拉萨地块和羌塘地块多个二叠纪基性岩及一个古特提斯海山的初步古地磁结果:对模拟东冈瓦纳晚古生代裂解的暗示

Detachment of the sliver-like Cimmerian terrane from eastern Gondwana in the Early Permian triggered mafic volcanism in many parts of the rift zone. To understand this tectonic episode we have carried out paleomagnetic investigations on mafic volcanic for-mations that were erupted on key terranes that now form part of Tibet. Specifically, we will present data from sections near Lhasa City (central Lhasa block) and Tuotuohe (central Qiangtang Block) as well as near Gyanyima (Paleotethyan sea-mount) that was emplaced onto the floor of Palaeotethys during the Late Permian. Paleomagnetic plots from each location will be used for tectonic calculations. Our new data will be used to evaluate regional scale models con-cerned with how the Cimmerian terranes in southern and SE Asia (from Iran-Tibet-SW China-Myanmar- Thailand-Sumatra) formerly abutted eastern Gond-wana.     

拉萨地体的起源和古生代构造演化

早期由于资料有限,对拉萨地体古生代时期的裂解、漂移、俯冲和碰撞历史的认知程度还很低。本文利用目前已有
地质和地球化学资料,分析了拉萨地体的中生代岩石圈结构,探讨了拉萨地体的起源和古生代演化历史。大量长英质岩石
的锆石Hf 同位素和全岩Nd 同位素表明,南部和北部拉萨地体以新生地壳为主,部分地区可能存在前寒武纪结晶基底,而
中部拉萨地体是具有古元古代甚至太古代结晶基底的条带状微陆块。大量古生代沉积岩的碎屑锆石U-Pb 年龄数据表明,拉
萨地体约1170 Ma 的碎屑锆石年龄指标,明显不同于以约950 Ma 为碎屑锆石年龄指标的安多、羌塘和特提斯喜马拉雅。拉
萨地体起源于澳大利亚大陆北缘是目前资料情况下的最合理解释。中部拉萨地体约492 Ma 的双峰式火山岩形成于活动大陆
边缘背景,代表了古地理上位于澳大利亚大陆北缘的岩浆弧的一部分,可能与原特提斯洋岩石圈板片的断离有关。拉萨地
体南缘和南羌塘的泥盆纪末期-石炭纪早期片麻状花岗岩类为存在明显幔源物质输入的S 型花岗岩,可能形成于最终演化
为松多特提斯洋的弧后盆地背景。中二叠世末期发生的拉萨地体与澳大利亚大陆北缘的碰撞造山事件可能触发了班公湖-
怒江特提斯洋岩石圈的南向俯冲,并随后对拉萨地体的中生代构造岩浆演化发挥关键性作用。     

东准噶尔构造带晚古生代地层时代的厘定及其对区域构造演化意义

新疆东准噶尔(东准)构造带晚古生代地层广泛出露,其沉积时限的精确限定对理解该地区及中亚造山带的构造框架具有深远意义。然而东准构造带的地层时代标定存在多种划分方案,分歧较大。依据自测的5个安山岩和9个砂岩的锆石U-Pb年龄以及收集整理的岩浆岩和砂岩的锆石U-Pb年龄约束,认为东准噶尔构造带地质体的形成时代主要在336~268Ma,336Ma地质体沿额尔齐斯、阿尔曼太和卡拉麦里构造带零星分布。原前石炭纪和原石炭纪海相地层主体属于石炭系宾夕法尼亚亚系,部分层段应为同期异相;原石炭纪陆相地层属于二叠系乌拉尔统。东准构造带晚古生代洋盆在晚石炭世同期碰撞拼贴,将其演化阶段分为400~336Ma次生洋盆同期俯冲阶段、336~300Ma洋盆最终闭合消亡阶段、300~270Ma后碰撞伸展阶段及二叠纪中晚期南缘湖相沉积阶段。     

阿尔泰山南缘晚古生代火山岩的地质地球化学特征及其对构造演化的启示

阿尔泰山南缘晚古生代火山岩十分发育,从早泥盆世到早二叠世均有发育。其中中泥盆世北塔山组为一套中基性火山岩,并且底部含有厚度超过100m的苦橄岩;中泥盆世蕴都喀拉组为一套浅海相细碎屑沉积岩夹中性、中基性火山岩;晚泥盆世江孜尔库都克组为火山碎屑岩夹中基性和中酸性火山岩组合;而晚石炭世巴塔玛依内山组以玄武岩和玄武安山岩为主,夹凝灰岩、粉砂岩和炭质页岩。对这4个组火山岩的主要元素、微量元素地球化学特征研究表明,北塔山组和蕴都喀拉组为拉斑和钙碱性系列,并且均具有大离子亲石元素(LILE)富集,而高场强元素与MORB相当,说明其为岛弧环境。江孜尔库都克组火山岩为钾玄岩系列,并且具有较高的LILE富集,表明其形成于岛弧演化的晚期阶段;巴塔玛依内山组火山岩为碱性系列,并且具有强烈富集LILE的特征,指示了其形成于大陆板内环境。因此,从火山岩的时间和空间演化来看,本区晚古生代火山岩与准噶尔洋板块向北的俯冲有关,西伯利亚板块和准噶尔板块的碰撞发生在早石炭-晚石炭世。     

秦岭岩群东段早古生代构造演化——来自界牌斜长角闪岩和长英质脉体的制约

北秦岭构造带早古生代构造格局和演化过程受到地质学界的长期关注,秦岭岩群在早古生代期间是否经历整体俯冲-深俯冲是存在较大争议的问题之一。西峡寨根地区界牌村附近寨根岩体围岩长英质片麻岩中出露了斜长角闪岩和长英质脉体,本文对其开展了详细的LA-ICP-MS锆石U-Pb定年、岩石地球化学、矿物化学和锆石包裹体分析,以期为该问题的探讨提供新的限定。锆石U-Pb年代学研究表明,界牌斜长角闪岩原岩年龄为820Ma,变质时代为(422±5) Ma,锆石中出现斜长石和石英包裹体。该岩石具有与区内榴辉岩相似的岩石地球化学特征,岩石中存在2类角闪石,分别形成于角闪岩相变质和之后的退变质阶段,长英质脉体中存在大量继承/捕获锆石。其中,1115～1576 Ma、502～517 Ma锆石来自秦岭岩群高压-超高压长英质片麻岩,908～935 Ma锆石来自寨根岩体,该岩石形成时代为(447±4) Ma,在420 Ma受到变质改造。长英质脉体具有富w(K₂O)、Rb和Ba,低w(CaO)、w(Fe₂O₃^T)、w(MgO)和w(TiO...     

内蒙古布林庙晚石炭世碱长花岗岩的发现及其对古亚洲洋演化的制约

对贺根山蛇绿岩带北缘的布林庙碱长花岗岩体进行了LA-ICP-MS锆石U-Pb定年、岩石地球化学特征研究, 以期解释其岩石成因及地质意义。研究表明: 碱长花岗岩体的锆石U-Pb年龄为304±1 Ma, 为晚石炭世岩浆活动的产物; 所有样品的地球化学特征相似, 表现为高硅、富碱且相对富钾、弱过铝质的特点, 富集Rb、K等大离子亲石元素, 贫P、Sr、Ti等元素。结合样品的10000Ga/Al值、TFeO含量、Zr含量、锆石饱和温度等相关指标, 认为岩体为高钾钙碱性(钾玄岩)系列的A型花岗岩。岩体形成于贺根山洋盆闭合后, 是古亚洲洋造山后伸展阶段早期阶段的产物。     

西藏冈底斯带东段早侏罗世英云闪长岩的岩浆起源及其对拉萨地体地壳演化的意义

西藏冈底斯岩浆岩带除了大范围分布的晚白垩世以来的花岗岩类以外,还发育少量晚三叠世—侏罗纪花岗岩,目前关于其岩石成因还存在很多争议。为了进一步认识冈底斯早侏罗世花岗岩的岩浆起源,本文选择代表性的加查县香木村英云闪长岩开展了岩相学、岩石地球化学、锆石U-Pb年代学和Hf同位素研究。所研究的英云闪长岩主要由斜长石、石英、黑云母和少量的角闪石组成。LA-ICP-MS锆石U-Pb定年结果表明其结晶年龄为184±4Ma。锆石εHf(t)值均为正值,变化范围为7.9~10.3。在全岩地球化学组成上,英云闪长岩为中钾钙碱性、准铝质,并具有埃达克质岩石特征:高SiO2、Al2O3、Na2O/K2O(1)和Sr/Y(35.5~106),低Y(4.46×10-6~12.9×10-6)和Yb(0.51×10-6~1.39×10-6),富集Rb、Ba、K、Pb等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素。在稀土元素配分图中呈现轻稀土元素富集、中稀土亏损的右倾"凹"型的式样,无明显Eu异常。岩石地球化学和锆石Hf同位素特征表明其岩浆可能起源于下地壳基性物质的部分熔融,残留相主要为角闪石、石榴子石,无斜长石。综合前人资料,冈底斯晚三叠世—早侏罗世花岗岩的锆石Hf同位素具有由西向东、由南向北逐渐富集的规律,反映古老地壳组分的贡献逐渐增多,这暗示了南冈底斯带东部也可能存在古老的地壳基底。     

甘肃龙首山—合黎山晚志留世—早泥盆世花岗岩类的成因及其对阿拉善地块西南缘早古生代构造演化的约束

阿拉善地块西南缘在中志留世—早泥盆世究竟是处于古亚洲洋俯冲的构造环境,还是因受控于祁连造山带而处于后碰撞伸展环境?这是探讨该区早古生代构造演化不可回避的重要科学问题。阿拉善地块西南缘出露的早古生代岩浆岩是探讨该问题的重要研究对象,但前人的工作集中于北大山和龙首山的东段。本文在龙首山西段及更西部的合黎山地区选择三个花岗岩体进行了LA-ICP-MS锆石U-Pb定年和元素及同位素地球化学研究。结果表明,龙首山西段的大佛寺碱性长石花岗岩形成于晚志留世(426±2 Ma),主量元素具有高SiO₂(78.03%)、富碱(ALK=7.96%)、低CaO(0.60%)、贫MgO(0.13%)的特征,稀土分布呈明显的"V"型,大离子亲石元素(LILEs)高度富集而高场强元素(HFSEs)中等富集,Ba、Sr、Eu负异常显著,属于铝质A2型花岗岩。合黎山地区的五坝黑云母花岗岩和张家窑花岗闪长岩分别形成于晚志留世(421±2 Ma)和早泥盆世(406±4 Ma),都属于高钾钙碱性I型花岗岩,轻、重稀土分异((La/Yb)_N=10.69～13.79),Eu负异常显著...     

大别超高压变质地体的岩石组合及其演化--以皖西南碧溪岭和双河地区为例

碧溪岭和双河地区是大别超高压地体内2个典型的露头区,通过野外露头观察、岩相学和岩石化学研究发现,岩石组合主要为榴辉岩、斜长角闪岩、片麻岩和面理化花岗岩。榴辉岩具有壳源的特点,是地壳岩石在地幔深处发生超高压变质作用形成的;斜长角闪岩为板块折返期间榴辉岩的退变质产物;片麻岩为斜长角闪岩在折返过程中在合适的环境下深熔递进演变的产物;而面理化花岗岩是片麻岩部分熔融的结果。榴辉岩与片麻岩和面理化花岗岩之间为经过改造的原地关系。     

“黔中隆起”和贵州晚古生代古地理演化及其对铝土矿的控矿作用*

早古生代的区域隆升形成的古地貌和晚古生代海平面变化明显控制了贵州晚古生代古地理与古地貌的演化,“黔中隆起”表现尤为明显。然而对“黔中隆起”的形成时间及演化存在较大争议,限制了对贵州铝土矿的沉积古地理与古地理演化史的认识。通过野外踏勘、资料收集和整理,建立了贵州晚寒武世至二叠纪数个重要地质历史时期的古地理图,对“黔中”隆起的形成时间、演化等进行了再认识,揭示其与贵州铝土矿成矿的耦合关系。寒武纪至早志留世早—中期,“黔中隆起”北缘缺失与之相关的古陆边缘相沉积,黔中地区大规模的隆起时间应以下志留统韩家店组潮坪相沉积的出现作为开始。在“黔中隆起”的显著影响下,黔中和遵义地区经历长期而强烈的风化剥蚀,于早石炭世分别形成喀斯特洼地和漏斗、峡谷地貌,为九架炉组含铝岩系的形成提供了物质条件和成矿场所,并在晚古生代冰盖消长带来的海平面和气候变化的影响下,通过强烈的淋滤作用形成铝土矿。黔北务正道地区经历了长期的风化剥蚀后,在海平面高频变化下形成有利于下二叠统大竹园组铝土矿形成的滨岸湿地环境和洼地地貌。贵州早二叠世的铝土矿与晚古生代冰期具有更明显的耦合关系。     

Paleozoic terranes of eastern Australia and the drift history of Gondwana

Critical assessment of Paleozoic paleomagnetic results from Australia shows that paleopoles from locations on the main craton and in the various terranes of the Tasman Fold Belt of eastern Australia follow the same path since 400 Ma for the Lachlan and Thomson superterranes, but not until 250 Ma or younger for the New England superterrane. Most of the paleopoles from the Tasman Fold Belt are derived from the Lolworth-Ravenswood terrane of the Thomson superterrane and the Molong-Monaro terrane of the Lachlan superterrane. Consideration of the paleomagnetic data and geological constraints suggests that these terranes were amalgamated with cratonic Australia by the late Early Devonian. The Lolworth-Ravenswood terrane is interpreted to have undergone a 90° clockwise rotation between 425 and 380 Ma. Although the Tamworth terrane of the western New England superterrane is thought to have amalgamated with the Lachlan superterrane by the Late Carboniferous, geological syntheses suggest that movements between these regions may have persisted until the Middle Triassic. This view is supported by the available paleomagnetic data. With these constraints, an apparent polar wander path for Gondwana during the Paleozoic has been constructed after review of the Gondwana paleomagnetic data. The drift history of Gondwana with respect to Laurentia and Baltica during the Paleozoic is shown in a series of paleogeographic maps.     

Late Paleozoic faults of the Altai region, Central Asia: tectonic pattern and model of formation

The present kinematic and dynamic analysis of large-scale strike-slip faults, which enabled the formation of a collage of Altai terranes as a result of two collisional events. The Late Devonian–Early Carboniferous collision of the Gondwana-derived Altai-Mongolian terrane and the Siberian continent resulted in the formation of the Charysh–Terekta system of dextral strike-slip faults and later the Kurai and Kuznetsk–Teletsk–Bashkauss sinistral strike-slip faults. The Late Carboniferous–Permian collision of the Siberian and Kazakhstan continents resulted in the formation of the Chara, Irtysh and North-East sinistral strike-slip zones. The age of deformation of both collisional events becomes younger toward the inner areas of the Siberian continent. In the same direction the amount of displacement of strike-slip faulting decreases from several thousand to several hundred kilometers. The width of the Late Paleozoic zone of deformation reaches 1500 km. These events deformed the accretion-collision continental margins and their primary paleogeographic pattern.     

Evolution of the Proto-Tethys in the Baoshan block along the East Gondwana margin: constraints from early Palaeozoic magmatism

Zircon U–Pb ages and geochemical and isotopic data for Late Ordovician granites in the Baoshan Block reveal the early Palaeozoic tectonic evolution of the margin of East Gondwana. The granites are high-K, calc-alkaline, metaluminous to strongly peraluminous rocks with A/CNK values of 0.93–1.18, are enriched in SiO₂, K₂O, and Rb, and depleted in Nb, P, Ti, Eu, and heavy rare earth elements, which indicates the crystallization fractionation of the granitic magma. Zircon U–Pb dating indicates that they formed at ca. 445 Ma. High initial ⁸⁷Sr/⁸⁶Sr ratios of 0.719761–0.726754, negative ?_Nd(t) values of –6.6 to –8.3, and two-stage model ages of 1.52–1.64 Ga suggest a crustal origin, with the magmas derived from the partial melting of ancient metagreywacke at high temperature. A synthesis of data for the early Palaeozoic igneous rocks in the Baoshan Block and adjacent Tengchong Block indicates two stages of flare-up of granitic and mafic magmatism caused by different tectonic settings along the East Gondwana margin. Late Cambrian to Early Ordovician granitic rocks (ca. 490 Ma) were produced when underplated mafic magmas induced crustal melting along the margin of East Gondwana related to the break-off of subducted Proto-Tethyan oceanic slab. In addition, the cession of the mafic magmatism between late Cambrian-Early Ordovician and Late Ordovician could have been caused by the collision of the Baoshan Block and outward micro-continent along the margin of East Gondwana and crust and lithosphere thickening. The Late Ordovician granites in the Baoshan Block were produced in an extensional setting resulting from the delamination of an already thickened crust and lithospheric mantle followed by the injection of synchronous mafic magma.     

滇西保山地块早古生代碎屑锆石U-Pb-Hf同位素研究及其对冈瓦纳大陆重建的制约

滇西地区出露的古生界公养河群和孟定街群分别位于保山地块的西部和东部,其沉积时代、构造归属、碎屑物质来源及在早古生代冈瓦纳大陆重建中的古地理位置具有重要研究意义。本文对公养河群2个砂岩样品和孟定街群的4个变质砂岩样品的碎屑锆石进行U-Pb定年和Lu-Hf同位素分析。其中,公养河群的碎屑锆石年龄谱范围是3862～533Ma,ε_(Hf)(t)值的范围是-37. 8～+11. 0,最小年龄峰期为549～533Ma,表明该群的最大沉积年龄为早寒武世早期,该群可能为寒武系地层。孟定街群的碎屑锆石年龄谱范围是3097～542Ma,ε_(Hf)(t)值的范围是-39. 5～+10. 5,其最小年龄峰期(576～458Ma)将该群的沉积下限时代限制在晚奥陶世。结合保山地块的其他古生代地层的碎屑锆石研究,我们认为保山地块在早古生代位于冈瓦纳大陆北缘,物源主要来自印度大陆,但～1. 17Ga年龄峰的出现说明其东部可能接受了一定比例来自西澳大利亚的沉积物质。这一结果表明保山地块在冈瓦纳大陆北缘重建中的位置应该靠近印度大陆,而其东缘接近澳大利亚大陆。     

保山地体寒武纪基性火山岩及其大地构造意义

保山地体位于青藏高原东南缘。有关保山地体的岩浆作用研究大多集中在中生代及新生代,针对古生代岩浆作用的讨论较少。对云南省保山邦迈地区蒲满哨群中变质基性岩的锆石U-Pb年代学、地球化学及Sm-Nd同位素组成进行了研究。这些变质基性岩可分为2组:一组为斜长角闪岩,另一组为黑云斜长角闪岩。锆石U-Pb测年结果表明,斜长角闪岩的形成时代为536.7Ma,黑云斜长角闪岩的形成时代为532.0Ma。地球化学特征显示,斜长角闪岩的原岩为玄武安山岩,黑云斜长角闪岩的原岩为碱性玄武岩。稀土和微量元素配分曲线及多种构造环境判别图解显示,二者分别具有富集型大洋中脊玄武岩和洋岛玄武岩的地球化学特征。结合区域大地构造背景认为,保山地体邦迈变质基性岩为洋脊俯冲的产物。在新元古末期—早古生代,保山地体与拉萨地体、喜马拉雅地体等类似,皆位于冈瓦纳大陆边缘,且共同经历了增生造山过程。     

青藏高原羌塘盆地晚三叠世古地磁数据及其构造意义

羌塘盆地作为青藏高原主要的地体之一,其中生代的地质演化对于研究古特提斯洋关闭和冈瓦纳大陆解体都具有重要的指示意义。为查明羌塘盆地中生代的演化过程,在南、北羌塘坳陷上三叠统扎拉组和土门格拉组地层中共采集200余件砂岩样品进行古地磁对比研究。热退磁实验显示,大部分样品均含有两个磁组分,并揭示出一组高温特征剩磁分量,在95%置信度下通过正倒转检验和正褶皱检验,说明这组高温分量很可能代表岩石形成时的原生剩磁。南、北羌塘坳陷中样品的平均特征剩磁方向分别为D/I=28°/45.5°(a₉₅＝3.6°)和D/I=35.3°/46.5°(a₉₅＝4.0°);其相近的古地磁极和古纬度表明,南、北羌塘在晚三叠世已经属于一个统一的地块,并且具有北纬27°的古纬度。再结合前人研究成果发现,羌塘盆地晚古生代位于南半球中纬度地区,晚二叠世时已靠近赤道,并逐渐从冈瓦纳大陆北缘裂解开来向北漂移。羌塘盆地与塔里木地块在晚三叠世实现了碰撞拼合;中白垩世时,又与拉萨地块完成了板块碰撞。至此,羌塘盆地与周缘各地块基本上完成了碰撞拼合。     

First Late Ordovician Paleomagnetic Pole for the Cuyania (Precordillera) Terrane of Western Argentina: a Microcontinent or a Laurentian Plateau

Time and tectonic processes involved in docking of the Argentine Precordillera (Cuyania terrane) against SW Gondwana has been a matter of much debate. A paleomagnetic study on the Early Caradoc Pavón Formation, exposed in the San Rafael block, province of Mendoza, Argentina, is presented. After detailed thermal and alternating field demagnetizations two geologically significant magnetic components were defined. A widespread post-tectonic component (A) is present in most sites of the Pavón Formation, with dual polarities, and is coincident with the characteristic remanence isolated from a Permo-Triassic rhyolitic dome intruding the sediments. Its pole position (83.7°S, 271.0°E, dp = 6.8°, dm = 9.0° N = 11 sites) falls on the Late Permian-Early Triassic South American reference poles suggesting that this component was acquired during the Choiyoi magmatic phase. A second component (B) also shows dual polarities and a positive fold test suggesting a primary origin. Unblocking temperatures and rock magnetic experiments indicate that B is carried either by hematite or magnetite at different sites. Anisotropy of magnetic susceptibility results suggest a depositional fabric and no remanence distortion due to deformation or compaction. A paleomagnetic pole computed from this remanence (PV) falls on 3.6°N, 346.4°E (dp = 2.9°, dm = 4.6° n = 22 samples). It indicates a paleolatitude around 26°S for deposition of Pavón sediments and constrains the paleogeographic evolution of Cuyania during the Ordovician, which was still at subtropical latitudes by the Early Caradoc. PV is consistent with the Laurentian Late Ordovician reference pole if Cuyania remains attached to SE Laurentia for the Early Caradoc, while it shows a significant cw rotation with no paleolatitude anomaly respect to the Gondwana reference pole when kept in its present position in SW South America. These comparisons are interpreted in three possible alternatives for the paleogeographic and tectonic setting of Cuyania in the Late Ordovician.     

Cambrian volcanism in the Lhasa terrane,southern Tibet: Record of an early Paleozoic Andean-type magmatic arc along the Gondwana proto-Tethyan margin

The present study reports new zircon LA–ICP–MS U–Pb ages, trace element and Hf isotope data, and whole-rock major and trace element data from Cambrian metarhyolites from Zhaqian and Zhakang in the central Lhasa subterrane of southern Tibet. One sample from Zhakang provides a weighted mean ²⁰⁶Pb/²³⁸U age of 510.4 ± 4.0 Ma and two samples from Zhaqian yield weighted mean ²⁰⁶Pb/²³⁸U ages of 510.6 ± 2.6 Ma and 524.8 ± 2.9 Ma, indicating that the Zhaqian and Zhakang metarhyolites were contemporaneous. Both are characterized by high SiO₂ and K₂O and low Na₂O. They are also primarily high-K calc-alkaline, are enriched in Th, U, and light rare earth elements (LREEs), and are depleted in Nb, Ta, Ti, and P. Thus, they are geochemically similar to typical arc volcanic rocks. Moreover, the Zhaqian metarhyolites exhibit varying zircon ε_Hf(t) values (−3.8 to +0.3) that are comparable to those of the Zhakang metarhyolites (−4.9 to −1.0). Both metarhyolites are interpreted as resulting from partial melting of Proterozoic metasedimentary rocks with mantle-derived magma contributions. Contemporaneous magmatism in the early Paleozoic has also been recognized in other microcontinents along the Gondwana proto-Tethyan margin. The emplacement of these magmatic rocks and the development of a Cambro–Ordovician angular unconformity in the central Lhasa subterrane can be attributed to subduction of proto-Tethys Ocean lithosphere in a Andean-type magmatic arc setting following the assembly of various continental components within the Gondwana supercontinent.     

西昆仑甜水海地块南屏雪山早古生代花岗岩地球化学、Hf同位素特征及其壳幔岩浆作用

南屏雪山早古生代花岗岩体位于西昆仑甜水海地块东段,主要岩性为中粒含斑黑云母二长花岗岩(485Ma)和中细粒黑云母二长花岗岩(528Ma)。化学组成上,两者均具有高硅、富碱,贫TFe2O3、MgO和CaO的特征,属高钾钙碱性弱过铝质系列;微量和稀土元素组成上,两者均富Rb、Th、U、K、Pb和轻稀土,贫Ba、Sr、Nb、Ta、Ti和P,Rb/Sr、Rb/Ba、Nb/Ta和Y/Yb比值高,具有明显的Eu负异常,其Zr、Nb、Ce、Y等高场强元素均较之典型A型花岗岩偏低,综合地质地球化学特征的判别表明南屏雪山花岗岩应属高分异的I型花岗岩。中粒含斑黑云母二长花岗岩和中细粒黑云母二长花岗岩均具有较均一的正εHf(t)值(0.9~5.3和1.4~5.6)和中元古代的二阶段模式年龄TDM2(1118~1398Ma和1136~1396Ma),相似的地球化学特征和锆石Hf同位素组分暗示两者可能是同源岩浆演化的产物。结合区域构造演化历史,推测在早古生代原特提斯洋存在双向俯冲,南屏雪山早古生代花岗岩则是在早寒武世-早奥陶世(528~485 Ma)原特提斯洋持续向南的俯冲消减-碰撞造山过程中,诱导幔源岩浆上涌底侵下地壳,诱发区内中元古代新生地壳物质至少两次部分熔融(早寒武世和早奥陶世),并经历一定程度的分离结晶作用而形成的。