Dongbo MORB-Type Isotropic Gabbro Emplaced as an Oceanic Core Complex in Western Yarlung Zangbo Suture Zone, Tibet
-
摘要: 为解决雅鲁藏布江缝合带西段南带中数个大型超镁铁岩体的成因问题，对南带西段约400 km2的东波蛇绿岩开展区域地质填图，研究蛇绿岩岩石组合和构造性质及西北缘均质辉长岩年代学和成因.研究表明，东波蛇绿岩以地幔橄榄岩、薄层洋壳和周缘出露大面积晚侏罗世-早白垩世残余海山为特征，地幔橄榄岩中发育大量拆离、韧性剪切和正断层及糜棱岩和糜棱岩化蛇纹岩和蛇绿角砾岩；均质辉长岩的锆石普遍受到流体交代，锆石U-Pb年龄为129.0±1.8 Ma，地球化学具有低Si、K、P、Fe和Ti，高Ca和Mg，N-MORB型的稀土配分特征及明显的Th、Nb、Sr和Pb负异常.认为均质辉长岩形成于慢速-超慢速大洋扩张阶段，在大洋核杂岩沿拆离断层侵位过程中形成.Abstract: The tectonic setting and genesis of the ophiolites in the southern belt (SB) of the western Yarlung Zangbo ophiolitic belt are still controversial.They occur much larger peridotite massifs in contrast with those in the northern belt that are made discontinuously of lensoidal ophiolitic bodies in serpentinite matrix mélanges. The Dongbo ophiolite in the SB has been investigated and mapped, especially a 1 002.06 m dominant peridotite core has been drilled in the northwestern margin in 2015. Geochemical and geochronological (U-Pb zircon age) data from isotropic gabbros are presented in this paper. Dongbo ophiolite consists dominantly of harzburgite, minor dunite and mafic intrusions, associated with thin oceanic crust.Dismembered Late Juarassic to Early Cretaceous volcanic-sedimentary sequences of seamounts overlie the peridotites in the margins.Detachment and ductile shear faults, mylonite and mylonitic serpentinite and ophiolitic breccia are found in the mantle peridotites. In-situ LA-ICP-MS analysis of zircon grains from isotropic gabbros yields 129.0±1.8 Ma.The geochemical data of these gabbros are characterized by low Si, K, P, Fe, Ti and high Ca, Mg, showing N-MORB-like chondrite-normalized REE patterns and remarkable Th, Nb, Sr and Pb negative anomalies in N-MORB normalized spider diagrams. It is proposed that part of Dongbo peridotite and isotropic gabbro formed in a slow-spreading mid-ocean ridge which exhumed along detachment faults as an oceanic core complex.
-
Key words:
- Tibet /
- Yarlung Zangbo suture zone /
- Dongbo ophiolite /
- zircon U-Pb age /
- geochemistry /
- oceanic core complex
-
0. 引言
喜马拉雅-阿尔卑斯造山带中的蛇绿岩分布在具有冈瓦纳大陆亲缘性的不同陆块之间，为新特提斯大洋岩石圈残余(Yang et al., 2015；Dilek, 2016).这些蛇绿岩记录了自大陆裂解漂移、大洋扩张和初始俯冲至最终闭合等一系列构造演化过程，及不同阶段相应的变质变形、沉积和岩浆事件(Dilek and Furnes, 2014；Saccani, 2015).
雅鲁藏布江缝合带(Yarlung Zangbo suture zone, YZSZ)位于喜马拉雅-阿尔卑斯特提斯带的东段(图 1a)，是青藏高原最南端的缝合带，代表了印度陆块和欧亚板块的界限(Molnar and Tapponnier, 1975；Hébert et al., 2012；Xu et al., 2015).长约2 000 km的YZSZ蛇绿岩带(图 1b)不仅普遍产出蛇绿岩型金刚石(杨经绥等，2011a; Yang et al., 2014；徐向珍等，2015)，还是我国最重要的铬铁矿成矿带(Zhou et al., 1996；王希斌等，2010；杨经绥等，2011b).然而该带蛇绿岩的产出分布和岩石组合明显不同：相比中东段，西段(自萨嘎以西)被仲巴地体分为南、北两个蛇绿岩亚带(图 1b，图 2a)，缺失席状岩墙群和亚碱性枕状熔岩，却出露如东波(面积约400 km2)、普兰(面积约650 km2)和休古嘎布(面积约700 km2)等大面积新鲜地幔橄榄岩块，明显不同于发育彭罗斯层序的中段日喀则蛇绿岩(Liu et al., 2018).YZSZ西段与中东段蛇绿岩的这些显著差异蕴含怎样的构造演化背景目前还不清楚.
图 1 西藏雅鲁藏布江缝合带(YZSZ)在东特提斯-喜马拉雅-缅马造山带中的位置(a)和西藏南部区域地质简图和YZSZ蛇绿岩分布(b)图a据Jagoutz et al.(2015)修改；图b据Xu et al.(2015)修改.GCT.大反冲逆冲断裂；GT.冈底斯逆冲断层；KKF.喀喇昆仑断裂；MBT.主边界逆冲断裂；MCT.主中央逆冲断裂；MFT.主前缘逆冲断裂；NB.南迦巴瓦构造结；NP.南迦帕尔特构造结；STD.藏南拆离系Fig. 1. Location of the Yarlung Zangbo suture zone (YZSZ), Tibet in the eastern Mediteranian-Ximalaya-Myanma orogenic belt (a), and simplified geological map of southern Tibet showing the locations of all the ophiolitic massifs in the YZSZ (b)
图 2 西藏南部雅鲁藏布江缝合带(YZSZ)和班公湖-怒江缝合带(BNSZ)分布简图(a)，YZSZ西段区域地质简图(b)普兰东和普兰西以拉昂错湖西缘为界Fig. 2. Distribution of ophiolitic massifs along the Yarlung Zangbo suture zone (YZSZ) and Bangonghu-Nujiang suture zone (BNSZ) in Tibet (a); simplified geological map of the western part of the YZSZ, Tibet (b)前人通过对地幔橄榄岩和上部洋壳的研究提出YZSZ西段蛇绿岩不同的构造成因模型，比如：(1)形成于洋中脊(MOR)环境(Miller, 2003；Liu et al., 2014；张利等，2016)；(2)形成于超俯冲带(SSZ)之上的弧前环境(Dai et al., 2011；Lian et al., 2016, 2017)；(3)先形成于MOR环境，随后受到SSZ环境改造的两阶段模式(徐向珍等，2011；Guo et al., 2015；Li et al., 2015b；Xiong et al., 2017)；(4)类似贫岩浆型洋陆过渡带的大陆边缘岩石圈地幔残余(Liu et al., 2015；Gong et al., 2016).上述不同角度的研究成果丰富了对YZSZ西段蛇绿岩成因的认识，也指示其可能经历了复杂的构造演化过程.作者在区域填图过程中，发现南亚带东波蛇绿岩北缘发育薄层均质辉长岩.本文报道了均质辉长岩和地幔橄榄岩的野外产出及前者的地球化学和年代学特征，认为均质辉长岩在慢速-超慢速洋盆扩张环境中，在大洋核杂岩沿拆离断层侵位至海底过程中形成，该研究对南亚带蛇绿岩成因具有重要限定意义.
1. 区域地质背景
根据蛇绿岩的产出和岩石组合特征及其南、北两侧地质单元差异，将YZSZ分为东、中、西段，东段自泽当经南迦巴瓦大拐弯转向南东，中段位于桑桑和仁布之间，西段自萨嘎以西至拉达克与印度缝合带相连(图 1b，图 2a).东段蛇绿岩夹持于南侧上三叠统朗杰学群复理石地层和北侧冈底斯岛弧、J3-K1火山岩和第三系砾岩之间(梁凤华等，2011)，未见日喀则弧前盆地沉积，包括泽当(宽小于1 km，~45 km2)、罗布莎(宽 < 4 km，~70 km2)和朗县等蛇绿岩(图 1b)，以不发育席状岩墙群及产出中国最大的罗布莎铬铁矿和100~300 m厚的堆晶纯橄岩为主要特征(高洪学和宋子季，1995；Zhou et al., 1996, 2005；Xu et al., 2011；Bao et al., 2014).中段蛇绿岩南侧为澳大利亚陆块亲缘性的上三叠统郎杰学群和印度陆块亲缘性的聂如组(Cai et al., 2016)，北侧为冈底斯岛弧和日喀则弧前盆地(图 1b)，主要包括日喀则东(仁布、大竹卡、德吉、群让和白马让)、日喀则西(吉定、柳区和昂仁)和桑桑蛇绿岩，以发育完整的彭罗斯型蛇绿岩层序和洋壳厚度小于3.5 km的日喀则蛇绿岩为代表(周云生等，1982；Pearce and Wanming, 1988；Bao et al., 2013；Orme and Laskowski, 2016).
北西西走向的西段蛇绿岩自萨嘎以西被仲巴地体分隔为达机翁-萨嘎蛇绿岩带(北带)和达巴-休古嘎布蛇绿岩带(南带).日喀则弧前盆地在萨嘎蛇绿岩附近尖灭，并于南侧位置出现仲巴地体(图 1b).仲巴地体为一套缺少前寒武系结晶基底，以震旦系至白垩系海相沉积为主的地质体(李祥辉等，2014)，出露少量早古生代花岗岩体(刘强等，2017).与特提斯喜马拉雅地体相比，其石炭系至二叠系地层略有不同，而三叠系地层岩性和沉积环境存在较大差异(刘飞等，2015a).北亚带蛇绿岩呈不规则条带状断续分布，受到中新生代以来多期构造事件的影响，蛇绿岩层序肢解破碎强烈，多以蛇绿混杂岩和增生杂岩的形式产出(刘飞等，2015a；Liu et al., 2018)，主要包括达机翁、卡站、巴尔、错布扎、扎来、公珠错和萨嘎蛇绿岩体(图 1b)，由地幔橄榄岩、基性岩脉和少量堆晶辉长岩组成.地幔橄榄岩普遍弱蛇纹石化，宽几米至几十米不等，最宽如卡站达300~500 m，岩性以方辉橄榄岩为主，含少量单斜辉石方辉橄榄岩和纯橄岩透镜体，二辉橄榄岩不发育(刘飞等，2015a).地幔橄榄岩上部被厚几至十几米的石英菱镁岩覆盖，其内部普遍发育纯橄岩和辉长岩、辉绿岩和异剥钙榴岩等透镜状岩脉，走向北西，宽0.5~3.0 m不等，最宽如错布扎达10 m.基性岩的锆石U-Pb年龄为128~122 Ma(刘飞等, 2015a, 2015b；Liu et al., 2018；Zheng et al., 2017)，与中东段类似产状的基性岩脉一致.公珠蛇绿混杂岩中可见宽度0.5~1.0 km的堆晶辉长岩.达机翁、巴尔和错不扎蛇绿岩中出露宽2~4 m、长5~10 m不等块状和浸染状铬铁矿的小矿点(连东洋等，2015；刘飞等，2015a).
北西长约400 km的南带排布如东波、普兰、扎嘎(又称南公珠错，张利等，2016)、休古嘎布、当穷和仲巴(图 1b, 2b)等数个大型浑圆状的蛇绿岩块.南带蛇绿岩主要由新鲜地幔橄榄岩、基性岩脉和少量堆晶辉长岩组成，不发育典型亚碱性枕状熔岩、席状岩墙群(Liu et al., 2015).虽然仲巴蛇绿岩有枕状玄武岩的报道，但其上部被泥岩、硅质岩和灰岩覆盖，具有碱性玄武岩地球化学特征，可能属于残余海山层序(Dai et al., 2012；He et al., 2016).南带地幔橄榄岩普遍由方辉橄榄岩、含Cpx方辉橄榄岩及少量二辉橄榄岩和纯橄岩透镜体组成(Bezard et al., 2011；Dai et al., 2011；Liu et al., 2015；Niu et al., 2015)，其中普兰东和扎嘎蛇绿岩以含Cpx方辉橄榄岩和二辉橄榄岩为主(周文达等，2014；Li et al., 2015b；张利等，2016)，东波蛇绿岩以发育大量亏损的方辉橄榄岩为主要特征(刘飞等，2013；王云鹏，2015).南带普遍可见宽几十厘米至几米不等、NW走向的辉石岩、辉长岩和辉绿岩等岩脉侵入地幔橄榄岩中，其锆石U-Pb年龄为120~130 Ma(Zhang et al., 2005；李建峰等，2008；刘钊等，2011；Chan et al., 2015)，与北带基性岩脉年龄一致.
2. 东波蛇绿岩产出特征
东波蛇绿岩位于南带最西端的札达县境内，岩块北缘逆冲到仲巴地体中下三叠统浅变质的浅海相碳酸盐岩和碎屑岩之上，南缘逆冲至特提斯喜马拉雅地体侏罗系-白垩系的浅海-半深海相碳酸盐岩和泥页岩之上(图 3).东波蛇绿岩包括构造地幔橄榄岩、堆晶镁铁-超镁铁岩和基性岩三部分，岩块南北缘被火山-沉积盖层覆盖，主要由硅质灰岩、硅质岩、泥页岩夹杂砂岩等沉积岩和玄武岩、以及玄武质碎屑岩和凝灰岩等组成，放射虫时代为晚侏罗世至早白垩世，玄武岩普遍具有洋岛玄武岩(OIB)型地球化学特征，该火山-沉积岩组合可能代表残余海山层序(刘飞等，2013；Liu et al., 2015).
图 3 雅鲁藏布江缝合带西段南带东波蛇绿岩地质简图样品L190(辉长岩，坐标N31°04′26.50″，E80°11′14.40″)和L178(辉石岩，N31°02′16.30″，E80°17′44.60″)熊发挥等(2011)；样品GCT329(粗粒辉长岩，N31°02′16.69″，E80°17′44.59″)引自Chan et al.(2015).白色五角星为文献样品，黄色五角星为本文样品Fig. 3. Geological map of the Dongbo ophiolite in the southern belt of the western Yarlung Zangbo suture zone地表填图和大陆科学钻探(DSD-1)显示，东波地幔橄榄岩由亏损方辉橄榄岩、含Cpx方辉橄榄岩和少量纯橄岩组成(刘飞等，2013；Niu et al., 2015；王云鹏，2015).方辉橄榄岩普遍高Mg、REE，低Al、Ca，相对富集轻稀土元素(LREE)，铂族元素(PGE)含量高于原始地幔，Os明显低于原始地幔，指示其经历了较高程度(30%以上)部分熔融，并受到俯冲带富硫化物、富不相容元素和高PGE熔体/流体的交代(牛晓露等，2013；Niu et al., 2015；刘飞等，2015a).纯橄岩呈透镜状和脉状出露于方辉橄榄岩中，北西走向，宽几厘米至数十米不等，以1~2 m宽常见，普遍可见稀疏浸染状北西排列的铬尖晶石，与方辉橄榄岩中辉石的拉伸线理方向一致.1 002.06 m科钻岩心的岩性明显分为上、下两层，上层(23.10~340.17 m)为含Cpx方辉橄榄岩，其斜方辉石(Opx)含量为15%~20%，Cpx含量 < 5%，铬尖晶石的Cr#值为11.1~23.0；下层(340.17~1 002.06 m)主要为亏损方辉橄榄岩，Opx含量约10%~15%，几乎不含Cpx，尖晶石Cr#值为40.5~62.8，含纯橄岩和基性岩，呈透镜体或脉体，纯橄岩最厚达14 m (王云鹏，2015).地幔橄榄岩中出露多个高铝和高铬型块状以及浸染状铬铁矿矿化点，规模普遍较小，呈透镜状分布于方辉橄榄岩中，局部发育纯橄岩薄壳.矿体与围岩接触关系截然，一般长1~3 m，厚0.2~2.0 m不等，矿体沿北西方向延伸与蛇绿岩构造线方向一致(Xiong et al., 2017).
堆晶镁铁-超镁铁岩出露在东波蛇绿岩东北部(图 3)，表现为纯橄岩与伟晶辉长岩呈堆晶层状相间分布(图 4a, 4b)，或纯橄岩呈不规则脉状分布于辉长岩中(图 4c).纯橄岩层厚一般2~5 cm至20~25 cm不等(图 4b)，最宽达1.5 m，其边部发育宽几厘米至十几厘米不等的斜方辉石岩脉，走向近南北，锆石U-Pb年龄为130±0.5 Ma(熊发挥等，2011).伟晶辉长岩厚度变化较大，从几厘米至几米不等(图 4a)，主要介于1.5 m至5~6 m，主要成分斜长石、单斜辉石和角闪石的粒度普遍在5 cm以上(图 4d)，局部达12 cm，最大可见30 cm×14 cm的角闪石，指示初始岩浆中水的存在.整体来说，纯橄岩为伟晶辉长岩内部的不规则脉体或透镜体，两者直接接触，局部可见纯橄岩周缘分布浅绿色的单斜辉石，指示流体参与的岩熔反应过程.
图 4 东波堆晶伟晶辉长岩夹纯橄岩透镜体野外特征Fig. 4. Occurrence of cumulate pegmatoidal gabbros interbedded with dunite lens in the Dongbo ophiolite东波基性岩包括侵入方辉橄榄岩的基性岩脉(辉绿岩、辉长岩、斜方辉石岩、单斜辉石岩和次级蚀变的异剥钙榴岩等)和出露岩块西北角的均质辉长岩(图 3).基性岩脉普遍北西走向，地表宽度一般在几厘米至几米不等(Liu et al., 2015)，DSD-1科钻岩心出露18 m厚的辉绿岩层(王云鹏，2015).均质辉长岩有两种产出类型，一种被酸性凝灰岩不整合覆盖，厚约80~100 m，与下伏蛇纹岩构造接触，出露于东波村二组的东波河边(12YL31，N31°07′07.25″，E80°07′5.39″，4 132 m)(刘飞等，2013)；另一种位于红色硅质岩和蛇纹石化方辉橄榄岩(或蛇纹岩)之间(图 5a, 5b，13YL45，N31°09′43.01″，E80°03′38.73″，4 177 m)，宽约8~10 m，走向330°，是本文的研究对象.其围岩普遍揉皱变形强烈，蛇纹石化地幔橄榄岩在靠近接触面片理化、糜棱岩化破碎强烈，远离接触面地幔橄榄岩透镜体粒径逐渐变大(图 5c)，指示逆时针逆冲推覆方向，与硅质岩中硅质和钙质条带的构造变形特征一致(图 5d).
图 5 雅鲁藏布江缝合带西段南带东波均质辉长岩的野外特征Fig. 5. Field photographs of the isotropic gabbros in the southern belt of the western Yarlung Zangbo suture zone均质辉长岩显微结构如图 6，岩石普遍发生绿片岩化，整体暗绿色(图 5b)，呈变辉长结构(图 6a~6d)，局部可见鳞片变晶结构(图 6e, 6f)，块状构造和少量片状构造，主体由角闪石、绢云母、绿帘石、方解石及少量磁铁矿、钠长石和石英组成，局部可见矿物定向排列(图 6e, 6f).
图 6 东波均质辉长岩的显微镜下特征a~d.样品13YL45-6；e, f.样品13YL45-8，左边单偏光，右边正交光Fig. 6. Photomicrographs of the isotropic gabbros in the southern belt of the western Yarlung Zangbo suture zone3. 测试方法
通过显微镜下薄片观察选择样品进行主、微量元素和锆石U-Pb测年.主微量元素测试在国家地质实验测试中心完成.主量元素用无水四硼酸锂和硝酸铵为氧化剂，于1 200 ℃左右熔融制成玻璃片，用X射线荧光光谱仪(XRF-PW4400)测试，分析精度小于2%~8%；FeO采用重铬酸钾标准溶液滴定法测量，分析精度小于10%；稀土微量元素采用等离子质谱仪(ICPMS-PE300D)测试，含量大于10×10-6的元素的测试精度为5%，而小于10×10-6的元素的分析精度为10%.测试结果见表 1.
表 1 东波蛇绿岩中均质辉长岩主量元素(%)和微量元素(10-6)含量Table Supplementary Table Major (%) and trace element (10-6) compositions of isotropic gabbros from the Dongbo ophiolite in the western YZSZ, Tibet样品号 均质辉长岩 辉石岩脉 辉长岩脉 13YL45-1 13YL45-2 13YL45-3 13YL45-4 13YL45-5 13YL45-7 13YL45-8 13YL45-9 L-178-3* L-190-2* SiO2 45.62 45.72 45.59 45.59 45.94 46.18 45.04 45.81 53.65 49.54 TiO2 1.08 1.07 0.91 1.00 0.98 0.91 1.03 1.05 0.10 0.94 Al2O3 13.72 13.53 13.59 12.98 14.07 14.02 14.70 13.46 3.03 15.66 Fe2O3 1.61 0.99 1.36 1.51 1.21 1.02 1.42 1.58 7.94 2.10 FeO 6.53 6.91 5.71 6.28 6.18 6.00 6.29 6.26 6.80 6.80 MnO 0.16 0.17 0.16 0.18 0.15 0.16 0.15 0.17 0.15 0.15 MgO 8.48 8.47 9.81 9.50 7.48 7.87 7.97 8.67 25.37 7.35 CaO 18.55 18.62 18.26 18.16 19.63 19.62 19.03 18.51 7.63 10.9 Na2O 0.32 0.33 0.32 0.34 0.32 0.29 0.28 0.34 0.09 3.29 K2O 0.07 0.08 0.07 0.07 0.07 0.08 0.07 0.09 0.02 0.09 P2O5 0.09 0.09 0.08 0.08 0.08 0.07 0.09 0.09 0.05 0.07 CO2 0.15 0.13 0.13 0.19 0.16 0.28 0.14 0.19 H2O+ 3.76 3.91 4.03 3.90 3.56 3.54 4.11 3.86 LOI 3.17 3.09 3.52 3.26 3.00 3.27 3.59 3.29 0.10 1.98 Total 100.14 100.02 100.02 99.79 99.84 100.04 100.32 100.07 98.36 98.68 FeOT 7.98 7.80 6.93 7.64 7.27 6.92 7.57 7.68 13.94 8.69 Mg# 65.67 66.15 71.80 69.12 64.94 67.19 65.47 67.01 76.61 60.36 M 70.04 68.81 75.56 73.14 68.54 70.25 69.52 71.37 87.04 66.05 Sc 35.10 33.50 30.80 33.60 31.60 31.20 32.60 33.40 Ti 6 806.00 6 353.00 5 547.00 6 201.00 6 149.00 5 740.00 6 276.00 6 672.00 Cr 154.00 150.00 185.00 184.00 155.00 177.00 167.00 154.00 V 226.00 215.00 189.00 211.00 205.00 193.00 208.00 232.00 305.00 210.00 Ni 59.90 58.00 61.50 61.70 58.10 61.20 58.90 56.30 Co 38.40 35.60 34.20 35.30 36.00 34.50 36.10 36.90 Cu 55.40 60.50 43.30 44.40 40.20 20.50 53.10 40.40 Zn 66.60 60.80 55.60 62.20 60.40 50.80 58.00 59.30 Ga 13.30 11.90 12.00 11.60 13.90 14.60 11.60 12.80 Mn 1 197.00 1 201.00 1 166.00 1 271.00 1 164.00 1 187.00 1 045.00 1 291.00 Mo 0.26 0.14 0.15 0.25 0.17 0.26 0.10 0.17 Pb 0.16 0.22 0.14 0.32 0.29 0.18 0.20 0.19 Rb 0.45 0.44 1.66 0.95 0.87 0.88 0.70 0.77 0.20 0.90 Sr 48.40 45.30 45.10 42.10 47.80 40.20 52.10 47.70 160.00 121.00 Y 25.00 23.40 19.70 21.40 21.10 19.60 21.20 22.80 23.20 19.60 Zr 71.20 74.50 63.10 66.10 68.30 59.80 69.70 71.90 Nb 0.92 0.87 0.83 0.81 0.90 0.84 0.86 0.96 0.50 0.70 Ba 17.40 13.30 21.60 11.60 6.15 10.40 11.70 10.60 1.70 7.50 La 2.13 2.00 1.94 1.87 1.98 1.89 2.06 2.16 1.00 1.80 Ce 6.81 6.95 6.16 6.44 6.49 6.08 6.85 6.95 3.90 5.70 Pr 1.24 1.27 1.10 1.18 1.18 1.09 1.24 1.31 0.87 1.04 Nd 7.58 7.43 6.62 6.79 7.25 6.39 7.32 7.08 5.40 5.80 Sm 2.43 2.41 2.17 2.35 2.31 2.07 2.40 2.41 2.37 2.03 Eu 1.02 0.95 0.88 0.88 0.92 0.86 0.94 1.03 0.85 0.92 Gd 3.37 3.32 2.77 3.15 2.90 2.97 3.25 3.19 3.20 2.86 Tb 0.56 0.58 0.47 0.53 0.51 0.47 0.54 0.56 0.66 0.56 Dy 3.96 3.92 3.37 3.70 3.52 3.35 3.85 3.91 4.29 3.77 Ho 0.82 0.87 0.71 0.77 0.77 0.72 0.83 0.82 0.95 0.81 Er 2.49 2.42 2.12 2.32 2.32 2.05 2.41 2.41 2.84 2.42 Tm 0.36 0.38 0.32 0.35 0.32 0.32 0.34 0.36 0.40 0.34 Yb 2.40 2.41 2.01 2.15 2.17 1.98 2.33 2.38 2.52 2.22 Lu 0.34 0.37 0.31 0.34 0.33 0.31 0.35 0.36 0.39 0.33 Hf 2.15 2.20 1.82 2.00 2.04 1.69 2.05 2.14 1.10 1.70 Ta 0.16 0.17 0.15 0.13 0.17 0.18 0.15 0.16 0.09 0.09 Th 0.09 0.08 0.11 0.09 0.09 0.09 0.10 0.10 0.05 0.07 注：*熊发挥等(2011). 锆石分选在廊坊市宇恒矿岩技术服务有限公司完成，采用常规粉碎、重液浮选和电磁选方法筛选出锆石精样，在双目镜下挑选锆石颗粒.锆石环氧树脂制靶和锆石阴极发光(CL)图像拍摄在中国地质科学院地质研究所大陆构造与动力学实验室进行.均质辉长岩(13YL45-13)的锆石U-Pb测年分析在中国科学技术大学激光剥蚀电感耦合等离子体质谱实验室(LA-ICP-MS)进行.采用193 nm波长GeoLas pro激光系统用于锆石/矿物样品的剥蚀进样，高纯氦气作为载气.剥蚀系统为Geolas2005激光剥蚀系统，激光器为193nmArF准分子激光器.激光剥蚀时氦气流速为0.9 L/min，频率为10 Hz，激光束能量为10 J/cm2，剥蚀直径为32 μm.Agilent7700型ICP-MS用于对样品气溶胶中U、Pb信号进行分析，实验时RF功率为1 350 W，雾化气流速为0.70 L/min.实验流程参考Yuan et al.(2004).标准锆石91500用来校正元素分馏，每测4个样品测试一次标准锆石.锆石的U、Pb含量用实测的91500含量进行校正，并以29Si的浓度作为内标.采用LaDating@Zrn软件处理U/Pb比值，采用ComPb corr#3-18软件校正普通Pb(Andersen, 2002).锆石年龄谐和图用Isoplot 3.0程序获得，结果见表 2.
表 2 东波蛇绿岩中均质辉长岩(样品13YL45-13)LA-ICP-MS锆石U-Pb定年结果Table Supplementary Table LA-ICP-MS zircon U-Pb isotopic data for an isotropic gabbro (sample 13YL45-13) from the Dongbo ophiolite测试点 普通206Pb*(10-6) 放射性206Pb(10-6) 元素(10-6) Th/U 同位素比值 年龄结果(Ma) U Th 207Pb/206Pb ±1σ 207Pb/235U ±1σ 206Pb/238U ±1σ 206Pb/238U* ±1σ 13YL-45-13-1 11.02 21.55 536.45 1 062.71 1.98 0.165 07 0.013 01 0.474 68 0.044 34 0.020 86 0.000 60 133.0 4.0 13YL-45-13-4 6.57 10.74 321.14 527.06 1.64 0.078 49 0.009 65 0.227 78 0.029 97 0.021 05 0.000 61 134.0 4.0 13YL-45-13-5 9.99 19.75 524.28 1 632.49 3.11 0.048 13 0.003 63 0.128 22 0.010 16 0.019 32 0.000 46 123.0 3.0 13YL-45-13-10 8.28 13.29 418.22 783.01 1.87 0.051 12 0.004 96 0.142 30 0.014 00 0.020 19 0.000 58 129.0 4.0 13YL-45-13-12 8.78 12.67 439.39 441.28 1.00 0.045 58 0.006 48 0.127 93 0.018 41 0.020 36 0.000 61 130.0 4.0 13YL-45-13-13 16.11 26.40 812.55 1 309.55 1.61 0.069 84 0.005 49 0.193 49 0.016 91 0.020 09 0.000 54 128.0 3.0 13YL-45-13-14 4.47 7.09 210.48 351.05 1.67 0.039 89 0.006 94 0.120 49 0.020 28 0.021 90 0.000 70 140.0 4.0 13YL-45-13-15 12.18 26.14 619.90 1 787.98 2.88 0.148 87 0.012 12 0.405 19 0.033 53 0.019 74 0.000 54 126.0 3.0 13YL-45-13-16 10.92 17.68 534.69 808.60 1.51 0.070 03 0.007 59 0.198 93 0.024 23 0.020 60 0.000 56 131.0 4.0 13YL-45-13-19 6.39 12.26 323.97 894.78 2.76 0.046 38 0.009 00 0.126 49 0.023 88 0.019 78 0.000 68 126.0 4.0 13YL-45-13-20 7.40 11.13 369.67 567.69 1.54 0.047 19 0.006 75 0.133 48 0.019 68 0.020 52 0.000 62 131.0 4.0 13YL-45-13-21 8.52 14.19 437.10 767.41 1.76 0.068 76 0.008 25 0.187 93 0.023 18 0.019 82 0.000 64 127.0 4.0 13YL-45-13-22 6.12 10.55 316.77 587.04 1.85 0.067 14 0.010 41 0.181 76 0.033 20 0.019 63 0.000 65 125.0 4.0 13YL-45-13-23 5.47 7.44 263.04 245.45 0.93 0.048 81 0.007 05 0.141 92 0.021 24 0.021 09 0.000 64 135.0 4.0 13YL-45-13-24 10.92 16.73 524.09 753.93 1.44 0.041 20 0.004 34 0.118 80 0.013 23 0.020 91 0.000 54 133.0 3.0 13YL-45-13-26 4.83 9.32 230.79 624.35 2.71 0.042 00 0.005 78 0.123 78 0.017 45 0.021 38 0.000 63 136.0 4.0 13YL-45-13-27 2.70 5.54 138.01 439.49 3.18 0.051 29 0.008 77 0.140 46 0.024 05 0.019 86 0.000 69 127.0 4.0 13YL-45-13-29 7.86 16.65 378.64 1 364.15 3.60 0.046 79 0.006 77 0.135 85 0.018 87 0.021 06 0.000 60 134.0 4.0 13YL-45-13-30 5.97 13.16 294.78 1 145.82 3.89 0.052 56 0.006 09 0.149 59 0.017 64 0.020 64 0.000 58 132.0 4.0 13YL-45-13-31 3.22 6.75 157.42 522.97 3.32 0.049 19 0.007 10 0.140 84 0.021 57 0.0207 6 0.000 64 132.0 4.0 13YL-45-13-32 6.22 12.75 317.55 1 024.59 3.23 0.051 26 0.006 48 0.139 63 0.018 06 0.01975 0.000 57 126.0 4.0 注：*由测定的204Pb计算. 4. 数据结果
4.1 岩石成分特征
东波均质辉长岩主量元素去除烧失量100%均一化以后进行岩石分类.其SiO2含量(平均47.23%)、K2O(平均0.09%)、P2O5(平均0.09%)、Na2O(平均0.56%)和Fe2O3(平均1.40%)相对较低，FeO含量平均为6.83%，全铁(FeOT)平均为7.84%，而TiO2(0.94%~1.12%，平均为1.10%)、Al2O3(平均14.36%)、CaO(平均18.72%)和MgO含量(平均8.75%)以及Mg#值(平均70.31)相对较高.在谐变图解中，均质辉长岩的Al2O3与MgO线性负相关，其他元素随MgO的升高变化不大，与西南印度洋洋中脊玄武岩和高铝玄武岩(Yang et al., 2017)类似(图 7).
图 7 东波均质辉长岩全岩化学成分谐变图解辉长岩脉熊发挥等(2011)；西南印度洋Seg 27玄武岩和高铝玄武岩引自Yang et al.(2017)Fig. 7. Selected chemical variation diagrams of isotropic gabbro samples from the Dongbo ophiolite均质辉长岩的稀土元素REE含量在30.55×10-6~35.51×10-6之间(平均33.41×10-6)，(La/Yb)N比值在0.69~0.60之间(平均0.65)，比典型正常洋中脊玄武岩(N-MORB，Sun and McDonough, 1989)含量稍低.REE球粒陨石标准化图解中，均质辉长岩与128 Ma东波辉长岩脉(熊发挥等，2011)、北带错布扎方辉橄榄岩中128~126 Ma辉绿岩脉(刘飞等，2015b)(图 8a)，以及西南印度洋扩张脊玄武岩(Gao et al., 2016；Yang et al., 2017) (图 8b)类似，但其重稀土元素(HREE)含量比N-MORB、全球MORB和全球弧后玄武岩(BAB)(Gale et al., 2013)，以及西太平洋Lau洋脊岛弧拉斑玄武岩(IAT)(Hergt and Woodhead, 2007)稍低(图 8a)，而位于西南印度洋扩张脊玄武岩和高铝玄武岩之间，与Mariana弧前玄武岩(FAB)(Reagan et al., 2010)类似(图 8b)；其LREE含量比FAB富集，与Lau的IAT类似(图 8a, 8b).
图 8 东波蛇绿岩中基性岩脉球粒陨石和N-MORB标准化图解东波辉石岩脉和辉长岩脉，据熊发挥等(2011)；YZSZ西段北带错布扎蛇绿岩中辉绿岩脉，据刘飞等(2015b)；BAB.全球弧后玄武岩平均值；MORB.全球洋中脊玄武岩平均值(包括MORB, N-MORB, MORB+BAB三条线)，据Gale et al.(2013)；Mariana FAB-D.马里亚纳弧前玄武质岩脉，据Reagan et al.(2010)；Lau-IAT.Lau洋脊岛弧拉斑玄武岩, 据Hergt and Woodhead(2007)；西南印度洋洋脊Seg 27玄武岩和高铝玄武岩，据Yang et al.(2017)；西南印度洋洋脊龙骨玄武岩，据Gao et al.(2016)；N-MORB和球粒陨石，据Sun and McDonough(1989)Fig. 8. Chondrite-normalized REE patterns and N-MORB normalized spider diagrams for the Dongbo gabbros微量元素N-MORB标准化蛛网图中，均质辉长岩曲线位于全球BAB和MORB平均值之下，相比N-MORB，明显亏损HFSE和HREE元素，富集Ba元素(图 8c, 8d).相比Lau的IAT和北带错布扎辉绿岩脉，均质辉长岩虽然具有相同明显Nb负异常，但不发育Sr、Pb正异常，无Zr、Hf和Ti异常，明显区别于洋内岛弧拉斑玄武岩(图 8c)，以及稍不同于具有Nb负异常和Sr无异常至正异常的西南印度洋中脊玄武岩(图 8d).
4.2 锆石U-Pb年龄
均质辉长岩(13YL45-13)的锆石大小和CL特征均一，呈自形至半自形粒状和柱状，粒径主要在50~150 μm之间，长宽比为1:1.2~1:3.CL图像呈平直振荡环带状、弱分带状、海绵状、火焰状、飞燕状等特征(图 9a)，类似于特罗多斯斜长花岗岩中的锆石(Grimes et al., 2013).前两者与YZSZ西段巴尔、错布扎等基性岩浆锆石一致(Liu et al., 2018)；后三者常见于流体作用的重结晶锆石(吴元保和郑永飞，2004).本样品锆石重结晶不彻底，普遍可见残留的岩浆环带被海绵状重结晶部位切割，两者界限清楚.选择流体重结晶较弱的岩浆锆石部位进行原位U-Pb定年，20个206Pb/238U测点的年龄位于140~123 Ma，加权平均年龄为129.6±1.6 Ma(图 9b, 9c).考虑到锆石26、27、29、31的测试位置位于海绵状部位，去除该4粒锆石，余下16粒锆石的加权平均年龄为129.0±1.8 Ma(图 9d, 9e).该年龄与20粒锆石的加权平均年龄(129.6±1.6 Ma)、辉长岩脉的年龄(128±1.1 Ma，熊发挥等，2011)以及单斜辉石岩脉的年龄(130±0.5 Ma，熊发挥等，2011)类似，结合其较高的Th/U比值(0.93~3.89)，笔者认为该年龄为均质辉长岩的结晶年龄.
图 9 东波均质辉长岩(13YL45-13)锆石阴极发光(CL)图像(a)，和锆石U-Pb年龄谐和图(b, d)及其加权平均年龄图(c, e)Fig. 9. Zircon cathodoluminescence (CL) images of isotropic gabbros in the Dongbo (a), zircon U-Pb concordia diagrams (b, d) and their weighted average results (c, e) in the Dongbo5. 讨论
5.1 地幔源区特征
东波均质辉长岩的MgO含量和Mg#平均值分别为8.75%和70.31，接近于最原始MORB熔体(MgO约为10.5%，Mg#>72含量)(Niu, 2016).均质辉长岩除Al2O3外，其他元素随MgO的升高没有明显变化(图 7)，与西南印度洋中脊玄武岩和高铝玄武岩类似(Yang et al., 2017)；辉长岩的稀土配分曲线与N-MORB趋势近于一致(图 8a)，指示其成分几乎未经历分离结晶，为地幔源区部分熔融的初始岩浆.
地幔源区发生部分熔融过程中，地幔中具有类似不相容性的元素比值相对保持不变，可以用于示踪源区特征(Condie, 2003).重稀土元素(HREE)在部分熔融过程中相容于石榴石，因此相比N-MORB，源自石榴石相的基性岩浆常常亏损(HREE)元素，该类玄武岩被命名为来自石榴石源区的玄武岩(G-MORB，Saccani, 2015).在球粒陨石标准化(Ce/Yb)N-(Dy/Yb)N图解中，所有样品落入N-MORB区域(图 10a)，指示源区为非石榴石相地幔橄榄岩.在La/Sm-Sm/Yb图解中，所有样品均落在由亏损地幔和初始地幔定义的近水平的地幔趋势线和延长线上，接近于N-MORB，说明东波均质辉长岩和辉长岩脉样品均源自尖晶石二辉橄榄岩部分熔融，经历了约12%~20%部分熔融(图 10b).
图 10 球粒陨石标准化的Ce/Yb-Dy/Yb图解(a)和La/Sm-Sm/Yb图解(b)图a据Saccani(2015)；图b中曲线和数字分别为非模式熔融模拟曲线和熔融程度(%)，据Aldanmaz et al.(2000).N-MORB.正常洋中脊玄武岩；G-MORB.源自石榴石相的洋中脊玄武岩；E-MORB.富集洋中脊玄武岩；DMM.亏损MORB地幔；EM.西安那托利亚富集地幔；PM.初始地幔.N代表球粒陨石标准化，据Sun and McDonough(1989)；东波辉长岩脉数据熊发挥等(2011)Fig. 10. Isotropic gabbro samples on the chondrite-normalized (Dy/Yb) versus (Ce/Yb) diagram used for discriminating between G-MORB and N-MORB (a) and La/Sm-Sm/Yb diagram (b)5.2 构造环境
构造地幔橄榄岩、深成杂岩、岩墙群及上部熔岩和沉积物等蛇绿岩端元均为鉴别蛇绿岩的构造环境和重建洋陆演化重要的研究对象(Pearce, 2014)，其中基性岩的地球化学对蛇绿岩构造环境的判别有重要的限定意义.然而近期国内外学者对玄武岩类地球化学构造环境判别图解的实用性进行重新评估(Velikoslavinsky and Krylov, 2014；Li et al., 2015；Wang et al., 2016；王金荣等, 2016, 2017；杨婧等，2016)，指出很多判别图解对鉴别不同类型的玄武质岩石存在严重重叠而难以区分，但并未全盘否定构造图解的使用，强调判别图解的选择需依据区域地质背景及岩石学、矿物学等研究综合考量(Li et al., 2015a；邓晋福等，2015)，认为Th、Nb、Ta、Ti元素能较好地判别岛弧和非岛弧玄武岩(杨婧等，2016)，微量元素蛛网图中Nb-Ta负异常可以有效判别MORB和岛弧玄武岩(Li et al., 2015).此外，N-MORB标准化的NbN-ThN图解强调Th元素基于俯冲或地壳混染等方式的富集，能够较好地区分俯冲不相关玄武岩(如大陆边缘裂解、洋陆转换带)与各种俯冲相关的玄武岩(Saccani, 2015).因此笔者采用Th、Nb、Ti等HFSE和HREE探讨东波基性岩的构造环境.
在球粒陨石标准化REE图解中，均质辉长岩具有与N-MORB类似的稀土元素配分模式(图 8a)，虽然在微量元素N-MORB标准化图解中，明显亏损HFSE和HREE元素，富集Ba元素，但是发育Nb、Sr、Pb负异常，无Zr、Hf和Ti异常，不同于洋内岛弧拉斑玄武岩(图 8c)，而与具有Nb负异常的西南印度洋中脊玄武岩相似，后者显示无Sr异常至正异常特征(图 8d).
一般认为，相比N-MORB，在微量元素蛛网图中Nb负异常和大离子亲石元素的富集为俯冲带岩浆的地球化学特征(Elliott et al., 1997；Whattam and Stern, 2011；Zheng and Chen, 2016)，并认为该特征主要由俯冲板片脱水熔融产生的流体或熔体交代地幔楔，使后者发生部分熔融(Todd et al., 2012；肖庆辉等，2016).Baier et al.(2008，及其内部文献)对俯冲带岩浆的Nb和Ta负异常进行了论述，不认为地幔楔下部的俯冲板片赋存金红石保留了Nb和Ta而导致流体中亏损Nb和其他HFSE，因为正常地幔橄榄岩中不含金红石，而玄武岩中的金红石的溶解度相对较高，这种亏损Nb流体也不可能向上运移几千米而不与周围地幔橄榄岩发生再平衡反应，认为地幔橄榄岩或榴辉岩中高铝单斜辉石是导致Nb亏损的主要原因，Nb受四次配位的Al控制(Baier et al., 2008).西南印度洋中脊玄武岩和高铝玄武岩普遍具有Nb负异常(图 8d)，可能源自新元古代莫桑比克洋岛弧地幔或者早期地幔柱熔体熔离后的地幔残余，这种Nb的亏损是由地幔源区铝单斜辉石引起的(Zhou and Dick, 2013；Gao et al., 2016).东波蛇绿岩发育极薄的洋壳(Liu et al., 2015)，以方辉橄榄岩和纯橄榄岩为主体的地幔橄榄岩经历了高达35%的部分熔融(Niu et al., 2015)，与西南印度洋慢速和超慢速扩张洋中脊的岩石组合和高亏损的地幔橄榄岩类似(Zhou and Dick, 2013；Mallick et al., 2015).东波均质辉长岩在N-MORB标准化图解中不仅具有Nb负异常，还具有Sr和Pb负异常，相比N-MORB亏损Th元素(图 8c)，指示初始岩浆没有壳源物质的加入，Nb负异常是由亏损的地幔源区决定的.此推断与Ta/Yb-Th/Yb图解(图 11a)和Ti/1 000-V图解(图 11b)中均质辉长岩样品显示MORB的地球化学特征一致，也与N-MORB标准化Nb-Th图解结果一致(图 11c, 11d)，指示一种洋中脊扩张环境.
图 11 东波均质辉长岩的构造判别图解图a据Pearce(2003)；图b据引自Pearce(2014)；图c和图d引自Saccani(2015).辉石岩脉和辉长岩脉熊发挥等(2011).AB.碱性玄武岩；BBAB.弧后盆地玄武岩；D/N/G-MORB.亏损/正常/石榴石相-洋中脊玄武岩；WPB.板内玄武岩Fig. 11. Tectonic discrimination diagrams for the Dongbo isotropic gabbros5.3 侵位机制
威尔逊旋回，即从大陆裂解漂移、裂陷盆地持续扩张至成熟大洋、洋壳俯冲消减至陆陆碰撞导致大洋彻底消亡，可相应产生俯冲相关和俯冲不相关蛇绿岩(Dilek et al., 2005；Pearce, 2014)，而与俯冲相关的蛇绿岩是目前世界上最主要的蛇绿岩类型(Dilek and Furnes, 2011；Furnes et al., 2015).欧亚大陆南部、东南亚洲、新几内亚、斐济和新西兰代表了一个长期构造汇聚由大陆碎块、洋内岛弧、蛇绿岩带和边缘海盆地组成的复杂构造增生带(Zahirovic et al., 2016).太平洋板块向西北俯冲至菲律宾板块之下形成长约2 800 km的伊豆-小笠原-马里亚纳(Izu-Bonin-Mariana，IBM)(Bryant et al., 2013)和太平洋板块俯冲到澳大利亚板块之下形成长约2 500 km的斐济-汤加-克马德克(Fiji-Tonga-Kermadec，FTK，Escrig et al., 2009；Todd et al., 2012)是现代大洋最重要的俯冲带之一.位于欧亚大陆南部的雅鲁藏布江缝合带普遍被认为代表了新特提斯洋开合及印度-亚洲碰撞的界限(Molnar and Tapponnier, 1975；Tapponnier et al., 1981；Yang et al., 2014；吴福元等，2014；Xu et al., 2015)，然而雅鲁藏布蛇绿岩的成因还存在较大争论：包括目前大部分学者认可的可与IBM-FTK对比的SSZ弧前-弧-弧后环境(Hébert et al., 2012；Bao et al., 2013；Dai et al., 2013；Lian et al., 2016, 2017；Maffione et al., 2015)、慢速扩张的洋中脊环境(Nicolas et al., 1981; Girardeau and Mercier, 1988; Miller et al., 2003; Liu et al., 2014)，以及贫岩浆型大陆边缘洋盆(Liu et al., 2015, 2018；Gong et al., 2016)等，前人从岩浆、热液交代和构造等不同角度解释了雅鲁藏布新特提斯洋的构造演化过程.
梁凤华等(2011)和Xu et al.(2015)等概述了雅鲁藏布蛇绿岩的侵位机制，认为其普遍经历了白垩纪向南褶皱逆冲到特提斯喜马拉雅复理石地层和新生代早期向北反冲逆冲至中东段的日喀则弧前盆地、西段仲巴地体和冈底斯岛弧之上.然而，李源等(2016)在白马让蛇绿岩中鉴别出高温流动构造的方辉橄榄岩穹隆及其两侧发育拆离断层性质的糜棱岩化蛇纹岩带，提出日喀则蛇绿岩为类似于大洋核杂岩构造侵位形成.其他学者在桑桑和普兰蛇绿岩中也鉴别出拆离断层促使岩石圈地幔在伸展环境下剥露至海底的侵位机制(Liu et al., 2014；Maffione et al., 2015).大洋核杂岩是由低角度正断层拆离作用形成的大型洋底穹窿状凸起构造，具有以下特征：出露岩性主要为地幔橄榄岩和辉长岩；超基性岩-基性岩规模较大、直接出露洋底导致发育一定规模的蛇绿质角砾岩；基性熔岩少或缺失，一般相对为晚期产物；蛇绿岩中发育辉长岩、辉绿岩、斜长花岗岩等侵入脉体；灰岩和硅泥质岩等深海沉积物或枕状熔岩直接覆盖在超基性岩之上；发育强韧性剪切变形拆离断层带和垂直扩张脊的线理(如窗棱构造)，局部可发育高角度正断层，拆离断层一般可持续活动1~2 Ma(Morris et al., 2009；Canales, 2010；余星等，2013；敖松坚等，2017).
雅鲁藏布江缝合带南带出露多个大型的(如东波、普兰、扎嘎和休古嘎布等)超镁铁岩块(Liu et al., 2018)和少量辉长岩体(刘飞等，2015a)，未发现典型亚碱性基性熔岩和席状岩墙群，但普遍可见块状灰岩、硅质灰岩、硅泥页岩、硅质岩和碱性块状或枕状玄武岩等海山火山-沉积组合覆盖在地幔橄榄岩之上(Liu et al., 2015).笔者在东波蛇绿岩填图时发现多处拆离正断层(图 12a)、韧性剪切拆离断层(图 5c, 12b)、糜棱岩和糜棱岩化蛇纹岩(图 5c)以及断层滑擦产生的阶步构造(图 12c)，并在东波和普兰发现多处可能在拆离伸展过程中形成的基质为蛇纹质、角砾为地幔橄榄岩的蛇绿角砾岩(图 12d~12f)，指示东波地幔橄榄岩可能与普兰和白马让蛇绿岩一样经历了类似大洋核杂岩的伸展作用直接出露于海底(图 13).东波地幔橄榄岩上部的火山-沉积组合虽然破碎，但部分露头仍可鉴别原始层序，类似于混杂岩中的破坏地层(broken formation，Festa et al., 2010)，代表拆离面上部的海相火山沉积端元，其中硅质岩放射虫时代为晚侏罗-早白垩世(刘飞等，2013)，稍早于均质辉长岩的年龄.在拆离过程中，岩石圈下部亏损的地幔源区上涌发生部分熔融形成均质辉长岩和辉长岩脉，其中蛇纹石化地幔橄榄岩和均质辉长岩的接触部位可能为拆离断层面(图 5a)，前者发生强烈的蛇纹石化和糜棱岩化(图 5c)，后者发生由角闪石、绿帘石和少量绿泥石和钠长石组成的绿片岩相变质(图 6).拆离时间发生在130 Ma左右，持续约2 Ma.
图 12 雅鲁藏布江缝合带西段南带地幔橄榄岩的野外构造特征a.东波地幔橄榄岩中拆离正断层；b.韧性剪切拆离断层(断层面被碳酸盐矿物充填)；c.阶步构造；d.东波地幔橄榄质角砾岩；e，f.普兰地幔橄榄质角砾岩Fig. 12. Field photographs of structural features of mantle peridotite in the southern belt of the western Yarlung Zangbo suture zone
图 13 东波蛇绿岩在慢速扩张脊附近沿转换断层侵位Fig. 13. Schematic model of the Dongbo ophiolite formation as an oceanic core complex near a slow-spreading ridge6. 结论
雅鲁藏布江缝合带西段蛇绿岩以出露大面积地幔橄榄岩、发育极薄洋壳(如辉长岩)，以及出露大面积晚侏罗-早白垩世残余海山为主要特征，明显不同于相同特提斯带上的典型彭罗斯层序的日喀则、东地中海和波斯湾-阿曼蛇绿岩(图 1a).东波蛇绿岩北部的均质辉长岩位于蛇纹石化地幔橄榄岩和硅质岩之间，彼此构造接触，锆石U-Pb年龄为129.0±1.8 Ma.相比全球N-MORB平均值(Gale et al., 2013)，均质辉长岩具有低Si、K、P、Fe和Ti，高Ca和Mg的特点，稀土元素配分曲线具有N-MORB(Sun and McDonough, 1989)特征.锆石CL图像呈平直振荡环带状、弱分带状、海绵状、火焰状和飞燕状等复杂特征，指示结晶锆石普遍受到流体交代.微量元素蛛网图中不仅具有岛弧特征的Nb负异常，还具有明显Th负异常，以及流体活动性较强的Sr和Pb元素的负异常，指示岩浆源区没有源身俯冲板片脱水熔融的流体，而可能在洋中脊附近，岩石圈下部亏损地幔在拆离伸展过程中部分熔融形成均质辉长岩，其锆石年龄129.0±1.8 Ma代表拆离时间.该推测与东波和普兰蛇绿岩中发育大量拆离和韧性剪切断层(图 12a, 12b)、糜棱岩和糜棱岩化蛇纹岩(图 5c)以及可能在拆离伸展过程中形成的基质为蛇纹质、角砾为地幔橄榄岩的蛇绿角砾岩(图 12d~12f)相吻合.由此笔者提出东波蛇绿岩形成于慢速-超慢速大洋扩张过程中沿转换断层拆离伸展侵位至海底，类似于现代西南印度洋和大西洋中的大洋核杂岩的形成过程.
致谢: 迈阿密大学Yildirim Dilek教授在全球蛇绿岩分布和成因方面给予很多指导，野外考察得到许志琴院士和梁凤华副研究员在构造侵位方面的指导，成文过程中吴魏伟博士给予有益帮助，迈阿密大学的解艳雪博士、中国地质大学(武汉)的周文达，中国地质大学(北京)的赵一珏、王云鹏、高健和李观龙硕士参与了野外工作，审稿专家提出了宝贵的修改意见，在此一并表示真挚的谢意. -
图 1 西藏雅鲁藏布江缝合带(YZSZ)在东特提斯-喜马拉雅-缅马造山带中的位置(a)和西藏南部区域地质简图和YZSZ蛇绿岩分布(b)
图a据Jagoutz et al.(2015)修改；图b据Xu et al.(2015)修改.GCT.大反冲逆冲断裂；GT.冈底斯逆冲断层；KKF.喀喇昆仑断裂；MBT.主边界逆冲断裂；MCT.主中央逆冲断裂；MFT.主前缘逆冲断裂；NB.南迦巴瓦构造结；NP.南迦帕尔特构造结；STD.藏南拆离系
Fig. 1. Location of the Yarlung Zangbo suture zone (YZSZ), Tibet in the eastern Mediteranian-Ximalaya-Myanma orogenic belt (a), and simplified geological map of southern Tibet showing the locations of all the ophiolitic massifs in the YZSZ (b)
图 2 西藏南部雅鲁藏布江缝合带(YZSZ)和班公湖-怒江缝合带(BNSZ)分布简图(a)，YZSZ西段区域地质简图(b)
普兰东和普兰西以拉昂错湖西缘为界
Fig. 2. Distribution of ophiolitic massifs along the Yarlung Zangbo suture zone (YZSZ) and Bangonghu-Nujiang suture zone (BNSZ) in Tibet (a); simplified geological map of the western part of the YZSZ, Tibet (b)
图 3 雅鲁藏布江缝合带西段南带东波蛇绿岩地质简图
样品L190(辉长岩，坐标N31°04′26.50″，E80°11′14.40″)和L178(辉石岩，N31°02′16.30″，E80°17′44.60″)熊发挥等(2011)；样品GCT329(粗粒辉长岩，N31°02′16.69″，E80°17′44.59″)引自Chan et al.(2015).白色五角星为文献样品，黄色五角星为本文样品
Fig. 3. Geological map of the Dongbo ophiolite in the southern belt of the western Yarlung Zangbo suture zone
图 4 东波堆晶伟晶辉长岩夹纯橄岩透镜体野外特征
Fig. 4. Occurrence of cumulate pegmatoidal gabbros interbedded with dunite lens in the Dongbo ophiolite
图 5 雅鲁藏布江缝合带西段南带东波均质辉长岩的野外特征
Fig. 5. Field photographs of the isotropic gabbros in the southern belt of the western Yarlung Zangbo suture zone
图 6 东波均质辉长岩的显微镜下特征
a~d.样品13YL45-6；e, f.样品13YL45-8，左边单偏光，右边正交光
Fig. 6. Photomicrographs of the isotropic gabbros in the southern belt of the western Yarlung Zangbo suture zone
图 7 东波均质辉长岩全岩化学成分谐变图解
辉长岩脉熊发挥等(2011)；西南印度洋Seg 27玄武岩和高铝玄武岩引自Yang et al.(2017)
Fig. 7. Selected chemical variation diagrams of isotropic gabbro samples from the Dongbo ophiolite
图 8 东波蛇绿岩中基性岩脉球粒陨石和N-MORB标准化图解
东波辉石岩脉和辉长岩脉，据熊发挥等(2011)；YZSZ西段北带错布扎蛇绿岩中辉绿岩脉，据刘飞等(2015b)；BAB.全球弧后玄武岩平均值；MORB.全球洋中脊玄武岩平均值(包括MORB, N-MORB, MORB+BAB三条线)，据Gale et al.(2013)；Mariana FAB-D.马里亚纳弧前玄武质岩脉，据Reagan et al.(2010)；Lau-IAT.Lau洋脊岛弧拉斑玄武岩, 据Hergt and Woodhead(2007)；西南印度洋洋脊Seg 27玄武岩和高铝玄武岩，据Yang et al.(2017)；西南印度洋洋脊龙骨玄武岩，据Gao et al.(2016)；N-MORB和球粒陨石，据Sun and McDonough(1989)
Fig. 8. Chondrite-normalized REE patterns and N-MORB normalized spider diagrams for the Dongbo gabbros
图 9 东波均质辉长岩(13YL45-13)锆石阴极发光(CL)图像(a)，和锆石U-Pb年龄谐和图(b, d)及其加权平均年龄图(c, e)
Fig. 9. Zircon cathodoluminescence (CL) images of isotropic gabbros in the Dongbo (a), zircon U-Pb concordia diagrams (b, d) and their weighted average results (c, e) in the Dongbo
图 10 球粒陨石标准化的Ce/Yb-Dy/Yb图解(a)和La/Sm-Sm/Yb图解(b)
图a据Saccani(2015)；图b中曲线和数字分别为非模式熔融模拟曲线和熔融程度(%)，据Aldanmaz et al.(2000).N-MORB.正常洋中脊玄武岩；G-MORB.源自石榴石相的洋中脊玄武岩；E-MORB.富集洋中脊玄武岩；DMM.亏损MORB地幔；EM.西安那托利亚富集地幔；PM.初始地幔.N代表球粒陨石标准化，据Sun and McDonough(1989)；东波辉长岩脉数据熊发挥等(2011)
Fig. 10. Isotropic gabbro samples on the chondrite-normalized (Dy/Yb) versus (Ce/Yb) diagram used for discriminating between G-MORB and N-MORB (a) and La/Sm-Sm/Yb diagram (b)
图 11 东波均质辉长岩的构造判别图解
图a据Pearce(2003)；图b据引自Pearce(2014)；图c和图d引自Saccani(2015).辉石岩脉和辉长岩脉熊发挥等(2011).AB.碱性玄武岩；BBAB.弧后盆地玄武岩；D/N/G-MORB.亏损/正常/石榴石相-洋中脊玄武岩；WPB.板内玄武岩
Fig. 11. Tectonic discrimination diagrams for the Dongbo isotropic gabbros
图 12 雅鲁藏布江缝合带西段南带地幔橄榄岩的野外构造特征
a.东波地幔橄榄岩中拆离正断层；b.韧性剪切拆离断层(断层面被碳酸盐矿物充填)；c.阶步构造；d.东波地幔橄榄质角砾岩；e，f.普兰地幔橄榄质角砾岩
Fig. 12. Field photographs of structural features of mantle peridotite in the southern belt of the western Yarlung Zangbo suture zone
图 13 东波蛇绿岩在慢速扩张脊附近沿转换断层侵位
Fig. 13. Schematic model of the Dongbo ophiolite formation as an oceanic core complex near a slow-spreading ridge
表 1 东波蛇绿岩中均质辉长岩主量元素(%)和微量元素(10-6)含量
Table 1. Major (%) and trace element (10-6) compositions of isotropic gabbros from the Dongbo ophiolite in the western YZSZ, Tibet
样品号 均质辉长岩 辉石岩脉 辉长岩脉 13YL45-1 13YL45-2 13YL45-3 13YL45-4 13YL45-5 13YL45-7 13YL45-8 13YL45-9 L-178-3* L-190-2* SiO2 45.62 45.72 45.59 45.59 45.94 46.18 45.04 45.81 53.65 49.54 TiO2 1.08 1.07 0.91 1.00 0.98 0.91 1.03 1.05 0.10 0.94 Al2O3 13.72 13.53 13.59 12.98 14.07 14.02 14.70 13.46 3.03 15.66 Fe2O3 1.61 0.99 1.36 1.51 1.21 1.02 1.42 1.58 7.94 2.10 FeO 6.53 6.91 5.71 6.28 6.18 6.00 6.29 6.26 6.80 6.80 MnO 0.16 0.17 0.16 0.18 0.15 0.16 0.15 0.17 0.15 0.15 MgO 8.48 8.47 9.81 9.50 7.48 7.87 7.97 8.67 25.37 7.35 CaO 18.55 18.62 18.26 18.16 19.63 19.62 19.03 18.51 7.63 10.9 Na2O 0.32 0.33 0.32 0.34 0.32 0.29 0.28 0.34 0.09 3.29 K2O 0.07 0.08 0.07 0.07 0.07 0.08 0.07 0.09 0.02 0.09 P2O5 0.09 0.09 0.08 0.08 0.08 0.07 0.09 0.09 0.05 0.07 CO2 0.15 0.13 0.13 0.19 0.16 0.28 0.14 0.19 H2O+ 3.76 3.91 4.03 3.90 3.56 3.54 4.11 3.86 LOI 3.17 3.09 3.52 3.26 3.00 3.27 3.59 3.29 0.10 1.98 Total 100.14 100.02 100.02 99.79 99.84 100.04 100.32 100.07 98.36 98.68 FeOT 7.98 7.80 6.93 7.64 7.27 6.92 7.57 7.68 13.94 8.69 Mg# 65.67 66.15 71.80 69.12 64.94 67.19 65.47 67.01 76.61 60.36 M 70.04 68.81 75.56 73.14 68.54 70.25 69.52 71.37 87.04 66.05 Sc 35.10 33.50 30.80 33.60 31.60 31.20 32.60 33.40 Ti 6 806.00 6 353.00 5 547.00 6 201.00 6 149.00 5 740.00 6 276.00 6 672.00 Cr 154.00 150.00 185.00 184.00 155.00 177.00 167.00 154.00 V 226.00 215.00 189.00 211.00 205.00 193.00 208.00 232.00 305.00 210.00 Ni 59.90 58.00 61.50 61.70 58.10 61.20 58.90 56.30 Co 38.40 35.60 34.20 35.30 36.00 34.50 36.10 36.90 Cu 55.40 60.50 43.30 44.40 40.20 20.50 53.10 40.40 Zn 66.60 60.80 55.60 62.20 60.40 50.80 58.00 59.30 Ga 13.30 11.90 12.00 11.60 13.90 14.60 11.60 12.80 Mn 1 197.00 1 201.00 1 166.00 1 271.00 1 164.00 1 187.00 1 045.00 1 291.00 Mo 0.26 0.14 0.15 0.25 0.17 0.26 0.10 0.17 Pb 0.16 0.22 0.14 0.32 0.29 0.18 0.20 0.19 Rb 0.45 0.44 1.66 0.95 0.87 0.88 0.70 0.77 0.20 0.90 Sr 48.40 45.30 45.10 42.10 47.80 40.20 52.10 47.70 160.00 121.00 Y 25.00 23.40 19.70 21.40 21.10 19.60 21.20 22.80 23.20 19.60 Zr 71.20 74.50 63.10 66.10 68.30 59.80 69.70 71.90 Nb 0.92 0.87 0.83 0.81 0.90 0.84 0.86 0.96 0.50 0.70 Ba 17.40 13.30 21.60 11.60 6.15 10.40 11.70 10.60 1.70 7.50 La 2.13 2.00 1.94 1.87 1.98 1.89 2.06 2.16 1.00 1.80 Ce 6.81 6.95 6.16 6.44 6.49 6.08 6.85 6.95 3.90 5.70 Pr 1.24 1.27 1.10 1.18 1.18 1.09 1.24 1.31 0.87 1.04 Nd 7.58 7.43 6.62 6.79 7.25 6.39 7.32 7.08 5.40 5.80 Sm 2.43 2.41 2.17 2.35 2.31 2.07 2.40 2.41 2.37 2.03 Eu 1.02 0.95 0.88 0.88 0.92 0.86 0.94 1.03 0.85 0.92 Gd 3.37 3.32 2.77 3.15 2.90 2.97 3.25 3.19 3.20 2.86 Tb 0.56 0.58 0.47 0.53 0.51 0.47 0.54 0.56 0.66 0.56 Dy 3.96 3.92 3.37 3.70 3.52 3.35 3.85 3.91 4.29 3.77 Ho 0.82 0.87 0.71 0.77 0.77 0.72 0.83 0.82 0.95 0.81 Er 2.49 2.42 2.12 2.32 2.32 2.05 2.41 2.41 2.84 2.42 Tm 0.36 0.38 0.32 0.35 0.32 0.32 0.34 0.36 0.40 0.34 Yb 2.40 2.41 2.01 2.15 2.17 1.98 2.33 2.38 2.52 2.22 Lu 0.34 0.37 0.31 0.34 0.33 0.31 0.35 0.36 0.39 0.33 Hf 2.15 2.20 1.82 2.00 2.04 1.69 2.05 2.14 1.10 1.70 Ta 0.16 0.17 0.15 0.13 0.17 0.18 0.15 0.16 0.09 0.09 Th 0.09 0.08 0.11 0.09 0.09 0.09 0.10 0.10 0.05 0.07 注：*熊发挥等(2011). 
下载: 导出CSV
表 2 东波蛇绿岩中均质辉长岩(样品13YL45-13)LA-ICP-MS锆石U-Pb定年结果
Table 2. LA-ICP-MS zircon U-Pb isotopic data for an isotropic gabbro (sample 13YL45-13) from the Dongbo ophiolite
测试点 普通206Pb*(10-6) 放射性206Pb(10-6) 元素(10-6) Th/U 同位素比值 年龄结果(Ma) U Th 207Pb/206Pb ±1σ 207Pb/235U ±1σ 206Pb/238U ±1σ 206Pb/238U* ±1σ 13YL-45-13-1 11.02 21.55 536.45 1 062.71 1.98 0.165 07 0.013 01 0.474 68 0.044 34 0.020 86 0.000 60 133.0 4.0 13YL-45-13-4 6.57 10.74 321.14 527.06 1.64 0.078 49 0.009 65 0.227 78 0.029 97 0.021 05 0.000 61 134.0 4.0 13YL-45-13-5 9.99 19.75 524.28 1 632.49 3.11 0.048 13 0.003 63 0.128 22 0.010 16 0.019 32 0.000 46 123.0 3.0 13YL-45-13-10 8.28 13.29 418.22 783.01 1.87 0.051 12 0.004 96 0.142 30 0.014 00 0.020 19 0.000 58 129.0 4.0 13YL-45-13-12 8.78 12.67 439.39 441.28 1.00 0.045 58 0.006 48 0.127 93 0.018 41 0.020 36 0.000 61 130.0 4.0 13YL-45-13-13 16.11 26.40 812.55 1 309.55 1.61 0.069 84 0.005 49 0.193 49 0.016 91 0.020 09 0.000 54 128.0 3.0 13YL-45-13-14 4.47 7.09 210.48 351.05 1.67 0.039 89 0.006 94 0.120 49 0.020 28 0.021 90 0.000 70 140.0 4.0 13YL-45-13-15 12.18 26.14 619.90 1 787.98 2.88 0.148 87 0.012 12 0.405 19 0.033 53 0.019 74 0.000 54 126.0 3.0 13YL-45-13-16 10.92 17.68 534.69 808.60 1.51 0.070 03 0.007 59 0.198 93 0.024 23 0.020 60 0.000 56 131.0 4.0 13YL-45-13-19 6.39 12.26 323.97 894.78 2.76 0.046 38 0.009 00 0.126 49 0.023 88 0.019 78 0.000 68 126.0 4.0 13YL-45-13-20 7.40 11.13 369.67 567.69 1.54 0.047 19 0.006 75 0.133 48 0.019 68 0.020 52 0.000 62 131.0 4.0 13YL-45-13-21 8.52 14.19 437.10 767.41 1.76 0.068 76 0.008 25 0.187 93 0.023 18 0.019 82 0.000 64 127.0 4.0 13YL-45-13-22 6.12 10.55 316.77 587.04 1.85 0.067 14 0.010 41 0.181 76 0.033 20 0.019 63 0.000 65 125.0 4.0 13YL-45-13-23 5.47 7.44 263.04 245.45 0.93 0.048 81 0.007 05 0.141 92 0.021 24 0.021 09 0.000 64 135.0 4.0 13YL-45-13-24 10.92 16.73 524.09 753.93 1.44 0.041 20 0.004 34 0.118 80 0.013 23 0.020 91 0.000 54 133.0 3.0 13YL-45-13-26 4.83 9.32 230.79 624.35 2.71 0.042 00 0.005 78 0.123 78 0.017 45 0.021 38 0.000 63 136.0 4.0 13YL-45-13-27 2.70 5.54 138.01 439.49 3.18 0.051 29 0.008 77 0.140 46 0.024 05 0.019 86 0.000 69 127.0 4.0 13YL-45-13-29 7.86 16.65 378.64 1 364.15 3.60 0.046 79 0.006 77 0.135 85 0.018 87 0.021 06 0.000 60 134.0 4.0 13YL-45-13-30 5.97 13.16 294.78 1 145.82 3.89 0.052 56 0.006 09 0.149 59 0.017 64 0.020 64 0.000 58 132.0 4.0 13YL-45-13-31 3.22 6.75 157.42 522.97 3.32 0.049 19 0.007 10 0.140 84 0.021 57 0.0207 6 0.000 64 132.0 4.0 13YL-45-13-32 6.22 12.75 317.55 1 024.59 3.23 0.051 26 0.006 48 0.139 63 0.018 06 0.01975 0.000 57 126.0 4.0 注：*由测定的204Pb计算.
下载: 导出CSV
-
Aldanmaz, E., Pearce, J.A., Thirlwall, M.F., et al., 2000.Petrogenetic Evolution of Late Cenozoic, Post-Collision Volcanism in Western Anatolia, Turkey.Journal of Volcanology and Geothermal Research, 102(1-2):67-95.https://doi.org/10.1016/s0377-0273(00)00182-7 doi: 10.1016/S0377-0273(00)00182-7 Andersen, T., 2002.Correction of Common Lead in U-Pb Analyses That do not Report 204Pb.Chemical Geology, 192(1-2):59-79.https://doi.org/10.1016/s0009-2541(02)00195-x doi: 10.1016/S0009-2541(02)00195-X Ao, S.J., Xiao, W.J., Yang, L., et al., 2017.The Typical Characteristics and Tectonic Implications of Fossil Oceanic Core Complex(OCC)in Orogenic Belt.Scientia Sinica Terrae, 47(1):1-22 (in Chinese). doi: 10.1360/N072016-00213 Baier, J., Audétat, A., Keppler, H., 2008.The Origin of the Negative Niobium Tantalum Anomaly in Subduction Zone Magmas.Earth and Planetary Science Letters, 267(S1-2):290-300.https://doi.org/10.1016/j.epsl.2007.11.032 https://www.sciencedirect.com/science/article/pii/S0012821X07007790 Bao, P.S., Su, L., Wang, J., et al., 2013.Study on the Tectonic Setting for the Ophiolites in Xigaze, Tibet.Acta Geologica Sinica (English Edition), 87(2):395-425.https://doi.org/10.1111/1755-6724.12058 doi: 10.1111/acgs.2013.87.issue-2 Bao, P.S., Su, L., Wang, J., et al., 2014.Origin of the Zedang and Luobusa Ophiolites, Tibet.Acta Geologica Sinica (English Edition), 88(2):669-698.https://doi.org/10.1111/1755-6724.12222 doi: 10.1111/acgs.2014.88.issue-2 Bezard, R., Hébert, R., Wang, C.S., et al., 2011.Petrology and Geochemistry of the Xiugugabu Ophiolitic Massif, Western Yarlung Zangbo Suture Zone, Tibet.Lithos, 125(1-2):347-367. https://doi.org/10.1016/j.lithos.2011.02.019 Bryant, C.J., Arculus, R.J., Eggins, S.M., 2013.The Geochemical Evolution of the Izu-Bonin Arc System:A Perspective from Tephras Recovered by Deep-Sea Drilling.Geochemistry, Geophysics, Geosystems, 4(11):1-37.https://doi.org/10.1029/2002gc000427 doi: 10.1029/2002GC000427 Cai, F.L, Ding, L., Laskowski, A.K., et al., 2016.Late Triassic Paleogeographic Reconstruction along the Neo-Tethyan Ocean Margins, Southern Tibet.Earth and Planetary Science Letters, 435:105-114. https://doi.org/10.1016/j.epsl.2015.12.027 Canales, J.P., 2010.Small-Scale Structure of the Kane Oceanic Core Complex, Mid-Atlantic Ridge 23°30'N, from Wave Form Tomography of Multichannel Seismic Data.Geophysical Research Letters, 37(21):1-6.https://doi.org/10.1029/2010gl044412 doi: 10.1029/2010GL044412 Chan, G.H.N., Aitchison, J.C., Crowley, Q.G., et al., 2015.U-Pb Zircon Ages for Yarlung Tsangpo Suture Zone Ophiolites, Southwestern Tibet and Their Tectonic Implications.Gondwana Research, 27(2):719-732. https://doi.org/10.1016/j.gr.2013.06.016 Condie, K.C., 2003.Incompatible Element Ratios in Oceanic Basalts and Komatiites:Tracking Deep Mantle Sources and Continental Growth Rates with Time.Geochemistry, Geophysics, Geosystems, 4(1):1-28.https://doi.org/10.1029/2002gc000333 doi: 10.1029/2002GC000333 Dai, J.G., Wang, C.S., Hébert, R., et al., 2011.Petrology and Geochemistry of Peridotites in the Zhongba Ophiolite, Yarlung Zangbo Suture Zone:Implications for the Early Cretaceous Intra-Oceanic Subduction Zone within the Neo-Tethys.Chemical Geology, 288(3-4):133-148. https://doi.org/10.1016/j.chemgeo.2011.07.011 Dai, J.G., Wang, C.S., Li Y.L., 2012.Relicts of the Early Cretaceous Seamounts in the Central-Western Yarlung Zangbo Suture Zone, Southern Tibet.Journal of Asian Earth Sciences, 53:25-37. https://doi.org/10.1016/j.jseaes.2011.12.024 Dai, J.G., Wang, C.S., Polat, A., et al., 2013.Rapid Forearc Spreading between 130 and 120 Ma:Evidence from Geochronology and Geochemistry of the Xigaze Ophiolite, Southern Tibet.Lithos, 172-173(4):1-16.https://doi.org/10.1016/j.lithos.2013.03.011 Deng, J.F., Liu, C., Feng, Y.F., et al., 2015.On the Correct Application in the Common Igneous Petrological Diagrams:Discussion and Suggestion.Geological Review, 61(4):717-734 (in Chinese with English abstract). doi: 10.1007/s00410-016-1292-2 Dilek, Y., 2016.Compositions & Melt Evolution of Upper Mantle Peridotites in the Tethyan Ophiolites.Acta Geologica Sinica (English Edition), 90(Suppl.1):211.https://doi.org/10.1111/1755-6724.12981 doi: 10.1021/la501406w Dilek, Y., Furnes, H., 2011.Ophiolite Genesis and Global Tectonics:Geochemical and Tectonic Fingerprinting of Ancient Oceanic Lithosphere.Geological Society of America Bulletin, 123(3-4):387-411.https://doi.org/10.1130/b30446.1 doi: 10.1130/B30446.1 Dilek, Y., Furnes, H., 2014.Ophiolites and Their Origins.Elements, 10(2):93-100. https://doi.org/10.2113/gselements.10.2.93 Dilek, Y., Shallo, M., Furnes, H., 2005.Rift-Drift, Seafloor Spreading, and Subduction Tectonics of Albanian Ophiolites.International Geology Review, 47(2):147-176. https://doi.org/10.2747/0020-6814.47.2.147 Elliott, T., Plank, T., Zindler, A., et al., 1997.Element Transport from Slab to Volcanic Front at the Mariana Arc.Journal of Geophysical Research:Solid Earth, 102(B7):14991-15019.https://doi.org/10.1029/97jb00788 doi: 10.1029/97JB00788 Escrig, S., Bézos, A., Goldstein, S.L., et al., 2009.Mantle Source Variations beneath the Eastern Lau Spreading Center and the Nature of Subduction Components in the Lau Basin-Tonga Arc System.Geochemistry, Geophysics, Geosystems, 10(4):1-33.https://doi.org/10.1029/2008gc002281 doi: 10.1029/2008GC002281?scrollTo=references Festa, A., Pini, G.A., Dilek, Y., et al., 2010.Mélanges and Mélange-Forming Processes:A Historical Overview and New Concepts.International Geology Review, 52(10-12):1040-1105. https://doi.org/10.1080/00206810903557704 Furnes, H., Dilek, Y., de Wit, M., 2015.Precambrian Greenstone Sequences Represent Different Ophiolite Types.Gondwana Research, 27(2):649-685. https://doi.org/10.1016/j.gr.2013.06.004 Gale, A., Dalton, C.A., Langmuir, C.H., et al., 2013.The Mean Composition of Ocean Ridge Basalts.Geochemistry, Geophysics, Geosystems, 14(3):489-518.https://doi.org/10.1029/2012gc004334 doi: 10.1029/2012GC004334 Gao, C.G., Dick, H.J.B., Liu, Y., et al., 2016.Melt Extraction and Mantle Source at a Southwest Indian Ridge Dragon Bone Amagmatic Segment on the Marion Rise.Lithos, 246-247(1):48-60.https://doi.org/10.1016/j.lithos.2015.12.007 https://www.sciencedirect.com/science/article/pii/S0024493715004570 Gao, H.X., Song, Z.J., 1995.New Progress in the Study of the Zetang Ophiolitic Mélange in Tibet.Regional Geology of China, 14(4):316-322 (in Chinese with English abstract). Girardeau, J., Mercier, J.C.C., 1988.Petrology and Texture of the Ultramafic Rocks of the Xigaze Ophiolite (Tibet):Constraints for Mantle Structure beneath Slow-Spreading Ridges.Tectonophysics, 147(1-2):33-58. https://doi.org/10.1016/0040-1951(88)90146-1 Gong, X.H., Shi, R.D., Griffin, W.L., et al., 2016.Recycling of Ancient Subduction-Modified Mantle Domains in the Purang Ophiolite (Southwestern Tibet).Lithos, 262:11-26. https://doi.org/10.1016/j.lithos.2016.06.025 Grimes, C.B., Ushikubo, T., Kozdon, R., et al., 2013.Perspectives on the Origin of Plagiogranite in Ophiolites from Oxygen Isotopes in Zircon.Lithos, 179(5):48-66.https://doi.org/10.1016/j.lithos.2013.07.026 https://www.sciencedirect.com/science/article/pii/S0024493713002430 Guo, G.L., Yang, J.S., Liu, X.D., et al., 2015.Mid-Ocean Ridge (MOR) and Suprasubduction Zone (SSZ) Geological Events in the Yarlung Zangbo Suture Zone:Evidence from the Mineral Record of Mantle Peridotites.Journal of Asian Earth Sciences, 110:33-54. https://doi.org/10.1016/j.jseaes.2015.02.012 He, J., Li, Y.L., Wang, C.S., et al., 2016.Plume-Proximal Mid-Ocean Ridge Origin of Zhongba Mafic Rocks in the Western Yarlung Zangbo Suture Zone, Southern Tibet.Journal of Asian Earth Sciences, 121:34-55. https://doi.org/10.1016/j.jseaes.2016.01.022 Hébert, R., Bezard, R., Guilmette, C., et al., 2012.The Indus-Yarlung Zangbo Ophiolites from Nanga Parbat to Namche Barwa Syntaxes, Southern Tibet:First Synthesis of Petrology, Geochemistry, and Geochronology with Incidences on Geodynamic Reconstructions of Neo-Tethys.Gondwana Research, 22(2):377-397. https://doi.org/10.1016/j.gr.2011.10.013 Hergt, J.M., Woodhead, J.D., 2007.A Critical Evaluation of Recent Models for Lau-Tonga Arc-Backarc Basin Magmatic Evolution.Chemical Geology, 245(1-2):9-44. https://doi.org/10.1016/j.chemgeo.2007.07.022 Jagoutz, O., Royden, L., Holt, A.F., et al., 2015.Anomalously Fast Convergence of India and Eurasia Caused by Double Subduction.Nature Geoscience, 8(6):475-478. https://doi.org/10.1038/ngeo2418 Li, C.S., Arndt, N.T., Tang, Q.Y., et al., 2015a.Trace Element in Discrimination Diagrams.Lithos, 232:76-83. https://doi.org/10.1016/j.lithos.2015.06.022 Li, X.P., Chen, H.K., Wang, Z.L., et al., 2015b.Spinel Peridotite, Olivine Websterite and the Textural Evolution of the Purang Ophiolite Complex, Western Tibet.Journal of Asian Earth Sciences, 110:55-71. https://doi.org/10.1016/j.jseaes.2014.06.023 Li, J.F., Xia, B., Liu, L.W., et al., 2008.SHRIMP U-Pb Zircon Dating of Diabase in the La'nga Co Ophiolite, Burang, Tibet, China, and Its Geological Significance.Geological Bulletin of China, 27(10):1739-1743 (in Chinese with English abstract). Li, X.H., Wang, C.S., Li, Y.L., et al., 2014.Definition and Composition of the Zhongba Microterrane in Southwest Tibet.Acta Geologica Sinica, 88(8):1372-1381 (in Chinese with English abstract). Li, Y., Li, R.B., Dong, T.C., et al., 2016.Structure of the Baimarang Massif in the Xigaze Ophiolite, Yarlung Zangbo Suture Zone, Southern Tibet, China.Chinese Science Bulletin, 61(25):2823-2833 (in Chinese with English abstract). Lian, D.Y., Yang, J.S., Liu, F., et al., 2017.Geochemistry and Tectonic Significance of the Gongzhu Peridotites in the Northern Branch of the Western Yarlung Zangbo Ophiolitic Belt, Western Tibet.Mineralogy and Petrology, 111(5):729-746. https://doi.org/10.1007/s00710-017-0491-5 Lian, D.Y., Yang, J.S., Robinson, P.T., et al., 2016.Tectonic Evolution of the Western Yarlung Zangbo Ophiolitic Belt, Tibet:Implications from the Petrology, Mineralogy, and Geochemistry of the Peridotites.The Journal of Geology, 124(3):353-376. https://doi.org/10.1086/685510 Lian, D.Y., Yang, J.S., Xiong, F.H., et al., 2015.Platinum-Group Element Characteristics of the Peridotite and Podiform Chromitite from Dajiweng Ophiolite of the Western Segment of Yarlung-Zangbo Suture Zone, Tibet.Geology in China, 42(2):525-546 (in Chinese with English abstract). Liang, F.H., Xu, Z.Q., Ba, D.Z., et al., 2011.Tectonic Occurrence and Emplacement Mechanism of Ophiolites from Luobusha-Zedang, Tibet.Acta Petrologica Sinica, 27(11):3255-3268 (in Chinese with English abstract). Liu, C.Z., Zhang, C., Yang, L.Y., et al., 2014.Formation of Gabbronorites in the Purang Ophiolite (SW Tibet) through Melting of Hydrothermally Altered Mantle along a Detachment Fault.Lithos, 205:127-141. https://doi.org/10.1016/j.lithos.2014.06.019 Liu, F., Dilek, Y., Xie, Y.X., et al., 2018.Melt Evolution of Upper Mantle Peridotites and Mafic Dikes in the Northern Ophiolite Belt of the Western Yarlung Zangbo Suture Zone (Southern Tibet).Lithosphere, 10(1):109-132.https://doi.org/10.1130/l689.1 doi: 10.1130/L689.1 Liu, F., Yang, J.S., Dilek, Y., et al., 2015.Geochronology and Geochemistry of Basaltic Lavas in the Dongbo and Purang Ophiolites of the Yarlung-Zangbo Suture Zone:Plume-Influenced Continental Margin-Type Oceanic Lithosphere in Southern Tibet.Gondwana Research, 27(2):701-718. https://doi.org/10.1016/j.gr.2014.08.002 Liu, F., Yang, J.S., Chen, S.Y., et al., 2013.Ascertainment and Environment of the OIB-Type Basalts from the Dongbo Ophiolite in the Western Part of Yarlung Zangbo Suture Zone.Acta Petrologica Sinica, 29(6):1909-1932 (in Chinese with English abstract). https://www.researchgate.net/publication/281424952_Ascertainment_and_environment_of_the_OIB-type_basalts_from_the_Dongbo_ophiolite_in_the_western_part_of_Yarlung_Zangbo_Suture_Zone Liu, F., Yang, J.S., Lian, D.Y., et al., 2015a.Genesis and Characteristics of the Western Part of the Yarlung Zangbo Ophiolites, Tibet.Acta Petrologica Sinica, 31(12):3609-3628 (in Chinese with English abstract). Liu, F., Yang, J.S., Lian, D.Y., et al., 2015b.The Genesis and Tectonic Significance of Mafic Dikes in the Western Part of the Yarlung Zangbo Suture Zone, Tibet.Acta Geoscientica Sinica, 36(4):441-454 (in Chinese with English abstract). Liu, Q., Deng, Y.B., Xiang, S.Y., et al., 2017.Early Ordovician Tectono-Thermal Event in Zhongba Terrane and Its Geological Significance.Earth Science, 42(6):881-890 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSXB201205026.htm Liu, Z., Li, Y., Xiong, F.H., et al., 2011.Petrology and Geochronology of MOR Gabbro in the Purang Ophiolite of Western Tibet, China.Acta Petrologica Sinica, 27(11):3269-3279 (in Chinese with English abstract). Maffione, M., van Hinsbergen, D.J.J., Koornneef, L.M.T., et al., 2015.Forearc Hyperextension Dismembered the South Tibetan Ophiolites.Geology, 43(6):475-478.https://doi.org/10.1130/g36472.1 doi: 10.1130/G36472.1 Mallick, S., Standish, J.J., Bizimis, M., 2015.Constraints on the Mantle Mineralogy of an Ultra-Slow Ridge:Hafnium Isotopes in Abyssal Peridotites and Basalts from the 9-25°E Southwest Indian Ridge.Earth and Planetary Science Letters, 410(7):42-53.https://doi.org/10.1016/j.epsl.2014.10.048 https://www.sciencedirect.com/science/article/pii/S0012821X1400675X Miller, C., 2003.Geochemistry and Tectonomagmatic Affinity of the Yungbwa Ophiolite, SW Tibet.Lithos, 66(3-4):155-172.https://doi.org/10.1016/s0024-4937(02)00217-7 doi: 10.1016/S0024-4937(02)00217-7 Molnar, P., Tapponnier, P., 1975.Cenozoic Tectonics of Asia:Effects of a Continental Collision:Features of Recent Continental Tectonics in Asia can be Interpreted as Results of the India-Eurasia Collision.Science, 189(4201):419-426. https://doi.org/10.1126/science.189.4201.419 Morris, A., Gee, J.S., Pressling, N., et al., 2009.Footwall Rotation in an Oceanic Core Complex Quantified Using Reoriented Integrated Ocean Drilling Program Core Samples.Earth and Planetary Science Letters, 287(1-2):217-228. https://doi.org/10.1016/j.epsl.2009.08.007 Nicolas, A., Girardeau, J., Marcoux, J., et al., 1981.The Xigaze Ophiolite (Tibet):A Peculiar Oceanic Lithosphere.Nature, 294(5840):414-417. https://doi.org/10.1038/294414a0 Niu, X.L., Yang, J.S., Chen, S.Y., et al., 2013.The Reformation of the Dongbo Ultramafic Rock Massif in the Western Part of the Yarlung Zangbo Suture Zone by Subduction-Related Fluids:Evidence from the Platimun-Group Elements (PGE).Geology in China, 40(3):756-766 (in Chinese with English abstract). https://www.researchgate.net/publication/286393165_The_reformation_of_the_Dongbo_ultramafic_rock_massif_in_the_western_part_of_the_Yarlung_Zangbo_suture_zone_by_subduction-related_fluids_Evidence_from_the_platimun-group_elements_PGE Niu, X.L., Yang, J.S., Dilek, Y., et al., 2015.Petrological and Os Isotopic Constraints on the Origin of the Dongbo Peridotite Massif, Yarlung Zangbo Suture Zone, Western Tibet.Journal of Asian Earth Sciences, 110:72-84. https://doi.org/10.1016/j.jseaes.2014.09.036 Niu, Y.L., 2016.The Meaning of Global Ocean Ridge Basalt Major Element Compositions.Journal of Petrology, 57(11-12):2081-2103. https://doi.org/10.1093/petrology/egw073 Orme, D.A., Laskowski, A.K., 2016.Basin Analysis of the Albian-Santonian Xigaze Forearc, Lazi Region, South-Central Tibet.Journal of Sedimentary Research, 86(8):894-913. https://doi.org/10.2110/jsr.2016.59 Pearce, J.A., 2014.Immobile Element Fingerprinting of Ophiolites.Elements, 10(2):101-108. https://doi.org/10.2113/gselements.10.2.101 Pearce, J.A., Wanming, D., 1988.The Ophiolites of the Tibetan Geotraverses, Lhasa to Golmud (1985) and Lhasa to Kathmandu (1986).Philosophical Transactions of the Royal Society A:Mathematical, Physical and Engineering Sciences, 327(1594):215-238. https://doi.org/10.1098/rsta.1988.0127 Pearce, J.A., 2003.Supra-Subduction Zone Ophiolites:The Search for Modern Analogues.Special Papers-Geological Society of America, 269-294. http://orca.cf.ac.uk/8599/ Reagan, M.K., Ishizuka, O., Stern, R.J., et al., 2010.Fore-Arc Basalts and Subduction Initiation in the Izu-Bonin-Mariana System.Geochemistry, Geophysics, Geosystems, 11(3):1-17.https://doi.org/10.1029/2009gc002871 doi: 10.1029/2009GC002871?scrollTo=footer-citing Saccani, E., 2015.A New Method of Discriminating Different Types of Post-Archean Ophiolitic Basalts and Their Tectonic Significance Using Th-Nb and Ce-Dy-Yb Systematics.Geoscience Frontiers, 6(4):481-501. https://doi.org/10.1016/j.gsf.2014.03.006 Sun, S.S., McDonough, W.F., 1989.Chemical and Isotopic Systematics of Oceanic Basalts:Implications for Mantle Composition and Processes.Geological Society, London, Special Publications, 42(1):313-345.https://doi.org/10.1144/gsl.sp.1989.042.01.19 doi: 10.1144/GSL.SP.1989.042.01.19 Tapponnier, P., Mercier, J.L., Proust, F., et al., 1981.The Tibetan Side of the India-Eurasia Collision.Nature, 294(5840):405-410. https://doi.org/10.1038/294405a0 Todd, E., Gill, J.B., Pearce, J.A., 2012.A Variably Enriched Mantle Wedge and Contrasting Melt Types during Arc Stages Following Subduction Initiation in Fiji and Tonga, Southwest Pacific.Earth and Planetary Science Letters, 335-336:180-194. https://doi.org/10.1016/j.epsl.2012.05.006 Velikoslavinsky, S.D., Krylov, D.P., 2014.Geochemical Discrimination of Basalts Formed in Major Geodynamic Settings.Geotectonics, 48(6):427-439.https://doi.org/10.1134/s0016852114060077 doi: 10.1134/S0016852114060077 Wang, J.R., Chen, W.F., Zhang, Q., et al., 2017.Preliminary Research on Data Mining of N-MORB and E-MORB:Discussion on Method of the Basalt Discrimination Diagrams and the Character of MORB's Mantle Source.Acta Petrologica Sinica, 33(3):993-1005 (in Chinese with English abstract). https://www.researchgate.net/publication/316278054_Preliminary_research_on_data_mining_of_N-Morb_and_E-MORB_Discussion_on_method_of_the_basalt_discrimination_diagrams_and_the_character_of_MORB's_mantle_source Wang, J.R., Pan, Z.J., Zhang, Q., et al., 2016.Intra-Continental Basalt Data Mining:The Diversity of Their Constituents and the Performance in Basalt Discrimination Diagrams.Acta Petrologica Sinica, 32(7):1919-1933 (in Chinese with English abstract). https://www.researchgate.net/publication/306138109_Intra-continental_basalt_data_mining_The_diversity_of_their_constituents_and_the_performance_in_basalt_discrimination_diagrams Wang, X.C., Wilde, S.A., Xu, B., et al., 2016.Origin of Arc-Like Continental Basalts:Implications for Deep-Earth Fluid Cycling and Tectonic Discrimination.Lithos, 261:5-45. https://doi.org/10.1016/j.lithos.2015.12.014 Wang, X.B., Zhou, X., Hao, Z.G., 2010.Some Opinions on Further Exploration for Chromite Deposits in the Luobusha Area, Tibet, China.Geological Bulletin of China, 29(1):105-114 (in Chinese with English abstract). Wang, Y.P., 2015.Research on the Drilling Cores (DSD-1) of Dongbo Ophiolitic Massif in the Western Segement of Yarlung Zangbo Suture Zone(Dissertation).China University of Geosciences, Beijing (in Chinese with English abstract). Whattam, S.A., Stern, R.J., 2011.The 'Subduction Initiation Rule':A Key for Linking Ophiolites, Intra-Oceanic Forearcs, and Subduction Initiation.Contributions to Mineralogy and Petrology, 162(5):1031-1045. https://doi.org/10.1007/s00410-011-0638-z Wu, F.Y., Liu, C.Z., Zhang, L.L., et al., 2014.Yarlung Zangbo Ophiolite:A Critical Updated View.Acta Petrologica Sinica, 30(2):293-325(in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSXB201402001.htm Wu, Y.B., Zheng, Y.F., 2004.Genesis of Zircon and Its Constraints on Interpretation of U-Pb Age.Chinese Science Bulletin, 49(16):1589-1604 (in Chinese). https://www.researchgate.net/profile/Yong-Fei_Zheng/publication/225204011_Genesis_of_zircon_and_its_constraints_on_interpretation_of_U-Pb_age/links/53fe74800cf21edafd151294.pdf?origin=publication_detail Xiao, Q.H., Li, T.D., Pan, G.T., et al., 2016.Petrologic Ideas for Identification of Ocean-Continent Transition:Recognition of Intra-Oceanic Arc and Initial Subduction.Geology in China, 43(3):721-737(in Chinese with English abstract). http://www.refdoc.fr/Detailnotice?cpsidt=20695915 Xiong, F.H., Yang, J.S., Robinson, P.T., et al., 2017.High-Al and High-Cr Podiform Chromitites from the Western Yarlung-Zangbo Suture Zone, Tibet:Implications from Mineralogy and Geochemistry of Chromian Spinel, and Platinum-Group Elements.Ore Geology Reviews, 80:1020-1041.https://doi.org/10.13039/501100004613 doi: 10.1016/j.oregeorev.2016.09.009 Xiong, F.H., Yang, J.S., Liang, F.H., et al., 2011.Zircon U-Pb Ages of the Dongbo Ophiolite in the Western Yarlung Zangbo Suture Zone and Their Geological Significance.Acta Petrologica Sinica, 27(11):3223-3238(in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSXB201111006.htm Xu, X.Z., Yang, J.S., Ba, D.Z., et al., 2011.Petrogenesis of the Kangjinla Peridotite in the Luobusa Ophiolite, Southern Tibet.Journal of Asian Earth Sciences, 42(4):553-568. https://doi.org/10.1016/j.jseaes.2011.05.007 Xu, X.Z., Yang, J.S., Ba, D.Z., et al., 2015.Diamond Discovered from the Dongbo Mantle Peridotite in the Yarlung Zangbo Suture Zone, Tibet.Geology in China, 42(5):1471-1482(in Chinese with English abstract). Xu, X.Z., Yang, J.S., Guo, G.L., et al., 2011.Lithological Research on the Purang Mantle Peridotite in Western Yarlung-Zangbo Suture Zone in Tibet.Acta Petrologica Sinica, 27(11):3179-3196(in Chinese with English abstract). http://or.nsfc.gov.cn/bitstream/00001903-5/254331/1/1000012489102.pdf Xu, Z.Q., Dilek, Y., Yang, J.S., et al., 2015.Crustal Structure of the Indus-Tsangpo Suture Zone and Its Ophiolites in Southern Tibet.Gondwana Research, 27(2):507-524.https://doi.org/10.13039/501100001809 doi: 10.1016/j.gr.2014.08.001 Yang, A.Y., Zhao, T.P., Zhou, M.F., et al., 2017.Isotopically Enriched N-MORB:A New Geochemical Signature of Off-Axis Plume-Ridge Interaction-A Case Study at 50°28'E, Southwest Indian Ridge.Journal of Geophysical Research:Solid Earth, 122(1):191-213.https://doi.org/10.13039/501100001809 doi: 10.1002/2016JB013284 Yang, J., Wang, J.R., Zhang, Q., et al., 2016.Global IAB Data Excavation:The Performance in Basalt Discrimination Diagrams and Preliminary Interpretation.Geological Bulletin of China, 35(12):1937-1949(in Chinese with English abstract). https://www.researchgate.net/publication/306138109_Intra-continental_basalt_data_mining_The_diversity_of_their_constituents_and_the_performance_in_basalt_discrimination_diagrams Yang, J.S., Robinson, P.T., Dilek, Y., 2014.Diamonds in Ophiolites.Elements, 10(2):127-130. https://doi.org/10.2113/gselements.10.2.127 Yang, J.S., Robinson, P.T., Dilek, Y., 2015.Diamond-Bearing Ophiolites and Their Geological Occurrence.Episodes, 38(4):344-364.https://doi.org/10.18814/epigsi/2015/v38i4/82430 https://www.researchgate.net/publication/284064585_Diamond-bearing_Ophiolites_and_Their_Geological_Occurrence Yang, J.S., Xiong, F.H., Guo, G.L., et al., 2011a.The Dongbo Ultramafic Massif:A Mantle Peridotite in the Western Part of the Yarlung Zangbo Suture Zone, Tibet, with Excellent Prospects for a Major Chromite Deposit.Acta Petrologica Sinica, 27(11):3207-3222(in Chinese with English abstract). Yang, J.S., Xu, X.Z., Li, Y., et al., 2011b.Diamonds Recovered from Peridotite of the Purang Ophiolite in the Yarlung-Zangbo Suture of Tibet:A Proposal for a New Type of Diamond Occurrence.Acta Petrologica Sinica, 27(11):3171-3178(in Chinese with English abstract). Yu, X., Chu, F.Y., Dong, Y.H., et al., 2013.Detachment Fault and Oceanic Core Complex:A New Mode of Seafloor Spreading.Earth Science, 38(5):995-1004(in Chinese with English abstract). http://www.nature.com/srep/2013/130801/srep02336/metrics/citations Yuan, H.L., Gao, S., Liu, X.M., et al., 2004.Accurate U-Pb Age and Trace Element Determinations of Zircon by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry.Geostandards and Geoanalytical Research, 28(3):353-370.https://doi.org/10.1111/j.1751-908x.2004.tb00755.x doi: 10.1111/ggr.2004.28.issue-3 Zahirovic, S., Matthews, K.J., Flament, N., et al., 2016.Tectonic Evolution and Deep Mantle Structure of the Eastern Tethys since the Latest Jurassic.Earth-Science Reviews, 162:293-337. https://doi.org/10.1016/j.earscirev.2016.09.005 Zhang, L., Yang, J.S., Liu, F., et al., 2016.The South Gongzhucuo Peridotite Massif:A Typical MOR Type Peridotite in the Western Yarlung Zangbo Suture Zone.Acta Petrologica Sinica, 32(12):3649-3672(in Chinese with English abstract). http://www.ysxb.ac.cn/ysxb/ch/reader/view_abstract.aspx?file_no=20161207 Zhang, S.Q., Mahoney, J.J., Mo, X.X., et al., 2005.Evidence for a Widespread Tethyan Upper Mantle with Indian-Ocean-Type Isotopic Characteristics.Journal of Petrology, 46(4):829-858. https://doi.org/10.1093/petrology/egi002 Zheng, H., Huang, Q., Kapsiotis, A., et al., 2017.Early Cretaceous Ophiolites of the Yarlung Zangbo Suture Zone:Insights from Dolerites and Peridotites from the Baer Upper Mantle Suite, SW Tibet (China).International Geology Review, 59(11):1471-1489.https://doi.org/10.13039/501100001809 doi: 10.1080/00206814.2016.1276867 Zheng, Y.F., Chen, Y.X., 2016.Continental versus Oceanic Subduction Zones.National Science Review, 3(4):495-519.https://doi.org/10.1093/nsr/nww049 https://www.researchgate.net/publication/306072657_Continental_versus_oceanic_subduction_zones Zhou, H.Y., Dick, H.J.B., 2013.Thin Crust as Evidence for Depleted Mantle Supporting the Marion Rise.Nature, 494(7436):195-200. https://doi.org/10.1038/nature11842 Zhou, M.F., Robinson, P.T., Malpas, J., et al., 1996.Podiform Chromitites in the Luobusa Ophiolite (Southern Tibet):Implications for Melt-Rock Interaction and Chromite Segregation in the Upper Mantle.Journal of Petrology, 37(1):3-21. https://doi.org/10.1093/petrology/37.1.3 Zhou, M.F., Robinson, P.T., Malpas, J., et al., 2005.REE and PGE Geochemical Constraints on the Formation of Dunites in the Luobusa Ophiolite, Southern Tibet.Journal of Petrology, 46(3):615-639.https://doi.org/10.1093/petrology/egh091 Zhou, W.D., Yang, J.S., Zhao, J.H., et al., 2014.Mineralogical Study and the Origin Discussion of Purang Ophiolite Peridotites, Western Part of Yarlung-Zangbo Suture Zone(YZSZ), Southern Tibet.Acta Petrologica Sinica, 30(8):2185-2203(in Chinese with English abstract). Zhou, Y.S., Wu, H.R., Zheng, X.L., et al., 1982.Geology of the Ophiolite in Xigaze Prefecture of the Southern Xizang (Tibet), China.Scientia Geologica Sinica, 17(1):30-40(in Chinese with English abstract). 敖松坚, 肖文交, 杨磊, 等, 2017.造山带中古洋壳核杂岩的识别与地质意义.中国科学:地球科学, 47(1):1-22. 邓晋福, 刘翠, 冯艳芳, 等, 2015.关于火成岩常用图解的正确使用:讨论与建议.地质论评, 61(4):717-734. http://www.cnki.com.cn/Article/CJFDTotal-DZLP201504002.htm 高洪学, 宋子季, 1995.西藏泽当蛇绿混杂岩研究新进展.中国区域地质, 14 (4):316-322. 李建峰, 夏斌, 刘立文, 等, 2008.西藏普兰地区拉昂错蛇绿岩中辉绿岩的锆石SHRIMP U-Pb年龄及其地质意义.地质通报, 27(10):1739-1743. doi: 10.3969/j.issn.1671-2552.2008.10.016 李祥辉, 王成善, 李亚林, 等, 2014.仲巴微地体之定义及构成.地质学报, 88(8):1372-1381. https://www.researchgate.net/profile/Xianghui_Li2/publication/288623395_Definition_and_composition_of_the_Zhongba_microterrane_in_the_southwest_Tibet_in_Chinese_with_English_abstract/links/56a7ea3508aeded22e371c57.pdf?origin=publication_detail 李源, 李瑞保, 董天赐, 等, 2016.日喀则蛇绿岩白马让岩体的穹窿形结构及构造意义.科学通报, 61(25):2823-2833. http://www.cqvip.com/QK/94252X/201625/669986427.html 连东洋, 杨经绥, 熊发挥, 等, 2015.雅鲁藏布江缝合带西段达机翁地幔橄榄岩及铬铁矿的铂族元素特征.中国地质, 42 (2):525-546. doi: 10.3969/j.issn.1000-3657.2015.02.013 梁凤华, 许志琴, 巴登珠, 等, 2011. 西藏罗布莎-泽当蛇绿岩体的构造产出与侵位机制探讨岩石学报, 27(11): 3255-3268. 刘飞, 杨经绥, 陈松永, 等, 2013.雅鲁藏布江缝合带西段东波蛇绿岩OIB型玄武岩的厘定及其形成环境.岩石学报, 29(6):1909-1932. http://www.ysxb.ac.cn/ysxb/ch/reader/download_pdf.aspx?file_no=20130605&year_id=2013&quarter_id=6&falg=1 刘飞, 杨经绥, 连东洋, 等, 2015a.西藏雅鲁藏布江缝合带西段南北亚带蛇绿岩的成因探讨.岩石学报, 31(12):3609-3628. 刘飞, 杨经绥, 连东洋, 等, 2015b.雅鲁藏布江缝合带西段北亚带的基性岩成因和构造意义.地球学报, 36(4):441-454. http://www.cqvip.com/QK/98325X/201504/665698151.html 刘强, 邓玉彪, 向树元, 等, 2017.藏南仲巴地体早奥陶世构造-热事件及其地质意义.地球科学, 42(6):881-890. http://www.earth-science.net/WebPage/Article.aspx?id=3585 刘钊, 李源, 熊发挥, 等, 2011.西藏西部普兰蛇绿岩中的MOR型辉长岩:岩石学和年代学.岩石学报, 27(11):3269-3279. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=ysxb201111009&dbname=CJFD&dbcode=CJFQ 牛晓露, 杨经绥, 陈松永, 等, 2013.雅鲁藏布江西段东波超镁铁岩体经历了俯冲带流体的改造:来自铂族元素的证据.中国地质, 40(3):756-766. http://d.wanfangdata.com.cn/Periodical_zgdizhi201303008.aspx 王金荣, 陈万峰, 张旗, 等, 2017.N-MORB和E-MORB数据挖掘——玄武岩判别图及洋中脊源区地幔性质的讨论.岩石学报, 33(3):993-1005. http://www.cnki.com.cn/Article/CJFDTOTAL-YSXB201703023.htm 王金荣, 潘振杰, 张旗, 等, 2016.大陆板内玄武岩数据挖掘:成分多样性及在判别图中的表现.岩石学报, 32(7):1919-1933. http://www.ysxb.ac.cn/ysxb/ch/reader/create_pdf.aspx?file_no=20160701&journal_id=ysxb&year_id=2016 王希斌, 周详, 郝梓国, 2010.西藏罗布莎铬铁矿床的进一步找矿意见和建议.地质通报, 29(1):105-114. 王云鹏, 2015. 雅鲁藏布江缝合带西段东波地幔橄榄岩体钻孔(DSD-1)岩心研究(硕士学位论文). 北京: 中国地质大学. 吴福元, 刘传周, 张亮亮, 等, 2014.雅鲁藏布蛇绿岩——事实与臆想.岩石学报, 30(2):293-325. http://www.ysxb.ac.cn/ysxb/ch/reader/create_pdf.aspx?file_no=20140201&journal_id=ysxb&year_id=2014 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 肖庆辉, 李廷栋, 潘桂棠, 等, 2016.识别洋陆转换的岩石学思路——洋内弧与初始俯冲的识别.中国地质, 43(3):721-737. doi: 10.12029/gc20160303 熊发挥, 杨经绥, 梁凤华, 等, 2011.西藏雅鲁藏布江缝合带西段东波蛇绿岩中锆石U-Pb定年及地质意义.岩石学报, 11(27):3223-3238. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=ysxb201111006&dbname=CJFD&dbcode=CJFQ 徐向珍, 杨经绥, 巴登珠, 等, 2015.西藏雅鲁藏布江缝合带东波地幔橄榄岩中金刚石的发现及地质意义.中国地质, 42(5):1471-1482. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=dizi201505019&dbname=CJFD&dbcode=CJFQ 徐向珍, 杨经绥, 郭国林, 等, 2011.雅鲁藏布江缝合带西段普兰蛇绿岩中地幔橄榄岩的岩石学研究.岩石学报, 27(11):3179-3196. http://www.ysxb.ac.cn/ysxb/ch/reader/view_abstract.aspx?file_no=20111103 杨经绥, 熊发挥, 郭国林, 等, 2011a.东波超镁铁岩体:西藏雅鲁藏布江缝合带西段一个甚具铬铁矿前景的地幔橄榄岩体.岩石学报, 27(11):3207-3222. http://www.cnki.com.cn/Article/CJFDTOTAL-YSXB201111005.htm 杨经绥, 徐向珍, 李源, 等, 2011b.西藏雅鲁藏布江缝合带的普兰地幔橄榄岩中发现金刚石:蛇绿岩型金刚石分类的提出.岩石学报, 27(11):3171-3178. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=ysxb201111002&dbname=CJFD&dbcode=CJFQ 杨婧, 王金荣, 张旗, 等, 2016.全球岛弧玄武岩数据挖掘——在玄武岩判别图上的表现及初步解释.地质通报, 35(12):1937-1949. doi: 10.3969/j.issn.1671-2552.2016.12.001 余星, 初凤友, 董彦辉, 等, 2013.拆离断层与大洋核杂岩:一种新的海底扩张模式.地球科学, 38(5):995-1004. http://www.earth-science.net/WebPage/Article.aspx?id=2788 张利, 杨经绥, 刘飞, 等, 2016.南公珠错地幔橄榄岩:雅鲁藏布江缝合带西段一个典型的大洋地幔橄榄岩.岩石学报, 32(12):3649-3672. http://www.ysxb.ac.cn/ysxb/ch/reader/view_abstract.aspx?file_no=20161207 周文达, 杨经绥, 赵军红, 等, 2014.西藏雅鲁藏布江缝合带西段普兰蛇绿岩地幔橄榄岩矿物学研究和成因探讨.岩石学报, 30(8):2185-2203. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=ysxb201408005&dbname=CJFD&dbcode=CJFQ 周云生, 吴浩若, 郑锡澜, 等, 1982.西藏南部日喀则地区蛇绿岩地质.地质科学, 17(1):30-39. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=dzkx198201004&dbname=CJFD&dbcode=CJFQ 期刊类型引用(16)
1. 张克信，宋博文，何卫红，骆满生，寇晓虎，徐亚东，王嘉轩，王盛栋，王丽君，柯学，任飞，陈奋宁，陈锐明. 青藏中-南部特提斯洋板块地层分布与演化. 地球科学. 2025(03): 1162-1200 . 
本站查看2. 任飞，尹福光，彭智敏，潘桂棠，魏栋. 班公湖—怒江俯冲增生杂岩带东段晚古生代辉绿岩锆石U-Pb年龄、Hf同位素特征及其构造意义. 地学前缘. 2022(02): 164-179 . 
百度学术3. 刘飞，杨经绥，冯光英，牛晓露，李观龙，张超凡. 古太平洋板片晚二叠-早三叠世俯冲后撤：来自海南岛弧岩浆作用的制约. 岩石学报. 2022(11): 3455-3483 . 百度学术4. 刘飞，李观龙，薄容众，杨经绥. 班公湖-怒江洋的扩张脊俯冲：宗白增生杂岩中侏罗世辉长岩脉地球化学和Sr-Nd同位素特征. 地质通报. 2021(08): 1247-1264 . 百度学术5. 刘飞，杨经绥，牛晓露，李观龙，冯光英. 西藏雅鲁藏布江缝合带西段东波蛇绿岩:记录了地幔柱影响的超慢速伸展和洋内俯冲过程. 岩石学报. 2021(10): 2971-2994 . 百度学术6. 刘函，王保弟，陈莉，王立全，张予杰，李俊，苟正彬，张士贞. 日喀则夏鲁N-MORB型辉长岩与辉绿岩：雅鲁藏布江特提斯洋早白垩世初始俯冲记录. 地质通报. 2021(11): 1836-1851 . 百度学术7. 刘飞，杨经绥，连东洋，熊发挥，吴魏伟. 蛇绿岩中金刚石和异常矿物的全球记录. 地质学报. 2020(09): 2588-2605 . 百度学术8. 刘飞，杨经绥，连东洋，李观龙. 青藏高原新特提斯蛇绿岩的地质特征及其构造演化. 岩石学报. 2020(10): 2913-2945 . 百度学术9. 刘海永，岳鋆璋，顿珠旺堆，旺姆，毛国正，吴浩. 青藏高原中部麻米地区晚侏罗世火山岩岩石成因及其地质意义. 地球科学. 2019(07): 2368-2382 . 本站查看10. 赵岩，寇林林，张朋，毕中伟，李东涛，陈聪. 辽东半岛隆昌地区～2113 Ma变辉长岩地球化学与Hf同位素研究：对胶辽吉造山带构造演化的制约. 地球科学. 2019(10): 3333-3345 . 本站查看11. 连东洋，杨经绥，刘飞，吴魏伟. 金刚石分类、组成特征以及我国金刚石研究展望. 地球科学. 2019(10): 3409-3453 . 本站查看12. 王云鹏，牛晓露，杨经绥，李源，徐向珍，冯光英，熊发挥，刘飞，刘钊，田亚洲，郭国林，连东洋，赵一珏. 雅鲁藏布江缝合带西段东波地幔橄榄岩体钻孔岩心研究. 地质学报. 2019(10): 2486-2508 . 百度学术13. 刘飞，牛晓露，连东洋，冯光英，赵慧. 西藏仲巴地体中433Ma伸展热事件：波库二云母花岗岩锆石年代学、地球化学和Hf同位素制约. 地质学报. 2019(10): 2556-2574 . 百度学术14. 薄容众，杨经绥，李观龙，芮会超，熊发挥，张承杰，董玉飞，卢雨潇，陈晓坚. 班-怒带东段丁青蛇绿岩中镁铁质岩石年代学及构造背景. 地质学报. 2019(10): 2617-2638 . 百度学术15. Songjie Wang，Xu-Ping Li，Wenyong Duan，Fanmei Kong，Zeli Wang. Record of Early-Stage Rodingitization from the Purang Ophiolite Complex, Western Tibet. Journal of Earth Science. 2019(06): 1108-1124 . 必应学术16. 董磊，李光明，黄勇，曹华文. 藏南雅鲁藏布江结合带东段琼结杂岩早白垩世变辉绿岩地球化学特征及其地质意义. 沉积与特提斯地质. 2018(04): 1-12 . 百度学术其他类型引用(5)
-
下载:
百度学术
点击查看大图
计量
- 文章访问数: 5150
- HTML全文浏览量: 1813
- PDF下载量: 96
- 被引次数: 21
