Detrital Zircon U-Pb Geochronology and Geochemical Characteristics of Permian Sandstones in NW Laos and Its Tectonic Implications
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摘要: 老挝西北部的沉积演化历史一直未能很好地界定.因此，在老挝西北部地区出露较好的二叠纪地层中采集了4个砂岩样品，并系统开展了岩石学、地球化学和碎屑锆石U-Pb年代学的研究.岩相学表明该套样品主要包括了长石石英砂岩、岩屑砂岩和杂砂岩.全岩地球化学结果显示这些砂岩样品以高SiO2（64.9%~91.2%）、高Al2O3（5.0%~17.4%）和高CIA（59.6~89.9）为特征，说明它们经历了中等至强的风化作用.另外，样品的微量元素地球化学特征也暗示其物源主要为来自岛弧环境和活动大陆边缘的长英质岩石，并伴有少量再循环沉积物.碎屑锆石U-Pb年代学结果显示出这4个样品具有1 880~1 870 Ma、1 470~1 450 Ma、890~860 Ma、450~415 Ma和275~252 Ma的5个主要年龄峰，其中275~252 Ma为最大的沉积年龄，因此，可以将研究区地层时代限定在不早于晚二叠世.综合前人研究及与邻近盆地碎屑锆石U-Pb年龄谱系的对比，认为前志留纪的锆石大多来自于扬子板块古老基底的再循环沉积物，志留纪至二叠纪的碎屑锆石主要来源于长山带、昌宁-孟连带、临沧-素可泰岩浆岩带和邻近金三角地区，证明了印支板块北缘与思茅地块在古特提斯演化时期为一个整体，在二叠纪时期具有扬子板块的亲缘性.Abstract: The sedimentary evolution history of Northwest Laos has not been well defined. Therefore, it studied the petrology, geochemistry and detrital zircon U-Pb geochronology systematically by using four sandstone samples collected from the well-exposed strata of Permian in NW Laos. Petrography shows that this set of samples mainly includes feldspathic quartz sandstone, lithic sandstone and greywacke. Whole-rock geochemical analyses suggest that these samples are characterized by high SiO2 (64.9%-91.2%), high Al2O3 content (5.0%-17.4%) and high CIA index (59.6-89.9), indicating that they have undergone moderate to strong weathering. Moreover, the trace elements of these samples reveal that the sediment provenance includes felsic rocks from an active continental margin or continental arc with minor amounts of recycled materials. Detrital zircon U-Pb ages suggest 5 significant peaks: 1 880-1 870 Ma, 1 470-1 450 Ma, 890-860 Ma, 450-415 Ma and 275-252 Ma. The youngest age spectrum of all the detrital zircons is 275-252 Ma, which constrains the deposited age to the Late Permian. Based on our studies and comparisons through the detrital zircons from adjacent basins, it proposes that the Pre-Silurian zircons were mainly originated from the recycled sediments of the Yangtze block, the Silurian to Permian detrital zircons were originated from the Truong Son, Changning-Menglian, Lincang-Sukhothai zones and Golden Triangle region. It is proved that the northern margin of the Indochina block and Simao block was a whole during the Paleotethys evolution period. Northern Indochina block showed affinity to Yangtze block in the Permian period.
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Key words:
- Northern Laos /
- Permian /
- detrital zircon /
- provenance analysis /
- geochemistry
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0. 引言
沉积碎屑岩的矿物组分和地球化学的特征蕴含了重要的物源信息.因此，研究沉积岩的地球化学特征及其碎屑物的组成特征，有助于揭示其源区背景，进而反演大地构造环境（Nesbitt and Young, 1982）.锆石在漫长的地质历史演化过程中受后期岩浆作用、风化剥蚀和变质作用的影响较小，因此具有较高的稳定性，其U-Th-Pb同位素体系也不会受到明显的改变（Dickinson and Gehrels, 2009）.因此，碎屑锆石在物源分析、构造演化历史和限定物源区时代等研究方面具有广泛的应用（Gehrels et al., 2002；Cawood et al., 2003；Fedo et al., 2003）.例如，碎屑锆石中最年轻的年龄记录代表了最晚的一期岩浆-热事件，也可用于代表地层沉积年龄的上限（Fildani et al., 2003）.
老挝位于中南半岛中北部，北邻中国云南，东临泰国.老挝及其邻区隶属于东古特提斯构造域，发育有众多微陆块和构造带/缝合带，地质构造较为复杂（图 1），其所代表的古特提斯洋是存在于晚古生代至早中生代（中三叠世）冈瓦纳大陆和劳亚大陆之间的古洋盆，其位置与当今的印度洋和南亚等地区相当（黄汲清和陈炳蔚，1987；钟大赉，1998；Wang et al., 2018；吴福元等，2020）.其中，泰国北部的因他暖缝合带为东古特提斯洋的主缝合带，介于滇缅马苏板块和印支板块之间，向北经老挝西北部地区可以延伸至滇西南的昌宁-孟连缝合带，向南接马来半岛的文冬-劳勿缝合带（Ueno and Hisada, 2001；Feng et al., 2005；Metcalfe, 2006, 2013；Sone and Metcalfe, 2008；Qian et al., 2016, 2020；Metcalfe et al., 2017；Wang et al., 2017a, 2018）.而在该缝合带东侧的素可泰构造岩浆带是一个古特提斯岛弧系统，向北经过老挝西北部地区与临沧带相连，向南则与庄他武里和东马来西亚带相连（Sone and Metcalfe, 2008；Sone et al., 2012；Metcalfe，2013；Wang et al., 2018）.由此可见老挝北部地区是研究古特提斯构造演化和岩浆活动的关键区域.
图 1 中南半岛构造纲要简图Fig. 1. Tectonic sketch map of Indo-China Peninsula已有的研究表明，临沧-素可泰-庄他武里-东马来西亚构造岩浆带在老挝西北部地区所保留的大量火成岩与沉积岩形成于东古特提斯洋二叠-三叠纪时期的俯冲及随后的晚三叠世的滇缅马苏板块和印支板块的碰撞拼合过程（Srichan et al., 2009；Metcalfe，2013；Gardiner et al., 2016a, 2016b；Qian et al., 2016, 2017, 2020；Wang et al., 2016b, 2018）.但研究多集中于火成岩方面，并在该区识别出了与俯冲及碰撞后有关的岩浆作用（Qian et al., 2015, 2016, 2020；Rossignol et al., 2016；Ueno et al., 2018）.老挝北部地区的沉积地层研究主要集中于勐赛盆地的中生代地层.Wang et al.（2017b）认为勐赛盆地在大地构造划分上属于思茅盆地的南延，且在晚白垩世时期思茅盆地和泰国呵叻盆地距离较近并大致呈E-W向分布.而钟维敷等（2012）对老挝西北部前侏罗系地层进行研究后认为老挝西北部地区二叠纪和三叠纪地层可以和滇西南地区思茅盆地景谷小区地层序列进行对比.但是，上述研究均集中在中生代地层，而未对关键的晚古生代地层开展研究，对老挝北部晚古生代时期的沉积构造演化历史仍未能很好地界定.
因此，本文选择老挝西北部二叠纪地层中的砂岩作为研究对象，通过岩石学、全岩地球化学和碎屑锆石U-Pb年代学，试图揭示其地球化学特征和沉积年代，探讨其源区特征和构造背景，进而为印支板块北缘的构造演化研究提供新的证据.
1. 区域地质背景及样品描述
东南亚地区主要存在3个大的构造单元，分别为印支板块、素可泰地体和滇缅马苏板块，它们之间分别以难河-程逸缝合带和因他暖-清迈缝合带为界（Sone and Metcalfe, 2008；Metcalfe，2013；Wang et al., 2018）.其中难河-程逸缝合带呈南北向展布，一般认为其发育有不连续的蛇绿岩序列，并推断它代表了古特提斯洋的残余部分或弧后盆地，将素可泰地体（弧）和印支板块分隔开来（Ferrari et al., 2008；Qian et al., 2016, 2020；Yang et al., 2016）.该缝合带向北延伸主要有2种观点：一种认为其连接哀牢山缝合带，另一种认为其连接琅勃拉邦构造带和景洪弧后盆地（Ueno and Hisada, 2001；Metcalfe，2006；Qian et al., 2016, 2020；Yang et al., 2016；Wang et al., 2018, 2020）.根据晚古生代地层组合和放射虫组合关系推断其向南延伸至沙缴缝合带（Sone and Metcalfe, 2008；Sone et al., 2012；Metcalfe，2013）.琅勃拉邦-黎府带位于印支板块西缘，跨越柬埔寨泰国老挝三国，大致呈北东-南西走向，全长大于1 500 km.该缝合带发育有枕状玄武岩、玻质碎屑岩和含放射虫的层状硅质岩（Udchachon et al., 2011）.有学者认为琅勃拉邦-黎府缝合带是古特提斯洋主洋盆东北部一系列弧后盆地的残余.该缝合带与西南的难河缝合带相连，向北可延伸至哀牢山缝合带（Qian et al., 2016；Wang et al., 2020）.长山构造带位于印支板块东北部，大致呈北西-南东走向，研究程度较高，也是东南亚地区主要的成矿富集区之一（Qian et al., 2019）.
印支板块地质结构复杂，其包含了多条碰撞造山带，是经历了长期演变而形成的复合大陆（王宏等，2015）.印支板块与华南板块于早-中泥盆时拼贴（Thanh et al., 1996），两者以哀牢山缝合带和马江缝合带为界（Li et al., 2018）.传统认为印支板块与思茅地块相连（Sone and Metcalfe, 2008；Sone et al., 2012；钟维敷等，2012；Wang et al., 2014）.滇缅马苏板块由Metcalfe（1984）提出，包括中国西南部、缅甸东部、泰国西部、马来西亚半岛和苏门答腊等地区.
本次研究区域为老挝西北部地区，整体处于印支板块内，西部区域处于素可泰地体内.区内北北东向断裂发育.地质历史上该区域的发展演化主要经历了前碰撞、强烈碰撞、陆内变形和裂陷作用3个阶段.前碰撞阶段发生在晚古生代至早-中三叠纪，这一阶段形成了主动大陆边缘的岛弧；碰撞阶段发生在晚三叠至早侏罗世；陆内变形和裂陷作用阶段发生在晚白垩纪至古新世和渐新世-中新世，该阶段以伸展构造为主要形式，形成断陷盆地等（Morley，2007）.
研究区内出露的最老地层为石炭纪地层，以粉砂岩、石英砂岩、砾岩、灰色粘土岩、碳酸盐岩和透镜状煤质页岩层为代表，厚度为600~700 m.二叠纪地层被命名为康开组，主要为一套火山-陆源和碳酸盐沉积物，火山岩组合主要包括了斑状流纹岩、凝灰岩和少量安山岩，沉积岩主要包括黑色碳质页岩、杂砂岩、薄层石灰岩和黏土质页岩等，厚度大于1 000 m.老挝西北部与泰国缅甸交界的金三角地区出露有一套晚古生代-三叠纪火山岩组合，主要为安山岩、流纹岩和凝灰岩等，北边延伸至云南境内的澜沧江火山岩带，并与南边泰国境内的清孔-南邦岩浆岩带相连（Srichan et al., 2009；Qian et al., 2017）.三叠纪地层主要为陆源沉积和泥灰岩，可见部分长英质火山岩和凝灰质岩石，总厚度为1 100~1 500 m.侏罗-白垩纪地层主要为红色至红褐色的砾岩、砂岩、粉砂岩、粘土质粉砂岩和泥灰岩等，湖相泥岩和薄石膏盐层十分常见，厚度均在500~800 m.新近纪和第四纪为砾石、砂、泥土和少量玄武岩，古近纪地层缺失.研究区的地层柱状图如图 3所示.
老挝西北部地区的岩浆岩研究较少，主要集中于与成矿有关的活动之上，出露有片麻岩、花岗片麻岩和花岗岩，可能为古老的结晶基底，并分布有小规模的早三叠世花岗质侵入体，并在沙耶武里一带出露.同时，琅勃拉邦省境内可见辉长岩-辉绿岩侵入体及玄武岩等基性岩浆岩组合（Qian et al., 2016）.在老挝西北部金三角地区，广泛分布的花岗岩类被认为是晚古生代-早中生代花岗岩带的一部分，该带从滇西南延伸至缅甸东部、老挝西北部和泰国西北部地区，并进入马来半岛（Ueno et al., 2018；Qian et al., 2020）.最近Qian et al.（2020）在老挝西北部金三角地区报道了231~220 Ma的I型花岗岩，与滇西南和泰国西北部的花岗岩带年龄相仿，并认为其是在碰撞后背景的产物.
本文研究的样品主要采自老挝西北部的勐赛-金三角一线，具体采样位置见图 2和图 3，其中17NL-6A1为长石砂岩，碎屑成分主要为斜长石，含量在50%以上，岩屑含量达40%，但由于矿物粒径小于0.2 mm，肉眼难以识别岩屑为中酸性岩屑或沉积岩屑，另可见少量石英，分选磨圆较好，镜下观察具定向排列（图 4a），可能经历了后期应力作用改造，矿物较破碎；17NL-35A1为细粒石英岩屑砂岩，碎屑成分主要为石英和岩屑，石英主要以单晶石英为特征，含量约占60%，岩屑含量约为30%，基质约为10%；17NL-42A1为岩屑石英砂岩，岩屑含量较高，约为50%，石英粒径较小，含量约为40%，可见泥质成分；17NL-47A1为细粒岩屑杂砂岩，岩屑含量在50%以上，石英含量较少（图 4d）.
图 4 老挝西北部地区砂岩样品显微镜下照片Q.石英；Pl.斜长石；L.岩屑Fig. 4. Microscopic photographs for the sandstones from northwestern Laos2. 分析方法
2.1 LA-ICP-MS锆石U-Pb定年
将新鲜样品粉碎后进行重力浮选和磁力浮选，在双目显微镜下挑选出透明干净、晶型较好的锆石.选好的锆石颗粒需要固定在无色环氧树脂上，抛光镀金制成锆石靶.锆石的阴极发光图（CL图）分析在中山大学Carl ZEISS ΣIGMA场发射扫描电镜上完成，随后通过阴极发光图来观察锆石内部结构构造，以便在测试中选择点位，为后续年龄解释提供依据.锆石U-Pb同位素定年使用LA-ICP-MS，在中山大学广东省地球动力作用与地质灾害重点实验室完成，电感耦合等离子质谱仪为iCAP-RQ，激光剥蚀系统使用GeoLas2005.测试过程中使用氦气作为载气，以提高烧蚀粒子在系统中的传输效率.光斑直径为32 μm、频率为5 Hz，每个样品分析时间为90 s.选择锆石点位时需要借助CL图，尽量避开裂隙和包裹体.外标样为国际标准锆石91500（1 065 ± 5 Ma）和Plešovice（337 ± 0.4 Ma），每隔15个样品点测试两次91500和Plešovice，用以同位素分馏校正.样品分析前后以及每隔30个样品点测试两次NIST610标准锆石用作内标，用以测定锆石中U、Th、Pb等元素含量.锆石分析信号的选择及校正采用软件GLITTER4.4（Griffine et al., 2008），锆石年龄谐和图由Isoplot 3.0程序获得（Ludwig，2001），碎屑锆石年龄峰值图由程序Density Plotter获得（Vermeesch，2012）.
2.2 主-微量元素分析
首先在无污染环境下将采集的岩石样品粉碎至200目.主量元素测试使用熔片法，将样品粉末与硼酸锂熔剂于铂金坩埚中按1:10的比例混合，加入脱模剂NH4I后在950 ℃高温下烧制成玻璃片，最后在中山大学ARLTM PERFORM’X4200型X射线荧光光谱仪（XRF）上进行上机测试，分析精度优于5%，具体实验操作流程见Wang et al.（2020）.微量元素分析需要将约50 mg的全岩粉末加入聚四氟乙烯容器中，然后加入二次蒸馏的HNO3+HF混合液并在185 ℃的烘箱中溶解3 d，待溶液干燥以蒸发HF，随后加入2%硝酸将溶液稀释4 000倍并加入91×10-9的61Ni和6×10-9的Rh、In、Re内标溶液，最后在中山大学iCAP-RQ-ICP-MS和Neptune-Plus多收集质谱仪上进行上机测试.对于 > 10×10-6和 < 10 ×10-6的元素，分析精度分别优于5%和8%，过渡金属的分析精度约优于10%.样品具体的前处理方法和测试方法详见Wang et al.（2020）.
3. 分析结果
3.1 锆石U-Pb年代学
本文对老挝西北部地区4件二叠纪地层的砂岩样品（17NL-6A1、17NL-35A1、17NL-42A1、17NL-47A1）进行了锆石U-Pb年代学分析，分析结果见附表 1.锆石外观多为自形-半自形柱状，部分锆石有一定的磨圆度，说明其经历了搬运过程.在阴极发光图（图 5）下观察样品锆石多呈典型的振荡环带结构，部分锆石可见核边结构，锆石颗粒长度为50~130 μm，颜色以深灰色和褐色为主.所有锆石的Th/U比值为0.03~2.68，大部分大于0.4，结合其CL特征表明大部分的锆石为岩浆成因锆石（Hoskin，2003；吴元保和郑永飞，2004）.
图 5 代表性锆石阴极发光(CL)照片Fig. 5. Cathodoluminescence images (CL) of the representative zircon grains of samples本文研究的锆石年龄谐和度均在90%以上.对于年龄大于1 000 Ma的数据，考虑到放射性成因的Pb含量较高，故采用207Pb/206Pb的年龄数据，而相应年龄小于1 000 Ma的数据则采用206Pb/238U的年龄数据.4个砂岩样品中共获得225个符合要求的测年分析点，最年轻的锆石年龄值为252 Ma，最老的锆石年龄值为3 147 Ma.由碎屑锆石U-Pb年龄图及年龄频谱图（图 6）可以看出，4个样品在420 Ma和1 870 Ma前后都出现了强烈的峰值.除了17NL-6A1外，其余3个样品都具有~267 Ma左右的峰；17NL-35A1与其余3个样品相比明显缺少1 500~ 1 400 Ma峰期的锆石；样品17NL-35A1和17NL-42A1可见新元古代870~846 Ma的次级峰期.
图 6 老挝西北部地区二叠纪砂岩碎屑锆石U-Pb谐和图及年龄频谱图Fig. 6. U-Pb concordia diagrams and histograms of U-Pb ages of detrital zircons from study area4个砂岩样品碎屑锆石年龄频谱图（图 6）显示5个主要的年龄谱段：1 880~1 870 Ma、1 470~1 450 Ma、890~860 Ma、450~415 Ma和275~252 Ma.其中在1 880~1 870 Ma，450~415 Ma和275~252 Ma为3个强烈的峰值，对应的峰值年龄约为1 872 Ma、422 Ma和265 Ma.
3.2 全岩主微量元素特征
本次研究样品的全岩主微量元素分析结果见附表 2.来自老挝西北部地区的4个砂岩样品的主量元素变化范围较大，SiO2含量介于64.90%~91.22%，Al2O3含量为5.07%~17.39%，Fe2O3T含量为0.50%~6.80%.根据Blatt et al.（1980）所提出的砂岩分类图（图 7），本文研究的样品可以进一步划分为岩屑砂岩（17NL-35A1和17NL-42A1）、长石砂岩（17NL-6A1）和杂砂岩（17NL-47A1）.
图 7 老挝西北部地区砂岩样品主量元素分类图Fig. 7. Chemical classification diagram of sandstone samples based on major elements砂岩样品的球粒陨石标准化稀土元素图解见图 8a，所有样品的变化特征相似，均呈现明显的右倾型配分模式，轻稀土元素富集（La/Yb）N=4.90~10.88（平均值为7.14）以及重稀土元素平坦（Gd/Yb）N=1.00~1.60（平均值为1.34）.样品均具明显的Eu负异常（Eu/Eu*=0.53~0.73，平均值为0.64）和弱的Ce异常（Ce/Ce*=0.82~1.00，平均值为0.93）.砂岩样品的澳大利亚后太古代页岩（PAAS）标准化稀土元素图如图 8b所示，样品的配分模式也与大陆岛弧杂砂岩或活动大陆边缘杂砂岩相似.
图 8 老挝西北部二叠纪砂岩球粒陨石标准化(a)和澳大利亚后太古代页岩(PAAS)标准化(b)稀土元素配分图解Fig. 8. Chondrite (a) and post-Archean Australian shale (PAAS) (b) normalized rare earth element distribution patterns for the samples from study area4. 讨论
4.1 风化特征与再循环
引起碎屑沉积岩化学成分变化的因素包括了化学风化和沉积再循环等.漫长的搬运和沉积过程，矿物的分选作用以及成岩作用都会改变沉积物的粒度大小和矿物组成等特征（McLennan，1989）.当风化程度较低或近源沉积时，沉积物粒度通常较大，当风化程度较高或远源沉积时，沉积物粒度通常较小，且沉积物中的粘土矿物含量增加（Cullers et al., 1988）.因此，在利用沉积岩地球化学特征进行分析前，需要先探讨其物质源区的风化特征（Roddaz et al., 2006）.
随着化学风化程度的增加，稳定阳离子（Al3+等）倾向于富集在细粒沉积物中，而不稳定阳离子（Na+、K+、Ca2+等）则倾向于流失（Fedo et al., 1995）.Nesbitt and Young（1982）提出使用化学蚀变系数（CIA）（CIA=[Al2O3/（Al2O3+K2O+Na2O+CaO*）]×100）来衡量源区风化程度.为了去除碳酸盐和磷酸盐中的钙，McLennan et al.（1993）提出CaO*=CaO-（10/3P2O5），若校正后的CaO*摩尔数≤Na2O摩尔数，计算时采用校正后的CaO*摩尔数，反之则使用Na2O摩尔数代替CaO*摩尔数进行计算（Bock et al., 1998）.本次研究的4个砂岩样品CIA值为59.6~89.9（平均值为77.9），1个样品（17NL-47A1）风化程度较弱，其余3个样品均经历了中等至强的风化作用.另外，Cox et al.（1995）提出成分分异指数（ICV）（Fe2O3+ K2O+Na2O+CaO+MgO+TiO2）/Al2O3来衡量砂岩成熟度和原始组成，当ICV值较低时，表明岩石中的Al2O3含量相对于其他阳离子较高，可能含有较多的粘土矿物，说明样品经历了较强的风化作用，沉积物在被动构造环境下经历了再循环（Cox et al., 1995）.本次研究的4个砂岩样品ICV值为0.52~1.31（平均值为0.84），变化范围较大，表明其源区同时具有成分相对成熟的岩石和相对不成熟的岩石.
Nesbitt and Young（1982）提出了大陆风化的A-CN-K模型，该模型的原理为：UCC（大陆上地壳）向PAAS（澳大利亚后太古宙平均页岩）的风化趋势为典型的大陆初期风化趋势，大致平行于A-CN方向，其产物为伊利石等粘土矿物；而随着风化不断进行，该趋势会到达A-K连线，表明此时斜长石已被完全风化，生成钾长石和伊利石等矿物；当风化程度更为剧烈时，含钾矿物释放钾元素，风化趋势开始平行于A-K连线，逐渐向A点靠近，生成高岭石、三水铝石和绿泥石等矿物.运用A-CN-K模型对本次研究样品进行分析，可以看出有3个样品（17NL-6A1、17NL-35A1、17NL-42A1）几乎落在了A-K连线上，且对应CIA值较高，证明了这些样品经历了中等至较强的风化作用.样品17NL-47A1成分与上地壳相仿，表明其受到风化作用改造的程度较弱（图 9）.
图 9 老挝西北部地区二叠纪砂岩风化特征A-CN-K图Fig. 9. A-CN-K diagram for evaluating Permian sandstones weathering process of northwestern Laos4.2 物源特征及其构造背景
Wronkiewicz and Condie(1989)提出沉积物的Cr/Zr比值指标能反映长英质岩石在物源的参与度.本文研究样品的Cr/Zr比值为0.11~0.30(平均值为0.19)，明显小于1，表明长英质岩石物源参与度高.Cullers(1994)提出酸性岩Cr/Th比值一般集中在2.5~17.5，而本文样品的Cr/Th比值为2.57~7.29，同样表明样品的源区很可能来自酸性物源区.Bhatia and Crook(1986)认为在地质作用过程中，La、Th、Hf、Sc、Co等不活泼元素倾向于转移至碎屑物中，因此这些元素的含量和比值特征能够反映沉积物源区的信息.根据上述特征，Floyd and Leveridge(1987)提出了La/Th-Hf判别图，而本文研究的样品主要落入酸性岛弧源区及其附近区域(图 10a).而在La-Th-Sc和Th-Sc-Zr/10判别图中(图 10b和10c；Bhatia，1983；Bhatia and Crook, 1986)，本文研究的样品落入岛弧环境和活动大陆边缘区域，均指示本文研究的砂岩样品形成于活动大陆边缘环境.
图 10 老挝西北部地区二叠纪砂岩构造环境的判别图La/Th-Hf判别图(a), La-Th-Sc判别图(b), Th-Sc-Zr/10判别图(c)a.据Floyd and Leveridge(1987)；b.据Bhatia(1983)；Bhatia and Crook(1986)；c.据Bhatia(1983)；Bhatia and Crook(1986)Fig. 10. Diagrams for discriminating tectonic settings of Permian sandstones from northwestern Laos4.3 沉积年限及物源分析
碎屑锆石的年龄频谱的对比是物源分析的重要手段，两个不同地体的碎屑锆石频谱图上年龄峰值越接近，它们经历同一构造-岩浆事件的可能性越高.研究区的碎屑锆石年龄频谱图与思茅盆地（Wang et al., 2014）和勐赛盆地（Wang et al., 2017b）尽管在不同年龄峰的碎屑锆石含量上有一定区别，但都具有非常相似的年龄峰值，因此可以认为它们之间具有较高的一致性，可能在相似的沉积环境下接受了同一来源物质的供给（图 11）.古元古代碎屑锆石共85颗，在所有碎屑锆石中占比38%，可见一个主要峰期（1.89~1.56 Ga），其峰值年龄为~1.87 Ga，这部分锆石具有多环形态特征，表明它们可能是显生宙岩石的再循环，该峰值也与Wang et al.（2014）在思茅盆地白垩纪地层中砂岩样品所获的碎屑锆石年龄1.9~ 1.8 Ga相一致.区内太古代锆石共获得5个年龄，年龄从3.14~2.50 Ga，破碎明显并具较高的磨圆度，反映了长距离的搬运过程.最老的锆石年龄为3.14 Ga也与扬子克拉通变沉积岩崆岭地体的时代（3.2 Ga）相吻合（Qiu et al., 2000）.另外，陈岳龙等（2004）也在扬子西缘的康定杂岩发现了2.6~2.4 Ga的继承锆石和捕获锆石.综合岩相学分析和前文的地球化学指标，我们认为这部分古元古代锆石来自于扬子板块古老基底的再循环沉积物，经思茅盆地进入到了老挝西北部地区.
图 11 老挝西北部地区碎屑锆石U-Pb同位素年龄特征与邻区对比Fig. 11. Detrital zircon U-Pb age distribution for NW Laos region, comparing with those from Muang Xai basin (Wang et al., 2017b), Simao basin (Wang et al., 2014), western margin of South China (Xu et al., 2019) and Lhasa terrane (Leier et al., 2007)中元古代碎屑锆石共30颗，占总数的13%，可见一个明显的年龄谱段（1.5~1.4 Ga），峰值年龄在1.46 Ga左右.中元古代碎屑锆石在相邻盆地的碎屑锆石频谱图中没有形成明显的峰，目前研究也没有对印支板块~1.46 Ga的岩浆事件进行报道，表明该期碎屑物质可能是外来的，潜在来源可能为海南岛石碌群（Zhang et al., 2019）、华夏板块万全群（Yao et al., 2017）和扬子板块西南缘昆阳群黑山头组的再循环沉积物（Wang et al., 2012）.新元古代碎屑锆石共22颗，约占总数的10%，形成一个次级峰（890~860 Ma），峰值年龄为868 Ma.该期岩浆活动对应罗迪尼亚超大陆裂解事件，扬子板块向华夏板块开始俯冲.扬子板块广泛记录有该时期的岩浆活动（郑永飞，2003），如扬子板块西缘关刀山岩体的年龄在860 Ma左右（Sun et al., 2008；Du et al., 2014）.同时，Wang et al.（2012）也在扬子板块西缘埃迪卡拉系沉积物中报道了850~750 Ma的碎屑锆石年龄，因此推断这部分新元古代碎屑锆石来自于扬子板块西缘的岩浆作用和埃迪卡拉系的再循环沉积物.
古生代锆石共获得83个数据，占总体碎屑锆石的37%，年龄区间为522~252 Ma，形成了两个明显的年龄峰，即450~415 Ma和275~252 Ma，峰值年龄分别对应422 Ma和265 Ma.这两个年龄峰的锆石形态大多呈自形状，Th/U比值均大于0.2，说明这些锆石多为岩浆锆石且搬运距离相对较短.450~415 Ma的碎屑锆石属于晚奥陶世-早泥盆世锆石，这部分锆石略晚于受泛非运动影响的拉萨地体（600~500 Ma）（Leier et al., 2007），而与加里东时期的岩浆活动吻合，代表了原特提斯洋的俯冲-闭合事件（Ba et al., 2018）.这部分奥陶世-泥盆世锆石的潜在来源可能为Wang et al.（2016a）和Wang et al.（2021）在老挝东北部长山缝合带发现的446~404 Ma的花岗岩.
275~252 Ma的碎屑锆石均属于二叠纪岩浆成因锆石，这部分锆石代表了研究区地层的最大沉积年龄，将其沉积时代限定为不早于晚二叠世.另外，该年龄谱段在265 Ma处形成了一个强烈的峰值，对应的构造-热事件为东古特提斯洋的持续俯冲过程（范蔚茗等，2009；Wang et al., 2018），这部分二叠纪碎屑锆石指示了素可泰-临沧弧存在古特提斯洋闭合前的弧岩浆作用.金沙江-哀牢山缝合带、昌宁-孟连缝合带、因他暖、琅勃拉邦-黎府缝合带、难河-程逸缝合带、素可泰-临沧弧等地均保存有大量与古特提斯洋演化有关的火成岩记录（Wang et al., 2018）.Fan et al.（2010）对哀牢山构造带西侧雅轩桥玄武质安山岩报道了265 ± 7 Ma的年龄，且地球化学特征具有岛弧特征，认为其形成环境与哀牢山洋盆壳的俯冲消减相关.Jian et al.（2009）在昌宁-孟连带识别出了270~264 Ma的蛇绿岩套，指示古特提斯洋俯冲事件.另外，Deng et al.（2018）在昌宁-孟连缝合带的临沧岩体报道了261 Ma和252 Ma的年龄，认为古特提斯洋在252 Ma前持续俯冲.Gardiner et al.（2016b）在缅甸的大其力花岗岩体报道了265.8 ± 2.1 Ma的年龄，限定了素可泰岩浆带在缅甸东部的位置.这些地区都可能为研究区的二叠纪碎屑锆石提供潜在的物源.晚二叠世-早三叠世古特提斯洋支洋盆相继俯冲-闭合，形成马江、黎府、难河-程逸等缝合带（Wang et al., 2018），并使得印支地块（素可泰火山弧、思茅-呵叻地块和长山地块）与扬子-华南陆块拼合到统一的陆内环境中，印证了印支板块北缘是思茅盆地在大地构造上的南延的观点.
通过碎屑锆石年龄频谱图的对比发现（图 11），老挝西北部勐赛-金三角地区二叠纪砂岩碎屑锆石主要具有1 880~1 870 Ma、1 470~1 450 Ma、890~860 Ma、450~415 Ma和275~252 Ma的年龄峰值，缺乏冈瓦纳南大陆泛非构造事件的特征年龄峰值（如~550 Ma、~900 Ma、~1 100 Ma）（Leier et al., 2007）.与此同时，华南板块广泛报道的加里东期（~440 Ma）构造岩浆事件（Wang et al., 2013）和新元古代的岩浆活动事件（~860~ 750 Ma）（郑永飞，2003）在研究区的碎屑锆石年龄频谱图均有所体现.结合扬子板块西缘的~1.8 Ga和~2.4 Ga的碎屑锆石记录（Xu et al., 2019），本文认为老挝西北部的基底更接近于扬子板块而非冈瓦纳大陆，与扬子板块具有亲缘性.
5. 主要结论
（1）老挝西北部二叠纪砂岩样品主要来自于以长英质岩石为代表的中酸性物源和再循环沉积物源，其构造背景为活动大陆边缘或岛弧环境.
（2）老挝西北部二叠纪砂岩的碎屑锆石的最小年龄为252 Ma，对应晚二叠世，将其沉积时代限定为不早于晚二叠世.
（3）样品前志留纪的锆石主要来源为扬子板块的再循环沉积物，而450~415 Ma和275 ~252 Ma的锆石则主要来自长山带、昌宁-孟连带、临沧-素可泰岩浆带以及邻近的金三角地区，指示素可泰地区在晚二叠世存在岛弧岩浆作用.碎屑锆石频谱图显示老挝西北部在二叠纪时是思茅盆地在大地构造上的南延，具有亲扬子板块的特征.
附表见本刊官网（http://www.earth-science.net）.
致谢: 野外样品采集得到了何慧莹博士的帮助；实验测试分析方面得到了甘成势、王玉琨和杨雪博士的建议和帮助；审稿老师和编辑部老师对本文的修改提出了宝贵的意见；在此一并致以诚挚谢意！ -
图 1 中南半岛构造纲要简图
修改自Sone and Metcalfe（2008）；Wang et al.（2018）；Qian et al.（2020）；审图号为GS（2021）5443号
Fig. 1. Tectonic sketch map of Indo-China Peninsula
图 4 老挝西北部地区砂岩样品显微镜下照片
Q.石英；Pl.斜长石；L.岩屑
Fig. 4. Microscopic photographs for the sandstones from northwestern Laos
图 5 代表性锆石阴极发光(CL)照片
Fig. 5. Cathodoluminescence images (CL) of the representative zircon grains of samples
图 6 老挝西北部地区二叠纪砂岩碎屑锆石U-Pb谐和图及年龄频谱图
Fig. 6. U-Pb concordia diagrams and histograms of U-Pb ages of detrital zircons from study area
图 7 老挝西北部地区砂岩样品主量元素分类图
Fig. 7. Chemical classification diagram of sandstone samples based on major elements
图 8 老挝西北部二叠纪砂岩球粒陨石标准化(a)和澳大利亚后太古代页岩(PAAS)标准化(b)稀土元素配分图解
球粒陨石标准值引自Sun and McDonough（1989）；PAAS据Taylor and McLennan（1985）；大陆岛弧杂砂岩和活动大陆边缘杂砂岩数据来自Bhatia（1986）
Fig. 8. Chondrite (a) and post-Archean Australian shale (PAAS) (b) normalized rare earth element distribution patterns for the samples from study area
图 9 老挝西北部地区二叠纪砂岩风化特征A-CN-K图
Fig. 9. A-CN-K diagram for evaluating Permian sandstones weathering process of northwestern Laos
图 10 老挝西北部地区二叠纪砂岩构造环境的判别图La/Th-Hf判别图(a), La-Th-Sc判别图(b), Th-Sc-Zr/10判别图(c)
a.据Floyd and Leveridge(1987)；b.据Bhatia(1983)；Bhatia and Crook(1986)；c.据Bhatia(1983)；Bhatia and Crook(1986)
Fig. 10. Diagrams for discriminating tectonic settings of Permian sandstones from northwestern Laos
图 11 老挝西北部地区碎屑锆石U-Pb同位素年龄特征与邻区对比
Fig. 11. Detrital zircon U-Pb age distribution for NW Laos region, comparing with those from Muang Xai basin (Wang et al., 2017b), Simao basin (Wang et al., 2014), western margin of South China (Xu et al., 2019) and Lhasa terrane (Leier et al., 2007)
-
Ba, J., Zhang, L., He, C., et al., 2018. Zircon and Monazite Ages Constraints on Devonian Magmatism and Granulite-Facies Metamorphism in the Southern Qaidam Block: Implications for Evolution of Proto-and Paleo-Tethys in East Asia. Journal of Earth Science, 29(5): 1132-1150. https://doi.org/10.1007/s12583-018-0853-x Bhatia, M.R., 1983. Plate Tectonics and Geochemical Composition of Sandstones. The Journal of Geology, 91(6): 611-627. doi: 10.1086/628815 Bhatia, M. R., Crook, K. A. W., 1986. Trace Element Characteristics of Graywackes and Tectonic Setting Discrimination of Sedimentary Basins. Contributions to Mineralogy and Petrology, 92(2): 181-193. https://doi.org/10.1007/BF00375292 Blatt, H., Middleton, G.V., Murray, R.C., 1980. Origin of Sedimentary Rocks. Pretice-Hall, New Jersey. Bock, B., McLennan, S.M., Hanson, G.N., 1998. Geochemistry and Provenance of the Middle Ordovician Austin Glen Member (Normanskill Formation) and the Taconian Orogeny in New England. Sedimentology, 45: 635-655. doi: 10.1046/j.1365-3091.1998.00168.x Cawood, P.A., Nemchin, A.A., Freeman, M., et al., 2003. Linking Source and Sedimentary Basin: Detrital Zircon Record of Sediment Flux along a Modern River System and Implications for Provenance Studies. Earth and Planetary Science Letters, 210: 259-268. doi: 10.1016/S0012-821X(03)00122-5 Chen, Y.L., Luo, Z.H., Zhao, J.X., et al., 2004. Genesis of the Mianning Kangding Complex in Sichuan Province from Zircon SHRIMP Age and Petrogeochemical Characteristic. Science in China (Series D: Earth Sciences), 34(8): 687-697 (in Chinese). Cox, R., Lowe, D.R., Cullers, R.L., 1995. The Influence of Sediment Recycling and Basement Composition on Evolution of Mudrock Chemistry in the Southwestern United States. Geochimica et Cosmochimica Acta, 59: 2919-2940. doi: 10.1016/0016-7037(95)00185-9 Cullers, R.L., 1994. The Controls on the Major and Trace Element Variation of Shale, Siltstone and Sandstone of Pennsylvanian-Permian Age from Uplifted Continental Blocks in Colorado to Platform Sediments in Kansas, U.S.A. . Geochimica et Cosmochimica Acta, 58: 4955-4972. doi: 10.1016/0016-7037(94)90224-0 Cullers, R.L., Basu, A., Suttner, L.J., 1988. Geochemical Signature of Provenance in Sand-Size Material in Soils and Stream Sediments near the Tobacco Root Batholith, Montana, U.S.A. . Chemical Geology, 70(4): 335-348. doi: 10.1016/0009-2541(88)90123-4 Deng, J., Wang, C.M., Zi, J.W., et al., 2018. Constraining Subduction-Collision Processes of the Paleo-Tethys along the Changning-Menglian Suture: New Zircon U-Pb Ages and Sr-Nd-Pb-Hf-O Isotopes of the Lincang Batholith. Gondwana Research, 62: 75-92. doi: 10.1016/j.gr.2017.10.008 Dickinson, W. R., Gehrels, G. E., 2009. Use of U-Pb Ages of Detrital Zircons to Infer Maximum Depositional Ages of Strata: A Test against a Colorado Plateau Mesozoic Database. Earth and Planetary Science Letters, 288(1/2): 115-125. http://www.sciencedirect.com/science?_ob=ShoppingCartURL&_method=add&_eid=1-s2.0-S0012821X09005469&originContentFamily=serial&_origin=article&_ts=1493864661&md5=de8d075e418b9ca85f230e9f3efcc2d9 Du, L. L, Guo, J.H., Nutman, A.P., et al., 2014. Implications for Rodinia Reconstructions for the Initiation of Neoproterozoic Subduction at~860 Ma on the Western Margin of the Yangtze Block: Evidence from the Guandaoshan Pluton. Lithos, 196-197: 67-82. doi: 10.1016/j.lithos.2014.03.002 Fan, W.M., Peng, T.P., Wang, Y.J., 2009. Triassic Magmatism in the Southern Lancangjiang Zone, Southwestern China and Its Constraints on the Tectonic Evolution of Paleo-Tethys. Earth Science Frontiers, 16(6): 291-302 (in Chinese with English abstract). Fan, W.M., Wang, Y.J., Zhang, A.M., et al., 2010. Permian Arc-back-Arc Basin Development along the Ailaoshan Tectonic Zone: Geochemical, Isotopic and Geochronological Evidence from the Mojiang Volcanic Rocks, Southwest China. Lithos, 119: 553-568. doi: 10.1016/j.lithos.2010.08.010 Fedo, C.M., Nesbitt, H.W., Young, G.M., et al., 1995. Unraveling the Effects of Potassium Metasomatism in Sedimentary Rocks and Paleosols, with Implications for Paleoweathering Conditions and Provenance. Geology, 23: 921-924. doi: 10.1130/0091-7613(1995)023<0921:UTEOPM>2.3.CO;2 Fedo, C.M., Sircombe, K.N., Rainbird, R.G., 2003. Detrital Zircon Analysis of the Sedimentary Record. Reviews in Mineralogy and Geochemistry, 53: 277-303. doi: 10.2113/0530277 Feng, Q.L., Chonglakmani, C., Helmcke, D., et al., 2005. Correlation of Triassic Stratigraphy between the Simao and Lampang-Phrase Basins: Implications for the Tectonopaleogeography of Southeast Asia. Journal of Asian Earth Sciences, 24: 777-785. doi: 10.1016/j.jseaes.2004.11.008 Ferrari, O.M., Hochard, C., Stampfli, G.M., 2008. An Alternative Plate Tectonic Model for the Paleozoic-Early Mesozoic Paleotethyan Evolution of Southeast Asia (Northern Thailand-Burma). Tectonophysics, 451: 346-365. doi: 10.1016/j.tecto.2007.11.065 Fildani, A., Cope, T.D., Graham, S.A., et al., 2003. Initiation of the Magallanes Foreland Basin: Timing of the Southernmost Patagonian Andes Orogeny Revised by Detrital Zircon Provenance Analysis. Geology, 31(12): 1081-1084. doi: 10.1130/G20016.1 Floyd, P.A., Leveridge, B.E., 1987. Tectonic Environment of the Devonian Gramscatho Basin, South Cornwall: Framework Mode and Geochemical Evidence from Turbiditic Sandstones. Journal of the Geological Society, 144(4): 531-542. doi: 10.1144/gsjgs.144.4.0531 Gardiner, N.J., Roberts, N.M.W., Morley, C.K., et al., 2016a. Did Oligocene Crustal Thickening Precede Basin Development in Northern Thailand? A Geochronological Reassessment of DoiInthanon and DoiSuthep. Lithos, 240-243: 69-83. doi: 10.1016/j.lithos.2015.10.015 Gardiner, N.J., Searle, M.P., Morley, C.K., et al., 2016b. The Closure of Palaeo-Tethys in Eastern Myanmar and Northern Thailand: New Insights from Zircon U-Pb and Hf Isotope Data. Gondwana Research, 39: 401-422. doi: 10.1016/j.gr.2015.03.001 Gehrels, G.E., Stewart, J.H., Ketner, K.B., 2002. Cordilleran-Margin Quartzites in Baja California-Implications for Tectonic Transport. Earth and Planetary Science Letters, 199: 201-210. doi: 10.1016/S0012-821X(02)00542-3 Griffine, W.L., Powell, W.J., Pearson, N.J., et al., 2008. GLITTER: Data Reduction Software for Laser Ablation ICP-MS. Laser Ablatio-ICP-MS in the Earth Sciences. Mineral. Assoc. Canada Short Curse Series, 40: 204-207. http://ci.nii.ac.jp/naid/20001269558 Hoskin, P.W.O., 2003. The Composition of Zircon and Igneous and Metamorphic Petrogenesis. Reviews in Mineralogy and Geochemistry, 53(1): 27-62. doi: 10.2113/0530027 Huang, J.Q., Chen, B.W., 1987. Evolution of the Tethys Sea in China and Its Adjacent Regions. Geological Publishing House, Beijing (in Chinese). Jian, P., Liu, D.Y., Kröner, A., et al., 2009. Devonian to Permian Plate Tectonic Cycle of the Paleo-Tethys Orogen in Southwest China (Ⅱ): Insights from Zircon Ages of Ophiolites, Arc/Back-Arc Assemblages and Within-Plate Igneous Rocks and Generation of the Emeishan CFB Province. Lithos, 113: 767-784. doi: 10.1016/j.lithos.2009.04.006 Leier, A.L., Kapp, P., Gehrels, G.E., et al., 2007. Detrital Zircon Geochronology of Carboniferous-Cretaceous Strata in the Lhasa Terrane, Southern Tibet. Basin Research, 19: 361-378. https://doi.org/10.1111/j.1365-2117.2007.00330.x Li, S. B., He, H. Y., Qian, X., et al., 2018. Carboniferous Arc Setting in Central Hainan: Geochronological and Geochemical Evidences on the Andesitic and Dacitic Rocks. Journal of Earth Science, 29(2): 265-279. doi: 10.1007/s12583-017-0936-0 Ludwig, K.R., 2001. Using Isoplot/EX, Version 2.49. In: A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronological Center Special Publication, Berkeley, 1-55. McLennan, S.M., 1989. Rare Earth Elements in Sedimentary Rocks: Influence of Provenance and Sedimentary Processes. Mineralogical Society of America Reviews in Mineralogy, 21: 169-200. http://www.researchgate.net/publication/303145235_Rare_earth_elements_and_sedimentary_rocks_influence_of_provenance_and_sedimentary_processes McLennan, S.M., Hemming, S., McDaniel, D.K., et al., 1993. Geochemical Approaches to Sedimentation, Provenance, and Tectonics. Special Paper of the Geological Society of America, 284: 21-40. doi: 10.1130/SPE284 Metcalfe, I., 1984. Southeast Asia. Publication-International Union of Geological Sciences, 16: 213-243. Metcalfe, I., 2000. The Bentong-Raub Suture Zone. Journal of Asian Earth Sciences, 18: 691-712. doi: 10.1016/S1367-9120(00)00043-2 Metcalfe, I., 2006. Paleozoic and Mesozoic Tectonic Evolution and Paleogeography of East Asian Crustal Fragments: The Korean Peninsula in Context. Gondwana Research, 9: 24-46. doi: 10.1016/j.gr.2005.04.002 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 Metcalfe, I., Henderson, C.M., Wakita, K., 2017. Lower Permian Conodonts from Palaeo-Tethys Ocean Plate Stratigraphy in the Chiang Mai-Chiang Rai Suture Zone, Northern Thailand. Gondwana Research, 44: 54-66. doi: 10.1016/j.gr.2016.12.003 Morley, C.K., 2007. Variation in Late Cenozoic-Recent Strike-Slip and Oblique-Exetensional Geometries, within Indochina: The Influence of Pre-Existing Fabrics. Journal of Structural Geology, 29: 405-437. http://www.sciencedirect.com/science?_ob=ShoppingCartURL&_method=add&_eid=1-s2.0-S019181410600174X&originContentFamily=serial&_origin=article&_ts=1475093625&md5=15918bcc1d4d48fae0a3c0679e00f408 Nesbitt, H.W., Young, G.M., 1982. Early Proterozoic Climates and Plate Motions Inferred from Major Element Chemistry of Lutites. Nature, 299(5885): 715-717. doi: 10.1038/299715a0 Qian, X., Feng, Q.L., Wang, Y.J., et al., 2016. Geochronological and Geochemical Constraints on the Mafic Rocks along the Luang Prabang Zone: Carboniferous Back-Arc Setting in Northwest Laos. Lithos, 245: 60-75. doi: 10.1016/j.lithos.2015.07.019 Qian, X., Feng, Q.L., Yang, W.Q., et al., 2015. Arc-Like Volcanic Rocks in NW Laos: Geochronological and Geochemical Constraints and Their Tectonic Implications. Journal of Asian Earth Sciences, 98: 342-357. doi: 10.1016/j.jseaes.2014.11.035 Qian, X., Wang, Y.J., Srithai, B., et al., 2017. Geochronological and Geochemical Constraints on the Intermediate-Acid Volcanic Rocks along the Chiang Khong-Lampang-Tak Igneous Zone in NW Thailand and Their Tectonic Implications. Gondwana Research, 45: 87-99. doi: 10.1016/j.gr.2016.12.011 Qian, X., Wang, Y.J., Zhang, Y.Z., et al., 2019. Petrogenesis of Permian-Triassic Felsic Igneous Rocks along the Truong Son Zone in Northern Laos and Their Paleotethyan Assembly. Lithos, 328-329: 101-114. doi: 10.1016/j.lithos.2019.01.006 Qian, X., Wang, Y.J., Zhang, Y.Z., et al., 2020. Late Triassic Post-Collisional Granites Related to Paleotethyan Evolution in Northwestern Lao PDR: Geochronological and Geochemical Evidence. Gondwana Research, 84: 163-176. doi: 10.1016/j.gr.2020.03.002 Qiu, Y.M., Gao, S., McNaughton, N.J., et al., 2000. First Evidence of >3.2 Ga Continental Crust in the Yangtze Craton of South China and Its Implications for Archean Crustal Evolution and Phanerozoic Tectonics. Geology, 28: 11-14. doi: 10.1130/0091-7613(2000)028<0011:FEOGCC>2.0.CO;2 Roddaz, M., Viers, J., Brusset, S., et al., 2006. Controls on Weathering and Provenance in the Amazonian Foreland Basin: Insights from Major and Trace Element Geochemistry of Neogene Amazonian Sediments. Chemical Geology, 226: 31-45. doi: 10.1016/j.chemgeo.2005.08.010 Rossignol, C., Bourquin, S., Poujol, M., et al., 2016. The Volcaniclastic Series from the Luang Prabang Basin, Laos: A Witness of a Triassic Magmatic Arc?. Journal of Asian Earth Sciences, 120: 159-183. doi: 10.1016/j.jseaes.2016.02.001 Sone, M., Metcalfe, I., 2008. Parallel Tethyan Sutures in Mainland SE Asia: New Insights for Paleo-Tethys Closure and Implications for the Indosinian Orogeny. Comptes Rendus Geoscience, 340: 166-179. doi: 10.1016/j.crte.2007.09.008 Sone, M., Metcalfe, I., Chaodumrong, P., 2012. The Chanthaburi Terrane of Southeastern Thailand: Stratigraphic Confrmation as a Disrupted Segment of the Sukhothai Arc. Journal of Asian Earth Sciences, 61: 16-32. doi: 10.1016/j.jseaes.2012.08.021 Srichan, W., Crawford, A.J., Berry, R.F., 2009. Geochemistry and Geochronology of Late Triassic Volcanic Rocks in the Chiang Khong Region, Northern Thailand. Island Arc, 18: 32-51. doi: 10.1111/j.1440-1738.2008.00660.x 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. doi: 10.1144/GSL.SP.1989.042.01.19 Sun, W.H., Zhou, M.F., Yan, D.P., et al., 2008. Provenance and Tectonic Setting of the Neoproterozoic Yanbian Group, Western Yangtze Block (SW China). Precambrian Research, 167: 213-236. doi: 10.1016/j.precamres.2008.08.001 Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution, an Examination of the Geochemical Record Preserved in Sedimentary Rocks. Blackwell Scientific Publication, Berkeley. Thanh, T.D., Janvier, P., Phuong, T.H., 1996. Fish Suggests Continental Connections between the Indochina and South China Blocks in Middle Devonian Time. Geology, 24: 571-574. doi: 10.1130/0091-7613(1996)024<0571:FSCCBT>2.3.CO;2 Udchachon, M., Thassanapak, H., Feng, Q. L., et al., 2011. Geochemical Constraints on the Depositional Environment of Upper Devonian Radiolarian Cherts from Loei, North-Eastern Thailand. Frontiers of Earth Science, 5(2): 178-190. https://doi.org/10.1007/s11707-011-0153-6 Ueno, K., Hisada, K., 2001. The Nan-Uttaradit-Sa Kaeo Suture as a Main Paleotethyan Suture in Thailand: Is It Real?. Gondwana Research, 4: 804-806. doi: 10.1016/S1342-937X(05)70590-6 Ueno, K., Kamata, Y., Uno, K., et al., 2018. The Sukhothai Zone (Permian-Triassic Island-Arc Domain of Southeast Asia) in Northern Laos: Insights from Triassic Carbonates and Foraminifers. Gondwana Research, 61: 88-99. doi: 10.1016/j.gr.2018.04.013 Vermeesch, P., 2012. On the Visualisation of Detrital Age Distributions. Chemical Geology, 312: 190-194. http://www.ucl.ac.uk/~ucfbpve/papers/VermeeschChemGeol2012.pdf Wang, H., Lin, F.C., Li, X.Z., et al., 2015. The Division of Tectonic Units and Tectonic Evolution in Laos and Its Adjacent Regions. Geology in China, 42(1): 71-84 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DIZI201501005.htm Wang, L.C., Liu, C.L., Gao, X., et al., 2014. Provenance and Paleogeography of the Late Cretaceous Mengyejing Formation, Simao Basin, Southeastern Tibetan Plateau: Whole-Rock Geochemistry, U-Pb Geochronology, and Hf Isotopic Constraints. Sedimentary Geology, 304: 44-58. doi: 10.1016/j.sedgeo.2014.02.003 Wang, L.J., Yu, J.H., Griffin, W.L., et al., 2012. Early Crustal Evolution in the Western Yangtze Block: Evidence from U-Pb and Lu-Hf Isotopes on Detrital Zircons from Sedimentary Rocks. Precambrian Research, 222-223: 368-385. doi: 10.1016/j.precamres.2011.08.001 Wang, S.F., Mo, Y.S., Wang, C., et al., 2016a. Paleotethyan Evolution of the Indochina Block as Deduced from Granites in Northern Laos. Gondwana Research, 38: 183-196. doi: 10.1016/j.gr.2015.11.011 Wang, Y.J., He, H.Y., Cawood, P.A., et al., 2016b. Geochronological, Elemental and Sr-Nd-Hf-O Isotopic Constraints on the Petrogenesis of the Triassic Post-Collisional Granitic Rocks in NW Thailand and Its Paleotethyan Implications. Lithos, 266-267: 264-286. doi: 10.1016/j.lithos.2016.09.012 Wang, Y.J., Fan, W.M., Zhang, G.W., et al., 2013. Phanerozoic Tectonics of the South China Block: Key Observations and Controversies. Gondwana Research, 23: 1273-1305. doi: 10.1016/j.gr.2012.02.019 Wang, Y.J., He, H.Y., Zhang, Y.Z., et al., 2017a. Origin of Permian OIB-Like Basalts in NW Thailand and Implication on the Paleotethyan Ocean. Lithos, 274-275: 93-105. doi: 10.1016/j.lithos.2016.12.021 Wang, Y. L., Wang, L. C., Wei, Y. S., et al., 2017b. Provenance and Paleogeography of the Mesozoic Strata in the Muang Xai Basin, Northern Laos: Petrology, Whole-Rock Geochemistry, and U-Pb Geochronology Constraints. International Journal of Earth Sciences, 106(4): 1409-1427. https://doi.org/10.1007/s00531-017-1469-6 Wang, Y.J., Qian, X., Cawood, P.A., et al., 2018. Closure of the East Paleotethyan Ocean and Amalgamation of the Eastern Cimmerian and Southeast Asia Continental Fragments. Earth-Science Reviews, 186: 195-230. doi: 10.1016/j.earscirev.2017.09.013 Wang, Y.J., Yang, T.X., Zhang, Y.Z., et al., 2020. Late Paleozoic Back-Arc Basin in the Indochina Block: Constraints from the Mafic Rocks in the Nan and Luang Prabang Tectonic Zones, Southeast Asia. Journal of Asian Earth Sciences, 195: 1-20. http://www.sciencedirect.com/science/article/pii/S1367912020301140 Wang, Y.J., Zhang, Y.Z., Qian, X., et al., 2021. Ordo-Silurian Assemblage in the Indochina Interior: Geochronological, Elemental, and Sr-Nd-Pb-Hf-O Isotopic Constraints of Early Paleozoic Granitoids in South Laos. Geological Society of America Bulletin, 133(1-2): 325-346. doi: 10.1130/B35605.1 Wronkiewicz, D.J., Condie, K.C., 1989. Geochemistry and Provenance of Sediments from the Pongola Supergroup, South Africa: Evidence for a 3.0-Ga-Old Continental Craton. Geochimica et Cosmochimica Acta, 53(7): 1537-1549. doi: 10.1016/0016-7037(89)90236-6 Wu, F.Y., Wan, B., Zhao, L., et al., 2020. Tethyan Geodynamics. Acta Petrologica Sinica, 36(6): 1627-1674 (in Chinese with English abstract). doi: 10.18654/1000-0569/2020.06.01 Wu, Y. B., Zheng, Y. F., 2004. Mineralogical Study of Zircon Genesis and Its Constraints on U-Pb Age Interpretation. Chinese Science Bulletin, 49(16): 1589-1604 (in Chinese). doi: 10.1360/csb2004-49-16-1589 Xu, J., Xia, X.P., Lai, C.K., et al., 2019. When Did the Paleotethys Ailaoshan Ocean Close: New Insights from Detrital Zircon U-Pb Age and Hf Isotopes. Tectonics, 38: 1798-1823. doi: 10.1029/2018TC005291 Yang, W.Q., Qian, X., Feng, Q.L., et al., 2016. Zircon U-Pb Geochronologic Evidence for the Evolution of Nan-Uttaradit Suture Zone in Northern Thailand. Journal of Asian Earth Sciences, 27: 378-390. http://kns.cnki.net/KCMS/detail/detail.aspx?dbcode=CJFD&filename=ZDDY201603004 Yao, J.L., Shu, L.S., Cawood, P.A., et al., 2017. Constraining Timing and Tectonic Implications of Neoproterozoic Metamorphic Event in the Cathaysia Block, South China. Precambrian Research, 293: 1-12. doi: 10.1016/j.precamres.2017.01.032 Zhang, L.M., Zhang, Y.Z., Cui, X., et al., 2019. Mesoproterozoic Rifting of SW Hainan Revealed from Gneissic Granites and Metasedimentary Rocks in the Baoban Complex. Precambrian Research, 325: 69-87. doi: 10.1016/j.precamres.2019.02.013 Zheng, Y. F., 2003. Neoproterozoic Magmatism and Global Change. Chinese Science Bulletin, 48(16): 1705-1720 (in Chinese). doi: 10.1360/csb2003-48-16-1705 Zhong, D.L., 1998. The Gutethys Orogenic Belt in Western Yunnan and Sichuan. Science Press, Beijing, 1-231 (in Chinese). Zhong, W.F., Feng, Q.L., Chonglakmani, C., et al., 2012. Permian Triassic Stratigraphic Correlation between Laos and Yunnan and Its Tectonic Significance. Earth Science, 37(S2): 73-80 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DQKX2012S2015.htm 陈岳龙, 罗照华, 赵俊香, 等, 2004. 从锆石SHRIMP年龄及岩石地球化学特征论四川冕宁康定杂岩的成因. 中国科学(D辑: 地球科学), 34(8): 687-697. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK200408000.htm 范蔚茗, 彭头平, 王岳军, 2009. 滇西古特提斯俯冲-碰撞过程的岩浆作用记录. 地学前缘, 16(6): 291-302. doi: 10.3321/j.issn:1005-2321.2009.06.031 黄汲清, 陈炳蔚, 1987. 中国及邻区特提斯海的演化. 北京: 地质出版社. 王宏, 林方成, 李兴振, 等, 2015. 老挝及邻区构造单元划分与构造演化. 中国地质, 42(1): 71-84. doi: 10.3969/j.issn.1000-3657.2015.01.006 吴福元, 万博, 赵亮, 等, 2020. 特提斯地球动力学. 岩石学报, 36(6): 1627-1674. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB202006001.htm 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 郑永飞, 2003. 新元古代岩浆活动与全球变化. 科学通报, 48(16): 1705-1720. doi: 10.3321/j.issn:0023-074X.2003.16.001 钟大赉, 1998. 滇川西部古特提斯造山带. 北京: 科学出版社, 1-231. 钟维敷, 冯庆来, Chonglakmani, C., 等, 2012. 老挝与云南二叠纪三叠纪地层对比及其构造意义. 地球科学, 37(S2): 73-80. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX2012S2015.htm 期刊类型引用(7)
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