles:Report of the Subcommittee on Amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names. The Canadian Mineralogist, 35: 219-246. |
Li SZ, Zhao SJ, Liu X, Cao HH, Yu S, Li XY, Somerville I, Yu SY and Suo YH. 2017a. Closure of the Proto-Tethys Ocean and Early Paleozoic amalgamation of microcontinental blocks in East Asia. Earth-Science Reviews. DOI:10.1016/j.earscirev.2017.01.011 |
Li SZ, Jahn BM, Zhao SJ, Dai LM, Li XY, Suo YH, Guo LL, Wang YM, Liu XC, Lan HY, Zhou ZZ, Zheng QL and Wang PC. 2017b. Triassic southeastward subduction of North China Block to South China Block:Insights from new geological, geophysical and geochemical data. Earth-Science Reviews, 166: 270-285. DOI:10.1016/j.earscirev.2017.01.009 |
Liou JG, Wang XM, Coleman RG, Zhang ZM and Maruyama S. 1989. Blueschists in major suture zones of China. Tectonics, 8(3): 609-619. DOI:10.1029/TC008i003p00609 |
Liu YJ, Neubauer F, Genser J, Takasu A, Ge XH and Handler R. 2006. 40Ar/39Ar ages of blueschist facies pelitic schists from Qingshuigou in the northern Qilian Mountains, western China. The Island Arc, 15(1): 187-198. DOI:10.1111/iar.2006.15.issue-1 |
Liu YS, Gao S, Hu ZC, Gao CG, Zong KQ and Wang DB. 2010. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating, Hf isotopes and trace elements in zircons from mantle xenoliths. Journal of Petrology, 51(1-2): 537-571. DOI:10.1093/petrology/egp082 |
Mattinson JM, Kimbrough DL and Bradshaw JY. 1986. Western Fiordland orthogneiss:Early Cretaceous arc magmatism and granulite facies metamorphism, New Zealand. Contributions to Mineralogy and Petrology, 92(3): 383-392. DOI:10.1007/BF00572167 |
Miyashiro A. 1961. Evolution of metamorphic belts. Journal of Petrology, 2(3): 277-311. DOI:10.1093/petrology/2.3.277 |
Miyashiro A. 1973. Metamorphism and Metamorphic Belts. London:George Allen and Unwin
|
Niu YL. 2016. Testing the geologically testable hypothesis on subduction initiation. Science Bulletin, 61: 1231-1235. DOI:10.1007/s11434-016-1144-5 |
Peng YB, Yu SY, Zhang JX, Li SZ, Tong LX, Sun DY. 2017. Early Paleozoic arc magmatism and metamorphism in the northern Qilian Block, western China:Petrological and geochronological constraints. Geological Journal, https://doi.org/10.1002/gj.3041
|
Rudnick RL. 1995. Making continental crust. Nature, 378(6557): 571-578. DOI:10.1038/378571a0 |
Schreurs J. 1985. Prograde metamorphism of metapelites, garnet-biotite thermometry and prograde changes of biotite chemistry in high-grade rocks of West Uusimaa, Southwest Finland. Lithos, 18: 69-80. DOI:10.1016/0024-4937(85)90011-8 |
Scott JM, Copper AF, Palin JM, Tulloch AJ, Kula J, Jongens R, Spell TL and Pearson NJ. 2009. Tracking the influence of a continental margin on growth of a magmatic arc, Fiordland, New Zealand, using thermobarometry, thermochronology, and zircon U-Pb and Hf isotopes. Tectonics, 28(6): TC6007. DOI:10.1029/2009TC002489 |
Smith AD, Lian FR, Chung CH and Yang HY. 1997. Isotopic evidence from metasediments in the Qilian fold belt for a North China-Antarctica connection in the Early Paleozoic. Journal of the Geological Society of China, 40(3): 481-497. |
Smith AD. 2006. The geochemistry and age of ophiolitic strata of the Xinglongshan Group:Implications for the amalgamation of the Central Qilian belt. Journal of Asian Earth Sciences, 28(2-3): 133-142. DOI:10.1016/j.jseaes.2005.09.014 |
Smith AD and Yang HY. 2006. The neodymium isotopic and geochemical composition of serpentinites from ophiolitic assemblages in the Qilian fold belt, Northwest China. Journal of Asian Earth Sciences, 28(2-3): 119-132. DOI:10.1016/j.jseaes.2005.09.013 |
Sobel ER and Arnaud N. 1999. A possible Middle Paleozoic suture in the Altyn Tagh, NW China. Tectonics, 18(1): 64-74. DOI:10.1029/1998TC900023 |
Song SG. 1997. Tectonic evolution of subductive complex belts in the North Qilian Mountains. Advances in Earth Sciences, 12(4): 351-365. |
Song SG, Zhang LF, Niu YL, Song B, Zhang GB and Wang QJ. 2004. Zircon U-Pb SHRIMP ages of eclogites from the North Qilian Mountains in NW China and their tectonic implication. Chinese Science Bulletin, 49(8): 848-852. DOI:10.1007/BF02889759 |
Song SG, Zhang LF, Niu YL, Su L, Song B and Liu DY. 2006. Evolution from oceanic subduction to continental collision:A case study from the northern Tibetan Plateau based on geochemical and geochronological data. Journal of Petrology, 47(3): 435-455. DOI:10.1093/petrology/egi080 |
Song SG, Zhang LF, Niu YL, Wei CJ, Liou JG and Shu GM. 2007. Eclogite and carpholite-bearing metasedimentary rocks in the North Qilian suture zone, NW China:Implications for Early Palaeozoic cold oceanic subduction and water transport into mantle. Journal of Metamorphic Geology, 25(5): 547-563. DOI:10.1111/jmg.2007.25.issue-5 |
Song SG, Niu YL, Zhang LF, Wei CJ, Liou JG and Su L. 2009. Tectonic evolution of Early Paleozoic HP metamorphic rocks in the North Qilian Mountains, NW China:New perspectives. Journal of Asian Earth Sciences, 35(3-4): 334-353. DOI:10.1016/j.jseaes.2008.11.005 |
Song SG, Niu YL, Su L and Xia XH. 2013. Tectonics of the North Qilian orogen, NW China. Gondwana Research, 23(4): 1378-1401. DOI:10.1016/j.gr.2012.02.004 |
Tseng CY, Yang HJ, Yang HY, Liu DY, Wu CL, Cheng CK, Chen CH and Ker CM. 2009. Continuity of the North Qilian and North Qinling orogenic belts, Central Orogenic System of China:Evidence from newly discovered Paleozoic adakitic rocks. Gondwana Research, 16(2): 285-293. DOI:10.1016/j.gr.2009.04.003 |
Tung KA, Yang HJ, Yang HY, Liu DY, Zhang JX, Wan YS and Tseng CY. 2007. SHRIMP U-Pb geochronology of the zircons from the Precambrian basement of the Qilian Block and its geological significances. Chinese Science Bulletin, 52(19): 2687-2701. DOI:10.1007/s11434-007-0356-0 |
Tung KA, Yang HY, Liu DY, Zhang JX, Yang HJ, Shau YH and Tseng CY. 2012. The amphibolite-facies metamorphosed mafic rocks from the Maxianshan area, Qilian Block, NW China:A record of Early Neoproterozoic arc magmatism. Journal of Asian Earth Sciences, 46: 177-189. DOI:10.1016/j.jseaes.2011.12.006 |
Tung KA, Yang HY, Liu DY, Zhang JX, Yang HJ, Shau YH and Tseng CY. 2013. The Neoproterozoic granitoids from the Qilian Block, NW China:Evidence for a link between the Qilian and South China blocks. Precambrian Research, 235: 163-189. DOI:10.1016/j.precamres.2013.06.016 |
Vavra G, Schmid R and Gebauer D. 1999. Internal morphology, habit and U-Th-Pb microanalysis of amphibolite-to-granulite facies zircons:Geochronology of the Ivrea Zone (Southern Alps). Contributions to Mineralogy and Petrology, 134(4): 380-404. DOI:10.1007/s004100050492 |
Wan YS, Xu ZQ, Yan JS and Zhang JX. 2001. Ages and compositions of the Precambrian high-grade basement of the Qilian Terrane and its adjacent areas. Acta Geologica Sinica, 75(4): 375-384. |
Wang CY, Zhang Q, Qian Q and Zhou MF. 2005. Geochemistry of the Early Paleozoic Baiyin volcanic rocks (NW China):Implications for the tectonic evolution of the North Qilian Orogenic Belt. The Journal of Geology, 113(1): 83-94. DOI:10.1086/425970 |
Wang JR, Wu CJ, Cai ZH, Guo YS, Wu JC and Liu XH. 2006. Early Paleozoic high-Mg adakite from Yindongliang in the eastern section of the North Qilian:Implications for geodynamics and Cu-Au mineralization. Acta Petrologica Sinica, 22(11): 2655-2664. |
Wei CJ and Powell R. 2003. Phase relations in high-pressure metapelites in the system KFMASH (K2O-FeO-MgO-Al2O3-SiO2-H2O) with application to natural rocks. Contributions to Mineralogy and Petrology, 145(3): 301-315. DOI:10.1007/s00410-003-0454-1 |
Wei CJ, Powell R and Clarke GL. 2004. Calculated phase equilibria for low-and medium-pressure metapelites in the KFMASH and KMnFMASH systems. Journal of Metamorphic Geology, 22(5): 495-508. DOI:10.1111/jmg.2004.22.issue-5 |
Wei CJ, Clarke G, Tian W and Qiu L. 2007. Transition of metamorphic series from the kyanite-to andalusite-types in the Altai orogen, Xinjiang, China:Evidence from petrography and calculated KMnFMASH and KFMASH phase relations. Lithos, 96(3-4): 353-374. DOI:10.1016/j.lithos.2006.11.004 |
Wei CJ and Song SG. 2008. Chloritoid-glaucophane schist in the North Qilian orogen, NW China:Phase equilibria and P-T path from garnet zonation. Journal of Metamorphic Geology, 26(3): 301-316. DOI:10.1111/jmg.2008.26.issue-3 |
Wells PRA. 1980. Thermal models for the magmatic accretion and subsequent metamorphism of continental crust. Earth and Planetary Science Letters, 46(2): 253-265. DOI:10.1016/0012-821X(80)90011-4 |
White RW, Powell R and Phillips GN. 2003. A mineral equilibria study of the hydrothermal alteration in mafic greenschist facies rocks at Kalgoorlie, Western Australia. Journal of Metamorphic Geology, 21(5): 455-468. DOI:10.1046/j.1525-1314.2003.00454.x |
Whitney DL and Evans BW. 2010. Abbreviations for names of rock-forming minerals. American Mineralogist, 95(1): 185-187. DOI:10.2138/am.2010.3371 |
Wu CL, Yang JS, Yang HY, Wooden JL, Shi RD, Chen SY and Zheng QG. 2004. Dating of two types of granite from North Qilian, China. Acta Petrologica Sinica, 20(3): 425-432. |
Wu CL, Yao SZ, Yang JS, Zeng LS, Chen SY, Li HB, Qi XX, Wooden JL and Mazdab FK. 2006. Double subduction of the Early Paleozoic North Qilian oceanic plate:Evidence from granites in the central segment of North Qilian, NW China. Geology in China, 33(6): 1197-1208. |
Wu CL, Xu XY, Gao QM, Li XM, Lei M, Gao YH, Frost RB and Wooden JL. 2010. Early Palaezoic grranitoid magmatism and tectonic evolution in North Qilian, NW China. Acta Petrologica Sinica, 26(4): 1027-1044. |
Wu CL, Gao YH, Frost BR, Robinson PT, Wooden JL, Wu SP, Chen QL and Lei M. 2011. An early Paleozoic double-subduction model for the North Qilian oceanic plate:Evidence from zircon SHRIMP dating of granites. International Geology Review, 53(2): 157-181. DOI:10.1080/00206810902965346 |
Wu HQ, Feng YM and Song SG. 1993. Metamorphism and deformation of blueschist belts and their tectonic implications, North Qilian Mountains, China. Journal of Metamorphic Geology, 11(4): 523-536. DOI:10.1111/jmg.1993.11.issue-4 |
Wu YB and Zheng YF. 2004. Mineralogy study on the origin of zircon and constraints on U-Pb chronology. Chinese Science Bulletin, 49(16): 1589-1604. |
Xia LQ, Xia ZC and Xu XY. 2003. Magma genesis in the Ordovician backarc basins of the northern Qilian Mountains, China. Geological Society of America Bulletin, 115(12): 1510-1522. DOI:10.1130/B25269.1 |
Xia LQ, Li XM, Yu JY and Wang GQ. 2016. Mid-Late Neoproterozoic to Early Paleozoic volcanism and tectonic evolution of the Qilian Mountain. Geology in China, 43(4): 1087-1138. |
Xiao WJ, Windley BF, Yong Y, Yan Z, Yuan C, Liu CZ and Li JL. 2009. Early Paleozoic to Devonian multiple-accretionary model for the Qilian Shan, NW China. Journal of Asian Earth Sciences, 35(3-4): 323-333. DOI:10.1016/j.jseaes.2008.10.001 |
Xiong ZL, Zhang HF and Zhang J. 2012. Petrogenesis and tectonic implications of the Maozangsi and Huangyanghe granitic intrusions in Lenglongling area, the eastern part of North Qilian Mountains, NW China. Earth Science Frontiers, 19(3): 214-227. |
Xu WC, Zhang HF and Liu XM. 2007. U-Pb zircon dating constraints on formation time of Qilian high-grade metamorphic rock and its tectonic implications. Chinese Science Bulletin, 52(4): 531-538. DOI:10.1007/s11434-007-0082-7 |
Xu ZQ, Xu HF, Zhang JX, Li HB, Zhu ZZ, Qu JC, Chen DZ, Chen JL and Yang KC. 1994. The Zoulang Nanshan Caledonian subduction Complex in the northern Qilian Mountains and its dynamics. Acta Geologica Sinica, 7(3): 225-241. |
Xu ZQ, Yang JS, Zhang JX, Jiang M, Li HB and Cui JW. 1999. A comparison between the tectonic units on the two sides of the Altun sinistral strike-slip fault and the mechanism of lithospheric shearing. Acta Geologica Sinica, 73(3): 193-205. |
Yang JS, Xu ZQ, Song SG, Zhang JX, Wu CL, Shi RD, Li HB and Brunel M. 2001. Discovery of coesite in the North Qaidam Early Palaeozoic ultrahigh pressure (UHP) metamorphic belt, NW China. Comptes Rendus de l'Académie des Sciences-Series ⅡA-Earth and Planetary Science, 333: 719-724. |
Yin A, Manning CE, Lovera O, Menold CA, Chen XH and Gehrels GE. 2007. Early Paleozoic tectonic and thermomechanical evolution of ultrahigh-pressure (UHP) metamorphic rocks in the northern Tibetan Plateau, Northwest China. International Geology Review, 49(8): 681-716. DOI:10.2747/0020-6814.49.8.681 |
Yu SY, Zhang JX, Li HK, Hou KJ, Mattinson CG and Gong JH. 2013. Geochemistry, zircon U-Pb geochronology and Lu-Hf isotopic composition of eclogites and their host gneisses in the Dulan area, North Qaidam UHP terrane:New evidence for deep continental subduction. Gondwana Research, 23(3): 901-919. DOI:10.1016/j.gr.2012.07.018 |
Yu SY, Zhang JX, Qin HP, Sun DY, Zhao XL, Cong F and Li YS. 2015. Petrogenesis of the early Paleozoic low-Mg and high-Mg adakitic rocks in the North Qilian orogenic belt, NW China:Implications for transition from crustal thickening to extension thinning. Journal of Asian Earth Sciences, 107: 122-139. DOI:10.1016/j.jseaes.2015.04.018 |
Zhang JX, Xu ZQ, Chen W and Xu HF. 1997. A tentative discussion on the ages of the subduction-accretionary Complex/volcanic arcs in the middle sector of North Qilian Mountain. Acta Petrologica et Mineralogica, 16(2): 112-119. |
Zhang JX, Xu ZQ, Xu HF and Li HB. 1998. Framework of North Qilian Caledonian subduction-accretionary wedge and its deformation dynamics. Scientia Geologica Sinica, 33(3): 290-299. |
Zhang JX, Zhang ZM, Xu ZQ, Yang JS and Cui JW. 2001. Petrology and geochronology of eclogites from the western segment of the Altyn Tagh, northwestern China. Lithos, 56(2-3): 187-206. DOI:10.1016/S0024-4937(00)00052-9 |
Zhang JX, Meng FC and Yang JS. 2005. A new HP/LT metamorphic terrane in the northern Altyn Tagh, western China. International Geology Review, 47(4): 371-386. DOI:10.2747/0020-6814.47.4.371 |
Zhang JX and Meng FC. 2006. Lawsonite-bearing eclogites in the North Qilian and North Altyn Tagh:Evidence for cold subduction of oceanic crust. Chinese Science Bulletin, 51(10): 1238-1244. DOI:10.1007/s11434-006-1238-6 |
Zhang JX, Meng FC and Wan YS. 2007. A cold Early Palaeozoic subduction zone in the North Qilian Mountains, NW China:Petrological and U-Pb geochronological constraints. Journal of Metamorphic Geology, 25(3): 285-304. DOI:10.1111/jmg.2007.25.issue-3 |
Zhang JX, Li JP, Yu SY, Meng FC, Mattinson CG, Yang HJ and Ker CM. 2012. Provenance of eclogitic metasediments in the North Qilian HP/LT metamorphic terrane, western China:Geodynamic implications for early Paleozoic subduction-erosion. Tectonophysics, 570-571: 78-101. DOI:10.1016/j.tecto.2012.08.018 |
Zhang JX, Yu SY and Mattinson CG. 2017. Early Paleozoic polyphase metamorphism in northern Tibet, China. Gondwana Research, 41: 267-289. DOI:10.1016/j.gr.2015.11.009 |
Zhang LF, Wang QJ and Song SG. 2009. Lawsonite blueschist in northern Qilian, NW China:P-T pseudosections and petrologic implications. Journal of Asian Earth Sciences, 35(3-4): 354-366. DOI:10.1016/j.jseaes.2008.11.007 |
Zhang ZM, Dong X, Xiang H, Liou JG and Santosh M. 2013. Building of the deep Gangdese arc, South Tibet:Paleocene plutonism and granulite-facies metamorphism. Journal of Petrology, 54(12): 2547-2580. DOI:10.1093/petrology/egt056 |
Zhao GC, Wilde SA, Cawood PA and Lu LZ. 1998. Thermal evolution of Archean basement rocks from the eastern part of the North China Craton and its bearing on tectonic setting. International Geology Review, 40(8): 706-721. DOI:10.1080/00206819809465233 |
Zhao GC and Zhai MG. 2013. Lithotectonic elements of Precambrian basement in the North China Craton:Review and tectonic implications. Gondwana Research, 23(4): 1207-1240. DOI:10.1016/j.gr.2012.08.016 |
Zuo GC and Liu JC. 1987. The evolution of tectonic of Early Paleozoic in North Qilian Range, China. Scienta Geologica Sinica, 17(1): 14-24. |
侯可军, 李延河, 邹天人, 曲晓明, 石玉若, 谢桂青. 2007. LA-MC-ICP-MS锆石Hf同位素的分析方法及地质应用. 岩石学报, 23(10): 2595-2604. DOI:10.3969/j.issn.1000-0569.2007.10.025 |
葛肖虹, 刘俊来. 1999. 北祁连造山带的形成与背景. 地学前缘, 6(4): 223-230. |
王金荣, 吴春俊, 蔡郑红, 郭原生, 吴继承, 刘晓煌. 2006. 北祁连山东段银硐粱早古生代高镁埃达克岩:地球动力学及成矿意义. 岩石学报, 22(11): 2655-2664. |
吴才来, 杨经绥, 杨宏仪, Wooden JL, 史仁灯, 陈松永, 郑秋光. 2004. 北祁连东部两类Ⅰ型花岗岩定年及其地质意义. 岩石学报, 20(3): 425-432. |
吴才来, 姚尚志, 杨经绥, 曾令森, 陈松永, 李海兵, 戚学祥, Wooden JL, Mazdab FK. 2006. 北祁连洋早古生代双向俯冲的花岗岩证据. 中国地质, 33(6): 1197-1208. |
吴才来, 徐学义, 高前明, 李向民, 雷敏, 郜源红, Frost RB, Wooden JL. 2010. 北祁连早古生代花岗质岩浆作用及构造演化. 岩石学报, 26(4): 1027-1044. |
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. DOI:10.3321/j.issn:0023-074X.2004.16.002 |
夏林圻, 李向民, 余吉远, 王国强. 2016. 祁连山新元古代中-晚期至早古生代火山作用与构造演化. 中国地质, 43(4): 1087-1138. |
熊子良, 张宏飞, 张杰. 2012. 北祁连东段冷龙岭地区毛藏寺岩体和黄羊河岩体的岩石成因及其构造意义. 地学前缘, 19(3): 214-227. |
许志琴, 杨经绥, 张建新, 姜枚, 李海兵, 崔军文. 1999. 阿尔金断裂两侧构造单元的对比及岩石圈剪切机制. 地质学报, 73(3): 193-205. |
张建新, 许志琴, 陈文, 徐惠芬. 1997. 北祁连中段俯冲-增生杂岩/火山弧的时代探讨. 岩石矿物学杂志, 16(2): 112-119. |
张建新, 许志琴, 徐惠芬, 李海兵. 1998. 北祁连加里东期俯冲-增生楔结构及动力学. 地质科学, 33(3): 290-299. |
左国朝, 刘寄陈. 1987. 北祁连早古生代大地构造演化. 地质科学, 17(1): 14-24. |