2022, Vol. 38
2. 中国科学院大学地球与行星科学学院, 北京 100049;
3. 中国地质科学院地质研究所, 北京 100037;
4. 河南省岩石矿物测试中心, 郑州 450012
2. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;
3. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;
4. Rock and Mineral Analysis Center of Henan Province, Zhengzhou 450012, China
沉凝灰岩是介于火山碎屑岩和正常沉积岩之间的过渡类型岩石，是火山喷发事件的直接记录(邱家骧, 1985)。沉凝灰岩的成分以火山碎屑物质为主，混有少量陆源碎屑物质，来源于沉积盆地周缘的火山喷发活动。通过观察和统计沉积地层中沉凝灰岩厚度、层数及粒度等特征，可推测火山灰搬运的距离以及火山喷发活动的频次和强度(Huang et al., 1980; Rose et al., 2003; Carey et al., 2010)。更重要的是，随着近年锆石U-Pb定年技术的发展，可用沉凝灰岩中的岩浆锆石年龄准确测定盆地沉积时代，尤其是缺乏化石的“哑”地层，这也为区域地层划分与对比以及生物灭绝事件的时限厘定提供重要的年代学依据(Lehrmann et al., 2003, 2006; Shen et al., 2011, 2019; 高林志等, 2013, 2014)。此外，有研究者通过分析沉凝灰岩全岩地球化学特征及锆石微量元素和Hf同位素等信息，探讨其火山物质(岩浆)源区特征和构造环境，进而揭示造山过程和盆地演化之间的耦合关系(张辉等, 2014; Scudder et al., 2016; Chen and Robertson, 2021; Liu et al., 2021)。
近年来，有关华南地区古特提斯分支洋盆俯冲闭合过程的研究已成为地学界关注的热点(Yang et al., 2012; 宋博等, 2013, 2014; Faure et al., 2014, 2016; Halpin et al., 2016; Xia et al., 2021)，位于中越边境地区的八布-Song Hien构造带(即滇-琼缝合带西段，Cai and Zhang, 2009)是解答上述科学问题的关键区域(图 1)。然而，关于该构造带的大地构造属性，国内外学者仍存在不同认识，包括：(1)印支期古特提斯分支洋盆俯冲闭合形成的缝合带(吴根耀等, 2001; Cai and Zhang, 2009; Halpin et al., 2016)；(2)峨眉山地幔柱成因的被动大陆边缘裂谷(Hoa et al., 2008a; Tran et al., 2016; Faure et al., 2014, 2016)；及(3)古特提斯分支洋盆或古太平洋俯冲形成的弧后裂谷或弧后洋盆(方维萱等, 2011; Thanh et al., 2014; Duan et al., 2020)。随着国内外学者对该构造带内八布地区及北越Cao Bang地区超镁铁质-铁镁质岩石开展构造成因和形成时代方面的深入研究，进一步证实它们属于晚古生代(328~265Ma)洋中脊型(N-MORB型)蛇绿岩(图 1b，Wu et al., 1999; Zhong et al., 1999; 吴根耀等, 2001; 张斌辉等, 2013; Halpin et al., 2016; Liu et al., 2018; 向忠金等, 2020)，其形成时代明显早于峨眉山地幔柱活动时间(~260Ma, He et al., 2007)。这些蛇绿岩组合或以逆冲推覆岩片的形式构造就位于三叠系浊积岩之上(Zhong et al., 1999)，或连同晚古生代碳酸盐岩、晚二叠世-早三叠世岛弧火山岩和花岗岩一起，以岩块形式构造裹挟至三叠系浊积岩中，从而形成构造混杂带(Halpin et al., 2016)。在八布-Song Hien构造带北-东部的富宁、靖西及凭祥地区断续出露晚二叠世-晚三叠世岛弧火山岩(吴根耀等, 2000, 2001; 覃小锋等, 2011; Qin et al., 2012; 胡丽沙等, 2012; 刘兵等, 2018; 李政林等, 2019; Gan et al., 2021; 向忠金等, 2021)。此外，部分学者对该构造带内那坡盆地及北侧南盘江盆地中的晚古生代深水硅质岩进行了系统研究，结果表现出成熟洋盆的地球化学特征，指示自晚泥盆世至中二叠世南盘江盆地已然发生裂解，并逐渐演化至开阔洋盆(黄虎等, 2013; 黄志强等, 2013)。上述研究成果揭示，华南地块南缘存在古特提斯分支洋盆(八布-Cao Bang分支洋盆)，该洋盆于晚二叠世-中三叠世向北俯冲消减，但其最终闭合时限和过程仍不确定。
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图 1 华南地块南缘区域大地构造纲要图(a, 据Cai and Zhang, 2009; Metcalfe, 2013; Faure et al., 2014, 2016修改)与地质构造简图(b, 据Xia et al., 2021修改) (a)AS-哀牢山缝合带；DQS-滇-琼缝合带；SCS-Song Chay缝合带；SMS-Song Ma缝合带；RRF-红河断裂；SCF-Song Chay断裂；HHF-合浦-河台断裂；DBPF-奠边府断裂；(b)DNCVT-大象山微地块. 同位素年龄数据来源：a-吴根耀等, 2001; Hoa et al., 2008a; 张斌辉等, 2013; Thanh et al., 2014; Halpin et al., 2016; Liu et al., 2018; 向忠金等, 2020; b-胡丽沙等, 2012; 刘兵等, 2018; 向忠金, 2018; 向忠金等, 2021; c-Qin et al., 2012; d-覃小锋等, 2011; 李政林等, 2019; Gan et al., 2021; e-Halpin et al., 2016; f-Roger et al., 2012; Chen et al., 2014 Fig. 1 Tectonic sketch map (a, modified after Cai and Zhang, 2009; Metcalfe, 2013; Faure et al., 2014, 2016) and simplified geological map (b, modified after Xia et al., 2021) of the southern margin of the South China block and adjacent areas (a) AS-Ailaoshan suture; DQS-Dian-Qiong suture; SCS-Song Chay suture; SMS-Song Ma suture; RRF-Red River fault; SCF-Song Chay fault; HHF-Hepu-Hetai fault; DBPF-Dien Bien Phu fault; (b) DNCVT-Dai Nui Con Voi micro-terrane. Geochronology data sources: a-Wu et al., 2001; Hoa et al., 2008a; Zhang et al., 2013; Thanh et al., 2014; Halpin et al., 2016; Liu et al., 2018; Xiang et al., 2020; b-Hu et al., 2012; Liu et al., 2018; Xiang, 2018; Xiang et al., 2021; c-Qin et al., 2012; d-Qin et al., 2011; Li et al., 2019; Gan et al., 2021; e-Halpin et al., 2016; f-Roger et al., 2012; Chen et al., 2014 |
那坡盆地位于八布-Song Hien构造带中段的Cao Bang混杂岩与富宁弧火山岩之间，发育早-中三叠世岩浆岩和巨厚海相碎屑岩系，是研究华南地块南缘古特提斯造山过程的理想载体。笔者所在团队通过对那坡盆地开展了详细的沉积相序及其组合特征分析，结合岩相学、地球化学和碎屑锆石年代学证据，确定其构造原型为早-中三叠世弧前盆地，充填物主要来自盆地北侧晚二叠世-中三叠世中-基性岛弧火山岩和晚古生代地层(夏磊等, 2018; Xia et al., 2021)。然而，关于那坡盆地沉积时代的上限仍缺少确切的年龄约束，碎屑锆石最年轻峰值年龄仅能限定地层的最大沉积时代。因此，在详细的剖面测量基础上，本文选取那坡盆地上部中三叠统河口组中的沉凝灰岩为研究对象，开展了系统的岩石学、全岩地球化学和锆石U-Pb-Hf同位素分析与研究，准确测定了那坡盆地沉积充填的时代上限，并分析了沉凝灰岩中火山物质的源区性质和构造环境，为进一步探讨华南地块南缘古特提斯分支洋盆俯冲闭合时限和过程提供依据。
1 地质背景那坡早-中三叠世盆地位于滇桂两省交界且与越南接壤的边境地区，部分延伸至越南境内。大地构造位置上，该盆地位于八布-Song Hien构造带中段(图 1b)，盆地内充填物以下-中三叠统巨厚海相碎屑岩为主，可见少量滑塌堆积，受后期构造作用影响与盆地周缘古生界(中-上寒武统、泥盆系-二叠系)呈断层接触关系(图 2)。1:20万区域地质调查结果(广西壮族自治区地质局, 1976①; 云南省地质局, 1978②)显示，那坡地区下-中寒武统以白云岩、白云质灰岩夹粉砂质泥岩为主，奥陶系缺失。下泥盆统为富含生物化石的细碎屑岩，中-上泥盆统为灰岩夹含燧石结核灰岩、薄层硅质岩夹硅质泥岩。石炭系和下-中二叠统以厚层碳酸盐岩为主，包括块状灰岩、生物碎屑灰岩、内碎屑灰岩和白云岩。上二叠统以灰岩和燧石灰岩为主，局部夹硅质岩和火山碎屑岩。
① 广西壮族自治区地质局. 1976. 1:20万百色幅、德隆幅地质图及区域地质调查报告
② 云南省地质局. 1978. 1:20万富宁幅地质图及区域地质调查报告
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图 2 广西那坡区域地质简图(据广西壮族自治区地质局, 1976; 云南省地质局, 1978) BNF-百大-那坡断裂；DPF-德隆-平孟断裂；NGF-那布-戈造断裂；NNF-弄内-念银断裂.已报道岩浆岩时代：a-皮桥辉等(2016)；b-Zhou et al. (2006)；c-刘兵等(2018)；d-向忠金等(2021)；e-胡丽沙等(2012)；f-向忠金(2018) Fig. 2 Simplified geological map of Napo area, Guangxi BNF-Baida-Napo fault; DPF-Delong-Pingmeng fault; NGF-Nabu-Gezao fault; NNF-Nongnei-Nianyin fault. Reported ages of magmatic rocks: a-Pi et al. (2016); b-Zhou et al. (2006) c-Liu et al. (2018); d-Xiang et al. (2021); e-Hu et al. (2012); f-Xiang (2018) |
研究区岩浆岩普遍发育，以基性侵入岩为主，局部出露中-基性喷出岩。前人根据基性侵入岩地球化学特征及相互穿插关系(云南省地质局, 1978)，将其划分为二期：第一期为高Ti碱性辉长辉绿岩(又称“半瓦型”岩体)；第二期为低Ti辉长苏长岩和辉长闪长岩(又称“安定型”岩体)。Zhou et al. (2006)测得二期侵入岩的SHRIMP锆石U-Pb年龄为260~258Ma，将其解释为峨眉山地幔柱作用的产物。然而，最新的野外地质调查和年代学结果表明，“安定型”岩体的形成时代要晚于“半瓦型”岩体，其时代介于244~215Ma(皮桥辉等, 2016; 刘兵等, 2018; 江文等, 2017; Jiang et al., 2021)，为中-晚三叠世。
研究区的喷出岩可划分为二期。第一期是晚泥盆世拉斑玄武岩及早石炭世碱性玄武岩，出露于那坡县城以南，被解释为古特提斯分支洋盆打开时的产物(吴根耀等，2000；Xiang et al., 2021; Guo et al., 2004)；第二期是晚二叠世-中三叠世钙碱性中-基性玄武岩和玄武安山岩(胡丽沙等，2012；向忠金等，2021)，主要出露于盆地以北的富宁皈朝-架街一带，部分沿那坡百都-德隆一线展布，具有典型岛弧火山岩的地球化学特征，是古特提斯分支洋盆的俯冲作用的产物。
此外，覃小锋等(2011)、Qin et al. (2012)及Gan et al. (2021)对靖西和凭祥一带的基性-酸性火山岩开展了系统的地球化学和年代学研究，发现这些火山岩同样具有弧岩浆岩特征，其形成时代为晚二叠世-中三叠世(251~246Ma，图 1b)，与富宁-那坡地区的弧火山岩高度一致。李政林等(2019)对凭祥地区岛弧英安岩的锆石定年结果表明，与古特提斯分支洋盆俯冲导致的弧岩浆作用可能持续至晚三叠世早期(228Ma)。在北越Song Hien地区沿Cao Bang-Lang Son断裂零星出露一些早三叠世流纹岩和英安岩(Hoa et al., 2008a; Halpin et al., 2016)，这些岩石多被后期构造作用裹挟至三叠系浊积岩中。
2 样品采集与分析方法 2.1 样品采集与描述本文研究的样品采自那坡盆地南部中三叠统河口组中部和上部，均为沉凝灰岩(图 3)。其中，用于LA-ICP-MS锆石U-Pb定年的样品19BN-1和19BN-3坐标分别为23°01′27.2″N、105°49′21.5″E和23°01′35.1″N、105°48′57.1″E。
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图 3 广西那坡地区清华-百南早-中三叠世地层综合柱状图(据Xia et al., 2021修改) Ms-泥岩；si-粉砂岩；f-细砂岩；m-中砂岩；c-粗砂岩；co-砾岩；*-碎屑锆石最年轻峰值年龄(据Xia et al., 2021) Fig. 3 Stratigraphic column of the Early-Middle Triassic sequence from Qinghua to Bainan village, Napo area, Guangxi (modified after Xia et al., 2021) Ms-mudstone; si-siltstone; f-fine-grained sandstone; m-medium-grained sandstone; c-coarse-grained sandstone; co-conglomerate; *-youngest age peaks of detrital zircon (after Xia et al., 2021) |
野外观察显示，河口组沉凝灰岩呈灰绿色-浅灰色，块状构造，局部夹硅质泥岩，可见细小的水平纹层，偶见轻微的软沉积变形构造(图 4a-c)。河口组下部为一套浊积扇外扇-盆地平原相粉砂质泥岩和含Mn泥岩(Xia et al., 2021)。由此分析，沉凝灰岩沉积于地形相对平坦的深海平原环境，轻微的软沉积变形可能与火山、地震活动引发的重力失稳有关。镜下薄片观察显示，沉凝灰岩主要由细小的石英和长石晶屑组成，具明显定向性，绢云母化蚀变强，基质则以隐晶质和黏土矿物为主，整体表现为凝灰结构(图 4d, e)。
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图 4 广西那坡地区中三叠统河口组沉凝灰岩野外地质特征(a-c)和显微照片(d-e) (a)灰绿色-浅灰色沉凝灰岩，块状构造，岩层产状为200°∠75°；(b、c)沉凝灰岩夹薄层硅质泥岩，发育水平纹层，可见轻微的软沉积变形；(d、e)单偏光(-)和正交光(+)下可见细小的石英和长石晶屑，呈棱角状，具定向排列特征，大部分长石发生绢云母化蚀变，基质以隐晶质和黏土矿物为主；Qtz-石英；Pl-长石；Ser-绢云母 Fig. 4 Field photographs (a-c) and photomicrographs (d-e) of the tuffite in the Middle Triassic Hekou Formation, Napo area, Guangxi (a) greyish-green to light gray tuffite with massive structure (attitude of stratum: 200°∠75°); (b, c) laminated tuffite interbedded with thin-bedded cherty mudstone, with slight soft-sediment deformation structure; (d, e) under plane-polarized (-) and cross-polarized (+) photomicrographs showing some small quartz and feldspar grains with distinct directional property, strong feldspar seriatization and matrix dominated by cryptocrystalline and clay minerals; Qtz-quartz; Pl-plagioclase; Ser-sericite |
锆石挑选在河北廊坊宇能岩石矿物分选技术服务有限公司完成，采用常规重力和磁力分选方法分选，在双目镜下手工精选出透明、无裂隙锆石。将待测样品的锆石颗粒粘置环氧树脂中，磨至约1/2，然后进行透射、反射和阴极发光(CL)照相，观察其表面和内部结构特征，以便选取合适的测定分析部位。锆石制靶和阴极发光(CL)照相均在北京锆年领航科技有限公司完成。
锆石U-Pb定年和Lu-Hf同位素测试分析在北京科荟测试技术有限公司完成。U-Pb同位素分析采用AnlyitikJena PQMS Elite型ICP-MS进行测定，剥蚀系统为ESI NWR 193nm，激光束斑直径为32μm，频率为8Hz，能量密度约为2.01J/cm2，采用氦气作为剥蚀物质的载气。详细测试流程以及仪器运行条件等参见侯可军等(2009)。测定时采用国际标准锆石91500作为外标，微量元素含量校正采用NIST SRM 610作为外标，29Si作为内标。数据处理基于ICPMSDataCal程序(Liu et al., 2010)，年龄计算及谐和图绘制采用Isoplot 4.15完成(Ludwig, 2012)，单个测点误差为1σ，采用206Pb/238U年龄，其加权平均值具95%置信度，分析结果见表 1。
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表 1 广西那坡地区河口组沉凝灰岩LA-ICP-MS锆石U-Pb同位素分析结果 Table 1 LA-ICP-MS zircon U-Pb isotope analysis results for tuffites in the Hekou Formation, Napo area, Guangxi |
Lu-Hf同位素测试采用Neptune plus型多接收电感耦合等离子体质谱(MC-ICP-MS)及配套的Resolution SE 193nm准分子激光剥蚀系统，激光束斑直径为35μm，频率为10Hz，能量密度为7~8J/cm2，测试时同样采用标准锆石GJ-1作为外标，氦气作为载气。利用175Lu和172Yb对176Lu和176Yb进行同质异位素的干扰校正，采用179Hf/177Hf=0.7325对176Hf/177Hf比值进行指数归一化校正(Wu et al., 2006)。176Hf/177Hf初始值和εHf(t)值参考球粒陨石均一库(CHUR)计算，亏损地幔模式年龄(tDM)采用现今的亏损地幔176Hf/177Hf=0.28325和176Lu/177Hf=0.0384计算(Griffin et al., 2000)，而Hf同位素地壳模式年龄(tDMC)则是通过假设其母岩浆来自平均大陆地壳(176Lu/177Hf=0.015)计算获得(Griffin et al., 2002)，分析结果见表 2。
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表 2 广西那坡地区河口组沉凝灰岩锆石Lu-Hf同位素分析结果 Table 2 Zircon Lu-Hf isotope analysis results for tuffites in the Hekou Formation, Napo area, Guangxi |
沉凝灰岩样品13NP-1、13NP-2、13NP-3及13NP-6的全岩主量、微量和稀土元素含量测定在中国地质调查局国家地质实验测试中心完成，样品19BN-1和19BN-3的元素含量测定在北京科荟测试技术有限公司完成。主量元素通过X射线荧光光谱仪(XRF-1800/3080E)测定，分析精度为5%。微量和稀土元素通过电感耦合等离子体质谱仪(ICP-MS-Excel/Agilent 7500)测定，含量大于10×10-6的元素测试精度为5%，含量小于10×10-6的元素测试精度为10%，分析结果见表 3。
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表 3 广西那坡河口组沉凝灰岩主量元素(wt%)和微量元素(×10-6)分析结果 Table 3 Major (wt%) and trace element (×10-6) analysis results for the tuffites in the Hekou Formation, Napo area, Guangxi |
那坡盆地南部河口组沉凝灰岩中的锆石呈短柱或长柱状，半自形-自形，粒径70~150μm，发育清晰的振荡环带，个别锆石具核幔结构(图 5a)。绝大部分锆石Th/U比值大于0.01(表 1)，轻、重稀土分馏明显，呈向左倾斜的轻稀土亏损型模式(数据略)，整体表现出典型的岩浆锆石特征(图 5b)。
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图 5 广西那坡地区中三叠统河口组沉凝灰岩锆石阴极发光(CL)图像、U-Pb年龄与εHf(t)值(a)、锆石球粒陨石标准化稀土元素配分图(b)、LA-ICP-MS锆石U-Pb年龄谐和图和206Pb/238U年龄加权平均值(c、d) (a)实线圆圈代表锆石U-Pb定年测点位置，虚线圆圈代表Lu-Hf同位素测点位置；(b)标准化值据Sun and McDonough (1989) Fig. 5 Cathodoluminescence (CL) images of zircons with U-Pb ages and εHf(t) values (a), chondrite-normalized REE patterns for zircons (b), LA-ICP-MS U-Pb concordia diagrams with weighted mean ages (c, d) of zircons from the tuffites in the Middle Triassic Hekou Formation, Napo area, Guangxi (a) solid line circles indicate the analytical spots for U-Pb ages, dashed line circles indicate the analytical spots for Lu-Hf isotopic values; (b) normalized values after Sun and McDonough (1989) |
样品19BN-1共测试了30个点，获得了27个谐和年龄，仅测点#10、#20及#22谐和度小于95%。其中，22个测点的206Pb/238U谐和年龄介于231~238Ma之间，加权平均年龄为236.3±0.8Ma(MSWD=0.55)(图 5c)，为晚三叠世早期(卡尼期)。另有4个测点年龄介于241~248Ma之间，记录了早期的岩浆活动，测点#25获得495±4Ma的较老年龄，为捕获的早古生代锆石。
样品19BN-3测点共计30个，仅测点#10、#13及#18年龄不谐和。14个测点的年轻206Pb/238U谐和年龄介于238~242Ma之间，加权平均年龄为240.6±1.0Ma(MSWD=0.35)(图 5d)，为中三叠世晚期(拉丁期)。其余测点年龄在244~256Ma范围内，推测来自早期的岩浆活动，测点#22获得913±7Ma的古老年龄，代表捕获的新元古代锆石。
3.2 锆石Hf同位素对沉凝灰岩样品19BN-1和19BN-3中已测定U-Pb年龄的部分锆石开展Lu-Hf同位素原位分析。分析结果显示(表 2)，样品19BN-1中锆石(t=232~248Ma，206Pb/238U年龄)的176Hf/177Hf初始值为0.282102~0.282445，εHf(t)为-18.6~-6.6(图 6a)，其对应的亏损地幔模式年龄(tDM)为1157~1608Ma，地壳模式年龄(tDMC)介于1680~2434Ma之间(图 6b)。
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图 6 沉凝灰岩锆石εHf(t)-年龄图解(a)与地壳模式年龄(b、c) 对比数据来源于凭祥北泗组酸性火山岩(据Gan et al., 2021) Fig. 6 Diagram of εHf(t) vs. age (a) and histograms of crust model ages (b, c) for zircons from the tuffite samples Data for comparison are based on acidic volcanic rocks from the Beisi Formation, Pingxiang area (after Gan et al., 2021) |
样品19BN-3中锆石年龄(t=238~256Ma)较老于前者，但具有相近的176Hf/177Hf初始值(0.282123~0.282449)和εHf(t)=-17.6~-6.3(图 6a)，及亏损地幔模式年龄(1134~1600Ma)和地壳模式年龄(1664~2383Ma)(图 6c)。上述结果表明，两套沉凝灰岩为同源岩浆演化的产物，且均来源于古老地壳物质的再造。
3.3 岩石地球化学特征沉凝灰岩相学特征表明，两套沉凝灰岩均含有大量石英和长石晶屑及隐晶质和黏土矿物基质。通过与下部砂岩碎屑锆石年龄谱及邻区弧火山岩年龄分布特征进行对比分析，结果发现广泛分布于砂岩中的两组碎屑锆石(分别为480~420Ma和400~320Ma，Xia et al., 2021)在该沉凝灰岩样品中几乎不可见，同时沉凝灰岩锆石年龄分布集中，且与富宁、凭祥弧火山岩基本一致(覃小锋等, 2011; Gan et al., 2021; 向忠金等, 2021)。因此，结合沉凝灰岩镜下特征分析，我们认为河口组沉凝灰岩中绝大多数组分来源于火山灰，而陆源碎屑物质极为有限，其地球化学特征能够反映其火山源区特征。
分析结果(表 3)表明，那坡盆地河口组沉凝灰岩主量元素总体具有较高的SiO2(74.02%~82.41%)和K2O(2.15%~5.81%)，较低的TiO2(0.20%~0.28%)、Al2O3(9.78%~15.04%)、Na2O(0.26%~2.50%)和CaO(0.10%~0.28%)。所有样品的MgO、FeOT和P2O5明显较低，含量分别为0.37%~0.48%、1.27%~1.48%和0.03%~0.12%。铝饱和指数(A/CNK)为1.6~2.8，平均值为2.2，表现出壳源岩石过铝质的特征。全碱含量(Na2O+K2O)为3.32%~7.46%，平均值为5.57%。在火成岩TAS(SiO2-Na2O+K2O)分类图上，本文分析的6个样品均投点在流纹岩区域内(图 7a)，显示为亚碱性。考虑到样品本身存在轻微的硅化和绢云母化蚀变作用，可能会导致样品中SiO2含量偏高。因此，本文采用抗蚀变元素图解进一步确定岩石类型。在Nb/Y-Zr/TiO2×0.0001判别图上，本文分析的样品均投在英安岩区域内(图 7b)，暗示这些沉凝灰岩样品是中酸性火山喷发的产物。结合镜下薄片鉴定结果，本文分析的沉凝灰岩样品属于亚碱性英安质，与凭祥和北越Lang Son地区的酸性火山岩较为相近(覃小锋等, 2011; Halpin et al., 2016; 李政林等, 2019; Gan et al., 2021)。
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图 7 广西那坡地区中三叠统河口组沉凝灰岩SiO2-ALK图解(a, 据Le Maitre et al., 2002)和Nb/Y-Zr/TiO2×10-4图解(b，据Winchester and Floyd, 1977) 数据来源：1-那坡河口组沉凝灰岩(本文)；2-凭祥北泗组酸性火山岩(覃小锋等, 2011; 李政林等, 2019)；3-那坡百逢组中-基性火山岩(胡丽沙等, 2012)；4-富宁中-基性火山岩(向忠金等, 2021)；5-Lang Son酸性火山岩(Halpin et al., 2016)；6-Truong Son酸性火山岩(Hoa et al., 2008b)；图 8数据来源同此图 Fig. 7 Diagrams of SiO2 vs. ALK (a, after Le Maitre et al., 2002) and Nb/Y vs. Zr/TiO2×10-4 (b, after Winchester and Floyd, 1977) for the tuffites in the Middle Triassic Hekou Formation, Napo area, Guangxi Data sources: 1-tuffites of Hekou Formation in Napo area; 2-volcanic rocks of Beisi Formation in Pingxiang area (Qin et al., 2011, Li et al., 2019); 3-intermediate-basic volcanic rocks of Baifeng Formation in Napo area (Hu et al., 2012); 4-intermediate-basic volcanic rocks in Funing area (Xiang et al., 2021); 5-acidic volcanic rocks in Lang Son area (Halpin et al., 2016); 6-acidic volcanic rocks in Truong Son tectonic belt (Hoa et al., 2008b); also in Fig. 8 |
沉凝灰岩稀土总量为124×10-6~236×10-6，平均值181×10-6。在球粒陨石标准化稀土元素配分图(图 8a)上，样品具有一致的配分曲线，表现为轻稀土元素(LREEs)相对富集、重稀土元素(HREEs)相对平坦的特征，轻、重稀土元素分异明显，(La/Yb)N比值介于4.5~7.3之间，具明显Eu负异常(δEu=0.18~0.26)，指示岩浆演化过程中经历了斜长石分离结晶作用。对比发现，研究区6件沉凝灰岩样品的稀土配分曲线较为一致，推测为同源区不同期次火山活动的产物，且与凭祥、越南Lang Son及Truong Son地区的酸性火山岩稀土元素含量基本一致。
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图 8 广西那坡地区中三叠统河口组沉凝灰岩球粒陨石标准化稀土元素配分图(a)和原始地幔标准化微量元素蛛网图(b)(标准化值据Sun and McDonough, 1989) Fig. 8 Chondrite-normalized REE patterns (a) and primitive mantle-normalized spider diagrams (b) of the tuffites from the Middle Triassic Hekou Formation, Napo area, Guangxi (normalization values after Sun and McDonough, 1989) |
在原始地幔标准化微量元素蛛网图(图 8b)上，所有样品相对富集大离子亲石元素(LILEs)、Rb、Th和U，亏损高场强元素(HFSEs)，具有显著的Nb、Ta和Ti负异常，整体反映出较多的壳源物质加入，与岛弧火山岩地球化学特征一致。
4 讨论 4.1 沉积时代20世纪70年代，前人对那坡地区巨厚的海相碎屑岩开展了区域地质调查工作(广西壮族自治区地质局, 1976; 云南省地质局, 1978)，将这套海相碎屑岩划分为下三叠统罗楼组、中三叠统百逢组和河口组。由于该套碎屑岩中化石记录稀缺，这套碎屑岩的确切沉积时代一直存在争议。最近，夏磊等(2018)、Xia et al. (2021)通过开展详细的野外地质调查和沉积学研究，结合碎屑锆石U-Pb定年分析结果，认为沿德隆-平孟断裂出露的下三叠统罗楼组为一套斜坡相火山岩-碳酸盐岩混杂型滑塌堆积，并紧密伴生有碎屑流和钙质浊积岩，其砂岩碎屑锆石最年轻峰值年龄为247Ma，位于奥罗尼克期与安尼期界线处。中三叠统百逢组和河口组由北向南可识别出扇三角洲相和浊积扇相，整体表现为一套向南变深变细的沉积序列。百逢组下-中段砂岩碎屑锆石最年轻峰值年龄分别为247Ma和240Ma，指示沉积时期为安尼期至早拉丁期。河口组下-中段砂岩碎屑锆石最年轻峰值年龄分别为243Ma和239Ma，指示拉丁期的沉积时代。
本文研究的两个沉凝灰岩样品(19BN-3和19BN-1)分别采自河口组中部和上部，除部分捕获的较老锆石外(如锆石19BN-1#25与19BN-3#22)，其余年轻锆石206Pb/238U加权平均年龄分别为240.6±1.0Ma和236.3±0.8Ma。这一测年结果准确地限定了那坡盆地河口组碎屑岩沉积时代为中三叠世拉丁期，部分为晚三叠世卡尼期早期，可与滇东南地区兰木组进行对比(张斌辉等, 2019)。
4.2 岩石成因岩相学和地球化学特征表明，广西那坡盆地南部河口组沉凝灰岩属于亚碱性系列英安质岩石，REE配分模式呈右倾型，相对富集LREEs和LILEs，亏损HFSEs，具明显的Eu、Nb、Ta负异常，与中越边境地区中-酸性火山岩高度相似，均表现出与俯冲相关的岛弧火山岩一致的地球化学特征。
考虑到火山碎屑和火山尘在搬运、堆积、固结成岩过程中受流体影响会导致部分活动性较强的元素含量发生变化，因此本文选择活动性较弱、稳定性强的不相容元素(如Nb、Ta、Rb、Y等)含量及其比值来判别沉凝灰岩源区构造环境。研究区河口组沉凝灰岩的Nb和Ta含量分别为6.30×10-6~12.0×10-6和0.68×10-6~1.13×10-6，Nb/Ta比值介于8.7~10.8之间，平均值为9.9，明显低于亏损地幔(Nb/Ta=15.5±1.0，Rudnick et al., 2000)，与大陆地壳(Nb/Ta=10~14，Taylor and McLennan, 1985)相近。在沉凝灰岩全岩(Y+Nb)-Rb判别图中，大部分样品投在Syn-COLG(同碰撞)和VAG(火山弧)区域，仅样品13NP-1投在WPG(板内)区域(图 9a)。在Y-Nb判别图中，除样品13NP-1和19BN-3投在ORG(大洋中脊花岗岩)区域，其余样品均投在VAG+Syn-COLG区域(图 9b)。对比发现，那坡河口组酸性沉凝灰岩与凭祥、越南Lang Son及Truong Son地区的酸性岛弧火山岩具有相似的地球化学特征。
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图 9 那坡地区中三叠统河口组沉凝灰岩构造环境判别图(据Pearce et al., 1984) 区域对比数据来自Hoa et al. (2008b)、覃小锋等(2011)、Halpin et al. (2016)和李政林等(2019). WPG-板内花岗岩；VAG-火山弧花岗岩；Syn-COLG-同碰撞花岗岩；ORG-大洋中脊花岗岩 Fig. 9 Tectonic discrimination diagrams for tuffites of the Middle Triassic Hekou Formation, Napo area (after Pearce et al., 1984) Data for regional comparison is based on Hoa et al. (2008b), Qin et al. (2011), Halpin et al. (2016) and Li et al. (2019). WPG-within plate granite; VAG-volcanic arc granite; Syn-COLG-syn-collision granite; ORG-ocean ridge granite |
Grimes et al.(2007, 2015)通过大量统计大洋中脊、大洋岛弧及岩浆弧环境下锆石的微量元素含量及其比值后发现，利用Hf-U/Yb图解能够有效区分来自洋壳和陆壳的锆石。在锆石Hf-U/Yb构造环境判别图(图 10a)中，研究区所有沉凝灰岩锆石样品均投在陆壳范围内。Yang et al. (2012)提出利用锆石Th/Nb与Hf/Th相关性将其划分为弧相关/造山带环境和板内/非造山带环境。在Th/Nb-Hf/Th图解(图 10b)中，绝大多数锆石样品投在弧相关/造山带区域内，仅样品19BN-3#22落在两者的重叠区域。结合沉凝灰岩锆石较低的εHf(t)值(-18.6~-6.3)、较老的地壳模式年龄(1664~2434Ma)以及俯冲环境微量元素特征分析，推断形成该沉凝灰岩的火山灰来源于岛弧火山岩，且岩浆源区存在壳源物质的加入。
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图 10 河口组沉凝灰岩锆石Hf-U/Yb(a, 据Grimes et al., 2015)和Th/Nb-Hf/Th(b, 据Yang et al., 2012)构造环境判别图 Fig. 10 Tectonic discrimination diagrams of Hf vs. U/Yb (a, after Grimes et al., 2015) and Th/Nb vs. Hf/Th (b, after Yang et al., 2012) for zircons of the tuffites in the Hekou Formation |
考虑到那坡地区河口组两套酸性沉凝灰岩厚度大(分别为94m和93m)、连续性好，推测其火山灰沉降区与火山口距离较近，因此排除来自Truong Son弧的可能。从火山喷发时间分析，河口组沉凝灰岩(240~236Ma)对应的火山活动要明显晚于北越Lang Son地区的酸性火山岩(252~250Ma, Halpin et al., 2016)，与凭祥酸性弧火山岩的时代一致(246~228Ma, 覃小锋等, 2011; 李政林等, 2019; Gan et al., 2021)。因此，本文认为那坡盆地河口组酸性沉凝灰岩与凭祥地区中-晚三叠世弧火山岩密切相关，记录了华南板块南缘古特提斯分支洋盆俯冲过程中的岛弧火山喷发活动。
4.3 构造意义印支造山带是由古特提斯分支洋盆(哀牢山-Song Ma-Song Chay洋盆与八布-Cao Bang洋盆)俯冲闭合、华南地块与北越、印支地块发生汇聚拼合形成的(Cai and Zhang, 2009; Metcalfe, 2013; Faure et al., 2014, 2016; Xia et al., 2021)。研究表明，哀牢山-Song Ma-Song Chay古特提斯分支洋盆自晚古生代开始向南俯冲消减(Liu et al., 2012; Faure et al., 2014, 2016; Li et al., 2021)，并于早三叠世-中三叠世早期沿Song Chay缝合带闭合，这使得印支地块东部与北越地块首先发生碰撞(图 11a)，从而导致北越地块形成大量同碰撞花岗岩(252~245Ma, Roger et al., 2012; Chen et al., 2014)和NE指向的逆冲推覆构造(Lepvrier et al., 2011)。这也使得北越地块不断向北推进，在一定程度上促进了八布-Cao Bang洋盆俯冲消减、闭合。此外，Zhang et al. (2013)测得Song Ma缝合带内的榴辉岩锆石SHRIMP U-Pb年龄为230.5±8.2Ma。Xu et al. (2019)通过对哀牢山缝合带东西两侧三叠纪碎屑岩开展了锆石U-Pb-Hf同位素详细研究，发现在中-晚三叠世之交(~237Ma)沉积物源存在明显变化。上述结果表明，华南地块与印支地块沿哀牢山-Song Ma缝合带完全碰撞拼合的时限为晚三叠世早期(图 11b)。
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图 11 华南地块南缘三叠纪构造演化模式(据Faure et al., 2014, 2016; Xiang et al., 2021修改) Fig. 11 Triassic tectonic evolution model along the southern margin of South China block (modified after Faure et al., 2014, 2016; Xiang et al., 2021) |
如前文所述，华南地块与北越地块之间的八布-Cao Bang古特提斯分支洋盆在晚石炭世-中二叠世已然形成，并于晚二叠世-中三叠世向北俯冲，形成了沿富宁-那坡-靖西-凭祥一带分布的岛弧火山岩(图 11a, 覃小锋等, 2011; Qin et al., 2012; 胡丽沙等, 2012; 刘兵等, 2018; 李政林等, 2019; Gan et al., 2021; Xiang et al., 2021; 向忠金等, 2021)及与之配套的那坡-凭祥弧前盆地沉积(宋博等, 2013, 2014; Xia et al., 2021)。然而，关于八布-Cao Bang分支洋盆闭合的时限仍不明确。前人对八布蛇绿岩中的角闪岩(变玄武岩)开展了40Ar-39Ar定年(231~230Ma, Wu et al., 1999)，结果指示其构造就位的时限为晚三叠世早期，暗示八布-Cao Bang洋盆于该时期闭合，这与哀牢山-SongMa洋盆闭合时间基本一致。但最新的研究成果表明，凭祥地区酸性岛弧火山岩的时代介于246~228Ma之间(覃小锋等, 2011; 李政林等, 2019; Gan et al., 2021)，说明在凭祥地区该分支洋盆的俯冲作用可能持续至晚三叠世。本文研究结果同样揭示，那坡盆地中三叠统河口组上部的英安质沉凝灰岩的火山物质来源于凭祥地区的岛弧火山岩，其记录的火山喷发时代(241~236Ma)与凭祥岛弧火山岩极为一致。考虑到研究区沉凝灰岩的沉积环境为深海盆地平原相，进一步暗示在那坡南部地区八布-Cao Bang洋盆于晚三叠世早期尚未闭合，该时期那坡弧前盆地南部仍处于深海环境，并持续接受沉积。
综上所述，本文推断华南地块南缘八布-Cao Bang分支洋盆是自西向东呈“剪刀”式俯冲闭合的(图 11b)，这可能受华南地块南缘不规则大陆形态的影响。具体来说，华南地块与北越地块在滇东南八布地区首先发生碰撞拼合(时代约为230Ma)，这与该区域局部出露的晚三叠世磨拉石相砾岩沉积相吻合(张斌辉等, 2019)；而在桂西南凭祥地区两者碰撞拼合可能发生在晚三叠世中晚期，这与凭祥盆地中三叠世残余弧前盆地沉积(宋博等, 2013, 2014)，以及八布-Song Hien构造带东南段上三叠统与下伏地层的不整合接触关系(Lepvrier et al., 2011)相匹配。
5 结论(1) 广西那坡盆地南部中三叠统河口组两套沉凝灰岩LA-ICP-MS锆石U-Pb年龄约为241Ma和236Ma，准确限定河口组碎屑岩属于中三叠世拉丁期沉积物，部分为晚三叠世卡尼期早期。
(2) 河口组中-晚三叠世沉凝灰岩属于亚碱性英安质，富集LREE和LILEs，具有明显的Nb、Ta和Ti负异常，结合锆石微量元素和Hf同位素特征分析，认为形成该沉凝灰岩的火山灰与俯冲作用密切相关，推测其来源于凭祥地区中-晚三叠世酸性岛弧喷发活动。
(3) 华南地块南缘八布-Cao Bang古特提斯分支洋盆于晚二叠世至晚三叠世早期向北俯冲，随后自西向东呈“剪刀”式逐渐闭合。华南地块与北越地块完全碰撞拼合的时间发生在晚三叠世中晚期。
致谢 中国地质大学(北京)时上钧、中国科学院地质与地球物理研究所硕士生张钰哲参与了野外地质调查和采样工作；样品全岩地球化学和锆石同位素测试分析得到了中国地质调查局国家地质实验测试中心和北京科荟测试技术有限公司的支持；感谢侯泉林教授和卫巍副研究员在野外调查过程中给予的指导；衷心感谢中国地质科学院地质研究所闫臻研究员、中国科学院地质与地球物理研究所张晓晖研究员及中国科学院大学地球与行星科学学院孙金凤副教授对本文提出的宝贵意见和建议。
Cai JX and Zhang KJ. 2009. A new model for the Indochina and South China collision during the Late Permian to the Middle Triassic. Tectonophysics, 467(1-4): 35-43 DOI:10.1016/j.tecto.2008.12.003
|
Carey RJ, Houghton BF and Thordarson T. 2010. Tephra dispersal and eruption dynamics of wet and dry phases of the 1875 eruption of Askja Volcano, Iceland. Bulletin of Volcanology, 72(3): 259-278 DOI:10.1007/s00445-009-0317-3
|
Chen GH and Robertson AHF. 2021. Early Miocene calc-alkaline felsic tuffs within deep-marine turbidites in the Kyrenia Range, North Cyprus, with a possible post-collisional eruptive centre in western Anatolia. Geological Magazine, 158(8): 1358-1370 DOI:10.1017/S0016756820001399
|
Chen ZC, Lin W, Faure M, Lepvrier C, van Vuong N and van Tich V. 2014. Geochronology and isotope analysis of the Late Paleozoic to Mesozoic granitoids from northeastern Vietnam and implications for the evolution of the South China block. Journal of Asian Earth Sciences, 86: 131-150 DOI:10.1016/j.jseaes.2013.07.039
|
Duan L, Meng QR, Wu GL, Yang Z, Wang JQ and Zhan RR. 2020. Nanpanjiang basin: A window on the tectonic development of South China during Triassic assembly of the southeastern and eastern Asia. Gondwana Research, 78: 189-209 DOI:10.1016/j.gr.2019.08.009
|
Fang WX, Zhang H and Jia RX. 2011. Dynamics of Triassic back-arc rift basin and its metallogenic sequence in Gejiu of Yunnan Province to Napo of Guangxi Zhuang Autonomous Region, China. Geotectonica et Metallogenia, 35(4): 552-566 (in Chinese with English abstract)
|
Faure M, Lepvrier C, van Nguyen V, van Vu T, Lin W and Chen ZC. 2014. The South China Block-Indochina collision: Where, when, and how?. Journal of Asian Earth Sciences, 79: 260-274 DOI:10.1016/j.jseaes.2013.09.022
|
Faure M, Lin W, Chu Y and Lepvrier C. 2016. Triassic tectonics of the southern margin of the South China Block. Comptes Rendus Geoscience, 348(1): 5-14 DOI:10.1016/j.crte.2015.06.012
|
Gan CS, Wang YJ, Zhang YZ, Qian X and Zhang AM. 2021. The assembly of the South China and Indochina blocks: Constraints from the Triassic felsic volcanics in the Youjiang Basin. Geological Society of America Bulletin, 133(9-10): 2097-2112 DOI:10.1130/B35816.1
|
Gao LZ, Lu JP, Ding XZ, Wang HR, Liu YX and Li J. 2013. Zircon U-Pb dating of Neoproterozoic tuff in South Gaungxi and its implications for stratigraphic correlation. Geology in China, 40(5): 1443-1452 (in Chinese with English abstract)
|
Gao LZ, Chen JS, Dai CG, Ding XZ, Wang XH, Liu YX, Wang M and Zhang H. 2014. SHRIMP zircon U-Pb dating of tuff in Fanjingshan Group and Xiajiang Group from Guizhou and Hunan provinces and its stratigraphic implications. Geological Bulletin of China, 33(7): 949-959 (in Chinese with English abstract)
|
Griffin WL, Pearson NJ, Belousova E, Jackson SE, van Achterbergh E, O'Reilly SY and Shee SR. 2000. The Hf isotope composition of cratonic mantle: LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites. Geochimica et Cosmochimica Acta, 64(1): 133-147 DOI:10.1016/S0016-7037(99)00343-9
|
Griffin WL, Wang X, Jackson SE, Pearson NJ, O'Reilly SY, Xu XS and Zhou XM. 2002. Zircon chemistry and magma mixing, SE China: In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes. Lithos, 61(3-4): 237-269 DOI:10.1016/S0024-4937(02)00082-8
|
Grimes CB, John BE, Kelemen PB, Mazdab FK, Wooden JL, Cheadle MJ, Hanghøj K and Schwartz JJ. 2007. Trace element chemistry of zircons from oceanic crust: A method for distinguishing detrital zircon provenance. Geology, 35(7): 643-646 DOI:10.1130/G23603A.1
|
Grimes CB, Wooden JL, Cheadle MJ and John BE. 2015. "Fingerprinting" tectono/magmatic provenance using trace elements in igneous zircon. Contributions to Mineralogy and Petrology, 170(5): 46
|
Guo F, Fan WM, Wang YJ and Li CW. 2004. Upper Paleozoic basalts in the southern Yangtze Block: Geochemical and Sr-Nd isotopic evidence for asthenosphere-lithosphere interaction and opening of the Paleo-Tethyan Ocean. International Geology Review, 46(4): 332-346 DOI:10.2747/0020-6814.46.4.332
|
Halpin JA, Tran HT, Lai CK, Meffre S, Crawford AJ and Zaw K. 2016. U-Pb zircon geochronology and geochemistry from NE Vietnam: A 'tectonically disputed' territory between the Indochina and South China blocks. Gondwana Research, 34: 254-273 DOI:10.1016/j.gr.2015.04.005
|
He B, Xu YG, Huang XL, Luo ZY, Shi YR, Yang QJ and Yu SY. 2007. Age and duration of the Emeishan flood volcanism, SW China: Geochemistry and SHRIMP zircon U-Pb dating of silicic ignimbrites, post-volcanic Xuanwei Formation and clay tuff at the Chaotian section. Earth and Planetary Science Letters, 255(3-4): 306-323 DOI:10.1016/j.epsl.2006.12.021
|
Hoa TT, Izokh AE, Polyakov GV, Borisenko AS, Anh TT, Balykin PA, Phuong NT, Rudnev SN, Van VV and Nien BA. 2008a. Permo-Triassic magmatism and metallogeny of northern Vietnam in relation to the Emeishan plume. Russian Geology and Geophysics, 49(7): 480-491 DOI:10.1016/j.rgg.2008.06.005
|
Hoa TT, Anh TT, Phuong NT, Dung PT, Anh TV, Izokh AE, Borisenko AS, Lan CY, Chung SL and Lo CH. 2008b. Permo-Triassic intermediate-felsic magmatism of the Truong Son belt, eastern margin of Indochina. Comptes Rendus Geoscience, 340(2-3): 112-126 DOI:10.1016/j.crte.2007.12.002
|
Hou KJ, Li YH and Tian YR. 2009. In situ U-Pb zircon dating using laser ablation-multi ion counting-ICP-MS. Mineral Deposits, 28(4): 481-492 (in Chinese with English abstract)
|
Hu LS, Du YS, Yang JH, Huang H, Huang HW and Huang ZQ. 2012. Geochemistry and tectonic significance of Middle Triassic volcanic rocks in Nalong, Guangxi area. Geological Review, 58(3): 481-494 (in Chinese with English abstract)
|
Huang H, Du YS, Huang ZQ, Yang JH, Huang HW, Xie CX and Hu LS. 2013. Depositional chemistry of chert during late Paleozoic from western Guangxi and its implication for the tectonic evolution of the Youjiang Basin. Science China (Earth Sciences), 56(3): 479-493 DOI:10.1007/s11430-012-4496-y
|
Huang TC. 1980. A volcanic sedimentation model: Implications of processes and responses of deep-sea ashes. Marine Geology, 38(1-3): 103-122 DOI:10.1016/0025-3227(80)90054-7
|
Huang ZQ, Huang H, Du YS, Yang JH, Huang HW, Hu LS and Xie CX. 2013. Depositional chemistry of cherts of the Late Paleozoic in Napo rift basin, Guangxi and its implication for the tectonic evolution. Earth Science (Journal of China University of Geosciences), 38(2): 253-265 (in Chinese with English abstract) DOI:10.3799/dqkx.2013.026
|
Jiang W, Xiang ZJ, Xia WJ, Xia L, Zhang H, Pham VT, Yan QR and Wei W. 2017. Are the mafic intrusive rocks in the Funing area, Southeast Yunnan (Southwest China), really derived from the Emeishan plume? New evidence from geological surveys of the Dongbo and Guichao sheets (1:50000). Acta Petrologica Sinica, 33(10): 3109-3122 (in Chinese with English abstract)
|
Jiang W, Yan QR, Xia WJ and Deng L. 2021. Geochronology and petrogenesis of Triassic low-Ti mafic intrusions in Funing: Implications for the tectonic evolution of Nanpanjiang Basin, SW China. Geological Journal, 56(10): 5235-5254 DOI:10.1002/gj.4234
|
Le Maitre RW, Streckeisen A, Zanettin B, Le Bas MJ, Bonin B, Bateman P, Bellieni G, Dudek A, Efremova S, Keller J, Lamere J, Sabine PA, Schmid R, Sørensen H and Woolley AR. 2002. Igneous Rocks. A Classification and Glossary of Terms. Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. 2nd Edition. Cambridge: Cambridge University Press, 1-236
|
Lehrmann DJ, Payne JL, Felix SV, Dillett PM, Wang HM, Yu YY and Wei JY. 2003. Permian-Triassic boundary sections from shallow-marine carbonate platforms of the Nanpanjiang Basin, South China: Implications for oceanic conditions associated with the end-Permian extinction and its aftermath. Palaios, 18(2): 138-152 DOI:10.1669/0883-1351(2003)18<138:PBSFSC>2.0.CO;2
|
Lehrmann DJ, Ramezani J, Bowring SA, Martin MW, Montgomery P, Enos P, Payne JL, Orchard MJ, Wang HM and Wei JY. 2006. Timing of recovery from the end-Permian extinction: Geochronologic and biostratigraphic constraints from South China. Geology, 34(12): 1053-1056 DOI:10.1130/G22827A.1
|
Lepvrier C, Faure M, Van VN, Vu TV, Lin W, Trong TT and Hoa PT. 2011. North-directed Triassic nappes in northeastern Vietnam (East Bac Bo). Journal of Asian Earth Sciences, 41(1): 56-68 DOI:10.1016/j.jseaes.2011.01.002
|
Li QL, Lin W, Wang Y, Faure M, Meng LT, Wang H, van Nguyen V, Thu HLT, Lepvrier C, Chu Y, Wei W and Van Vu T. 2021. Detrital zircon U-Pb age distributions and Hf isotopic constraints of the Ailaoshan-Song Ma Suture Zone and their paleogeographic implications for the eastern Paleo-Tethys evolution. Earth-Science Reviews, 221: 103789 DOI:10.1016/j.earscirev.2021.103789
|
Li ZL, Liu XJ, Xiao WJ, Bao HY, Shi Y, Liu L, Liao S and Qin XZ. 2019. Geochronology, geochemistry and Hf isotopes of volcanic rocks in Pingxiang area, Southwest Guangxi: Implications for the latest stage of Paleo-Tethyan ocean northward subduction. Journal of Geomechanics, 25(5): 932-946 (in Chinese with English abstract)
|
Liu B, Li XJ, Guan Q, Chen K, Chen GY, Li WK, Hu SB, Zhang H and Yu SY. 2018. The age of basic intrusive and extrusive rocks in Funing area, Southeast Yunnan Province. Geological Bulletin of China, 37(11): 2021-2031 (in Chinese with English abstract)
|
Liu HC, Peng TP and Guo XF. 2018. Geochronological and geochemical constraints on the coexistent N-MORB- and SSZ-type ophiolites in Babu area (SW China) and tectonic implications. Journal of the Geological Society, 175(4): 667-678 DOI:10.1144/jgs2017-121
|
Liu JL, Tran MD, Tang Y, Nguyen QL, Tran TH, Wu WB, Chen JF, Zhang ZC and Zhao ZD. 2012. Permo-Triassic granitoids in the northern part of the Truong Son belt, NW Vietnam: Geochronology, geochemistry and tectonic implications. Gondwana Research, 22(2): 628-644 DOI:10.1016/j.gr.2011.10.011
|
Liu TJ, Wang ZT, Wang XL, Liu XF, Ju PC and Zhong JA. 2021. The source and tectonic setting of the Changhsingian K-bentonites in the Huaying Mountain region, South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 583: 110642 DOI:10.1016/j.palaeo.2021.110642
|
Liu YS, Gao S, Hu ZC, Gao CG, Zong KQ and Wang DB. 2010. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen: U-Pb dating, Hf isotopes and trace elements in zircons from mantle xenoliths. Journal of Petrology, 51(1-2): 537-571 DOI:10.1093/petrology/egp082
|
Ludwig KR. 2012. User's Manual for Isoplot version 3.75: A geochronological toolkit for Microsoft Excel. Berkeley: Berkeley Geochronological Center, Special Publication No. 5
|
Metcalfe I. 2013. Gondwana dispersion and Asian accretion: Tectonic and palaeogeographic evolution of eastern Tethys. Journal of Asian Earth Sciences, 66: 1-33 DOI:10.1016/j.jseaes.2012.12.020
|
Pearce JA, Harris NBW and Tindle AG. 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, 25(4): 956-983 DOI:10.1093/petrology/25.4.956
|
Pi QH, Hu RZ, Peng KQ, Wu JB, Wei ZW and Huang Y. 2016. Geochronology of the Zhesang gold deposit and mafic rock in Funing County of Yunnan Province, with special reference to the dynamic background of Carlin-type gold deposits in the Dian-Qian-Gui region. Acta Petrologica Sinica, 32(11): 3331-3342 (in Chinese with English abstract)
|
Qin XF, Wang ZQ, Zhang YL, Pan LZ, Hu GA and Zhou FS. 2011. Geochronology and geochemistry of Early Mesozoic acid volcanic rocks from Southwest Guangxi: Constraints on tectonic evolution of the southwestern segment of Qinzhou-Hangzhou joint belt. Acta Petrologica Sinica, 27(3): 794-808 (in Chinese with English abstract)
|
Qin XF, Wang ZQ, Zhang YL, Pan LZ, Hu GA and Zhou FS. 2012. Geochemistry of Permian mafic igneous rocks from the Napo-Qinzhou Tectonic Belt in Southwest Guangxi, Southwest China: Implications for arc-back arc basin magmatic evolution. Acta Geologica Sinica, 86(5): 1182-1199 DOI:10.1111/j.1755-6724.2012.00740.x
|
Qiu JX. 1985. Igneous Petrology. Beijing: Geological Publishing House, 1-340 (in Chinese)
|
Roger F, Maluski H, Lepvrier C, Vu VT and Paquette JL. 2012. LA-ICPMS zircons U/Pb dating of Permo-Triassic and Cretaceous magmatisms in northern Vietnam-Geodynamical implications. Journal of Asian Earth Sciences, 48: 72-82 DOI:10.1016/j.jseaes.2011.12.012
|
Rose WI, Riley CM and Dartevelle S. 2003. Sizes and shapes of 10-Ma distal fall pyroclasts in the Ogallala Group, Nebraska. The Journal of Geology, 111(1): 115-124 DOI:10.1086/344668
|
Rudnick RL, Barth M, Horn I and McDonough WF. 2000. Rutile-bearing refractory eclogites: Missing link between continents and depleted mantle. Science, 287(5451): 278-281 DOI:10.1126/science.287.5451.278
|
Scudder RP, Murray RW, Schindlbeck JC, Kutterolf S, Hauff F, Underwood MB, Gwizd S, Lauzon R and McKinley CC. 2016. Geochemical approaches to the quantification of dispersed volcanic ash in marine sediment. Progress in Earth and Planetary Science, 3(1): 1 DOI:10.1186/s40645-015-0077-y
|
Shen SZ, Crowley JL, Wang Y, Bowring SA, Erwin DH, Sadler PM, Cao CQ, Rothman DH, Henderson CM, Ramezani J, Zhang H, Shen YN, Wang XD, Wang W, Mu L, Li WZ, Tang YG, Liu XL, Liu LJ, Zeng Y, Jiang YF and Jin YG. 2011. Calibrating the End-Permian mass extinction. Science, 334(6061): 1367-1372 DOI:10.1126/science.1213454
|
Shen SZ, Zhang H, Zhang YC, Yuan DX, Chen B, He WH, Mu L, Lin W, Wang WQ, Chen J, Wu Q, Cao CQ, Wang Y and Wang XD. 2019. Permian integrative stratigraphy and timescale of China. Science China (Earth Sciences), 62(1): 154-188 DOI:10.1007/s11430-017-9228-4
|
Song B, Yan QR, Xiang ZJ, Chen HM, Ma TQ and Yang GY. 2013. Sedimentary characteristics and tectonic setting of the Middle Triassic Pingxiang basin, Guangxi. Acta Geologica Sinica, 87(4): 453-473 (in Chinese with English abstract)
|
Song B, Yan QR, Xiang ZJ, Chen HM and Li JL. 2014. Petrography and geochemistry of clastic rocks and their constraints on the tectonic setting of the Middle Triassic Pingxiang basin, Southern Part of Guangxi. Geological Bulletin of China, 33(12): 2032-2050 (in Chinese with English abstract)
|
Sun SS and McDonough WF. 1989. Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes. In: Saunders AD and Norry MJ (eds.). Magmatism in the Ocean Basins. Geological Society, London, Special Publications, 42(1): 313-345
|
Taylor SR and McLennan SM. 1985. The Continental Crust: Its Composition and Evolution. Oxford: Blackwell, 57-114
|
Thanh NX, Hai TT, Hoang N, Lan VQ, Kwon S, Itaya T and Santosh M. 2014. Backarc mafic-ultramafic magmatism in Northeastern Vietnam and its regional tectonic significance. Journal of Asian Earth Sciences, 90: 45-60 DOI:10.1016/j.jseaes.2014.04.001
|
Tran TH, Polyakov GV, Tran TA, Borisenko AS, Izokh AE, Balykin PA, Ngo TP and Pham TD. 2016. Permian-Triassic pluton-volcanic magmatic associations in the Song Hien structure, Northeast Vietnam. In: Tran HT, Polyakov GV, Tran AT, Borisenko AS, Izokh AE, Balykin PA, Ngo TP and Pham DT (eds.). Intraplate Magmatism and Metallogeny of North Vietnam. Cham: Spring, 103-151
|
Winchester JA and Floyd PA. 1977. Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20: 325-343 DOI:10.1016/0009-2541(77)90057-2
|
Wu FY, Yang YH, Xie LW, Yang JH and Xu P. 2006. Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology. Chemical Geology, 234(1-2): 105-126 DOI:10.1016/j.chemgeo.2006.05.003
|
Wu GY, Zhong DL, Zhang Q and Ji JQ. 1999. Babu-Phu Ngu ophiolites: A geological record of Paleotethyan ocean bordering China and Vietnam. Gondwana Research, 2(4): 554-557 DOI:10.1016/S1342-937X(05)70193-3
|
Wu GY, Wu HR, Zhong DL, Kuang GD and Ji JQ. 2000. Volcanic rocks of Paleotethyan oceanic island and island-arc bordering Yunnan and Guangxi, China. Geoscience, 14(4): 393-400 (in Chinese with English abstract)
|
Wu GY, Ma L, Zhong DL, Wu HR, Ji JQ, Kuang GD and Xu KD. 2001. Indosinian Turkic-type orogen bordering Yunnan and Guangxi: With reference to coupled basin evolution. Petroleum Geology & Experiment, 23(1): 8-18 (in Chinese with English abstract)
|
Xia L, Yan QR, Xiang ZJ, Xia WJ, Shi SJ, Jiang W, Li XJ and Wei W. 2018. Olistotromes in the northern margin of the Napo forearc basin (Guangxi, South China): A special indicator for discriminating forearc domain. Acta Petrologica Sinica, 34(3): 685-700 (in Chinese with English abstract)
|
Xia L, Yan QR, Xiang ZJ, Zheng HB, Hou QL, Wei W and Xia WJ. 2021. Provenance and tectonic setting of the Triassic clastic deposits in the Napo basin, South China: Evidence from petrography, whole-rock geochemistry and detrital zircon U-Pb geochronology. Geological Magazine, 158(12): 2095-2114 DOI:10.1017/S0016756821000558
|
Xiang ZJ. 2018. Petrogenesis of Late Paleozoic to Early Mesozoic magmatic rocks in the Southwest Guangxi Province: Implication for its tectonic evolution. Ph. D. Beijing: Dissertation. University of Chinese Academy of Sciences, 1-121 (in Chinese)
|
Xiang ZJ, Yan QR, Xia L, Xia WJ and Li C. 2020. Re-Os geochronology of the Babu copper deposit in Southeast Yunnan Province and its geological implications. Acta Petrologica et Mineralogica, 39(5): 583-595 (in Chinese with English abstract)
|
Xiang ZJ, Yang JH, Yan QR, Xia L, Xia WJ and White JDL. 2021. Petrogenesis of the Early-Middle Triassic high-Mg andesitic rocks in the southern margin of the South China Block: Implications for the convergence between the South China and Indochina Blocks. Journal of Asian Earth Sciences, in press, doi. org/10.1016/j. jseaes. 2021.104994
|
Xiang ZJ, Yan QR, Xia L and Xia WJ. 2021. The tectonic setting of the Early-Middle Triassic volcanic-sedimentary succession in Funing-Napo area, the south margin of Nanpanjiang Basin, South China. Geological Bulletin of China, 40(1): 138-151 (in Chinese with English abstract)
|
Xu J, Xia XP, Lai C, Long XP and Huang C. 2019. When did the Paleotethys Ailaoshan Ocean Close: New insights from detrital zircon U-Pb age and Hf isotopes. Tectonics, 38(5): 1798-1823 DOI:10.1029/2018TC005291
|
Yang JH, Cawood PA, Du YS, Huang H and Hu LS. 2012. Detrital record of Indosinian mountain building in SW China: Provenance of the Middle Triassic turbidites in the Youjiang Basin. Tectonophysics, 574-575: 105-117 DOI:10.1016/j.tecto.2012.08.027
|
Zhang BH, Ding J, Zhang LK, Zhang B and Chen MH. 2013. SHRIMP zircon U-Pb chronology of the Babu ophiolite in southeastern Yunnan Province. Acta Geologica Sinica, 87(10): 1498-1509 (in Chinese with English abstract)
|
Zhang BH, Niu HB, Zhuo JW, Li Q, Zhang B and Lu SL. 2019. Determination of forming age of clastic rocks in the Malipo Babu area of southwestern Nanpanjiang basin and its tectonic significance. Acta Geologica Sinica, 93(9): 2187-2196 (in Chinese with English abstract)
|
Zhang H, Peng PA and Zhang WZ. 2014. Zircon U-Pb ages and Hf isotope characterization and their geological significance of Chang 7 tuff of Yanchang Formation in Ordos basin. Acta Petrologica Sinica, 30(2): 565-575 (in Chinese with English abstract)
|
Zhang RY, Lo CH, Chung SL, Grove M, Omori S, Iizuka Y, Liou JG and Tri TV. 2013. Origin and tectonic implication of ophiolite and eclogite in the song ma suture zone between the South China and Indochina Blocks. Journal of Metamorphic Geology, 31(1): 49-62 DOI:10.1111/jmg.12012
|
Zhong DL, Wu GY, Ji JQ, Zhang Q and Ding L. 1999. Discovery of ophiolite in Southeast Yunnan, China. Chinese Science Bulletin, 44(1): 36-41 DOI:10.1007/BF03182880
|
Zhou MF, Zhao JH, Qi L, Su WC and Hu RZ. 2006. Zircon U-Pb geochronology and elemental and Sr-Nd isotope geochemistry of Permian mafic rocks in the Funing area, SW China. Contributions to Mineralogy and Petrology, 151(1): 1-19 DOI:10.1007/s00410-005-0030-y
|
方维萱, 张海, 贾润幸. 2011. 滇桂个旧-那坡三叠纪弧后裂谷盆地动力学与成矿序列. 大地构造与成矿学, 35(4): 552-566. DOI:10.3969/j.issn.1001-1552.2011.04.009 |
高林志, 陆济璞, 丁孝忠, 王汉荣, 刘燕学, 李江. 2013. 桂北地区新元古代地层凝灰岩锆石U-Pb年龄及地质意义. 中国地质, 40(5): 1443-1452. DOI:10.3969/j.issn.1000-3657.2013.05.009 |
高林志, 陈建书, 戴传固, 丁孝忠, 王雪华, 刘燕学, 王敏, 张恒. 2014. 黔东地区梵净山群与下江群凝灰岩SHRIMP锆石U-Pb年龄. 地质通报, 33(7): 949-959. DOI:10.3969/j.issn.1671-2552.2014.07.002 |
侯可军, 李延河, 田有荣. 2009. LA-MC-ICP-MS锆石微区原位U-Pb定年技术. 矿床地质, 28(4): 481-492. DOI:10.3969/j.issn.0258-7106.2009.04.010 |
胡丽沙, 杜远生, 杨江海, 黄虎, 黄宏伟, 黄志强. 2012. 广西那龙地区中三叠世火山岩地球化学特征及构造意义. 地质论评, 58(3): 481-494. DOI:10.3969/j.issn.0371-5736.2012.03.009 |
黄虎, 杜远生, 黄志强, 杨江海, 黄宏伟, 谢春霞, 胡丽沙. 2013. 桂西晚古生代硅质岩地球化学特征及其对右江盆地构造演化的启示. 中国科学(地球科学), 43(2): 304-316. |
黄志强, 黄虎, 杜远生, 杨江海, 黄宏伟, 胡丽沙, 谢春霞. 2013. 广西那坡裂陷盆地晚古生代硅质岩地球化学特征及其地质意义. 地球科学(中国地质大学学报), 38(2): 253-265. |
江文, 向忠金, 夏文静, 夏磊, 张慧, Pham VT, 闫全人, 卫巍. 2017. 滇东南富宁地区基性侵入岩与峨眉山地幔柱存在成因关系吗?——来自1:5万洞波幅和皈朝幅地质填图的证据. 岩石学报, 33(10): 3109-3122. |
李政林, 刘希军, 肖文交, 鲍厚银, 时毓, 刘磊, 廖帅, 覃显著. 2019. 桂西南凭祥火山岩年代学、地球化学及Hf同位素研究——对古特提斯洋最晚北向俯冲事件的启示. 地质力学学报, 25(5): 932-946. |
刘兵, 李小军, 关奇, 陈棵, 陈光艳, 李维科, 胡绍斌, 张虎, 俞赛赢. 2018. 滇东南富宁地区基性侵入岩及喷出岩时代. 地质通报, 37(11): 2021-2031. |
皮桥辉, 胡瑞忠, 彭科强, 吴建标, 韦朝文, 黄勇. 2016. 云南富宁者桑金矿床与基性岩年代测定——兼论滇黔桂地区卡林型金矿成矿构造背景. 岩石学报, 32(11): 3331-3342. |
覃小锋, 王宗起, 张英利, 潘罗忠, 胡贵昂, 周府生. 2011. 桂西南早中生代酸性火山岩年代学和地球化学: 对钦-杭结合带西南段构造演化的约束. 岩石学报, 27(3): 794-808. |
邱家骧. 1985. 岩浆岩岩石学. 北京: 地质出版社, 1-340.
|
宋博, 闫全人, 向忠金, 陈辉明, 马铁球, 杨广元. 2013. 广西凭祥中三叠世盆地沉积特征与构造属性分析. 地质学报, 87(4): 453-473. |
宋博, 闫全人, 向忠金, 陈辉明, 李继亮. 2014. 广西南部凭祥中三叠世沉积盆地构造环境——来自岩相学和碎屑岩地球化学的证据. 地质通报, 33(12): 2032-2050. |
吴根耀, 吴浩若, 钟大赉, 邝国敦, 季建清. 2000. 滇桂交界处古特提斯的洋岛和岛弧火山岩. 现代地质, 14(4): 393-400. |
吴根耀, 马力, 钟大赉, 吴浩若, 季建清, 邝国敦, 徐克定. 2001. 滇桂交界区印支期增生弧型造山带: 兼论与造山作用耦合的盆地演化. 石油实验地质, 23(1): 8-18. |
夏磊, 闫全人, 向忠金, 夏文静, 时上钧, 江文, 李晓剑, 卫巍. 2018. 广西那坡盆地火山岩-碳酸盐岩混杂型滑塌堆积: 特殊的弧前域构造指相标志及其大地构造意义. 岩石学报, 34(3): 685-700. |
向忠金. 2018. 桂西南晚古生代-早中生代岩浆岩成因和构造属性. 博士学位论文. 北京: 中国科学院大学, 1-121
|
向忠金, 闫全人, 夏磊, 夏文静, 李超. 2020. 滇东南八布杨万铜矿床硫化物Re-Os同位素年龄及其地质意义. 岩石矿物学杂志, 39(5): 583-595. |
向忠金, 闫全人, 夏磊, 夏文静. 2021. 南盘江盆地南缘富宁-那坡地区早-中三叠世火山-沉积组合形成环境. 地质通报, 40(1): 138-151. |
张斌辉, 丁俊, 张林奎, 张彬, 陈敏华. 2013. 滇东南八布蛇绿岩的SHRIMP锆石U-Pb年代学研究. 地质学报, 87(10): 1498-1509. |
张斌辉, 牛浩斌, 卓皆文, 李卿, 张彬, 陆生林. 2019. 南盘江盆地西南缘麻栗坡八布地区碎屑岩时代的厘定及其构造意义. 地质学报, 93(9): 2187-2196. |
张辉, 彭平安, 张文正. 2014. 鄂尔多斯盆地延长组长7段凝灰岩锆石U-Pb年龄、Hf同位素组成特征及其地质意义. 岩石学报, 30(2): 565-575. |