青藏中‒南部特提斯洋板块地层分布与演化

Distribution and Evolution of the Tethyan OPS in the Central⁃Southern Qinghai⁃Xizang Region

摘要

青藏高原造山域经历了原特提斯、古特提斯和新特提斯洋的形成、分布与多期次洋‒陆转化，是铜、金、铌、钽等多金属成矿有利区.在整个显生宙特提斯洋的形成‒消亡演化历程中，形成了各演化阶段独特的洋板块地层（oceanic plate stratigraphy，简称OPS）.重建青藏高原造山域各演化阶段各构造‒地层区划单元的OPS序列，以及划分对比格架，是造山域多金属矿产勘查和重大工程建设的重要基柱.本文系统梳理分析了青藏高原各时代约130多个出露点的蛇绿混杂岩等洋壳残迹的物质组成、256个蛇绿岩等洋壳残块的测年数据，以及相伴的硅质岩放射虫化石，依据构造环境和时代分布，区划出3个OPS构造‒地层大区和9个区，分别是巴颜喀拉‒三江、龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连和冈底斯‒雅鲁藏布大区.巴颜喀拉‒三江大区含西金乌兰、甘孜‒理塘、金沙江和哀牢山4个区；龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连大区含龙木错‒双湖、班公 湖‒怒江和昌宁‒孟连3个区；冈底斯‒雅鲁藏布大区含狮泉河‒嘉黎和雅鲁藏布2个区.按3大区和9区识别出对接带型和叠接带型两大类OPS和洋脊、洋岛‒海山、洋内弧、远洋和海沟沉积建造5个OPS亚类.依据同位素测年、古生物化石序列划分与对比，构建了青藏高原造山域首个显生宙OPS地层格架和时空演化模式，并对青藏高原特提斯演化模式进行了讨论.

Abstract

The Qinghai-Xizang Plateau orogenic domain has experienced the formation, distribution, and multi-stage ocean-continent transformation of the Proto-Tethys, Paleo-Tethys, and Neo-Tethys oceans, making it a favorable area for polymetallic mineralization such as copper, gold, niobium, and tantalum. Throughout the Phanerozoic evolution of the Tethys Ocean, unique oceanic plate stratigraphy (referred to as OPS) was formed during each evolutionary stage. Reconstructing the OPS sequences of various tectono-stratigraphic units in different evolutionary stages of the Qinghai-Xizang Plateau orogenic domain, as well as establishing a comparative framework, is an essential foundation for polymetallic mineral exploration and major engineering construction in the orogenic domain. This paper systematically reviews and analyzes the composition of ophiolitic mélange and other remnants of oceanic crust from over 130 exposure points in various geological periods of the Qinghai-Xizang Plateau, 256 dating data of ophiolitic remnants, and accompanying siliceous rock radiolarian fossils. Based on the tectonic environment and temporal distribution, three OPS tectono-stratigraphic mega-regions and nine districts have been delineated, namely the Bayankala-Sanjiang, Longmu Co-Shuanghu-Bangong-Nujiang-Changning-Menglian, and Gangdise-Yarlung Zangbo mega-regions. The Bayankala-Sanjiang mega-region includes the Xijinwulan, Ganzi-Litang, Jinsha River, and Ailao Mountain districts; the Longmu Co-Shuanghu-Bangong-Nujiang-Changning-Menglian mega-region includes the Longmu Co-Shuanghu, Bangong-Nujiang, and Changning-Menglian districts; the Gangdise-Yarlung Zangbo mega-region includes the Shiquanhe-Jiali and Yarlung Zangbo districts. Based on the three mega-regions and nine districts, two major types of OPS, namely suture zone type and subordinate suture zone type, and five subcategories of OPS, including oceanic ridge, oceanic island-seamount, oceanic arc, forearc, and trench sedimentary construction, have been identified. Using isotopic dating, paleontological fossil sequence division and correlation, the first Phanerozoic OPS stratigraphic framework and spatiotemporal evolution model for the Qinghai-Xizang Plateau orogenic domain have been constructed, and a discussion on the Tethyan evolution model of the Qinghai-Xizang Plateau has been conducted.

Graphical abstract

关键词

OPS / 时空分布 / 显生宙 / 特提斯演化 / 青藏 / 地层学 / 构造学.

Key words

oceanic plate stratigraphy / spatiotemporal distribution / Phanerozoic / Tethyan evolution / Qinghai⁃Xizang / stratigraphy / tectonics

0 引言

造山带是铜、金、铌、钽等多金属成矿有利区（侯增谦和王二七，2008； Barra and Valencia，2014）.正确重建造山带含洋壳残块增生杂岩带的地层序列，是恢复现今造山带三维结构、形成演化历程和多金属矿产勘查的重要基柱性工作.

造山带类型多样，结构和演化复杂，但所有的造山带在形成与演化过程中均有共性可循.其共性是，造山带形成与演化历程中，经历过洋盆形成、扩张、俯冲增生与陆‒陆碰撞的洋‒陆转化历程 （Wakita and Metcalfe， 2005； Cawood et al.， 2009； 许志琴等，2012； 李三忠等，2016a； 潘桂棠等，2016，2017； 肖文交等，2019； 吴福元等，2020）；在增生和洋‒陆转化过程中均经历了强烈的构造肢解、拼贴的构造混杂过程，即非史密斯化过程（Wakita and Metcalfe， 2005； Festa et al.， 2010； 张克信等，2014）.造山带研究中如何正确重建造山带混杂岩地层序列，是亟待解决的关键问题.为解决此重大问题，国际上洋板块地层学（ocean plate stratigraphy，简称OPS） 应运而生（Isozaki et al.，1990； Cawood et al.， 2009；Kusky et al.， 2013），国内与之类似的是非史密斯地层学的提出和应用（Non⁃Smith Stratigraphy，简称NSS） （冯庆来，1993；王乃文等，1994；张克信等，2001，2014；殷鸿福等，1998）.无论是OPS、还是NSS， 其共同目标旨在通过对造山带无序的混杂岩地层序列的精细重建， 恢复造山带组成、结构、形成和演化历程.当前，相对于NSS， OPS一词在国内外应用的更为普遍， 本文采用之.

本文针对青藏高原中‒南部特提斯域造山系OPS，从构造‒地层区划、不同构造阶段（原特提斯、古特提斯、新特提斯）OPS分布和序列重建，建立OPS地层格架，以及在构造环境和演化等方面总结和讨论，旨在为深化青藏高原中‒南部各构造阶段、各构造环境成矿地质背景研究提供OPS基础支撑.需说明的是，本文研究不涉及青藏高原北部由祁连‒阿尔金‒昆仑等造山带组成的特提斯域造山系，对高原北部的OPS总结与研究将有另文发表.

1 理论、方法与相关术语

本文以板块构造理论和OPS （Isozaki et al.， 1990；Wakita， 2012；Kusky et al.， 2013； 张克信等， 2016， 2020， 2021）理论方法为指导，其模型如图1所示.OPS最初是Isozaki et al. （1990）对日本造山带增生杂岩的序列重建研究中提出的，认为OPS是从洋壳辉长岩到玄武岩再到远洋沉积再到海沟浊积岩的序列，这个序列揭示了以下过程：在洋中脊新生洋壳辉长岩‒玄武岩等组合形成→洋中脊海岭碳酸盐岩海山形成→新生洋壳从洋中脊向两侧推出的洋脊岩石组合下沉被远洋硅质岩和泥岩覆盖→继续推近到海沟附近粗粒浊积岩覆盖其上→最终进入海沟被构造强烈肢解拼贴和混杂形成增生杂岩（混杂岩）；洋壳板块内产生的地幔柱热点导致玄武岩溢出形成洋岛（ocean island basalt，简称OIB），其上被生物礁等灰岩覆盖共同构成海山；如发生洋（壳）对洋（壳）俯冲，会产生以高镁安山岩等组合的洋内弧建造（图1）.OPS序列记录了洋壳从形成到消亡的演化历史.俯冲增生杂岩带经OPS重建后，所获得的远洋半远洋沉积的持续时间，等于从洋脊到海沟的运移时间（Isozaki et al.， 1990）.

Zamoras and Matsuoka（2001）和Wakita and Metcalfe（2005）对OPS进行了重新界定，提出OPS包括洋盆基底和具洋壳盆地的各种构造环境特征（如弧后盆地）.Kusky et al.（2013）将OPS定义为大洋岩石圈从洋中脊一直到海沟俯冲带间形成的基底火成岩序列，以及覆盖在洋底基底序列之上的沉积岩和火山‒沉积岩盖层序列；这种基底+盖层的原生成层有序层序，最终进入俯冲带经强烈构造混杂形成俯冲增生杂岩带.OPS的任务就是将增生杂岩带内无层无序基质包裹块体的混杂岩进行原位原序重建（Isozaki et al.， 1990；Wakita， 2012；Kusky et al.， 2013； 张克信等， 2021，2022）（图1）.

为更好理解如何从增生杂岩带重建OPS序列，合理开展OPS地层区划，从整体上形成造山系OPS格架和构造演化历程，本文对混杂岩、俯冲增生杂岩带、对接带和叠接带等关键术语进行说明.混杂岩（Mélange）是Greenly（2019）在英国Anglesey岛地质填图时提出的，定义为：坚硬的块体包裹于强变形的破碎的软质基质之中，原始层序完全被破坏.俯冲增生杂岩（subduction⁃accreation complex）是在板块俯冲消减作用下形成的混杂岩，是从俯冲板块上铲刮下来的物质增生到仰冲板块一侧，是不同时代、不同成因和不同板块物质的混杂体，是海沟‒俯冲带的典型产物（Hsü，1968； Wakabayashi and Dilek，2011； 潘桂棠等，2019）.混杂岩或俯冲增生杂岩是OPS的主要调查研究对象（张克信等，2021，2022）.

需明确的是，俯冲增生杂岩带的含义比蛇绿混杂岩带的含义大（图1和图2）.因为，在俯冲增生杂岩带中除含以蛇绿岩块为主的增生杂岩外，还含以洋岛‒海山为主的增生杂岩、以洋内弧为主的增生杂岩和以远洋深海沉积为主的增生杂岩等（潘桂棠等，2019；张克信等，2020，2022）.所以，不可将蛇绿混杂岩带与俯冲增生杂岩带两者等同起来，蛇绿混杂岩仅是俯冲增生杂岩中的一部分.另外，确定是否有洋壳存在，不能单凭蛇绿岩的有无；洋岛‒海山和洋内弧等与蛇绿岩同等重要，它们都是判别洋壳存在的有力证据.

王鸿祯（1985）将地壳缝合带划分为对接带和叠接带.对接带是指两古大陆之间的大洋洋盆（约持续2亿年以上）在闭合过程中逐步消减混杂形成的缝合带；叠接带是指活动大陆边缘弧后和弧间小洋盆（约持续2亿年以下）在闭合过程中逐步消减混杂形成的缝合带（王鸿祯，1985； 张克信等，2020）.本文认为，计算一个洋盆生存时间时，不可单用蛇绿岩的分布时间确定（张克信等，2021）.因为蛇绿岩产自洋脊，当洋脊全部俯冲完不再产生新生洋壳时，尚有近半数的洋壳还待俯冲消减.所以，洋盆生存时间大于蛇绿岩的分布时间.因蛇绿岩保存极不完整，洋岛‒海山、洋内弧和洋盆沉积都可确定洋的存在和年龄.

张克信等（2016，2020）运用大地构造相研究分析法，对OPS类型进行了划分.首先，按照王鸿祯（1985）所定义的对接（缝合）带和叠接（缝合）带，将OPS分为对接带型和叠接带型两大类型（图2）；然后，进一步将对接带和叠接带型划分为洋中脊型、深海平原型、洋岛‒海山型、洋内弧型、弧前俯冲增生楔型、弧前盆地型、边缘海小洋盆型（弧间和弧后盆地）等，如图2所示.

本文涉及造山域、造山系和造山带3个术语，含义是：造山带是单一洋盆汇聚俯冲关闭过程形成的（由单条蛇绿混杂岩带和相关岩浆弧等组成）；造山系是彼此相邻的多个洋盆（由多条蛇绿混杂岩带和相关岩浆弧等组成）在同一构造演化阶段内形成的多条造山带的复合体；造山域是多个造山系的复合体，它们在构造演化阶段上存在继承和转换等内在联系.例如，西金乌兰带、甘孜‒理塘带、金沙江带和哀牢山带各自都是单一的造山带，这4条造山带的复合体被称为“三江造山系”，它们紧密相邻并都是在古特提斯构造阶段形成的；本文图3展示的9个OPS分区对应了9个造山带，3个OPS区对应了3个造山系，它们共同构成了青藏中‒南部造山域.

2 材料与结果

本文系统梳理分析了青藏高原各时代约200多个出露点的蛇绿混杂岩等洋壳残迹的物质组成、岩石地球化学、测年和古生物化石，依据构造环境和时代分布，区划出OPS的3个构造‒地层大区和9个区（图3），分别是巴颜喀拉‒三江、龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连和冈底斯‒雅鲁藏布3个大区.巴颜喀拉‒三江大区含西金乌兰、甘孜‒理塘、金沙江和哀牢山4个区；龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连大区含龙木 错‒双湖、班公湖‒怒江和昌宁‒孟连3个区；冈底斯‒雅鲁藏布大区含狮泉河‒嘉黎和雅鲁藏布2个区.按3大区和9区识别出对接带型和叠接带型两大类OPS，并进一步划分出洋脊、洋岛‒海山、洋内弧、深海平原和海沟沉积建造5类OPS亚类；依据同位素测年、古生物化石序列划分与对比，构建了首个青藏高原造山域显生宙OPS地层格架（图3），并对其构造环境和演化历程进行了讨论.

2.1　巴颜喀拉‒三江大区

该大区从北西向东南分布西金乌兰、甘孜‒理塘、金沙江、哀牢山4条俯冲增生杂岩带.四带互连，自西藏北部羊湖、郭扎错经西金乌兰湖一直延到邓柯‒玉树，向南则经巴塘、得荣‒奔子栏‒点苍山西侧，转向南东经哀牢山延出国境.其中西金乌兰带在玉树之东分为甘孜‒理塘带和金沙江带，两带近平行向南在维西合并成一带，被称为哀牢山带（图3）.上述4带本文分别称之为西金乌兰区、甘孜‒理塘区、金沙江区和哀牢山区.该大区洋壳残块年龄分布范围是396.0~220.6 Ma（早泥盆世埃姆斯期至晚三叠世诺利期），总时限175.4 Ma（图3）.按分布时限，属叠接带型OPS分布区.

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2.1.1　西金乌兰区

该区混杂岩岩块主要有蛇纹石化橄榄岩、辉长岩、堆晶辉长岩、杏仁状或块状或枕状玄武岩、橄榄玄武岩、辉石玄武岩等，隆宝湖北发育榴闪岩（潘桂棠等，2017）.基质为片理化浊积砂板岩、绿泥钠长岩、云母石英片岩和放射虫硅质岩等.其上被上三叠统不整合覆盖.在该区7处蛇绿混杂岩分布点获得岩块年龄355~236 Ma （总时限119 Ma）（图3）.西金乌兰移山湖两处的辉绿岩年龄分别是345.69 Ma （莫宣学等，1993）和345.8 Ma（青海省地质调查院，2024）；西金乌兰明镜湖北辉绿岩年龄是345.9 Ma （青海省地质调查院，2024）；西金乌兰N⁃MORB玄武岩和P⁃MORB辉长岩年龄分别是274 Ma和347 Ma （青海省地质调查院，2024）；治多县巴音查乌马MORB辉长岩年龄是266 Ma （苟金，1990；青海省地质调查院，2024）；治多县多彩堆晶辉长岩年龄为252.5 Ma（刘银等，2014）；玉树歇武SSZ辉长岩年龄为236 Ma（刘彬，2014）.在治多县巴音查乌马放射虫硅质岩中获早二叠世放射虫带化石Pseudoalbaillella scalprata rhombothoracata（李德威等，2006）；治多县多彩放射虫硅质岩产Pseudoalbaillella fusifirmi，Pseudoalbaillella spp.等早‒中二叠世放射虫（王毅智，2006）；玉树隆宝湖放射虫硅质岩产早二叠世放射虫带化石Pseudoalbaillella scalprata rhombothoracata（西安地质调查中心，2006）.洋壳岩块测年和放射虫化石指示该区洋盆内原岩建造时代是早石炭世‒中二叠世.

2.1.2　甘孜‒理塘区

近南北向分布的含蛇绿岩等洋壳残块的混杂岩带，北东侧为可可西里‒松潘前陆盆地（T₃），西侧为义敦‒沙鲁里岛弧带.蛇绿岩等岩块由基性‒超基性堆晶岩、辉长岩、辉绿岩墙、洋脊型拉斑玄武岩和放射虫硅质岩组成，除理塘禾尼‒热水塘一带出露较完整的蛇绿岩层序外，大多被肢解呈构造岩块散布于基质中；基质主要是浊积杂砂岩夹板岩、千枚岩等（潘桂棠等，2017；四川省地质调查院，2024）.在该区9处获得蛇绿岩等岩块年龄356~271 Ma （总时限85 Ma）（图3）.石渠县扎仁铜矿床南辉长岩年龄为302.1 Ma（钟文丽，2012）；甘孜七公里水电站N⁃MORB辉长岩年龄为292 Ma（闫全人等，2005）；理塘县金沟MORB堆晶辉长岩年龄为346 Ma和292 Ma（四川省地质调查院，2024）；理塘县村戈乡理觉公路东侧OIB枕状玄武岩年龄为271 Ma（严松涛等，2019）；香格里拉老虎箐电站南E⁃MORB玄武岩年龄为345.4 Ma（四川省地质调查院，2018）；香格里拉市金江镇玄武岩和辉长岩年龄分别是341.6 Ma和272.8 Ma（云南省地质调查院，2024）；玉龙县石鼓镇玄武岩年龄为 356 Ma（云南省地质调查院，2024）.在道孚县鲜水河地区的硅质岩中获放射虫Paroertlispongus multispinosus，P. daofuensis，Pseudoertlispongus mostleri，P. angulatus，Oertlispongus inaequispinosus，Baumgartneria sp. cf. B. curvispina，B. ambigua，B.lata，B. retrospina，B. bifurcate，Falcispongus heinzi，F. calcaneum，F. pauliani，Cryptostephanidium sp.，C. cornigerum，Tetraspongodiscus nazarovi，Muelleritortis firma，M. sp. cf. M. cochleata，Hozmadia pyramidalis，Triassocampe scalaris， Triassocampe sp.，时代为中三叠世（Feng and Liang，2003， 梁斌等，2004）.在石渠地区的硅质岩中获放射虫Astrocentrus cf. pulcher，A canthosphaera cf. austrica，Cenosphaera sp.，Cryptostephanidium cf. cornigerum，Pseudostylosphaera nazarovic， Ps. cf. nazarovic，Triassocompe coronate （Feng et al.， 1996），地质时代为中三叠世安尼期（Feng et al.，1996）.

洋壳岩块测年和放射虫化石指示该区洋盆内原岩建造时代是早石炭世‒中三叠世.

2.1.3　金沙江区

潘桂棠等（2017）将该区从东向西分为3个亚带：（1）嘎金雪山‒贡卡‒霞若‒新主洋壳消减蛇绿混杂岩亚带，是该缝合带的主带，其岩块主要由洋脊玄武岩、准洋脊玄武岩与蛇纹岩（原岩为方辉橄榄岩）、堆晶辉长岩、辉绿岩墙、枕状玄武岩、放射虫硅质岩等组成，在岗托霞若等地均可见OIB洋岛海山岩块；（2）朱巴龙‒羊拉‒东竹林洋内弧消减杂岩带，位于芒康朱巴龙、西渠河桥‒德钦贡卡、东竹林大寺一线，主弧期火山岩为早二叠世晚期‒晚二叠世的钙碱性系列的安山岩、玄武岩、玄武安山岩、钠化英安岩等.玄武岩化学分析为洋壳拉斑玄武岩，在ATK图解中落在岛弧玻镁安山岩区；（3）西渠河‒雪压央口‒吉义独‒工农弧后盆地消减杂岩带，以发育早二叠世晚期‒晚二叠世辉长辉绿岩墙群、准洋脊型基性火山岩、少量超基性岩为特征.肢解的蛇绿岩残块赋存于强烈剪切的硅泥质砂板岩和绿片岩等基质中，并混入大小不等的灰岩或大理岩 （王立全等，2013； 潘桂棠等，2017）.在该区11处获得蛇绿岩等岩块年龄为396~237 Ma（总时限159 Ma）（图3）.金沙江E⁃MORB辉长岩年龄为304.1 Ma（吴涛，2015； 李旭拓，2018）、辉长岩年龄为338、320、264 Ma（Jian et al.，2008）、玄武岩年龄为245、237 Ma（Zi et al.， 2012）和246.1 Ma（Wang et al.，2014）、斜长花岗岩年龄为300、285 Ma（吴涛，2015）；得荣县徐麦基性岩年龄为292.6 Ma（四川省地质调查院，2014）；得荣县嘎金雪山玄武岩年龄为396、362 Ma（路远发，2000）；得荣县雪堆嘎校斜长花岗岩年龄为294 Ma（简平等，1999）；德钦县书松斜长岩年龄为320、340 Ma（简平等，1999； Jian et al.， 2008）和329 Ma（刘长垠，2005）；德钦县奔子栏镇白马雪山辉长岩年龄为329、285 Ma（简平等，2003a； Jian et al.，2008）和285~282 Ma（刘长垠，2005）；德钦县娘九丁斜长花岗岩年龄为285 Ma（简平等，2003b）、玄武岩年龄为333.34 Ma（四川省地质调查院，2014）；德钦县吉义独堆晶辉长岩年龄为264 Ma（莫宣学等，1993）；德钦县东竹林辉长岩年龄为354 Ma（刘长垠，2005）、353.9 Ma（王冬兵等，2012）和365.3 Ma（Wang et al.，2012）；川西雪堆斜长花岗岩年龄为300 Ma（简平等，2003b）；纳西县龙蟠辉绿岩年龄为262.3 Ma（任飞等，2021）.

在该带的德钦霞若产早石炭世放射虫Albaillella indensis indensis，Astroentactinia multispinosa，Belovea variabilis，Entactinia vugaris vugaris，E. parva，E. tortispina，E. cometes等（冯庆来等，1997）.在中甸喇嘛寺东北部的哈工组硅泥质岩的岩块中产中‒晚泥盆世放射虫Entactinosphaera palimbola，E. inusitata，E. egindyensis，Entactinia cometes，E. claviformis，与中‒晚泥盆世的竹节石Nawakia zlichovensis，N. tarrandei，N. praecursor，Nemipsila cf. tangdingensis，Styliolina cf. minuta 等共生.在喇嘛寺东北部的薄层硅质岩中还产侏罗纪放射虫Triactoma sp. cf. T. parablakei，Praeconocaryomma sp.，Paronaella sp. cf. P. denudata，Paronaella sp.等（冯庆来等，2002）.

2.1.4　哀牢山区

哀牢山蛇绿混杂岩带介于西侧兰坪‒思茅地块与东测扬子陆块之间，东以哀牢山断裂为界，西以墨江断裂为界.哀牢山带向南延至云南金平县三台坡分成南、东两支，向南一支与越南马江蛇绿岩带相接，向东一支与我国云南八布‒越南高平蛇绿岩带相接.该带洋壳残块主要由变质二辉橄榄岩、变质方辉橄榄岩、辉石岩、辉长岩、辉长斜长岩、斜长花岗岩、辉绿岩、钠长玄武岩、辉石玄武岩等超基性‒基性岩和含放射虫硅质岩等组成（王立全等，2013； 潘桂棠等，2017），含碳酸盐岩岩块；基质主要是变质的砂泥质和硅泥质浊积岩.在双高（双沟）‒平掌‒老王寨一带分布较多的洋脊玄武岩（潘桂棠等，2017）；哀牢山北东侧潘家寨出露蓝片岩（王义昭，1997）.元江县双高（双沟）辉长岩和斜长花岗岩年龄为328~362 Ma（简平，1998）、辉绿岩的年龄是382.9 Ma和375.9 Ma（Jian et al.，2009）； 早年报道的双高（双沟）斜长花岗岩年龄为256 Ma，以及蛇绿岩中的系列同位素年龄为345~320 Ma（杨岳清等， 2006）.楚雄市石格打洋内弧高镁安山岩‒英安岩年龄为248.1~237.9 Ma（云南省地质调查院，2024）.金平县勐拉河河谷三台坡出露的OIB变质玄武岩、OIA含橄榄玄武岩和绿片岩被年龄为251.4 Ma钾长花岗斑岩侵入，共生的碳酸盐岩岩块含Spathognathodus sp.，Pelygnathus sp.，Gnathus sp.等早石炭世牙形石（云南省地质调查院，2024）.哀牢山带的东支云南八布蛇绿混杂岩的蛇绿岩年龄是231.2 Ma和230.5 Ma（Wu et al.，1999）； SSZ变质玄武岩年龄是265.2 Ma、N⁃MORB变质辉长岩年龄为270 Ma（Liu et al.，2018）； MORB斜长角闪岩年龄为272 Ma（张斌辉等，2013）.八布蛇绿混杂岩中的硅质岩岩块中含早二叠世放射虫Pseudoalbaillella scalprata scalprata，Pseudoalbaillella sakmarensis，Pseudoalbaillella lomentaria，Quadriremis robusta，Polyfistula hexalobata，Latentifistula texana，Latentifistula crux，Tormentum sertulum，Nazarovella phlogidea，Ormistonella robusta，Hegleria mammilla等（冯庆来和刘本培，2002）.综上，哀牢山蛇绿混杂岩带原岩形成的时代为晚泥盆世‒中三叠世（382.9~230.5 Ma） （图3），总时限约152 Ma.

2.2　龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连大区

该大区是泛华夏大陆南缘羌塘‒三江造山系与冈瓦纳大陆北缘冈底斯‒喜马拉雅造山系的重要分界（潘桂棠等，2009，2017，2020），表现在晚古生代期间是冈瓦纳冰水沉积和冷水生物区系与北部的泛华夏大陆暖水沉积及生物区系的重要分界线（潘桂棠等， 2017）.该大区的西部分为北带和南带，北带为龙木错‒双湖蛇绿混杂岩带，本文称之为龙木错‒双湖区.南带为班公湖‒怒江蛇绿混杂岩带，本文称之为班公湖‒怒江区.班公湖‒怒江带向东经丁青至昌都南部则由原来的从西向东转变为从北向南，沿怒江东侧和澜沧江西测经梅里雪山、云龙、永平一直南下至昌宁.从昌宁向南至孟连习称昌宁‒孟连蛇绿混杂岩带，本文称昌宁‒孟连区；昌宁‒孟连带可分为西亚带（主带）和东亚带（次带）：西亚带从昌宁至孟连；东亚带与西亚带近平行，从昌宁经云县半坡至景洪向南出国境进入泰国.该大区洋壳残块年龄分布范围是517.1~120 Ma，总时限 397.1 Ma （图3）.按分布时限属对接带型OPS分布大区.该对接带是青藏高原中部一条最为重要的原特提斯‒古特提斯‒新特提斯大洋自北向南后退式俯冲消亡的巨型增生杂岩带（图4），构筑了冈瓦纳大陆与劳亚‒泛华夏大陆分界线（潘桂棠等，1997， 2015，2016，，2017，2020；李才等，2006a，2006b，2008；王立全等，2013； 张克信等，2015，2017）.对接带内广泛出露古生代‒中生代蛇绿混杂岩、洋岛‒海山消减增生楔、洋内弧俯冲增生杂岩，基底残块和大量古生代‒中生代碳酸盐岩等岩块，以及以蓝片岩、榴辉岩为代表的高压‒超高压变质岩带，是研究青藏“原‒古‒新特提斯大洋”连续演化极为重要的天然实验室.

2.2.1　龙木错‒双湖区

该区主体位于北羌塘地块与南羌塘增生弧盆系之间，其北界为龙木错‒清澈湖‒玉环湖‒大熊湖‒玛依岗日‒爱达江日‒双湖断裂，南界为龙木错‒清澈湖‒阿鲁错‒丁固‒肖茶卡‒双湖断裂.该带向西于龙木错附近被阿尔金大型走滑断裂截断.依据该区分段出露的空间展布特征，可将该区进一步分为龙木错‒双湖蛇绿混杂岩带和托和平错‒查多岗日洋岛增生杂岩带2个次级构造‒地层单元（潘桂棠等，2017，2020）.

龙木错‒双湖带（Pz⁃T₂）是南北宽达100多公里、东西全长约1 350 km的巨型俯冲增生杂岩带，西起龙木错，向东至清澈湖折向南，经羌马错后再折向东沿冈玛错‒戈木日‒玛依岗日‒查桑南‒双 湖‒阿尔下穷‒扎萨‒查吾拉一带分布，东延在拉龙贡村附近与北澜沧江蛇绿混杂岩带相接（潘桂棠等，2017）.该带混杂岩基质主要是强烈变形变质含砾板岩、绿片岩、石英片岩、千糜岩、糜棱岩等岩系（李才等，2006a，2008），分布其中的岩块由超基性岩、堆晶辉长岩、枕状玄武岩、放射虫硅质岩、结晶灰岩、大理岩等大小不等的岩块和辉长‒辉绿岩岩墙等组成.该带还分布由榴辉岩‒蓝片岩‒含多硅白云母片岩组合的高压‒超高压带，西起红脊山（陆济璞等，2006）、冈玛错（翟庆国等，2009a，2009b，2009c），经桃形湖、戈木、果干加年山（Kapp et al.，2000，2003；董永胜和李才，2009；张修政等，2010a，2010b），向东延伸到蓝岭（王根厚等，2009），再向东至索县巴青地区（Zhang et al.，2017），分布范围总体与龙木错‒双湖俯冲增生杂岩一致，断续出露达500 km，宽达百余公里.

托和平错‒查多岗日洋岛增生杂岩带（C₂⁃P₂）呈一巨大的构造岩片夹持于龙木错‒双湖结合带中，在托和平错、查多岗日一带晚古生代碳酸盐岩、碎屑岩及洋岛型基性‒中基性火山岩组合最为发育（潘桂棠等，2017，2020）；区域地质图的岩石地层单位主要是展金组（C₂⁃P₁）、日湾茶卡组（C₁）和鲁谷组（P₂），实际上这些“组”并非成层有序史密斯地层，而是总体无序局部有序的OPS.其中的“展金组”洋岛火山岩岩石类型有橄榄玄武岩、含气孔及杏仁状橄榄玄武岩、含气孔及杏仁状玄武岩、含气孔及杏仁状玄武安山岩、少量凝灰岩和杏仁状安山岩等，并夹有泥岩、硅质岩及珊瑚礁灰岩多层，总厚度达 700 m.玄武岩属钾质碱性系列，玄武安山岩属钙碱性系列，安山岩属低钾拉斑系列；稀土元素总量高，为轻稀土强富集型，球粒陨石配分模式与夏威夷洋岛碱性玄武岩大致平行（王权等，2006）.在该杂岩带东南日湾茶卡以北发现由独泉沟、天泉、屏风岭等9个洋岛构成的“岛链”，东西长达20 km以上，南北宽约1 km，岩石组合由厚层状玄武岩、枕状玄武岩、硅质岩、灰岩和角砾灰岩组成，时代为晚石炭世‒早二叠世，其基质是与其大致同时代的强变形低绿片岩相远源浊积岩（范建军，2014）.

在龙木错‒双湖区7处获得蛇绿岩等洋壳残块年龄25个（图3）.改则桃形湖辉长岩年龄为367 Ma（吴彦旺，2013）、斜长花岗岩年龄为352 Ma（胡培远等，2013）和358 Ma（吴彦旺，2013）、蓝闪石年龄为282 Ma和275 Ma（邓希光等，2000a，2000b，2002）和237~220 Ma（李才等，2006a）、多硅白云母年龄为219~217 Ma（李才等，2006a）、青铝闪石年龄为223 Ma（鲍佩声等，1999）；桃形湖东南10 km处的 N⁃MORB堆晶辉长岩年龄为467 Ma（Zhai et al.，2010）；桃形湖东SSZ斜长花岗岩年龄为442 Ma和441 Ma（胡培远等，2014）；桃形湖东20 km（岗玛措东南10 km处）堆晶岩和斜长花岗岩年龄分别为357 Ma和355 Ma（Zhai et al.，2013）；在果干加年山N⁃MORB堆晶辉长岩获得7个年龄数据，从大到小分别是517.1 Ma和505.3 Ma（吴彦旺，2013）、 461 Ma（王立全等，2008）、438 Ma和431 Ma（李才，2008）、355 Ma（吴彦旺等，2014）、345 Ma（Zhai et al.，2013），在块状辉长岩中获得273 Ma年龄（吴彦旺等，2010），果干加年山玄武岩年龄为275 Ma（吴彦旺等，2010）；驼背岭的斜长花岗岩年龄是 504.8 Ma和491.6 Ma（胡培远等，2014）；日湾茶卡堆晶辉长岩年龄为442.7 Ma（张天羽等，2014）.

在龙木错‒双湖区的角木日、黑石山、双湖东才多茶卡、才玛尔错以南等地发育放射虫硅质岩，产晚泥盆世法门期放射虫Stigmosphaerostylus oumonhaoensis、Triloneheechinata、Archocyrtium riedeli和晚二叠世长兴期放射虫Neoalbaillella ormithoformis、 N.optima等（李曰俊等，1997；朱同兴等，2006；李才等，2007a）.改则县黑石山东产晚泥盆世放射虫Triaenosphaera sp.，T. sicarius，Trilonche aff. cancellicula，Entactinia pantotolma，Entactinia foveolata，E. cf. xinjiangensis，E. oumonhaoensis，Spongentactinia cf. marina，Plenoentactinia cf. pinguis，Stigmosphaerostylus cf. duksundiensis，Spinoalius cf. paracorynacantha，Callela parvispinosa，Astroentactinia stellata，Archocyrtium wonae等（Li et al.，2024）.在改则县古姆乡北东的白日东南约4 km处的三叠系玄武岩与硅质岩和页岩互层序列中的硅质岩层中，富含中三叠世放射虫Cryptostephanidium longispinosum，Eptingium manfredi，Falcispomgus falciformis，Hindeosphaera spinulosa，Muelleritortis firmum，Oertilispongus inaequispinosus，Paroertlispongus chinensis，P. heimi，P. weddigei等（李亚等，2018）.改则县蓝岭高压‒超高压变质岩分布带硅质岩岩块含中‒晚三叠世放射虫Eptingium sp.，Astrocentrus sp. cf. A. pulcher，Triassocampe dumitricai，T. deweveri，T. scalaris，Pseudostylosphaera sp.，P. sp. cf. P. japonica，Striatotriassocampe sp.等（Liang et al.，2021）.

2.2.2　班公湖‒怒江区

该区习称班公湖‒怒江带，是条规模巨大的蛇绿混杂岩带，自西向东由近东西向、北西西向转为北西到近南北向展布，西起班公错，经改则、班戈、丁青，东至八宿、碧土一带，东西长2 000 km，南北宽8~50 km.该带自西向东还分布高压‒超高压变质岩石，如洞错榴闪岩、蓬错西镁质榴辉岩相蛇绿岩（夏斌等，2013）、安多高压麻粒岩（张修政等，2010a）、巴青北高压变粒岩（王根厚等，2006）、八宿嘉玉桥增生杂岩中的退变质榴辉岩和高压麻粒岩（董永胜，2007；王根厚，2008；张万平等，2010），是中生代班公湖‒怒江大洋向南深俯冲的产物.

班公湖‒怒江区可划分为西段、中段和东段（潘桂棠等，2017，2020）.（1）西段：班公湖至纳屋错、改则、色哇一带出露35个基性‒超基性岩块（片）群，单个面积一般几至十几平方千米；班公湖南岸及改则洞错等地发育完整的蛇绿岩层序，自下而上为变质橄榄岩→堆晶辉长岩→辉绿岩墙群→块状及枕状玄武岩和共生的放射虫硅质岩.在班公湖、洞错等地洋岛‒海山残块发育较好.该区西段的混杂岩基质被称为“木嘎岗日岩群”，由弱变质强变形的钙质岩屑砂岩、岩屑石英杂砂岩、长石石英杂砂岩、长石岩屑杂砂岩等浊积岩夹灰绿色凝灰质细砂岩和放射虫硅质岩组成.（2）中段：分布于尼玛‒东巧‒安多‒索县一带，东西长500 km，南北宽100 km，区内约有30多个基性‒超基性岩块（片），单个岩块（片）面积一般1~10 km²；自北而南可被进一步划分为其香错‒东巧‒安多、切里湖‒达如错和桂牙白拉‒觉翁‒依拉山3个亚带.除基性‒超基性岩块外，还混杂有志留纪‒二叠纪大小不等的大理岩和灰岩岩块、侏罗纪玄武岩岩块、侏罗纪安山岩及安山质角砾凝灰岩的层状透镜状岩块、早白垩世放射虫硅质岩，以及在其香错、扎楚藏布下游的塔仁本展露的早白垩世洋岛‒海山组合岩块；其在不同地段均被上白垩统竞柱山组区域性不整合覆盖，显示了班公湖‒怒江洋自日土经改则至安多东巧约1 500 km区域内在早白垩世末（100 Ma）闭合消亡.含超基性岩块的混杂岩之上局部被东巧组（J₃⁃K₁）不整合覆盖，东巧组属楔顶盆地沉积建造.因此，东巧组之底的不整合不能作为班公湖‒怒江洋于中侏罗世闭合的证据（潘桂棠等，1983，2017，2020）.（3）东段：分布在索 县‒巴青‒丁青‒八宿一带的蛇绿混杂岩带，岩块是一系列大小不等的基性、超基性岩，基质以砂板岩和云母石英片岩为主.丁青色扎区的加弄沟、宗白‒亚宗一带的蛇绿岩层序较完整，自下而上为橄榄岩（云辉橄榄岩、辉橄岩、二辉橄榄岩、含辉纯橄岩等， 厚>7 500 m）→堆晶岩（辉长苏长岩、二辉岩、角闪辉长岩，厚260 m）→辉长辉绿岩墙群→玄武岩（拉斑玄武岩、霓玄岩和钛辉玄武岩）→放射虫硅质岩（潘桂棠等，1983，2004，2020）.张旗和杨瑞英（1985）报道有洋内弧玻镁安山岩.在日隆山‒娃日拉一带由纯橄岩和二辉橄榄岩互层组成的堆晶岩厚> 1 200 m（潘桂棠等， 2020）.吴根耀（2006）报道班‒怒带在八宿‒左贡‒察瓦龙一带主要表现为左贡扎玉‒碧土蛇绿混杂岩带，混杂岩的基质为钙泥质浊积岩、钙硅质岩及薄层硅质灰岩，混入的岩块有镁铁质岩和超镁铁岩，以及扎玉区的西玉曲河西岸的洋岛玄武岩、碧土南海山玄武岩‒灰岩组合（瓦浦岩组）和含晚石炭世放射虫Albaillella sp的硅质岩.

在班公湖‒怒江区21处获得蛇绿岩等洋壳残块年龄40个（图3）.班公湖右湖边玄武岩和安山岩年龄为163.9 Ma（周涛等，2014）；日土县城附近获得7个年龄，分别是辉长岩的167 Ma（史仁灯，2007）、181.9 Ma和176.2 Ma（曲晓明等，2010）、MORB辉长岩的231.5 Ma（秦雅东等，2017）、SSZ辉长岩的168.8 Ma和164.6 Ma（江西省地质调查院，2005）、玄武岩的254 Ma（黄启帅等，2012）；热帮乡辉长岩的162 Ma（Liu et al.，2014）；改则县城北10 km处的堆晶橄榄辉石岩年龄为193.1 Ma（曲晓明等，2010）；改则舍玛拉沟辉长岩年龄为191 Ma（邱瑞照等，2004）；在洞错获得5个年龄，分别是堆晶辉长岩172 Ma（范建军等，2019）、辉长岩222~132 Ma（222 Ma，武勇等，2018）、221.6~190.8 Ma（曾庆高等，2014）、167 Ma（Wang et al.， 2016）、高压麻粒岩254 Ma（王保弟等，2015）；尼玛中仓辉长岩年龄为163 Ma（Tang Y et al.，2018）；东巧江错辉长岩年龄为189.8 Ma（黄强太等，2015），东巧西10 km堆晶辉长岩年龄为187.8 Ma（夏斌等，2008a），东巧橄榄岩热变质角闪石年龄为197 Ma（王希斌等，1987），东巧堆晶岩年龄为251 Ma（Shi et al.，2012），东巧辉长岩年龄为187.4 Ma （西藏自治区地质调查院，2024），东巧水帮屋里玄武岩年龄为145 Ma（郑有业等，2003），东巧觉翁辉长岩年龄为128 Ma（西藏自治区地质调查院，2002），东巧拉纳沟玄武岩年龄为120 Ma（西藏自治区地质调查院，2002）；安多县强玛镇堆晶辉长岩年龄为188.4 Ma（Liu et al.， 2016b），安多西错那湖北辉绿岩年龄为184.4 Ma（李小波，2016），安多块状玄武岩和枕状玄武岩年龄分别为228.6 Ma和220 Ma（Chen et al.，2015）；丁青县多伦辉长岩年龄为175.3 Ma（李小波，2016），丁青SSZ辉长岩年龄为163.1 Ma（西藏自治区地质调查院，2024），丁青东南辉长岩糜棱岩年龄为193.3 Ma（游再平，1998）；类乌奇县和丁青县交界处堆晶辉长岩年龄为217.8 Ma（强巴扎西等，2009）；类乌齐辉长岩年龄为280 Ma（胡培远等，2016）；那曲市达仁MORB辉长岩年龄为259~242 Ma（西藏自治区地质调查院，2005）.昌都曲登乡‒脚巴山MORB/OIB玄武岩年龄为361.4 Ma.昌都市八宿县邦达镇SSW嘉玉桥岩群中N⁃MORB玄武岩年龄为338 Ma（王冬兵等，2021）； 昌都市八宿县邦达镇SSW约1.6 km处邦达岩组中的N⁃MORB辉绿岩年龄为330.9 Ma（任飞等，2022）.综上，班公湖‒怒江区蛇绿岩等洋壳残块的年龄分布范围为361.4~120 Ma（晚泥盆世‒早白垩世），持续时长241.4 Ma.

在西藏日土县城北7 km处硅质岩中产晚侏罗世放射虫Archaeospongoprunum imlayi， Mirifusus baileyi， Paronaella pygmaea， Podobursa triacantha， Tritrabs exotica， Tetratrabs gratiosa等（李红生，1986）.日土县城南硅质岩中产晚侏罗世放射虫Mirifusus guadalupensis， Tripocyclia jomesi， Hsuum maxwelli等（杨群和王玉净，1990）.西藏日土县城东硅质岩中产早白垩世放射虫Archaeotritrabs sp.，Archaeocenosphaera clathrata，Archaeospongoprunum patricki，Archaeodictyomitra mitra，Crolanium puga，Cryptamphorella crepida，C. clivosa，Crucella sp.，Crococapsa sp.，Dictyomitra sp.，D communis，D. sp. cf. D. Formosa， Gongylothorax sp.，Halesium sp.，Hiscocapsa （？） sp.， Hemicryptocapsa capita，H. carpathica，Godia sp.，Pseudodictyomitra carpatica，Pseudoeucyrtis hanni，Orbiculiforma sp.，Spumellaria gen. et sp. indet.，Pseudodictyomitra sp.，Pseudodictyomitra hornatissima，Thanarla sp.，Thanarla brouweri，Pantanellium lanceola，Parvicingula boesii，Thanarla pacifica，Thanarla sp. cf. T. pulchra，Trisyringium （？） sp.，Triactoma hybum，Xitus sp.，X. clava，X. normalis，Zhamoidellum （？） sp. （Wang et al.， 2023）.在西藏那曲西南的嘎加村混杂岩带的“嘎加组”硅质岩产中三叠世安尼晚期的放射虫Oertlispongus inaequispinosus组合带（王玉净等，2021）.在丁青宗白产早侏罗世放射虫Paeconocaryomma media，Canutus izeemsis，Bagotum modestum，Canuptum rugosum等（李红生，1988）.丁青沙贡乡拉根拉紫红色硅质岩产晚三叠世Capnuchosphaera triassica放射虫组合（王玉净等，2002）.

2.2.3　昌宁‒孟连区

夹持在保山和临沧地块间，习称昌宁‒孟连蛇绿混杂岩带.从西向东横穿该增生杂岩带可划分出四排山洋岛‒海山增生杂岩带（C⁃P）、牛井山蛇绿混杂岩带（Pz₁）、勐峨含洋内弧残块增生杂岩带（O₂）、老七班远洋硅泥质沉积增生楔（Pz）、邦老电站弧‒沟间浊积岩增生楔、粟义含蓝片岩增生杂岩带、邦丙含榴辉岩超高压俯冲折返带（Pz₁）（潘桂棠等，2017）.在该带的耿马回爱、帕秋、曼信、拉巴、依柳、老厂、乌木龙‒蚂蝗箐公路一带晚古生代的洋岛‒海山很发育（朱勤文，1998； 沈上越等，2002； 潘桂棠等，2017）.曼信、孟连等地N⁃MORB洋脊及准洋脊玄武岩中见有多层呈透镜状产出的具枕状苦橄岩（莫宣学等，1993）.在云县铜厂街发育的N⁃MORB蛇绿岩主要由方辉橄榄岩、堆晶二辉岩‒辉长岩、席状岩墙群、玄武岩、放射虫硅质岩，以及外来灰岩块等组成；基质为强烈变形剪切和变质的浊积碎屑岩系，主要有绢云片岩、绢云石英片岩，以及由火山碎屑岩系变质形成的阳起片岩和绿帘阳起片岩等（潘桂棠等，2017）.近年前人在长期划归中元古界的“澜沧岩群”中解体出湾河（刘桂春等，2017）、清平（彭智敏等，2020）等多个蛇绿混杂岩亚带，确认原划“澜沧岩群”的大部分（除勐海一带尚存新元古界）并非中元古代基底岩系，主体是古生代原‒古特提斯洋俯冲消减形成的增生杂岩系（潘桂棠等，2017）.在双江勐库、挖角、那卡河、根恨河等地南北向带状断续分布近百余公里的榴辉岩及榴闪岩高压‒超高压变质带（李静等，2015； 彭智敏等，2019）.昌宁‒孟连洋在向东的俯冲消减制约了东侧临沧弧盆系的形成与演化，早三叠世的 弧‒陆碰撞使东边盆地带褶皱隆升被剥蚀，并向西部前渊供给物源，该区最终被上三叠统普遍不整合覆盖（李兴振等，1999，2002； 潘桂棠等，2017）.

在昌宁‒孟连区的9处蛇绿岩等洋壳残块已获同位素年龄16个（图3）.双江县勐库（退变）榴辉岩年龄为486 Ma和230 Ma（徐桂香等，2016）；铜厂街辉长岩年龄为385 Ma（从柏林等，1993）；南汀河辉长岩年龄为473~439 Ma（王保弟等，2013）；牛井山斜长角闪岩年龄为272 Ma（王冬兵等，2017）、“O”型埃达克质英云闪长岩年龄为468 Ma（王冬兵等，2016）；曼信辉长岩年龄为420 Ma（王保弟等，2018）；湾河变质堆晶辉长岩年龄为 470.8 Ma（刘桂春等，2017）；临沧市云县半坡辉长岩年龄为280 Ma和285.6 Ma（简平等，2004； Jian et al.， 2009）；南景谷县龙街乡田家辉长岩年龄为362 Ma、斜长花岗岩年龄为328 Ma、辉绿岩墙年龄为382.9 Ma（简平和汪啸风，1998；Jian et al.，2009），辉长岩单斜辉石年龄为339.2 Ma（钟大赉，1998）；景洪南安山岩（洋内弧）年龄为248.5 Ma（Peng et al.， 2008）.综上，昌宁‒孟连区蛇绿岩等洋壳残块的年龄分布范围为486~230 Ma（寒武纪末期‒晚三叠世初期），持续时长256 Ma.

在该区的西盟里拉和孟连岔河的腊组中获放射虫Eoalbaillella lilaensis等，与早泥盆世早‒中期的笔石化石Monograptus uniformmis，M. aegualoilis，M. microdou，M. yukonensis等共生（Feng and Liu，1993）.在孟连曼信和耿马等地获早石炭世放射虫化石，建立了4个组合带，Albaillella paradoxa组合带（见于孟连曼信），Albaillella deflandrei组合带（见于孟连曼信河东），Eostylodictya rota组合带（分布广，见于耿马弄巴、孟连曼信和中寨、孟连班顺）和Albaillella cartalla组合带（见于弄巴和小拉巴）（冯庆来等，1997）.在景谷县龙洞河和思茅县竹林乡大平掌北硅质岩中获早石灰世放射虫化石Astroentactinia multispinosa，Entactinosphaera palimbola，E. foremanae，E. egindyensis，E. inusitata，E. euthlasta，Latentifistula concenrtica（冯庆来等，2000）.在澜沧县南畔拉巴上部地层、澜沧老厂矿区老厂组和景洪县邦沙火山岩地层中获二叠纪放射虫Fullicucullus组合带（茅口期晚期‒吴家坪期早期）、Neoalbaillella optima组合带（吴家坪期晚期）和Neoalbaillella ornithoformis组合带（长兴期早期）（冯庆来和刘本培，1993a）.在澜沧县拉巴乡牡音河及南畔河河谷中的牡音河组中获晚二叠世‒中三叠世早期放射虫，自下向上建立了4个组合：Wangia组合（晚二叠世最晚期）、Shegia yini组合（早三叠世早期）、Pseudoeucyrits liui组合（早三叠世晚期）和Triassocampe deweveri组合（中三叠世晚早期） （冯庆来和刘本培，1993b）.在沧源北北东约20 km一带的硅质岩中产晚二叠世晚期放射虫Areolicaudatus semilobosa，Entatina parapycnoclada，E. itssukaichiensis，Triplanospongos musashiensis等（冯庆来等，1999）.在澜沧县南畔村北的硅质岩序列中自下向上识别出4个放射虫带：Triassocampe dumitricai带（安尼早期）、Tr. cronata inflate带（安尼中期）、Tr. cronata cronata带（安尼中期）、Tr. deweveri带（安尼晚期）（Feng et al.，2001）.在景洪市曼别村和大新山地区的大新山组红色硅质岩中产二叠纪放射虫Follicucullus scholasticus，Follicucullus sp.，Follicucullus sp.，Pseudoalbaillella spp.（Feng et al.，2002）.

2.3　冈底斯‒喜马拉雅大区

本大区位于班公湖‒双湖‒怒江‒昌宁‒孟连对接带以南、印度克拉通以北，主体是受控于班公湖‒双湖‒怒江‒昌宁‒孟连原‒新特提斯大洋向南俯冲、雅鲁藏布古‒新特提斯大洋向北俯冲制约的多岛弧盆系转化形成的造山系.该大区分布两条由近平行的蛇绿混杂岩带组成的OPS地层区，即北部的狮泉河‒嘉黎OPS区（蛇绿混杂岩带）、南部的雅鲁藏布OPS区（蛇绿混杂岩带）.狮泉河‒嘉黎和雅鲁藏布江蛇绿混杂岩是目前我国青藏高原乃至内陆地区保存最好、最完整的“三位一体”蛇绿岩组合（潘桂棠等，2017）.该区的其他区带如冈底斯‒察隅弧盆系、保山地块、喜马拉雅地块的火山‒沉积建造等均不属于OPS研究范畴.该大区洋壳残块年龄分布范围是253.00~ 59.29 Ma（晚二叠世‒古新世），总时限193.75 Ma（图3）.

2.3.1　狮泉河‒嘉黎区

位于南侧措勤‒申扎火山‒岩浆弧带和北侧班戈‒八宿‒腾冲岩浆弧带之间，呈NWW⁃NW⁃SE向延伸千余公里、宽3~35 km展布；北西自狮泉河，向南东经拉果错、麦堆、阿索、果芒错、格仁错、孜挂错，经申扎永珠、纳木错西，再向东经九子拉和嘉黎达波密.在云南省芒市三台山出露的早白垩世蛇纹石化橄榄岩可能是该带的南延（云南省地质调查院， 2024）.该带西延被喀喇昆仑北西向大型走滑断裂截切后，可能与国外勒搁博西山‒雅辛蛇绿岩带相连.受大型走滑断裂和逆冲构造的影响，蛇绿混杂岩空间上断续出露.永珠果芒错蛇绿岩主要由变质橄榄岩、辉长岩堆晶岩（残存厚达千米）和枕状玄武岩及辉绿岩墙，以及多层含晚三叠 世‒早白垩世的放射虫硅质岩组成（王永胜，2003）.综合研究表明该带是在弧间裂谷盆地基础上发展起来的一系列藕断丝连的小洋盆（潘桂棠等，2017）.

在狮泉河‒嘉黎区的14处蛇绿岩等洋壳残块已获同位素年龄43个（图3）.狮泉河辉长岩年龄为191~186 Ma（曾孝文，2022），狮泉河镇柯桑那堆晶橄榄辉石岩年龄为193.1 Ma（郑有业等，2006），狮泉河基性岩墙年龄为141 Ma和139 Ma（西藏自治区地质调查院，2024）；聂耳错辉石岩年龄为 222.51 Ma（西藏自治区地质调查院，2024）；改则县古昌辉长岩年龄为128.44 Ma和124.63 Ma（西藏自治区地质调查院，2024）；改则县拉果错细粒辉长岩年龄为172.8 Ma（西藏自治区地质调查院，2024），拉果错辉长岩年龄为183 Ma（徐建鑫等，2018），拉果错斜长花岗岩年龄为124 Ma和183~155 Ma （曾庆高等，2014）、167 Ma（张玉修等，2007）、166.6 Ma（张玉修等，2007）和189.9 Ma（樊帅权等，2010），拉果错角闪岩年龄为177.6 Ma和176 Ma（Wang et al.，2008）；尼玛县中仓堆晶辉长岩年龄为116.1 Ma和114.3 Ma，辉长岩岩墙年龄为113.4 Ma（徐梦婧，2014）；尼玛县阿索辉长岩年龄为117.5 Ma（曾孝文等，2018）、辉绿岩年龄为118.9 Ma（王保弟等，2020）和124 Ma（Zhang et al.，2014）、堆晶辉长‒辉绿岩和辉绿岩年龄为120~110 Ma（谢国刚等，2002）；尼玛县戈芒错西辉长岩年龄为207~ 193 Ma，玄武岩年龄为219 Ma（徐梦婧，2014）；申扎县北永珠辉长岩年龄为151 Ma（Zeng et al.，2018）和178 Ma（曲永贵，2003）、辉绿岩年龄为133~ 114 Ma（曲永贵，2003）；仁错辉长岩年龄为169~144 Ma（Tang et al.，2020）；生觉北侧辉长岩年龄为179 Ma（肖序常，2000）和173 Ma（吴珍汉等，2003）；纳木错辉长岩年龄为178 Ma（Zhong et al.，2015），橄榄岩年龄为166 Ma（叶培盛等，2004）；嘉黎县桑巴区凯蒙IAT/MORB橄长岩年龄为218.2 Ma（和钟烨等，2006）；波密县闯巴镁铁‒超镁铁岩年龄为215 Ma（朱伟元等，1995）；芒市三台山蛇纹石化橄榄岩年龄为190.5 Ma（云南省地质调查院， 2024）.综上，狮泉河‒嘉黎区蛇绿岩等洋壳残块的年龄分布范围为222.51~110.00 Ma（图3），持续时长112.5 Ma.

该区（带）发育与超基性‒基性洋壳残块伴生的放射虫硅质岩，狮泉河硅质岩产晚侏罗世‒早白垩世放射虫组合Pantanellium sethocapsa uterculus，Mirifusus dianae minor；尼玛县阿索硅质岩产晚三叠世‒白垩纪放射虫组合Archaeodictyomitra sp.， Pseudodictyomitra sp.， Praeconocaryomma sp.， Crucella sp.，Paronaella sp.，Thanarla sp（西藏自治区地质调查院，2024）. 申扎县北永珠硅质岩产晚三叠世‒白垩纪放射虫组合Acaeniotyle sp.， Crucella sp.， Parvicingula sp.（王玉净等，2002）.改则拉果错硅质岩产中侏罗世‒早白垩世放射虫：Acaeniotyle sp. cf. A. umbilicata，Archaeotritabs hattori，Bernoullius sp. cf. B. rectispinus s.l.， Crolanium puga，Dictyomitra communis，Parashuum sp. cf. P. izense，Parashuum izense，Parashuum sp. cf. P. officerense，Paronaella sp. cf. P. skowkonaensis，Pseudodictyomitra carpatica，Pseudoeucyrtis apochrypha，Sethocapsa orca，Tethysetta usotanensis，Thanarla brouweri，Thanarla pacifica，Xitus clava（Baxter et al.， 2009）.

2.3.2　雅鲁藏布区

习称雅鲁藏布江蛇绿混杂岩带，夹持在冈底斯‒察隅弧盆系（北）与喜马拉雅地块（南）之间，是印度与欧亚大陆间新特提斯大洋最终消亡和陆‒陆碰撞的结合带（潘桂棠等，2015，2017）.该区的北界断裂是达吉岭‒昂仁‒仁布‒朗县‒墨脱断裂，总体表现为反向南倾的逆冲断裂系.该区的南界断裂为北倾的向南逆冲系，又称仲巴‒拉孜‒邛多江断裂.西段呈北西向展布，沿噶尔河向西延出国境；中段大致沿雅鲁藏布江谷地近东西向延展至米林，南段从米林向东绕过雅鲁藏布江大拐弯转折向南东延入缅甸，在中国境内长达2 000 km以上.（1）雅鲁藏布江蛇绿混杂岩带西段：由南、北两支蛇绿混杂岩亚带及夹持在两亚带之间的仲巴地块（地块上是古生代‒白垩纪稳定海相沉积以及上新世以来陆相沉积）组成；北亚带（主带）的基质以“嘎学岩群”浊积岩（J₃K₁）为主，岩块有超镁铁质岩、堆晶辉长岩、席状岩墙群、枕状玄武岩和放射虫硅质岩；玄武岩为OIB型，常与灰岩伴生形成海山.南亚带（又称拉昂错‒牛库蛇绿混杂岩带）的基质主要为上三叠统“修康群”和上侏罗统‒下白垩统“嘎学群”，是斜坡‒深海盆地相的浊积砂板岩和放射虫硅质岩‒硅泥质岩夹块状或枕状玄武岩等的组合，其中混杂有大量的二叠纪‒白垩纪碎屑岩或灰岩等岩块.玄武岩为E⁃MORB和OIB型（孙立新，2005；潘桂棠等，2017）.（2）中‒东段（仲巴以东）：蛇绿岩保存好，由地幔橄榄岩‒堆晶岩‒均质辉长岩、席状岩墙‒枕状熔岩和硅质岩组成完整蛇绿岩层序.在东段的雅鲁藏布江大拐弯地区出露变质蛇绿混杂岩，东段蛇绿混杂岩带可分为马泉河‒罗布莎‒朗县蛇绿混杂岩亚带和中贝‒玉门蛇绿混杂岩亚带.在仁布以东至雅鲁藏布江大拐弯一带的“罗布莎混杂岩”的基质为上三叠统“修康群”和上侏罗统‒下白垩统“嘎学群”的弱变质强变形的浊积岩建造，含蛇绿岩岩块和硅质岩及二叠系大理岩等岩块.在罗布莎蛇绿岩及其豆荚状铬铁矿石中，杨经绥等 （2006）发现金刚石、硅金红石、柯石英、蓝晶石、TiFe合金和TiSi合金等系列高压矿物.郑来林等（2003）在南迦巴瓦地区旁辛蛇绿岩中发现玻安岩，是洋‒洋俯冲形成的洋内弧环境建造.在雅鲁藏布江蛇绿混杂岩带中段南部发育高压变质带（从萨嘎向东经昂仁、拉孜、日喀则、仁布，长达600 km、宽度5 km），其中卡堆蓝片岩年龄是59.29 Ma（李才等，2007b），代表了雅鲁藏布江洋壳消亡和印度‒亚洲大陆碰撞的时间.（3）郎杰学增生楔：属雅鲁藏布江东段蛇绿混杂岩南亚带，位于东段之北亚带‒泽当（罗布莎）‒加查‒朗县‒米林蛇绿混杂岩带南侧，南界与喜马拉雅地块以北倾的逆冲断裂分隔，沿仁布以东至琼结‒曲松‒扎日一带宽度出露较大.该带主要包括“上三叠统郎杰学群”及其南部的玉门蛇绿混杂岩.“郎杰学群”主要为一套绿片岩相变质浊积岩夹火山岩系，玉门蛇绿混杂岩中的块体主要有辉橄岩、辉长辉绿岩、玄武岩及玄武质火山角砾岩等（潘桂棠等，2017）.

在雅鲁藏布区的31处蛇绿岩等洋壳残块已获同位素年龄64个（图3）.从西到东南的年龄分布如下：达机翁、卡站和巴尔等地辉长岩和辉绿岩年龄是128~122 Ma（Liu et al.，2018）； 札达县东波辉长岩年龄为159.7 Ma（Chan et al.，2015）、130 Ma和128 Ma（熊发挥等，2011）， 辉石岩、辉长岩和辉绿岩年龄分别是130 Ma、128 Ma和121.1 Ma（西藏自治区地质调查院，2024），枕状玄武岩年龄为138~ 137 Ma（Liu et al.，2015）；噶尔县加纳崩杏仁状玄武岩年龄为89.81 Ma（河北省地质调查院，2004）；偏误单辉橄榄岩年龄为88.95 Ma（河北省地质调查院，2004）；普兰县城北35 km处拉昂措辉绿岩年龄为120.2 Ma（李建峰等，2008）；普兰县辉长岩年龄为130 Ma（刘钊等，2011），辉绿岩年龄为123 Ma（Chan et al.，2015）、122~118 Ma（Xia et al.，2011）和138.5 Ma（Zheng et al.，2019）；普兰县公珠错OIB玄武岩年龄为245 Ma（Liu et al.，2021）；普兰县拉昂错南侧拉斑玄武岩年龄为152 Ma和147 Ma（Miller et al.， 2003）；仲巴县休古嘎布变辉绿岩年龄为125.21 Ma（河北省地质调查院，2004）、122.3 Ma（韦振权等，2006）和126.7 Ma（Chan et al.，2015）；仲巴县辉绿岩年龄为125.7 Ma（Dai et al.，2011），OIB玄武岩年龄为253 Ma（Liu et al.，2023）；萨嘎OIB辉长岩和OIB玄武岩年龄分别为190.02 Ma和 168.49 Ma，萨嘎南桑单林玄武岩年龄为78.81 Ma，桑桑列定玄武岩年龄为101.42~ 67.43 Ma（河北省地质调查院，2002）；萨嘎县吉定镇辉长岩年龄为128 Ma（王冉等，2006）；桑桑城东辉绿岩年龄为125.2 Ma（夏斌等，2008b）；日喀则市东南约20 km N⁃MORB辉长岩年龄为125 Ma（李建峰等，2009）和123.8Ma（刘函等，2021）；日喀则市德吉辉绿岩年龄为125 Ma（Dai J et al.， 2013）；日喀则市吉定县辉长岩年龄为174 Ma（Wang et al.，2018）；日喀则市堆晶辉长岩年龄为129~124 Ma（Liu et al.，2016a），基性岩（未分）年龄为120 Ma（Göpel et al.，1984）；日喀则市卡堆中基性熔岩（未分） 年龄为179 Ma（胡敬仁，2002）；大竹卡斜长花岗岩年龄为139 Ma（王希斌等，1987）；仁布德吉林OIB玄武岩年龄为237.1 Ma（西藏自治区地质调查院，2024）；浪子卡县白地辉长岩年龄为233 Ma（谢尧武，2007）；山南市乃东区泽当枕状玄武岩年龄为215.57 Ma和 168.24 Ma （高洪学，1994）；乃东区泽东镇玄武岩年龄为154.9 Ma（刘维亮等，2013）；曲松县罗布莎辉绿岩年龄为162.9 Ma（钟立峰等，2006）和 148.4 Ma（Chan et al.，2015）、辉长‒辉绿岩年龄为177 Ma（周肃等，2001），枕状玄武岩年龄为 173.27 Ma（李海平等，1996）；卡堆蓝片岩年龄为59.29 Ma（李才等，2007b）；加查‒朗县玄武岩年龄为147.8 Ma，辉绿岩年龄为191.4 Ma和145.7 Ma（王立全等，2008）；朗县辉绿岩年龄为147 Ma（张万平，2012）；雅鲁藏布江大拐弯超镁铁质岩中辉石年龄为200 Ma（耿全如等，2004）；墨脱县马尼翁变质蛇绿岩斜长石和角闪石年龄为218.63 Ma和141.7 Ma（章振根等，1992）.综上，雅鲁藏布区蛇绿岩等洋壳残块的年龄分布范围为253.00~ 59.29 Ma（晚二叠世‒古新世），总时限193.75 Ma（图3）.

该区（带）与超基性‒基性洋壳残块伴生的紫红色放射虫硅质岩十分发育.仲巴县白弄北、仇仁玛北、杰玛央宗曲北岸、岗久东及奔德日等地硅质岩产中‒晚三叠世放射虫组合Cenosphaera⁃ Phormocyrtis、Capnuchosphaera⁃Angulobracchia 和Parahsuum⁃Citriduma（张计东等，2016）.山南市乃东区泽当西金鲁村硅质岩中产放射虫Copnuchosphoaera triassica，Pseudostylosphaera nazarovi，时代为中‒晚三叠世（王玉净等，2002）.Chen et al.（2019）也报道了泽当布若仓剖面层状硅质岩中发现的中三叠世安尼期放射虫动物群，识别出Oertilispongus inaequispinosus和Triassocampe deweveri两个组合.泽当金鲁乡鲁巴垂附近硅质岩含放射虫Becus triangulocentrum，Cecrops septemporatus，Cryptamphorella conara，Dicerosaturnalis dicranacanthos，Eucyrtidiellum pyramis，Hiscocapsa verbeeki，H. uterculus，Holocryptocanium barbui，Praeconosphaera sphaeroconus，Tethysetta boesii等重要分子，其时代为晚侏罗世提塘晚期‒早白垩世阿普特期（刘实佳等，2016）.拉孜县汤嘎、破姆弄和吉定紫红色硅质岩产晚侏罗世‒早白垩世放射虫Archaeodictyomitra psudomulticostata，A.mitra，A. tumandae，Ditrabs sp.，Godia cronata，Pseudodictyomitra sp.，P. liyae，Pseudocrolanium sp.，Thanarla conica等（朱杰等，2005）.嘎尔东红色硅质岩含放射虫化石Thanarla pulchra，Holocryptocaniumbarbui，Holocryptocanium cf. barbui，Thanarla？ sp.等，时代为早白垩世.加纳崩北的扎朗混杂岩紫红色硅质岩岩块中含放射虫Parvicingula sp.，Archaeospongoprunum？sp.，Siphocampium？ sp.，Siphocampium？ davidi，Rhopalosyringuim aff. majuroensis，Pseudodictyomitra sp.等，时代早白垩世.得不穷附近的扎朗混杂岩红色硅质岩岩块含放射虫化石Canoptum poissoni，Droltus（？） aff. probosus，Spumellaria等，时代是早侏罗世中期（张双增等，2004）.萨迦县赛区北部混杂岩中的硅质岩产晚白垩世放射虫Acanthocircus dicrancanthos，Dictyomitra turris，D.megnifica，D.turritu，Holocryptocanium aff. barbui，Pseudodictyomitra pseudomacrocephala，Thanarla pulchra，T.veveta（李国彪等，2003）.萨嘎桑单林硅质岩含晚白垩世放射虫Archaeospongoprunum tehamaensis带和Dictyomitra lamellicostata⁃Squinabollum fossilis组合以及晚古新世放射虫Bekoma campechensis带和B. bidartensis带.仲巴加柱红色硅质岩产早白垩世放射虫Katroma bicornis⁃Pantanellium lanceola组合、晚白垩世放射虫组合Thanarla lacrimula⁃ Tricapsula costata、Cryptamphorella conara⁃ Pseudoeucyrtis tavricus和Cavaspongia antelopensis⁃Acaeniotyle umbilicata组合，以及古新世晚期放射虫Buryella pentadica带（Ding， 2003； 梁银平，2012；Liang et al.， 2012； 王学恒等，2016）.

3 讨论

奥地利地质学家Eduard Suess 1893年首次将从加勒比海经阿尔卑斯山、土耳其、伊朗高原、喜马拉雅（我国青藏高原）至东南亚三叠纪以来的海洋，以希腊神话中的巨人女海神Tethys（特提斯）命名，代表了三叠纪以来横贯北方安加拉大陆（Angara）与南方冈瓦纳大陆（Gondwana）之间向东喇叭状张开的海洋（Şengör et al.，1984）.自特提斯提出以来，关于特提斯演化、特别是青藏高原特提斯演化及演化模型，一直是国际地学研究与争论的热点（Şengör and Yimaz，1981； Şengör et al.，1984； 黄汲清和陈炳蔚，1987； 潘桂棠，1994； Metcalfe，1996， 2021；潘桂棠等，1997； 殷鸿福等，1999； Stampfli and Borel， 2002；李三忠等，2016b； Torsvik， 2019；吴福元等，2020）.下文以青藏中‒南部的洋壳残片时空分布为依据（图3和图4），着重讨论青藏高原特提斯的演化模式、阶段及其OPS在重塑古洋盆演化历程中需遵循的几个基本原理.

3.1　青藏OPS时空分布与“传送带式”和“翻书式”特提斯洋的演化矛盾

基于从写实而不是从模型出发，通过系统集成前人对青藏高原所有蛇绿混杂岩带洋壳残块测年与构造环境判别的数据与信息，本文用图3和图4揭示了青藏高原特提斯OPS时空分布特征，如图所示，青藏高原的“古‒中‒新特提斯”三阶段“传送带式”（Stampfli and Borel， 2002； Torsvik， 2019）或“翻书式”（Metcalfe，1996， 2021）的演化模型不成立.按“传送带式”和“翻书式”，青藏高原从北到南，是由南半球的冈瓦纳大陆依次裂离并向北半球的劳伦大陆依次拼贴过程中形成的，从时间上依次从老变新.“传送带式”和“翻书式”的具体过程是：首先，晚古生代初巴颜喀拉地块裂离北漂，在其后方西金乌兰‒金沙江‒哀牢山古特提斯洋打开；然后，中生代初西金乌兰‒金沙江‒哀牢山古特提斯洋关闭，羌塘地块裂离北漂，在其后方班公湖‒怒江‒昌宁‒孟连中特提斯洋打开；最后，中生代中期班公湖‒怒江‒昌宁‒孟连中特提斯洋关闭，冈底斯地块裂离北漂，在其后方雅鲁藏布新特提斯洋打开，新特提斯洋在藏南于新生代早期关闭.

图3和图4显示的实际情况与上述“传送带式”和“翻书式”不符的主要理由是：

（1）原划为中特提斯的班公湖‒怒江‒昌宁‒孟连洋开启的时间不是三叠纪，而是在奥陶纪就开启了（图3和图4），如470.8 Ma的湾河变质堆晶辉长岩（刘桂春等，2017）、486 Ma的双江县勐库（退变）榴辉岩、473~439 Ma的南汀河辉长岩和420 Ma曼信辉长岩（王保弟等，2013， 2018），均表明原特提斯洋已存在.班公湖‒怒江‒昌宁‒孟连洋的古特提斯洋存在的事实更加丰富，如385 Ma的铜厂街辉长岩（从柏林等，1993），362 Ma、328 Ma和382.9 Ma的景谷县龙街乡田家辉长岩、斜长花岗岩和辉绿岩墙 （简平和汪啸风，1998； Jian et al.，2009）以及 339.2 Ma的辉长岩单斜辉石（钟大赉，1998）， 272 Ma的牛井山斜长角闪岩 （王冬兵等，2017），361.4 Ma的昌都曲登乡‒脚巴山MORB/OIB玄武岩，259 Ma的那曲市达仁MORB辉长岩（西藏自治区地质调查院，2005），280 Ma的类乌齐辉长岩（胡培远等，2016）和254 Ma的日土玄武岩（黄启帅等，2012）.

（2）前人的“传送带式”和“翻书式”模型中，在班公湖‒怒江洋之北不存在与其平行的龙木错‒双湖洋.2000年以来，对青藏高原地质填图空白区开展的1∶25万和1∶5万区域地质调查的一项重大进展是：在班公湖‒怒江蛇绿混杂岩带之北的南羌塘发现一条东西长一千多公里、南北宽一百多公里的富含蛇绿岩岩块和高压‒超高压变质岩的巨型俯冲增生杂岩带（潘桂棠等，2013，2017），该带中的蛇绿岩年龄贯穿整个古生代，如517.1 Ma、 505.3 Ma、461 Ma、438 Ma、431 Ma、355 Ma和345 Ma的果干加年山N⁃MORB堆晶辉长岩（李才，2008；王立全等，2008；Zhai et al.，2013；吴彦旺等，2014），以及467 Ma的桃形湖N⁃MORB堆晶辉长岩（Zhai et al.，2010）等（图3）.这些重大发现完全与“传送带式”和“翻书式”模型相背.

（3）关于雅鲁藏布蛇绿混杂岩带代表的新特提斯洋的开启时间，以往认为是在早侏罗世或晚三叠世开启，最近在该带发现存在中三叠世和晚二叠世的洋壳残块.在普兰县公珠错获得OIB玄武岩（245.1±2.5）Ma和（241.9±4.1）Ma的锆石LA⁃ICP⁃MS U⁃Pb年龄（Liu et al.，2021）；在仲巴获得OIB玄武岩锆石的SIMS U⁃Pb年龄（253±13）Ma （Liu et al.，2023）.这些年龄揭示出雅鲁藏布蛇绿混杂岩带含有古特提斯洋开启的信息，并非全是新特提斯洋.

从上述实际材料看，前人在青藏高原划分的各自在空间和时间上互不重叠的古、中、新特提斯洋（“传送带式”和“翻书式”）不成立.实际情况是，横亘于青藏高原中部的龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连巨型缝合带代表的大洋从寒武纪开始，连续演化至早白垩世消亡，是原特提斯、古特提斯、中特提斯和新特提斯洋长期连续演化的历程（图3和图4）.南部的雅鲁藏布洋从二叠纪开始，连续演化至古近纪消亡，经历了古特提斯、中特提斯和新特提斯洋的连续演化.

因此，青藏中‒南部的特提斯洋演化的实际情况是：最早的原特提斯大洋是从高原中央的龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连开始的，本文称之为“中央大洋”，然后分别向北和向南开启更晚的古、新特提斯洋，即向北、向南双向迁移（图3和图4），本文称之为“中央大洋双向迁移模型”.不存在前人提出的从北向南、从老到新依次单向迁移的“翻书式模型” （Metcalfe，1996， 2021）.基于此，本文认为，潘桂棠等（2002，2013，2017，，2020）依据青藏高原特提斯地质特征，将青藏及邻区的特提斯构造域的原型重建为一个特提斯大洋（龙木 错‒双湖‒班公湖‒怒江‒昌宁‒孟连大洋）、南北二个大陆边缘和三大多岛弧盆系，是非常切合实际的.

另外，需要对特提斯洋演化阶段重新定义.本文建议，将特提斯洋演化仅限于时间划分，不含彼此独立存在的空间概念.按时间，划分为原特提斯（新元古代晚期‒早古生代）、古特提斯（晚古生代‒中三叠世）和新特提斯（晚三叠世‒新生代），将“中特提斯”归入新特提斯，弃用“中特提斯”.

3.2　OPS拓宽了识别洋盆遗迹视觉

前人识别洋盆往往只看有无蛇绿岩存在，无视洋盆的其他物质建造.OPS研究打开了识别洋盆遗迹的新视觉和新领域.OPS揭示出，洋盆洋壳建造除蛇绿岩外，还有由洋壳板内上涌的地幔柱柱头形成的洋岛和海底高原，洋内洋壳与洋壳俯冲形成的洋内弧等，以及叠盖在洋脊、洋岛和洋内弧之上的碳酸盐岩海山，远洋深海盆地沉积和海沟沉积等（Isozaki et al.， 1990；Wakita， 2012；Kusky et al.， 2013； 张克信等， 2016， 2020， 2021）.

前人识别洋盆时往往只看到小洋，无视大洋.表现在岩石地球化学投图SZZ型蛇绿岩分布多，且甚者将SZZ型蛇绿岩视为裂谷而没了洋.基于习惯性地将识别洋的标志单一化和将古陆块面积歪曲放大的现象，在应用OPS时需注意：（1）洋大于陆律，地球历史时期，至少从元古宙开始，洋总是大于陆，揭示了大陆内所有的古缝合带都代表着消失的洋盆；如将古缝合带归到裂谷，岂不变成陆大于洋了？（2）洋互通律，揭示了地史时期各阶段的古大洋总是相互连通，存在着洋‒洋转换、洋陆位置不断变化，不存在原地反复开合的洋盆.（3）大洋生小洋律，揭示了具SSZ蛇绿岩的弧后或弧间小洋盆总要依附于某主大洋盆，因此在进行古洋盆性质恢复时，不可只见小洋盆，不见其主洋盆母体；不能单凭蛇绿岩岩石地球化学投图判断小洋盆和大洋盆（图3显示，几乎所有的蛇绿岩带的岩石地球化学判别时，在同条蛇绿岩带内甚至同一蛇绿岩露头上，N⁃MORB和SSZ往往同带同地同时出现，因此单凭 N⁃MORB和SSZ难以确定是大洋还是陆缘小洋）；缝合带内蛇绿岩、洋岛‒海山和洋内弧等洋壳残块分布的时限长与短，以及相伴的远洋和海沟沉积的时限长与短，是区分大洋盆（对接带）与小洋盆（叠接带）的关键.另外，有海分布，则洋必不远.重塑原型盆地时，当确定出陆棚浅海带和大陆斜坡半深海带时，与其紧邻的就是洋盆了.在原型盆地分布格架中，陆棚浅海带和大陆斜坡半深海带两者宽度之和，肯定远远小于洋盆带的宽度.因此按瓦尔特相律，通过沉积相带分布判明洋盆范围可能比蛇绿岩的存在与否判明洋盆更可信和更实用.（4）混杂岩总体无序律，揭示了在有序的克拉通盖层上建立的岩石地层单位“组”和“群”等，决不能直接照搬到俯冲增生杂岩带；在增生杂岩带某岩块或岩片所获年龄不能代表整个增生杂岩带的形成年龄，也不可将其年龄随意扩展到相邻的岩块或岩片.

某学科模型建立之后，需要系统创立一套定律引导学科健康发展，以避免无休止争论.所谓定律，就是对不争的客观事实和规律简单明了地表达.如同地层学奠基人史坦诺1669年提出的著名地层学三定律：层序叠加律——地层未经变动则下老上新；原始连续律——地层未经变动则呈连续体并逐渐尖灭；原始水平律——地层未经变动则呈水平或大致水平产状.300多年以来地层学的不断创新和发展得益于这三定律的奠基.

为更好理解OPS内涵，本文对OPS提出如下几条定律或公理：（1）洋大于陆——自现代板块构造启动以来地球表层的洋壳面积总大于陆壳面积；（2）洋互通——地球自有洋以来所有洋互通；（3）大洋生小洋——活动陆缘弧后和弧间小洋盆之母是大洋；（4）混杂岩总体无序——缝合带混杂岩总体无序但局部有序.

本文认为，这些看似简单明了的公理，往往会被忽视；正如上述地层学简单明了的三定律，在现代地层学调查中也会被一些学者忽视.如第四纪地层调查中，会误将同一盆地不同钻孔所见砾石层、砂层等作为同时代层相连，是误解“原始连续律”所致.同样，调查造山系缝合带混杂岩时，曾有学者用某一新获测年数据或新获化石出现的时代，来囊括整个混杂岩的地质时代，从而片面否认前人的认识，这是没有正确应用“混杂岩总体无序”之律所致.也有学者研究造山域内（如青藏高原）的多条蛇绿岩带时，将其统统视为SSZ型小洋盆，造成了只见小洋，不见小洋之母大洋，也造成陆壳面积大于洋壳面积之误.

4 结论

（1）在造山域，尽可能系统收集、梳理分析所有洋壳残块同位素测年和古生物化石，从整体上写实构建造山域OPS时空分布和地层格架，是对造山域不同时代洋陆分布与洋陆转换研究的基石.

（2）OPS研究有助打开识别古洋盆遗迹的新视觉和新领域.OPS揭示出，洋盆洋壳建造除蛇绿岩外，还有由洋壳板内上涌的地幔柱柱头形成的洋岛和海底高原，洋内洋壳与洋壳俯冲形成的洋内弧等，以及叠盖在洋脊、洋岛和洋内弧之上的碳酸盐岩海山，远洋深海盆地沉积和海沟沉积等.

（3）国际上流行的青藏特提斯演化模式是由南半球的冈瓦纳大陆依次裂离的地块链向北漂移时，在其后缘依次形成原特提斯洋、古特提斯洋、中特提斯洋和新特提斯洋，并依次向北半球的劳伦大陆拼贴（“单向传送带式”或“翻书式”），最终形成了青藏陆块.本文通过对青藏高原OPS时空分布写实，揭示出所谓的“传送带式”或“翻书式”模型不完全成立.

（4）本文认为，潘桂棠等（2002，2013，2017，，2020）依据青藏高原特提斯地质特征，将青藏及邻区的特提斯构造域的原型重建为一个特提斯大洋（龙木错‒双湖‒班公湖‒怒江‒昌宁‒孟连大洋）、南北二个大陆边缘和三大多岛弧盆系，是非常切合实际的，值得进一步深化研究.本文暂将青藏特提斯演化模型称之为“中央大洋双向迁移模型”.

（5）为更好理解OPS内涵，本文对OPS提出如下几条定律：一是洋大于陆律——自现代板块构造启动以来地球表层的洋壳面积总大于陆壳面积；二是洋互通律——地球自有洋以来，所有洋互通；其三是大洋生小洋律——活动陆缘弧后和弧间小洋盆之母是大洋；其四是混杂岩总体无序律——混杂岩总体无序但局部有序.

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基金资助

中国地质调查局项目(DD20221645)

国家自然科学基金项目(41772107)