Zircon U-Pb Ages of Dongcuo Ophiolite in Western Bangonghu-Nujiang Suture Zone and Their Geological Significance
-
摘要: 洞错蛇绿岩位于班公湖-怒江缝合带西段阿里地区,前人对其空间展布、构造环境及成因有过一定的探讨,但研究程度薄弱.选择洞错蛇绿岩中的辉长岩为研究对象,对其开展详细的岩相学、地球化学、年代学等工作,解读洋盆的形成时间及构造环境.结果表明,辉长岩与N-MORB相比具有较高的Mg#,低K、Na、P和Ti的元素特征,亏损Hf、Zr、Nb等高场强元素(HFSE),具有轻稀土亏损型配分模式,表明可能源于N-MORB型亏损地幔源区.地球化学元素研究表明辉长岩岩浆源自亏损的尖晶石二辉橄榄岩~30%部分熔融,可能形成于与洋内俯冲相关的岛弧或者弧前构造环境,属于SSZ型蛇绿岩.辉长岩锆石的U-Pb测年指示其结晶年龄为222±4.8 Ma(MSWD=0.5,n=28),代表了辉长岩的形成年龄,佐证了洞错蛇绿岩形成于晚三叠世,表明班公湖-怒江特提斯洋盆从晚三叠世开始存在洋内俯冲消减地质作用.Abstract: The Dongcuo ophiolite is located at the western part of Bangong-Nujiang River suture zone, Gaize County. In spite of previous studies on its spacious distribution, tectonic environment and genesis, the key problem remains unresolved. Taking the gabbro of Dongcuo ophiolite as the research object, a detailed study of petrography, geochemistry, petrology and geochronology is carried out to understand the formation of Bangong-Nujiang ocean basin, the tectonic settings of the Dongcuo ophiolite. Compared with N-MORB, the major and trace elements of Dongcuo ophiolite are characterized by high content in Mg# and low content in K, Na, P, and Ti, the depletion of high field-strength elements (HFSE) of Hf, Zr, Nb and light rare earth element depletion. Geochemistry characteristics of the Dongcuo ophiolite indicate that it is originated from~30% partial melting of depleted spinel lherzolite formed in the tectonic environment of subduction-related island arc or fore arc, belonging to super subduction zone (SSZ) ophiolite. The LA-ICP-MS of zircon U-Pb dating yields the age of 222±4.8 Ma (MSWD=0.5), providing the age constraint on the Dongcuo ophiolite (Late Triassic), and showing that it belongs to the Tethyan system of the Bangong-Nujiang River suture zone, which indicates the intra-oceanic subduction process.
-
Key words:
- ophiolite /
- gabbro /
- tectonic environment /
- zircon U-Pb dating /
- Bangong-Nujiang suture zone /
- geochronology
-
0. 引言
蛇绿岩是出露在板块缝合带中的一套由构造地幔橄榄岩、堆晶岩、席状岩墙、枕状熔岩以及海相沉积物构成的岩石组合,被认为是大洋岩石圈的残片,记录了古大洋的形成、汇聚和造山的过程,是厘定古板块边界的重要证据(Coleman, 1977; Dilek, 2003; Moores, 2003;许志琴等,2006; Dilek et al., 2007;周国庆,2008).尤其,近些年新的研究表明,它们有可能提供深地幔矿物金刚石重要的信息(杨经绥等, 2004, 2013).西藏班公湖-怒江缝合带(班怒带)是青藏高原内部一条重要板块边界,分隔了羌塘地块与拉萨地块(李才,1987;潘桂堂等,2004),该缝合带大致近东西向断续出露,长达2 000 km,南北宽约10~20 km,是我国规模最大的蛇绿岩构造混杂岩带之一(邱瑞照等,2002).对班怒带蛇绿岩的形成,前人主要存在不同认识:(1)班公湖-怒江洋盆在晚二叠世形成,早-中侏罗世洋壳开始俯冲消减,洋盆持续到早白垩世闭合(邱瑞照等,2002;和钟铧等,2006;鲍佩声等,2007;张玉修,2007;史仁灯,2007;强强巴扎西等,2009;黄启帅等,2012);(2)根据岩石地球化学特征,认为其形成于板内、洋岛、弧前、弧后盆地等构造环境(鲍佩声等,1996;刘文斌等,2002;邱瑞照等,2005;张玉修,2007),或认为其主要形成于消减带之上(SSZ)环境而并非正常洋中脊(MOR)环境(郑有业等,2004;叶培盛等,2004;夏斌等,2008);(3)由于班公湖-怒江带自身构造特征的复杂性,其俯冲极性仍然存在争议(Kapp et al., 2003;朱弟成等,2006;康志强等,2010).
蛇绿岩中的辉长岩和辉绿岩常被认为能够指示大洋构造演化阶段的岩浆事件,可以用来限定洋壳的形成年龄.已有年代学研究表明,班怒带中蛇绿岩中辉长岩等基性岩形成年龄在254~110 Ma之间(邱瑞照等,2004;和钟铧等,2006;郑有业等,2006;鲍佩声等,2007;史仁灯,2007;强巴扎西等,2009;孙立新等,2011;黄强太等,2015),尤其,班怒带西段的蛇绿岩年代学数据报道较少,因此开展班公湖-怒江带西段蛇绿岩的年代学、地球化学特征的研究,有助于限定班怒带所代表中特提斯洋盆的形成和演化过程.洞错蛇绿岩位于班公湖-怒江缝合带西段阿里地区,前人对其空间分布、产出环境和成因有过一定的探讨,但研究相对薄弱.尤其在蛇绿岩的形成地质年代,以及蛇绿岩形成的构造环境等方面分歧很大(邱瑞照等,2004;鲍佩声等,2007;密文天等,2012;李建峰等,2013;付佳俊等,2015).本文选择洞错蛇绿岩中的辉长岩为研究对象,对其开展详细的岩相学、地球化学、年代学等工作,探讨洋盆的形成时间及地质构造环境,为恢复中特提斯洋的形成和演化提供科学依据.
1. 地质背景
青藏高原作为世界上地形地貌最高的高原,处于特提斯-喜马拉雅构造域的东段,是印度板块与欧亚大陆碰撞、拼合的产物(潘桂堂,1997; Kapp et al., 2003;许志琴等,2006;Aitchison et al., 2007;杨经绥等,2013).沿班公湖-怒江缝合带断断续续发育有古洋壳的残片-蛇绿岩,据其空间展布,大致可划分为西段(班公湖-改则)、中段(安多-东巧)、东段(丁青-怒江)三部分(王希斌等,1987;Dewey et al., 1988)(图 1).
洞错蛇绿岩位于改则县城以东,呈长条状近东西向展布,向西延伸至班公湖地区,向东可以延伸到日干配错以南的孜如错一带,东西长约100 km,南北带宽5~10 km.蛇绿岩的展布与区域构造线基本一致,边界受主干断裂控制(图 2)(吴珍汉等,2013).蛇绿岩体南界与侏罗纪木噶岗日群(Jm)呈断层接触,或被第四系覆盖.侏罗纪木噶岗日群(Jm)呈片状或小块体产出,变形强烈,岩性单一,以深色板岩为主,主要为一套复理石碎屑沉积组合,形成于深海沉积相.蛇绿岩北界与一套洋岛火山岩(MZ)断层接触.仲岗洋岛火山岩(MZ)呈长条状东西向展布,主要由玄武岩和灰岩组成.玄武岩为灰绿色,致密块状构造为主,其次为枕状构造.岩石中斑晶主要为单斜辉石,含量约15%~25%,一些气孔中充填方解石和绿泥石等蚀变矿物.
洞错蛇绿岩被构造肢解,呈透镜状的断片产出,但基本上出露连续,主要由地幔橄榄岩和辉长岩组成.地幔橄榄岩出露约3 km,岩性为方辉橄榄岩、二辉橄榄岩、多数已经发生蛇纹石化和碳酸盐化.方辉橄榄岩新鲜面呈暗绿色,块状构造,粒径1~3 mm,主要组成矿物为橄榄石(75%~85%)、斜方辉石(5%~15%)、单斜辉石(1%~3%)和尖晶石(~1%).二辉橄榄岩主要在方辉橄榄岩中呈透镜体产出,呈暗绿色,块状构造,粒径1.0~3.5 mm,主要矿物组成为橄榄石(70%~75%)、斜方辉石(10%~15%)和单斜辉石(5%~7%).
在蛇绿岩中出露一套去申拉组(K1q)火山岩,近东西向展布,厚度大约2~3 km,南、北边界与辉长岩和地幔橄榄岩呈断层接触(图 3).去申拉组(K1q)火山岩在洞错地区主要以玄武岩安山岩为主,多呈灰色、灰绿色,斑状结构,块状构造,斑晶粒度0.5~1.0 mm,主要矿物组成为斜长石(15%~25%)和石英(1%~2%),基质粒径0.10~0.25 mm,其成分主要为斜长石(55%~60%)、绿泥石(5%~10%)、石英(4%~6%),岩石遭受蚀变,表现为绢云母化、绿泥石化及碳酸盐化.
辉长岩分布范围较大,与地幔橄榄岩多呈构造接触,分为层状堆晶辉长岩和均质块状辉长岩两类.均质辉长岩出露规模较大、分布范围广,出露厚度约4 km,主要呈单独岩体或块体产出.堆晶辉长岩呈带状产出,具有比较典型的堆晶结构,呈不同色调的韵律层,韵律层一般1~2 cm不等,表现为良好的似成层性(图 4a).部分地段见有辉绿岩脉侵入辉长岩体中(图 4b),呈暗绿色,脉体宽度2~15 cm,大致呈NNE走向.
2. 辉长岩岩相学特征
洞错辉长岩野外露头较新鲜,呈灰白色-暗绿色,可以识别出具有层状堆晶结构的辉长岩和块状均质辉长岩,两类构造与去申拉组火山岩(K1q)呈构造接触(图 4c).辉长岩为全晶质中细粒结构,块状构造(图 4d),矿物成分主要由斜长石(40%~45%)、辉石(35%~40%)、角闪石(1~5%)及少量的橄榄石矿物组成.
辉长岩中的斜长石呈自形-半自形中粒板条状,发育聚片双晶,粒径1.0~2.0 mm,遭受不同程度的蚀变,主要为绿泥石化.辉长岩中含有斜方辉石和单斜辉石两种辉石,两者均呈自形-半自形粒状.其中单斜辉石特征:正高突起,干涉色多为二级蓝绿,平行消光,粒径为0.5~2.0 mm,形态不规则.斜方辉石为中-高突起,干涉色为一级灰,斜消光.少量辉石蚀变成角闪石、绿泥石,分布于斜长石粒间(图 4e, 4f).橄榄石颗粒呈卵状自形晶.
3. 分析方法
本文对15件辉长岩样品进行了全岩分析.测试工作在国家地质测试中心完成,在测试之前,预先用酸溶液对样品进行了处理,其中主量元素用溶片X射线荧光光谱法(XRF)测定,仪器型号为PW4400型X射线光谱仪,并采用等离子光谱和化学测定进行互检,二价铁的测定是采用滴定法完成,分析精度优于0.01%.稀土、微量元素的测定采用仪器为等离子质谱仪(PE300D),仪器的分析误差优于0.5%,样品的烧失量(LOI)的测定采用马沸炉加热烧失法.
辉长岩单矿物锆石分选是在河北省廊坊宇能岩石矿物分选技术公司完成,主要步骤为:野外样品进行破碎、摇床,研磨至样品可以自由通过0.3 mm的筛子,再经过淘洗、磁法、电法分选出较纯的锆石单矿物,最后选用双目镜挑选出锆石矿物,获得本次样品的锆石数量约160余粒.样品制靶步骤:挑选出合适的锆石矿物按照一定的顺序粘贴在特制的双面胶上,以环氧树脂固定,树脂固化后对其打磨、抛光至锆石中心面出露,锆石的阴极发光(CL)显微照相是在中国地质科学院大陆构造与动力学实验室完成.
锆石LA-ICP-MS U-Pb同位素定年分析在中国科学技术大学壳幔与环境重点实验室完成,仪器是New Wave Research Inc.公司生产的193 nm激光剥蚀进样系统Aglilent 7500a型电感耦合等离子质谱仪,激光剥蚀工作频率为10 Hz,载气为0.7 L/min氦气,激光剥蚀束斑为32 μm,测试时间为90 s,其中激光剥蚀采样时间为50 s.锆石年龄的计算选用国际标准91500为外标,元素含量采用人工合成硅酸盐玻璃NIST SRM610作为外标,29Si作为内标元素进行校正.LA-ICP-MS锆石U-Pb同位素数据处理采用与中国地质大学(武汉)Liu et al.(2010)的方法,加权平均年龄的计算及谐和图的绘制均使用美国Berkeley大学开发的ISOPLOT(3.7版)(Ludwig, 2009)软件完成.
4. 辉长岩岩石化学特征
4.1 主量元素
本研究中岩石主量元素数据及讨论所成图件均采用的是标准化之后的结果(去除H2O、CO2).其中,两件样品LOI>5%(7.66%、5.64%),其余样品LOI<5%,平均LOI为3.77%(附表 1).洞错蛇绿岩中辉长岩的SiO2含量变化不大,在42.73%~48.46%之间,平均含量为46.54%,略低于MORB中的SiO2的含量(48.77%),Mg#平均值为84,具有原始岩浆的特征.辉长岩中Al2O3的平均含量16.37%,与N-MORB(15.9%)相当,CaO的平均含量为14.23%,含量比较高,MgO平均含量为16.16%,P2O5含量低.NaO和K2O的平均含量分别为0.77%、0.06%,(NaO+K2O)总含量平均值为0.84%,低于N-MORB(2.51%).TiO2含量为0.11%,低于N-MORB(1.15%)(Hofmann, 1988),碱-硅图及Zr/TiO2-Nb/Y(图 5)中,岩石落入亚碱性辉长岩区域、亚碱性玄武岩类区域.
图 5 洞错蛇绿岩中辉长岩的TAS和Zr/Ti-Nb/Y分类图解Ir-Irvine分界线,上方为碱性,下方为亚碱性.侵入岩:1.橄榄辉长岩;2a.碱性辉长岩;2b.亚碱性辉长岩;3.辉长闪长岩;4.闪长岩;5.花岗闪长岩;6.花岗岩;7.硅英岩;8.二长辉长岩;9.二长闪长岩;10.二长岩;11.石英二长岩;12.正长岩;13.副长石辉长岩;14.副长石二长闪长岩;15.副长石二长正长岩;16.副长正长岩;17.副长深长岩;18.霓方钠岩/磷霞岩/粗白榴岩.Andesite.安山岩;Andesite or Basalt.玄武安山岩;SubAlkaline Basalt.亚碱性玄武岩;Rhyolite.流纹岩;Com/Pant.钠闪碱流岩/碱流岩;TrachyAnd.粗面岩/安山岩;Phonolite.响岩;Trachyte.粗面岩;据文献Winchester and Floyd(1977)Fig. 5. TAS and Zr/Ti-Nb/Yb diagrams for the gabbro of the Dongcuo ophiolites总的来说,洞错蛇绿岩中辉长岩具有高Al2O3和CaO、低碱、低P2O5(0.009%)和低TiO2(0.11%)的特征,显示洞错蛇绿岩中辉长岩主量元素的地球化学特征与其所含的主要矿物成分有关,并且辉长岩具有N-MORB主量成分的地球化学特点.
4.2 稀土及微量元素特征
洞错蛇绿岩中辉长岩的稀土总量低(∑REE:3.31×10-6~5.70×10-6),轻重稀土元素分异不明显(LREE/HREE为~0.92),(La/Yb)N为0.44,与N-MORB(0.58)比值相当.δEu值为1.44(正异常),δCe值为0.91(轻微的负异常),这与辉长岩中存在大量的斜长石有关,稀土元素受后期蚀变、热液交代或后期变质改造作用影响较弱,故稀土配分形式可以很好地反映岩浆形成时的特点,辉长岩的球粒陨石标准化(图 6a)表现为平坦的模式,配分形式轻稀土元素略微亏损、重稀土元素略显富集,各样品REE配分形式相互平行,类似于N-MORB稀土配分形式,只是稀土的总量有所差别,显示其稀土元素分异程度相当.
图 6 洞错蛇绿岩中辉长岩稀土元素球粒陨石标准化图解(a)和微量元素原始地幔标准化图解(b)球粒陨石、原始地幔、OIB、N-MORB和E-MORB值据Sun and McDonough(1989)Fig. 6. REE pattern of Dongcuo ophiolite (a) and pattern of trace elements of Dongcuo ophiolite (b)微量元素原始地幔标准化图解(图 6b)显示,辉长岩的配分曲线非常相似,大离子亲石元素Rb、Ba、K呈现不强的规律性,高场强元素(HFSE)Nb、Zr、Ti亏损.从Nb向右各样品元素分布形式与N-MORB标准化模式曲线相似,除Sr元素明显的正异常之外,其他元素相对平坦,辉长岩的Nb、Zr、Ti等元素相比N-MORB明显亏损,表明辉长岩具有岛弧火山岩的特征,反映了消减作用的影响(赖绍聪和刘池洋,2003).根据稀土元素的标准化配分形式(图 7a),样品呈现LREE略亏损特征,指示亏损地幔的源区特征.辉长岩中富集高度不相容元素Rb、Ba、K,可能反映俯冲板片流体交代地幔橄榄岩导致岩浆相对富集大离子亲石元素的结果,由此可推测辉长岩母岩浆可能源自亏损地幔源区,形成于与俯冲相关的环境(Elliott et al., 1997;赖绍聪和刘池洋,2003).
5. 锆石同位素年代学研究
为获得洞错蛇绿岩中辉长岩的形成年龄,在约50 kg样品中挑选出160余粒锆石用于定年.锆石多为黄褐色、半透明、呈粒状,长宽比在1~2之间,粒径在70~180 μm之间,锆石内部见少量的裂隙和包裹体,多数锆石阴极发光图像(CL)表现出明显的岩浆振荡环带,环带分带之间宽度较窄,锆石显示出扇形分带结构和补丁状结构(图 7),锆石的Th/U比值为0.49~1.64,平均值为0.85,属于典型的岩浆锆石(Vavra et al., 1999).
本次测试共采集33个数据点,锆石的U-Pb测试数据见附表 2,扣除5个不谐和年龄1 939±24 Ma、338±5 Ma,这两个古老锆石年龄的可能原因:(1)测试过程没有有效避开裂隙、微小包裹体等区域,造成杂质元素进入质谱仪器分析而出现不谐和的年龄;(2)Lee et al.(1997)和Cherniak and Watson(2001)研究认为锆石本身的封闭温度>900 ℃,那么在岩石形成过程中存在保留古老锆石的可能性,新形成的辉长岩一定程度上会有古老地质事件的反映;而157±3 Ma、160±3 Ma、41±0.7 Ma这3个年轻年龄从锆石的CL图中显示(图 7),157±3 Ma、41±0.7 Ma年龄测试点区域靠近锆石颗粒的边部,造成数据质量不好;而160±3 Ma年龄的CL图像偏暗则反映了锆石的U含量高,对锆石晶格会有放射性的损伤,造成Pb丢失,进而对测年结果的准确获得带来误差,但也不排除这几个年轻的年龄数据的锆石在分选过程受到交叉污染.其余28个数据点的谐和年龄为222±4.8 Ma(MSWD=0.5)(图 8),综上所述,认为该年龄代表辉长岩的结晶年龄.
6. 讨论
6.1 辉长岩的岩石成因及地幔源区特征
岩浆岩岩石的不同元素地球化学特征可用于探讨岩石的源区特征(Pearce and Cann, 1973),其中高场强元素(Nb、Ta、Zr、Hf、Th)以及HREE元素能够不受后期热液蚀变改造作用的影响. Winchester and Floyd(1977)和Pearce and Stern(2006)利用Nb/Yb和Th/Yb作为判断地幔富集、俯冲影响程度的指示性元素.洞错蛇绿岩中辉长岩Nb/Yb比值在0.12~0.63之间,大多数比值低于N-MORB(0.76, Sun and McDonough, 1989),表明形成辉长岩的源区比正常的洋中脊玄武岩更为亏损,Pearce and Parkinson(1993)对地幔源区的高度不相容元素和相容元素进行了研究(如Nb、TiO2、Yb、Y等),并采用富集的MORB地幔标准化判断岩石形成的地幔源区特征和部分熔融程度,由图 9可知,辉长岩的标准配分形式为VHI<HI<MI,表明辉长岩来自中等亏损的FMM源区,熔融程度较高.
图 9 洞错蛇绿岩中辉长岩标准化的(FMM)形式标准值来自Pearce and Parkinson(1993).VHI.极高度不相容元素;HI.高度不相容元素;MI.中等不相容元素Fig. 9. The FMM-normalized patterns of the gabbro for Dongcuo ophioliteXu et al.(2001)利用不活动元素Dy/Yb、La/Yb比值表征岩石源区的形成特征,洞错蛇绿岩中辉长岩具有较高的的Dy/Yb比值(平均值为1.65)、较低的La/Yb比值(平均值为0.59),Dy/Yb-La/Yb(图 10a)显示源区为尖晶石二辉橄榄岩地幔经历过约30%的部分熔融,Sm/Yb-La/Sm(图 10b)显示辉长岩的源区岩浆为尖晶石二辉橄榄岩部分熔融,具有亏损源区的特征.Pearce(2008)研究认为,俯冲洋壳和沉积物中大离子亲石元素的加入导致辉长岩中明显富集这些元素,Pearce(2014)研究认为高的Sr/Nd比值归因于板片流体的交代作用,而高的Th/Yb比值则由于俯冲沉积物的带入,洞错蛇绿岩中辉长岩Sr/Nd比值约200,明显高于N-MORB值(12.33),表明辉长岩的形成可能受到强烈的俯冲板片流体影响.
6.2 辉长岩形成的构造环境分析
蛇绿岩的形成环境,部分学者提出只有少数蛇绿岩是大洋中脊(MOR)扩张的产物,而大多数形成于板块俯冲消减带之上(SSZ)环境(Pearce, 2008; Dilek and Furnes, 2014).前人对班公湖-怒江缝合带蛇绿岩构造环境的研究,认为安多、东巧、觉翁、蓬湖、拉弄地区的蛇绿岩形成于弧后盆地环境(赖绍聪和刘池阳,2003;陈玉禄等,2006;夏斌等,2008;韦振权等,2009);韦少港等(2016)对多龙蛇绿岩研究认为其形成于晚二叠世的洋内俯冲环境;和钟铧等(2006)对凯蒙蛇绿岩研究认为,其形成于SSZ之上的不成熟弧后盆地环境;史仁灯(2007)对查尔康错和班公湖地区蛇绿岩的研究认为其形成于岛弧和俯冲带环境,为SSZ型蛇绿岩.在洞错地区西北面及研究区构造混杂岩中零星出露一套岩浆弧型火山岩(K1q去申拉组火山岩)和中酸性侵入岩(曾庆高等, 2006, 中华人民共和国区域地质调查报告改则幅(1:250 000)),指示班公湖-怒江特提斯洋朝南向拉萨地块俯冲(朱弟成等,2006;康志强等,2010).洞错蛇绿岩的研究有以下认识:张玉修(2007)对洞错蛇绿岩地幔橄榄岩的矿物学和堆晶岩地球化学研究,认为洞错蛇绿岩形成于洋内俯冲带的环境;夏斌和钟富泰(1991)对洞错蛇绿岩构造环境研究认为是初始小洋盆;鲍佩声等(1996, 2007)则认为其形成于陆壳基底张裂的扩张环境.密文天等(2012)认为其形成于俯冲初始阶段的弧前、弧后盆地环境.
由此看来,有必要弄清楚辉长岩的岩石化学类型和形成的构造环境.洞错蛇绿岩中辉长岩TiO2为0.11%,低于N-MORB洋脊玄武岩含量(Hofmann, 1988),与岛弧火山岩(0.58%~0.85%)较为接近(Pearce and Cann, 1973);P2O5含量<0.01%,与洋脊玄武岩P2O5的平均含量0.09存在较大差别,二者一定程度暗示了洞错辉长岩非典型的大洋中脊的特征.在稀土配分图解中(图 6a),辉长岩的稀土形式均呈平坦形式;辉长岩的Ba/Th、Th/Yb等微量元素比值反映了N-MORB的地球化学特征,据Wilson(1989)研究,N-MORB的Zr/Nb比值>30,而洞错蛇绿岩Zr/Nb比值的平均值为26,与典型的洋脊玄武岩有差异;辉长岩微量元素标准化配分图并非为典型的洋中脊玄武岩分布形式,大离子亲石元素K、Rb、Ba没有明显规律,略富集,且Ti、Nb和Zr元素亏损,这与典型的大洋中脊玄武岩明显不同,而岛弧火山岩具有这样的地球化学特征,洞错蛇绿岩这些特征反映其形成过程受到俯冲消减作用的影响(赖绍聪和刘池洋,2003).元素Th、Nb在地幔部分熔融过程中属于高度不相容元素,其比值一般不发生强烈变化,当经受俯冲时,二者会出现解耦(Pearce, 2014).利用Th/Yb-Nb/Yb判别岩石形成的构造环境(图 11a),所有的数据点均落入大洋岛弧区域,V-Ti/1 000图解(Pearce, 2014)(图 11b)显示,辉长岩样品数据分布于玻安岩-低钛岛弧玄武岩和与俯冲作用相关的岛弧火山岩区.另外,洞错辉长岩在Y/15-La/10-Nb/8三角形图解中主要投入火山岩弧拉斑玄武岩区域(图 12).
图 11 构造环境判别图解a.Th/Yb-Nb/Yb图解鉴别SSZ、MOR型蛇绿岩;b.V-Ti/1 000图解鉴别与俯冲相关的构造环境(MORB、IAT型蛇绿岩).据Pearce(2014)Fig. 11. The diagrams to distinguish the tectonic settings图 12 Y/15-La/10-Nb/8图解1A.钙碱性玄武岩;1B、1A、1C.钙碱-拉斑系列;2A.大陆玄武岩;2B.弧后盆地玄武岩;3A.碱性玄武岩;3B、3C.富集洋中脊(E-MORB);3D.正常洋中脊(N-MORB).据Shervais(1982)Fig. 12. The diagram of Y/15-La/10-Nb/8综上所述,从不同元素比值判别图解可以看出,洞错蛇绿岩中辉长岩具有N-MORB的特征和大洋火山弧玄武岩的特征,兼具IAT和MORB地球化学特征,预示着洞错蛇绿岩形成环境可能是与洋内俯冲相关的岛弧环境,或者解释为形成于SSZ的不成熟弧后盆地环境.由此可知,班公湖-怒江缝合带不同区段的蛇绿岩具有不同的形成环境,一定程度上反映了蛇绿岩形成环境的差异和特提斯洋构造演化的复杂性.
6.3 辉长岩形成的年龄意义
蛇绿岩中辉长岩的结晶年龄代表了蛇绿岩或大洋洋壳的形成时代.辉长岩的锆石组成比较简单,锆石内部晶体结构特征决定了其在地质事件中具有良好的抗蚀变能力,同位素封闭体系不容易被重置.因而得出的年龄地质意义单一、明确.洞错辉长岩属于蛇绿岩的岩石单元,其形成构造环境类似于岛弧环境,或者为不成熟的弧后盆地环境.
结合前人的研究工作,洞错舍马拉沟层状辉长岩的Sm-Nd年龄为191±22 Ma,K-Ar年龄为140±4 Ma和152±3 Ma(邱瑞照等, 2002, 2004),辉长岩LA-ICP-MS U-Pb年龄为167±2 Ma(Wang et al., 2016); 洞错北蛇绿混杂岩中辉长岩锆石的SHRIMP U-Pb年龄为190.8±3 Ma(曾庆高等, 2006, 中华人民共和国区域地质调查报告改则幅(1:250 000));洞错地区洋岛玄武岩SHRIMP U-Pb地质年龄为122.9 Ma,K-Ar年龄为137±3 Ma(鲍佩声等,2007;张玉修,2007);角闪岩和变质辉长岩中角闪石的39Ar/40Ar年龄为152±3 Ma(邱瑞照等,2004),造成这种年龄差异的原因可能是采用不同的测年方法及其选用的测年对象的不同,且不同矿物的封闭温度存在差异.对比该缝合带蛇绿岩已经发表的年龄数据(图 13),由东段向西段年龄的变化:丁青地区蛇绿岩中辉长岩形成于晚三叠世-早侏罗世(217±2 Ma,强巴扎西等,2009;197±3.3 Ma,游再平,1997; 178±3 Ma, Wang et al., 2016);安多蛇绿岩中的斜长花岗岩年龄形成于早侏罗世(188±2 Ma,孙立新等,2011; 184±2 Ma, Wang et al., 2016);那曲蛇绿岩中基性岩形成于早三叠世(242 Ma、259 Ma,尼玛次仁和谢尧武,2005);拉弄蛇绿岩中辉绿岩形成于晚三叠世(244±3 Ma, Zhong et al., 2017);东巧地区蛇绿岩形成于早三叠世-早白垩世(187.8±3.7 Ma,叶培盛等,2004; 251 Ma,Shi, 2012; 187±2 Ma, Wang et al., 2016);西段蛇绿岩主要形成于早三叠世-晚侏罗世(254±28 Ma,黄启帅等,2012;167±4 Ma,史仁灯,2007; 181.9±2.6 Ma,曲晓明等,2009;252±1.5 Ma,韦少港等,2016; 169±2 Ma, Wang et al., 2016),以上同位素定年结果说明了班公湖-怒江缝合带不同区段蛇绿岩形成的时代都有差别.
图 13 班公湖-怒江缝合带主要蛇绿岩的年龄分布据潘桂堂等(2004)修改Fig. 13. The age of the main ophiolite in the Bangong-Nujiang suture zone本次获得洞错蛇绿岩中辉长岩的锆石年龄222±4.8 Ma,代表蛇绿岩的形成年龄,提高了对班公湖-怒江缝合带西段蛇绿岩形成时代的认识.与班公湖-怒江缝合带不同地区蛇绿岩中方辉橄榄岩的Re-Os等时线年龄254±28 Ma(黄启帅等,2012)、堆晶辉长岩锆石SHRIMP U-Pb年龄221.6±2.1 Ma(曾庆高等, 2006, 中华人民共和国区域地质调查报告改则幅(1:250 000))、辉长岩同位素Sm-Nd年龄190.8±3 Ma(邱瑞照等,2002)、地幔岩同位素年龄251 Ma(Shi et al., 2012)、辉长岩锆石SHRIMP U-Pb年龄242 Ma(尼玛次仁和谢尧武,2005)、辉长岩锆石年龄217.8±2 Ma(强巴扎西等,2009)、辉绿岩锆石SHRIMP U-Pb年龄218±5 Ma(和钟铧等,2006)存在一致性.因此,该地质年龄222±4.8 Ma反映洞错蛇绿岩形成于晚三叠世,代表洞错洋盆的形成时间,指示班公湖-怒江特提斯洋盆从晚三叠世开始可能存在洋内俯冲消减地质作用.
7. 结论
(1) 洞错蛇绿岩中辉长岩的地球化学特征显示辉长岩具有N-MORB特征,大离子亲石元素富集(K、Rb、Ba),亏损高场强元素(Nb、Zr、Ti),形成过程遭受俯冲流体交代地幔楔作用过程.
(2) 洞错蛇绿岩中辉长岩构造环境的研究表明,洞错蛇绿岩并非形成于典型MOR环境,很可能形成于洋内俯冲相关的岛弧或者不成熟的弧后盆地环境,属于SSZ型蛇绿岩.母岩浆源区原岩为尖晶石二辉橄榄岩经过约30%的部分熔融.
(3) 洞错蛇绿岩中辉长岩的锆石LA-ICP-MS年龄为222±4.8 Ma(晚三叠世),为辉长岩结晶年龄,表明班公湖-怒江特提斯洋盆从晚三叠世开始存在洋内俯冲消减地质作用.
致谢: 本文研究过程中,李毅斌老师、李源博士、刘飞博士给予了有益的建议和帮助,吴魏伟、赵一珏、安元参与了野外地质工作,国家测试中心和中国科技大学锆石年龄测试、数据处理等方面提供了帮助,匿名审稿专家提出了宝贵的修改建议,在此一并表示诚挚的感谢! -
图 1 班公湖-怒江缝合带蛇绿岩分布简图
Fig. 1. The simplified geological sketch of the Bangong-Nujiang suture ophiolites
图 5 洞错蛇绿岩中辉长岩的TAS和Zr/Ti-Nb/Y分类图解
Ir-Irvine分界线,上方为碱性,下方为亚碱性.侵入岩:1.橄榄辉长岩;2a.碱性辉长岩;2b.亚碱性辉长岩;3.辉长闪长岩;4.闪长岩;5.花岗闪长岩;6.花岗岩;7.硅英岩;8.二长辉长岩;9.二长闪长岩;10.二长岩;11.石英二长岩;12.正长岩;13.副长石辉长岩;14.副长石二长闪长岩;15.副长石二长正长岩;16.副长正长岩;17.副长深长岩;18.霓方钠岩/磷霞岩/粗白榴岩.Andesite.安山岩;Andesite or Basalt.玄武安山岩;SubAlkaline Basalt.亚碱性玄武岩;Rhyolite.流纹岩;Com/Pant.钠闪碱流岩/碱流岩;TrachyAnd.粗面岩/安山岩;Phonolite.响岩;Trachyte.粗面岩;据文献Winchester and Floyd(1977)
Fig. 5. TAS and Zr/Ti-Nb/Yb diagrams for the gabbro of the Dongcuo ophiolites
图 6 洞错蛇绿岩中辉长岩稀土元素球粒陨石标准化图解(a)和微量元素原始地幔标准化图解(b)
球粒陨石、原始地幔、OIB、N-MORB和E-MORB值据Sun and McDonough(1989)
Fig. 6. REE pattern of Dongcuo ophiolite (a) and pattern of trace elements of Dongcuo ophiolite (b)
图 9 洞错蛇绿岩中辉长岩标准化的(FMM)形式
标准值来自Pearce and Parkinson(1993).VHI.极高度不相容元素;HI.高度不相容元素;MI.中等不相容元素
Fig. 9. The FMM-normalized patterns of the gabbro for Dongcuo ophiolite
图 10 Dy/Yb-La/Y(a)和Sm/Yb-La/Sm(b)图解
据Xu et al.(2001); Aldanmaz et al.(2000)
Fig. 10. The diagram of Dy/Yb-La/Yb (a) and Sm/Yb-La/Sm (b) of the Dongcuo ophiolite
图 11 构造环境判别图解
a.Th/Yb-Nb/Yb图解鉴别SSZ、MOR型蛇绿岩;b.V-Ti/1 000图解鉴别与俯冲相关的构造环境(MORB、IAT型蛇绿岩).据Pearce(2014)
Fig. 11. The diagrams to distinguish the tectonic settings
图 12 Y/15-La/10-Nb/8图解
1A.钙碱性玄武岩;1B、1A、1C.钙碱-拉斑系列;2A.大陆玄武岩;2B.弧后盆地玄武岩;3A.碱性玄武岩;3B、3C.富集洋中脊(E-MORB);3D.正常洋中脊(N-MORB).据Shervais(1982)
Fig. 12. The diagram of Y/15-La/10-Nb/8
图 13 班公湖-怒江缝合带主要蛇绿岩的年龄分布
据潘桂堂等(2004)修改
Fig. 13. The age of the main ophiolite in the Bangong-Nujiang suture zone
-
[1] Aitchison, J.C., Ali, J.R., Davis, A.M., 2007.When and Where did India and Asia Collide?Journal of Geophysical Research, 112(B5):B05423. https://doi.org/10.1029/2006jb004706 [2] 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 [3] Bao, P.S., Xiao, X.C., Su, L., et al., 2007.Petrological, Geochemical and Chronological Constraints for the Tectonic Setting of the Dongco Ophiolite in Tibet.Science in China (Series D), 31(3):262-268 (in Chinese). doi: 10.1007/s11430-007-0045-5 [4] Bao, P.S., Xiao, X.C., Wang, J., 1996.Geochemistry and Genesis of the Dongcuo Ophiolite in Tibet.Geological Publishing House, Beijing, 190-194 (in Chinese). [5] Chen, Y.L., Zhang, K.Z., Yang, Z.M., et al., 2006.Discovery of a Complete Ophiolite Section in the Jueweng Area, Nagqu County, in the Central Segment of the Bangong Co-Nujiang Junction Zone, Qinghai-Tibet Plateau.Geological Bulletin of China, 25(6):694-699 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-ZQYD200606007.htm [6] Cherniak, D.J., Watson, E.B., 2001.Pb Diffusion in Zircon.Chemical Geology, 172(1/2):5-24. https://doi.org/10.1016/s0009-2541(00)00233-3 [7] Coleman, R.G, 1977.Ophiolites.Springer-Verlag, Berlin, 37(3):298-307. [8] Dewey, J.F., Shackleton, R.M., Chengfa, C., et al., 1988.The Tectonic Evolution of the Tibetan Plateau.Philosophical Transactions of the Royal Society A:Mathematical, Physical and Engineering Sciences, 327(1594):379-413. https://doi.org/10.1098/rsta.1988.0135 [9] Dilek, Y., 2003.Ophiolite Concept and Its Evolution.Geological Society of America Papers, 373:1-16. https://doi.org/10.1130/0-8137-2373-6.1 [10] Dilek, Y., Furnes, H., 2014.Ophiolite and Their Origins.Elements, 10(2):93-100. https://doi.org/10.2113/gselements.10.2.93 [11] Dilek, Y., Furnes, H., Shallo, M., 2007.Suprasubduction Zone Ophiolite Formation along the Periphery of Mesozoic Gondwana.Gondwana Research, 11(4):453-475. https://doi.org/10.1016/j.gr.2007.01.005 [12] 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 [13] Fu, J.J., Ding, L., Xu, Q., et al., 2015.Zircon U-Pb Geochronology and Hf Isotopic Composition of the Cretaceous Volcanic Rocks and Constraint of the Collision Age of Banggong-Nujiang Suture Zone in Dongco Area, Gaize, Tibet.Chinese Journal of Geology, 50(1):182-202 (in Chinese with English abstract). http://www.dzkx.org/EN/abstract/abstract11139.shtml [14] He, Z.H., Yang, D.M., Wang, T.W., 2006.Age, Geochemistry and Its Tectonic Significance of Kaimeng Ophiolites in Jiali Fault Belt, Tibet.Acta Petrologica Sinica, 22(2):653-660 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-KWYS200601012.htm [15] Hofmann, A.W., 1988.Chemical Differentiation of the Earth:The Relationship between Mantle, Continental Crust, and Oceanic Crust.Earth and Planetary Science Letters, 90(3):297-314. https://doi.org/10.1016/0012-821x(88)90132-x [16] Huang, Q.S., Shi, R.D., Ding, B.H., et al., 2012.Re-Os Isotopic Evidence of MOR-Type Ophiolite from the Bangong Co for the Opening of Bangong-Nujiang Tethys Ocean.Acta Petrologica et Mineralogica, 31(4):465-478 (in Chinese with English abstract). https://www.researchgate.net/publication/284761968_Re-Os_isotopic_evidence_of_MOR-type_ophiolite_from_the_Bangong_Co_for_the_opening_of_Bangong-Nujiang_Tethys_Ocean [17] Huang, Q.T., Li, J.F., Xia, B., et al., 2015.Petrology, Geochemistry, Chronology and Geological Significance of Jiang Tso Ophiolite in Middle Segment of Banggonghu-Nujiang Suture Zone, Tibet.Earth Science, 40(1):35-48 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DQKX201501003.htm [18] Kang, Z.Q., Xu, J.F., Wang, B.D., et al., 2010.Qushenla Formation Volcanic Rocks in North Lhasa Block:Products of Bangong Co-Nujiang Tethy's Southward Subduction.Acta Petrologica Sinica, 26(10):3106-3116 (in Chinese with English abstract). https://www.researchgate.net/publication/283768751_Qushenla_Formation_volcanic_rocks_in_north_Lhasa_block_Products_of_Bangong_Co-Nujiang_Tethy's_southward_subduction [19] Kapp, P., Yin, A., Manning, C.E., et al., 2003.Tectonic Evolution of the Early Mesozoic Blueschist-Bearing Qiangtang Metamorphic Belt, Central Tibet.Tectonics, 22(4):1043. https://doi.org/10.1029/2002tc001383 [20] Lai, S.C., Liu, C.Y., 2003.Geochemistry and Genesis of the Island-Arc Ophiolite in Anduo Area, Tibetan Plateau.Acta Petrologica Sinica, 19(4):675-682 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSXB200304007.htm [21] Lee, J.K.W., Williams, I.S., Ellis, D.J., 1997.Pb, U and Th Diffusion in Natural Zircon.Nature, 390(6656):159-162. https://doi.org/10.1038/36554 [22] Li, C., 1987.The Longmucuo-Shuanghu-Lancangjiang Plate Suture and the North Boundary of Distribution of Gondwana Facies Permo-Carboniferous System in Northern Xizang, China.Journal of Changchun College of Geology, 17(2):155-167 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-CCDZ198702003.htm [23] Li, J.F., Xia, B., Wang, R., et al., 2013.Mineralogical Characteristics of the Dong Tso Ophiolite and Its Tectonic Implications.Geotectonica et Metallogenia, 37(2):308-318 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DGYK201302015.htm [24] Liu, W.B., Qian, Q., Yue, G.L., et al., 2002.The Geochemical Characteristics of Fore-Arc Ophiolite from Dingqing Area, Tibet.Acta Petrologica Sinica, 18(3):392-400 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSXB200203014.htm [25] Liu, Y.S., Hu, Z.C., Zong, K.Q., et al., 2010.Reappraisement and Refinement of Zircon U-Pb Isotope and Trace Element Analyses by LA-ICP-MS.Chinese Science Bulletin, 55(15):1535-1546. https://doi.org/10.1007/s11434-010-3052-4 [26] Ludwig, K. R., 2009. ISOPLOT 3. 70: A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center, California. [27] Mi, W.T., Zhu, L.D., Li, Z.W., et al., 2012.Geochemical Characteristics of Gabbro and Diabase in the Shemalagou Ophiolite in Tibet.Xinjiang Geology, 30(4):465-470 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-XJDI201204018.htm [28] Moores, E.M., 2003.A Personal History of the Ophiolite Concept.Geological Society of America Special Papers, 373:17-29. https://doi.org/10.1130/0-8137-2373-6.17 [29] Nimaciren, Xie, Y.W., 2005.Discovery of Middle Triassic Strata in the Nagqu Area, Northern Tibet, China, and Its Geological Implications.Geological Bulletin of China, 24(12):1141-1149 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-ZQYD200512010.htm [30] Pan, G.T., 1997.Geological Tectonic Evolution in the Eastern Tethys.Geological Publishing House, Beijing (in Chinese). [31] Pan, G.T., Zhu, D.C, Wang, L.Q., et al., 2004.Bangong Lake-Nu River Suture Zone-The Northern Boundary of Gondwanaland:Evidence from Geology and Geophysics.Earth Science Frontiers, 11(4):371-382 (in Chinese with English abstract). http://industry.wanfangdata.com.cn/dl/Detail/Periodical?id=Periodical_dxqy200404004 [32] Pearce, J.A., 2008.Geochemical Fingerprinting of Oceanic Basalts with Applications to Ophiolite Classification and the Search for Archean Oceanic Crust.Lithos, 100(1/2/3/4):14-48. https://doi.org/10.1016/j.lithos.2007.06.016 [33] Pearce, J.A., 2014.Immobile Element Fingerprinting of Ophiolites.Elements, 10(2):101-108.doi.:10.2113/gselements.10.2.101 doi: 10.2113/gselements.10.2.101 [34] Pearce, J.A., Cann, J.R., 1973.Tectonic Setting of Basic Volcanic Rocks Determined Using Trace Element Analyses.Earth and Planetary Science Letters, 19(2):290-300. https://doi.org/10.1016/0012-821x(73)90129-5 [35] Pearce, J.A., Parkinson, I.J., 1993.Trace Element Models for Mantle Melting:Application to Volcanic Arc Petrogenesis.Geological Society, London, Special Publications, 76(1):373-403. https://doi.org/10.1144/gsl.sp.1993.076.01.19 [36] Pearce, J.A., Stern, R.J., 2006.Origin of Back-Arc Basin Magmas:Trace Element and Isotope Perspectives, Back-Arc Spreading Systems:Geological, Biological, Chemical, and Physical Interactions.Geophys.Monogr.Ser.AGU, Washington, DC, 63-86. https://doi.org/10.1029/166GM06 [37] Qiangba, Z.X., Xie, Y.W., Wu, Y.W., et al., 2009.Zircon SIMS U-Pb Dating and Its Significance of Cumulate Gabbro from Dengqen Ophiolite, Eastern Tibet, China.Geological Bulletin of China, 28(9):1253-1258 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-ZQYD200909014.htm [38] Qiu, R.Z., Deng, J.F., Zhou, S., et al., 2005.Ophiolite Types in Western Qinghai Tibetan Plateau-Evidences from Petrology and Geochemistry.Earth Science Frontiers, 12(2):277-291 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DXQY200502011.htm [39] Qiu, R.Z., Xiao, R., Zhou, S., et al., 2002.Geochronology and Nd and Sr Isotope Characteristics of Gabbro Dikes from the Shemalagou Area in the Middle Sector of the Bangonco-Nujiang Ophiolite Belt, North Tibet.Geological Review, 48(Suppl.):64-68 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DZLP2002S1012.htm [40] Qiu, R.Z., Zhou, S., Deng, J.F., et al., 2004.Dating of Gabbro in the Shemalagou Ophiolite in the Western Segment of the Bangong Co-Nujiang Ophiolite Belt, Tibet-With a Discussion of the Age of the Bangong Co-Nujiang Ophiolite Belt.Geology in China, 31(3):262-268 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DIZI200403003.htm [41] Qu, X.M., Wang, R.J., Xin, H.B., et al., 2009.Geochronology and Geochemistry of Igneous Rocks Related to the Subduction of the Tethys Oceanic Plate along the Bangong Lake Arc Zone, the Western Tibetan Plateau.Geochimica, 38(6):523-535 (in Chinese with English abstract). http://or.nsfc.gov.cn/bitstream/00001903-5/269773/1/1000014453093.doc [42] Qu, X.M., Xin, H.B., Xu, W.Y., et al., 2007.Petrogenesis of the Ore-Hosting Volcanic Rocks and Their Contribution to Mineralization in Xiongcun Superlarge Cu-Au Deposit, Tibet.Acta Geologica Sinica, 81(7):964-971 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DZXE200707011.htm [43] Qu, X.M., Xin, H.B., Zhao, Y.Y., 2010.Opening Time of Bangong Lake Middle Tethys Oceanic Basin of the Tibet Plateau:Constraints from Petro-Geochemistry and Zircon U-Pb LA-ICP-MS Dating of Mafic Ophiolites.Earth Science Frontiers, 17(3):53-63 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DXQY201003007.htm [44] Shervais, J.W., 1982.Ti-V Plots and the Petrogenesis of Modern and Ophiolitic Lavas.Earth and Plantary Science Letters, 59(1):101-118. doi: 10.1016/0012-821X(82)90120-0 [45] Shi, R.D., 2007.The Age of Bangonghu SSZ-Type Ophiolite and Restrict of the Ban-Nu Ocean.Chinese Science Bulletin, 52(2):223-227 (in Chinese). [46] Shi, R.D., Griffin, W.L., O'Reilly, S.Y., et al., 2012.Melt/Mantle Mixing Produces Podiform Chromite Deposits in Ophiolites:Implications of Re-Os Systematics in the Dongqiao Neo-Tethyan Ophiolite, Northern Tibet.Gondwana Research, 21:194-206. doi: 10.1016/j.gr.2011.05.011 [47] Sun, L.X., Bai, Z.D., Xu, D.B., et al., 2011.Geological Characteristics and Zircon U-Pb SHRIMP Dating of the Plagiogranite in Amduo Ophiolites, Tibet.Geological Survey and Research, 34(1):10-15 (in Chinese with English abstract). http://or.nsfc.gov.cn/bitstream/00001903-5/266436/1/1000014593461.pdf [48] 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 [49] Vavra, G., Schmid, R., 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. https://doi.org/10.1007/s004100050492 [50] Wang, B.D., Wang, L.Q., Chung, S.L., et al., 2016.Evolution of the Bangong-Nujiang Tethyan Ocean:Insights from the Geochronology and Geochemistry of Mafic Rocks within Ophiolites.Lithos, 245:18-33. https://doi.org/10.13039/100007834 [51] Wang, W.L., Aitchison, J.C., Lo, C.H., et al., 2008.Geochemistry and Geochronology of the Amphibolite Blocks in Ophiolite Melanges along Bangong-Nujiang Suture, Central Tibet.Joural of Asian Earth Sciences, 33(1-2):122-138. doi: 10.1016/j.jseaes.2007.10.022 [52] Wang, X.B., Bao, P.S., Deng, W.M., et al., 1987.Tibet Ophiolite.Geological Publishing House, Beijing (in Chinese). [53] Wei, S.G., Song, Y., Tang, J.X., et al., 2016.Geochemistry and Geochronology of Intra-Oceanic Subduction of the Bangong-Nujiang Tethyan Ocean during Late Permian (ca.252Ma).Geological Review, 62(Suppl.):194-196 (in Chinese with English abstract). [54] Wei, Z.Q., Xia, B., Xu, L.F., et al., 2009.Geochemistry and Tectonic Setting of Western Pung Co Lake Ophiolite, Xizang (Tibet).Geological Review, 55(6):785-794 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DZLP200906004.htm [55] Wei, Z.Q., Xia, B., Zhou, G.Q., et al., 2007.Geochemical Characteristics and Its Origin for Mid-Ocean Ridge Superposing Oceanic Island of Chongbe Ophiolite Mélange, Dingqing, Xizang (Tibet).Geological Review, 53(2):187-197 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DZLP200702007.htm [56] Wilson, M., 1989.Igneous Petrogenesis.Journal of Geology, 12:348-356. https://doi.org/10.1007/978-94-010-9388-0 [57] Winchester, J.A., Floyd, P.A., 1977.Geochemical Discrimination of Different Magma Series and Their Differentiation Products Using Immobile Elements.Chemical Geology, 20:325-343. https://doi.org/10.1016/0009-2541(77)90057-2 [58] Wu, Z.H., Ye, P.S., Yin, C.Y., et al., 2013.The Early Cenozoic Gerze Thrust System in Northern Tibet.Acta Geoscientica Sinica, 34(1):31-37 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DQXB201301006.htm [59] Xia, B, Xu, L.F., Wei, Z.Q., et al., 2008.SHRIMP Zircon Dating of Gabbro from the Donqiao Ophiolite in Tibet and Its Geological Implications.Acta Geologica Sinica, 82(4):528-531 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DZXE200804010.htm [60] Xia, B., Zhong, F.T., 1991.Geochemical Characteristics and Genetic Significance of Ophiolite from Dong Tso, Tibet.Geology of Tibet, (2):73-87 (in Chinese). [61] Xu, Y.G., Menzies, M.A., Thirlwall, M.F., et al., 2001.Exotic Lithosphere Mantle beneath the Western Yangtze Craton:Petrogenetic Links to Tibet Using Highly Magnesian Ultrapotassic Rocks.Geology, 29(9):863.https://doi.org/10.1130/0091-7613(2001)029<0863:elmbtw>2.0.co;2 doi: 10.1130/0091-7613(2001)029<0863:elmbtw>2.0.co;2 [62] Xu, Z.Q., Li, H.B., Yang, J.S., 2006.An Orogenic Plateau-The Orogenic Collage and Orogenic Types of the Qinghai Tibet Plateau.Earth Science Frontiers, 13(4):1-17(in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DXQY200604001.htm [63] Yang, J.S., Bai, W.J., Fang, Q.S., et al., 2004.Coesite Discovered from the Podiform Chromitite in the Luobusha Ophiolite, Tibet.Earth Science, 29(6):651-660 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DQKX200406002.htm [64] Yang, J.S., Xu, X.Z., Rong, H., et al., 2013.Deep Mineral in Ophiolitic Mantle Peridotites:Discovery and Progress.Bulletin of Mineralogy, Petrology and Geochemistry, 32(2):159-170 (in Chinese with English abstract). http://www.geojournals.cn/dzxb/ch/reader/view_abstract.aspx?file_no=dzxbcn2013z10011&flag=1 [65] Ye, P.S., Wu, Z.H., Hu, D.G., et al., 2004.Geochemical Characteristics and Tectonic Setting of Ophiolite of Dongqiao, Tibet.Geoscience, 18(3):309-315 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-XDDZ200403007.htm [66] You, Z.P., 1997.40Ar-39Ar Chronology of Dingqing Ophiolite, Tibet.Geology of Tibet, (2):24-30 (in Chinese with English abstract). [67] Zhang, Y. X., 2007. Tectonic Evolution of the Middle-Western Bangong-Nujiang Suture, Tibet (Dissertation). Chinese Academy of Sciences, Guangzhou (in Chinese with English abstract). [68] Zheng, Y.Y., Xu, R.K., He, L.X., et al., 2004.The Shiquan River Ophiolite Mélange Zone in Xizang:The Delineation and Significance of a New Archipelagic Arc-Basin System.Sedimentary Geology and Tetyan Geology, 24(1):13-20 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-TTSD200401001.htm [69] Zheng, Y.Y., Xu, R.K., Ma, G.T., et al., 2006.Ages of Generation and Subduction of Shiquan River Ophiolite:Restriction from SHRIMP Zircon Dating.Acta Petrologica Sinica, 22(4):895-904 (in Chinese with English abstract). http://www.oalib.com/paper/1473585 [70] Zhong, Y, Liu., W.L, Xia, B., et al., 2017.Geochemistry and Geochronology of the Mesozoic Lanong Ophiolitic Melange, Northern Tibet:Implications for Petrogenesis and Tectonic Evolution.Lithos, 292:111-131. https://doi.org/10.1016/j.lithos.2017.09.003 [71] Zhou, G.Q., 2008.Ophiolite:Some Key Aspects Regarding Its Definition and Classification.Journal of Nanjing University (Natural Sciences), 44(1):1-24 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-NJDZ200801002.htm [72] Zhou, M.F., Malpas, J.G., Robinson, P.T., et al., 1997.The Dynamothermal Aureole of the Donqiao Ophiolite (Northern Tibet).Canadian Journal of Earth Science., 34(1):59-65. doi: 10.1139/e17-005 [73] Zhu, D.C., Pan, G.T., Mo, X.X., et al., 2006.Late Jurassic-Early Cretaceous Geodynamic Setting in Middle-Northern Gangdese:New Insights from Volcanic Rocks.Acta Petrologica Sinica, 22(3):534-546 (in Chinese with English abstract). http://www.oalib.com/paper/1472180 [74] 鲍佩声, 肖序常, 苏梨, 等, 2007.西藏洞错蛇绿岩的构造环境:岩石学、地球化学和年代学制约.中国科学(D辑), 31(3):262-268. http://www.cqvip.com/Main/Detail.aspx?id=24393545 [75] 鲍佩声, 肖序常, 王军, 等, 1996.西藏洞错蛇绿岩的地球化学及其生因.北京:地质出版社, 190-194. [76] 陈玉禄, 张宽忠, 杨志民, 等, 2006.青藏高原班公湖-怒江结合带中段那曲县觉翁地区发现完整的蛇绿岩剖面.地质通报, 25(6):694-699. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=zgqydz200606007 [77] 付佳俊, 丁林, 许强, 等, 2015.西藏改则洞错地区白垩纪火山岩锆石U-Pb年代学、Hf同位素组成及对班公-怒江洋俯冲闭合的制约.地质科学, 50(1):182-202. http://www.dzkx.org/cn/abstract/abstract11139.shtml [78] 和钟铧, 杨德明, 王天武, 等, 2006.西藏嘉黎断裂带凯蒙蛇绿岩的年代学、地球化学特征及其大地构造意义.岩石学报, 22(2):653-660. http://www.ysxb.ac.cn/ysxb/ch/reader/view_abstract.aspx?file_no=20060370 [79] 黄启帅, 史仁灯, 丁炳华, 等, 2012.班公湖MOR型蛇绿岩Re-Os同位素特征对班公湖-怒江特提斯洋裂解时间的制约.岩石矿物学杂志, 31(4):465-478. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=yskwxzz201204001 [80] 黄强太, 李建峰, 夏斌, 等, 2015.西藏班公湖-怒江缝合带中段江错蛇绿岩岩石学、地球化学、年代学及地质意义.地球科学, 40(1):34-48. http://www.earth-science.net/WebPage/Article.aspx?id=3014 [81] 康志强, 许继峰, 王宝弟, 等, 2010.拉萨地块北部去申拉组火山岩:班公湖-怒江特提斯洋南向俯冲的产物?岩石学报, 26(10):3106-3116. http://industry.wanfangdata.com.cn/yj/Detail/Periodical?id=Periodical_ysxb98201010022 [82] 赖绍聪, 刘池阳, 2003.青藏高原安多岛弧蛇绿岩地球化学及其成因.岩石学报, 19(4):675-682. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=ysxb98200304008 [83] 李才, 1987.龙木错-双湖-澜沧江板块缝合带与石炭二叠纪冈瓦纳北界.长春地质学院学报, 17(2):155-167. http://www.cqvip.com/QK/91256B/198702/67676890495756554850484851.html [84] 李建峰, 夏斌, 王冉, 等, 2013.洞错地幔橄榄岩、均质辉长岩矿物化学特征及其构造意义.大地构造与成矿学, 37(2):308-318. http://d.wanfangdata.com.cn/Periodical_ddgzyckx201302013.aspx [85] 刘文斌, 钱青, 岳国利, 等, 2002.西藏丁青弧前蛇绿岩的地球化学特征.岩石学报, 18(3):392-400. http://d.old.wanfangdata.com.cn/Periodical/ysxb98200203015 [86] 密文天, 朱利东, 李智武, 等, 2012.西藏舍马拉沟蛇绿岩中辉长岩及辉绿岩地球化学特征.新疆地质, 30(4):465-470. http://www.cqvip.com/QK/82738X/201204/44124569.html [87] 尼玛次仁, 谢尧武, 2005.藏北那曲地区中三叠地层的新发现及其地质意义.地质通报, 24(12):1141-1149. doi: 10.3969/j.issn.1671-2552.2005.12.009 [88] 潘桂堂, 1997.东特提斯地质构造形成演化.北京:地质出版社. [89] 潘桂堂, 朱弟成, 王立全, 等, 2004.班公湖-怒江缝合带作为冈瓦纳大陆北界的地质地球物理证据.地学前缘, 11(4):371-382. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=dxqy200404004 [90] 强巴扎西, 谢荛武, 吴彦旺, 等, 2009.藏东丁青蛇绿岩中堆晶辉长岩锆石SIMS U-Pb定年及其地质意义.地质通报, 28(9):1253-1258. http://industry.wanfangdata.com.cn/dl/Detail/Periodical?id=Periodical_zgqydz200909013 [91] 邱瑞照, 邓晋福, 周肃, 等, 2005.青藏高原西部蛇绿岩类型:岩石学与地球化学证据.地学前缘, 12(2):277-291. http://www.cqvip.com/QK/98600X/2005002/15572659.html [92] 邱瑞照, 肖润, 周肃, 等, 2002.藏北班公湖-怒江带舍玛拉沟蛇绿岩中辉长岩Sm-Nd定年和Sr、Nd同位素研究.地质论评, 48(增刊):64-68. http://www.oalib.com/paper/4892600 [93] 邱瑞照, 周肃, 邓晋福, 等, 2004.西藏班公湖-怒江西段舍马拉沟蛇绿岩中辉长岩年龄测定——兼论班公湖-怒江蛇绿岩带形成时代.中国地质, 31(3):262-268. http://geochina.cgs.gov.cn/ch/reader/view_abstract.aspx?file_no=20040304&flag=1 [94] 曲晓明, 王瑞江, 辛洪波, 等, 2009.西藏西部与班公湖特提斯洋盆俯冲相关的火成岩年代学和地球化学, 地球化学, 38(6):523-535. http://www.cqvip.com/Main/Detail.aspx?id=31887686 [95] 曲晓明, 辛洪波, 徐文艺, 等, 2007.西藏雄村特大型铜金矿床容矿火山岩的成因及其对成矿的贡献.地质学报, 81(7):964-971. http://www.geojournals.cn/dzxb/ch/reader/view_abstract.aspx?file_no=200707112&flag=1 [96] 曲晓明, 辛洪波, 赵元艺, 等, 2010.西藏班公湖中特提斯洋盆的打开时间:镁铁质蛇绿岩地球化学与锆石U-Pb LA-ICP-MS定年结果.地学前缘, 17(3):53-63. http://www.earthsciencefrontiers.net.cn/CN/abstract/abstract4083.shtml [97] 史仁灯, 2007.班公湖SSZ型蛇绿岩年龄对班-怒洋时限的制约.科学通报, 52(2):223-227. http://www.oalib.com/paper/4274997 [98] 孙立新, 白志达, 徐德斌, 等, 2011.西藏安多蛇绿岩中斜长花岗岩地球化学特征及锆石U-Pb SHRIMP年龄.地质调查与研究, 34(1):10-15. http://www.cqvip.com/QK/71135X/201107/37382939.html [99] 王希斌, 鲍佩声, 邓万明, 等, 1987.西藏蛇绿岩.北京:地质出版社. [100] 韦少港, 宋扬, 唐菊兴, 2016.西藏班公湖-怒江西段特提斯洋晚二叠世(Ca. 252Ma)洋内俯冲的地球化学和年代学证据.地质论评, 62(S1):194-196. http://www.geojournals.cn/georev/ch/reader/view_abstract.aspx?file_no=dzlp201662s094&flag=1 [101] 韦振权, 夏斌, 徐力峰, 等, 2009.西藏蓬湖西蛇绿岩地球化学及构造背景研究.地质论评, 55(6):785-794. http://www.cqvip.com/Main/Detail.aspx?id=32209920 [102] 韦振权, 夏斌, 周国庆, 等, 2007.西藏丁青宗白蛇绿混杂岩地球化学特征及其洋中脊叠加洋岛的成因.地质论评, 53(2):187-197. http://www.geojournals.cn/georev/ch/reader/view_abstract.aspx?file_no=20070235 [103] 吴珍汉, 叶培盛, 殷才云, 等, 2013.藏北改则新生代早期逆冲推覆构造系统.地球学报, 34(1):31-37. doi: 10.3975/cagsb.2013.01.04 [104] 夏斌, 徐力峰, 韦振权, 等, 2008.西藏东巧蛇绿岩中辉长岩锆石SHRIMP定年及其地质意义.地质学报, 82(4):528-531. http://d.old.wanfangdata.com.cn/Periodical/dizhixb200804010 [105] 夏斌, 钟富泰, 1991.西藏北部洞错蛇绿岩地体的岩石地球化学特征及其成因意义.西藏地质, (2):73-87. http://www.cqvip.com/QK/97137X/199102/631548.html [106] 许志琴, 李海斌, 杨经绥, 等, 2006.造山的高原——青藏高原巨型造山带拼贴体和造山类型.地学前缘, 13(4):1-17. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=dxqy200604002 [107] 杨经绥, 白文吉, 方青松, 等, 2004.西藏罗布莎豆荚状铬铁矿中发现超高压矿物柯石英.地球科学, 29(6):651-660. http://www.earth-science.net/WebPage/Article.aspx?id=1466 [108] 杨经绥, 徐向珍, 戎合, 等, 2013.蛇绿岩地幔橄榄岩中的深部矿物:发现与研究进展.矿物岩石地球化学通报, 32(2):159-170. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=kwysdqhxtb201302002 [109] 叶培盛, 吴珍汉, 胡道功, 等, 2004.西藏东巧蛇绿岩的地球化学特征及其形成构造环境.现代地质, 18(3):309-315. http://www.cqvip.com/Main/Detail.aspx?id=10277771 [110] 游再平, 1997.西藏丁青蛇绿混杂岩40Ar-39Ar年代学.西藏地质, (2):24-30. http://www.cqvip.com/QK/97137X/199702/2874879.html [111] 张玉修, 2007. 班公湖-怒江缝合带中西段构造演化(博士学位论文). 广州: 中国科学院研究生院. [112] 郑有业, 许荣科, 何来信, 等, 2004.西藏狮泉河蛇绿混杂岩带——一个新的多岛弧盆系统的厘定及意义.沉积与特提斯地质, 24(1):13-20. http://www.cqvip.com/Main/Detail.aspx?id=9483237 [113] 郑有业, 许荣科, 马国桃, 等, 2006.锆石SHRIMP测年对狮泉河蛇绿岩形成和俯冲的时间约束.岩石学报, 22(4):895-904. http://www.ysxb.ac.cn/ysxb/ch/reader/view_abstract.aspx?file_no=20060495&journal_id=ysxb [114] 周国庆, 2008.蛇绿岩研究新进展及其定义和分类的再讨论.南京大学学报(自然科学), 44(1):1-24. https://www.wenkuxiazai.com/doc/a059b8d284254b35eefd345e.html [115] 朱弟成, 潘桂堂, 莫宣学, 等, 2006.冈底斯中北部晚侏罗世-早白垩世地球动力学环境:火山岩约束.岩石学报, 22(3):534-546. http://www.cnki.com.cn/Article/CJFDTOTAL-YSXB200603002.htm 期刊类型引用(19)
1. 钱青,孙宝璐,董飞羽. 藏东怒江峡谷蛇绿岩:早侏罗世拉萨地块被动陆缘俯冲起始的记录?. 中国科学:地球科学. 2025(03): 747-769 . 百度学术
2. Qing QIAN,Baolu SUN,Feiyu DONG. Nujiang Canyon ophiolites(eastern Tibetan Plateau): Records of early Jurassic subduction initiation at passive continental margin of the Lhasa block?. Science China Earth Sciences. 2025(03): 730-749 . 必应学术
3. 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
4. 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
5. 赵守仁,陈海霞. 西羌塘勒玛擦地区铜多金属矿成矿地质条件和找矿方向探讨. 资源环境与工程. 2022(03): 329-336 . 百度学术
6. 王冬兵,王保弟,潘桂棠,罗亮,唐渊. 班公湖-怒江结合带东段早石炭世洋壳残片及其古特提斯意义. 岩石学报. 2021(10): 3048-3066 . 百度学术
7. Yiming Liu,Jiaren Ye,Qiang Cao,Baolin Yang,Zhongrong Liu. Hydrocarbon Generation, Migration, and Accumulation in the Eocene Niubao Formation in the Lunpola Basin, Tibet, China: Insights from Basin Modeling and Fluid Inclusion Analysis. Journal of Earth Science. 2020(01): 195-206 . 必应学术
8. 尹滔,尹显科,秦宇龙,裴亚伦. 西藏隆巴俄桑地区玄武岩与安山玢岩的地球化学:对班公湖-怒江洋构造演化的启示. 地球科学. 2020(07): 2345-2359 . 本站查看
9. 张建珍,高莲凤,张振国,李广栋,范建军,潘志龙,贠杰,李强,张涛. 西藏日土早白垩世高镁流纹质岩石时代、地球化学特征及地质意义. 地球科学. 2020(08): 2868-2881 . 本站查看
10. 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
11. 宋扬,曾庆高,刘海永,刘治博,李海峰,德西央宗. 班公湖-怒江洋形成演化新视角:兼论西藏中部古-新特提斯转换. 岩石学报. 2019(03): 625-641 . 百度学术
12. 宋宇航,解超明,范建军,曾孝文,郝宇杰,李晓波. 西藏甲鲁朗地区叶巴组火山岩成因及其对新特提斯洋俯冲的约束. 地球科学. 2019(07): 2319-2338 . 本站查看
13. 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
14. 李应栩,李光明,黄永高,韩飞,杨青松,严刚,张林奎,魏启荣. 西藏中冈底斯成矿带晚三叠世铍铷稀有金属矿化:独居石U-Pb年代学证据. 地球科学. 2019(07): 2379-2393 . 本站查看
15. 罗安波,范建军,王明,曾孝文. 班公湖-怒江洋复理石沉积时代:来自改则县亚多村碎屑锆石的制约. 地球科学. 2019(07): 2426-2444 . 本站查看
16. Shuhua Fan,Zhaochong Zhang,Changqian Ma,Qiuhong Xie,Lianxun Wang,Yanjie Li,Yuzhe Zhang. Coronas around Olivine in the Miaowan Olivine Norite, Yangtze Craton, South China. Journal of Earth Science. 2019(05): 924-937 . 必应学术
17. 范建军,张博川,刘海永,刘一鸣,于云鹏,郝宇杰,阿旺旦增. 班公湖-怒江洋早-中侏罗世洋内俯冲:来自洞错蛇绿岩的证据. 岩石学报. 2019(10): 3048-3064 . 百度学术
18. 张以春,张予杰,袁东勋,徐海鹏,乔枫. 班公湖-怒江洋打开时间的地层古生物约束. 岩石学报. 2019(10): 3083-3096 . 百度学术
19. 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
其他类型引用(6)
-