China Block Research Articles

Genesis of the Madang Cenozoic sodic alkaline basalt in the eastern margin of the Tibetan Plateau and its continental dynamic implications

The Madang Cenozoic sodic alkaline basalt occurred in the eastern margin of the Tibetan Plateau, where is a key tectonic transform region of Tibet, North China, and Yangtze blocks. The basalts are characterized by the variation in SiO2=42%–51%, Na2O/K2O>4, belonging to the sodic alkaline basalt series. The rocks are enriched in Ba, Th, Nb, Ta, relative to a slight depletion in K, Rb in the trace and rare earth element (REE) spider diagrams that are similar to the typical oceanic island alkaline basalt. The Sr-Nd-Pb isotopic compositions suggest that they are derived from a mixed mantle reservoir. The western Qinling-Songpan tectonic region was controlled by Tibet, North China and Yangtze blocks since Cenozoic, therefore, the region was in the stage of the substance converge from the mantle to upper crust, producing a mixed mantle reservoir in the studied area. The Madang basalts occurred in the specific tectonic background, they result from partial melting of a mixed asthenospheric mantle reservoir in the western Qinling-Songpan tectonic node.

Dynamic patterns of latest Proterozoic‐Palaeozoic‐early Mesozoic marine biodiversity in South China

AbstractAnalyses of global biodiversity curves have been important for the interpretation of co‐evolution between organisms and environments through geological time. Global curves can be better understood if all the data collected from a multitude of palaeocontinents are analysed and explained separately. South China is a major block possessing more advantages for regional research than any of the other blocks in China. There exists a well‐developed succession of marine strata from the Ediacaran through to the Triassic with a relatively high resolution of bio‐ and chrono‐stratigraphy and an extensive marine fossil record. Stratigraphic occurrences of 5685 genera and 1386 families within 32 phyla or subphyla plus groups with uncertain affinities from this interval have been compiled by a large team of palaeontologists. With the exception of the Ediacaran, 50 time intervals with an average duration of 6.8 Ma are investigated. Diversity curves constructed at the levels of genus, family and order indicate that marine biodiversity peaked six times within the intervals: (1) Early Cambrian explosive radiation, (2) Early‐Mid Ordovician radiation mainly of the Paleozoic Evolutionary Fauna, (3) Early Silurian radiation, (4) late Early‐Mid Devonian radiation, (5) Mid‐Late Permian radiation and (6) Mid Triassic radiation chiefly of the Modern Evolutionary Fauna. Drops in biodiversity are controlled by various factors: (1) global catastrophes, which produced rapid losses of biodiversity during short time intervals; (2) global environmental perturbations with long term effects, as in the Carboniferous; (3) regional tectonics and palaeogeographical constraints, resulting in a lack of marine sedimentary rocks in many areas with biodiversity declining, as in the Wenlock; (4) unique sedimentary facies in large areas resulting in biodiversity losses, as in the Late Cambrian and (5) artifactual constraints associated with a lack of fossil record or low research intensity for some intervals, as in the period of about 30 Ma following the Early Cambrian explosive radiation. Copyright © 2007 John Wiley & Sons, Ltd.

Paleomagnetic study of Cretaceous rocks from Pu'er, western Yunnan, China: Evidence of internal deformation of the Indochina block

Cretaceous red sandstones and siltstones were collected at 31 sties for paleomagnetic investigation from the Jingxing and Nanxin Formation around Pu'er (23.0°N, 101.0°E), western part of Yunnan province, China, in order to examine quantitative amount of tectonic deformation of the Simao Terrane due to collision of India with Asia. After stepwise thermal demagnetization, the high-temperature component magnetization with unblocking temperature of around 680 °C is isolated. Positive field tests show that the high-temperature component magnetization from 25 sites is primary for the Cretaceous formations. A tilt-corrected mean direction is D = 59.9°, I = 45.2° with α 95 = 5.1°, corresponding to a paleopole at 35.8°N, 173.1°E with A 95 = 5.6°. Comparison with Cretaceous paleomagnetic pole of the whole China block indicates that amount of clockwise rotation in the Pu'er area is evaluated to be 46 ± 9° with respect to the whole China block, which is consistent with large amount of rotation in the Mengla and Jinggu areas (47° and 66°) in the central part of the Simao Terrane. Clockwise rotation of the central part is larger by more than 20° compared to the Yunlong and Yongping areas of northern part of the Simao Terrane, suggesting that the Simao Terrane experienced internal deformation. The southward displacement of the Pu'er area expected from inclination data is 7.5 ± 6.6° with respect to the Chuan Dian fragment, which is a similar estimate to other areas in the Simao Terrane and the Indochina block. While the Simao Terrane displaced southward by 800 km together with clockwise rotation of 30° as a whole, further clockwise rotation occurred in the central part.

Assemblages and Textural Evolution of UHP Eclogites from the Chinese Continental Scientific Drilling Main Hole

Coesite-bearing eclogite samples from the Chinese Continental Scientific Drilling main hole (100-2000 m) were examined. Three major evolutionary stages are distinguished from mineral assemblages and textural relations. (1) The pre-peak stage is indicated by inclusion assemblages in rutile eclogite such as amphibole and paragonite, with pre-peak P-T conditions of ~13 kbar and ~910°C. (2) The peak ultrahigh-pressure (UHP) metamorphic stage is characterized by the mineral assemblage garnet-omphacite-phengite-rutile-apatite-coesite/quartz pseudomorph ± kyanite; P-T conditions reached ~910°C and ~37 kbar for rutile eclogite, and ~850°C and ~35 kbar for phengite eclogite. (3) The retrograde stage produced decompression textures via back reactions, such as thin coronas of amphibole or zoisite on garnet, fine-grained amphibole-plagioclase symplectites on omphacite and biotite-plagioclase, or K-feldspar-albite on phengite, ilmenite or titanite on rutile, at P-T conditions of 530-560°C and 7-9 kbar. The presence of K-feldspar-albite symplectite on phengite and minor interstitial K-feldspar implies that post-peak decompressional partial melting occurred locally during rapid exhumation of the subducted UHP slab. Two alternative P-T paths may be constructed: (1) the first possesses a different pre-peak stage but similar peak UHP to post-peak decompression cooling for rutile and phengite eclogite; (2) the second shows a consistent evolution from a pre-peak stage via peak UHP stage to a post-peak stage of near-isothermal decompression, followed by near-isobaric cooling for both rutile and phengite eclogite. We prefer the first P-T path, because the inferred paths show a clear increase in pressure and temperature from near-peak to peak UHP stage, and this may be associated with subductionrelated tectonism as a result of continental collision between the North China and Yangtze blocks. Rapid subduction and fast retrograde exhumation is likely responsible for preservation of some pre-peak inclusion assemblages and prograde mineral growth zoning.

Ordovician 40Ar/39Ar phengite ages from the blueschist-facies Ondor Sum subduction-accretion complex (Inner Mongolia) and implications for the early Paleozoic history of continental blocks in China and adjacent areas

We obtained 453.2 ± 1.8 Ma and 449.4 ± 1.8 Ma (2σ) laser step-heating ⁴⁰Ar/³⁹Ar plateau ages for phengite from quartzite mylonites from the blueschist-facies Ondor Sum subduction-accretion complex in Inner Mongolia (northern China). These ages are within error of the inverse isochron ages calculated using the plateau steps and the weighted mean ages of total fusion of single grains. The compositional change from glaucophane in the cores to crossite in the rims of blue amphiboles, as revealed by electron microprobe analysis, points to decompression, probably caused by progressive exhumation of the subducted material. The Late Ordovician ages were not affected by excess argon incorporation because in all likelihood the oceanic sediments were wet on arrival at the trench and free of older detrital mica. The ca. 450 Ma ages are, hence, interpreted as the time of crystallization during mylonitization under high fluid activity at fairly low temperatures. This means that accretion of the quartzite mylonite unit occured about 200 Ma before final closure of the Paleo-Asian Ocean, amalgamation of the Siberian, Tarim and North China cratons, and formation of the end-Permian Solonker suture zone. We argue that the Early Paleozoic evolution of the Ondor Sum complex occurred along the northeastern Cimmerian margin of Gondwana, which was composed of micro-continents fringed by subduction-accretion complexes and island arcs. The later evolution took place during the building of the Eurasian continent following middle Devonian and younger rifting along the East Gondwanan margin and northward drift of the detached North China craton. An extensive review shows that this type of two-stage scenario probably also applies to the geodynamic evolution of other micro-continents like, South China, Tarim, a number of Kazakh terranes, Alashan, Qaidam and Kunlun, as well as South Kitakami and correlatives in Japan, and probably Indochina. Like the North China craton, these were bordered by Early Paleozoic subduction-accretion complexes, island arcs or contained calc-alkaline volcanic margins, like for example, the central Tienshan, North Qinling, North Qaidam-Altun, North Qilian and Kunlun belts in China, as well as the Oeyama and Miyamori ophiolites and Matsugadaira-Motai blueschist belt of Japan and the dismembered Sergeevka ophiolite of the southern part of the Russian Far East. This implies that a vast orogenic system, comprising an archipelago of micro-continents, seems to have existed along the Cimmerian margin of East Gondwana in Early Paleozoic time in which the ultrahigh-pressure metamorphism that characterizes the early evolution of many of the Asian micro-continents occurred.

Time-lapse seismic reservoir monitoring technology in China

Digital surveys of the T block in China's Daqing oil field began in 1988, and the first high-resolution seismic survey in the area was conducted from the winter of 1998 to the spring of 1999. These 2D seismic data sets of 1988 and 1999 have been used in a time-lapse seismic reservoir monitoring study. Figure 1 shows the quality of the seismic data is good, and three events can be clearly seen in the seismic profiles.

High‐resolution mantle tomography of China and surrounding regions

A high‐resolution P wave tomographic model of the crust and mantle down to 1100 km depth under China and surrounding regions is determined by using about one million arrival times of P, pP, PP, and PcP waves from 19,361 earthquakes recorded by 1012 seismic stations. The subducting Pacific slab is imaged clearly as a high‐velocity zone from the oceanic trenches down to about 600 km depth, and intermediate‐depth and deep earthquakes are located within the slab. The Pacific slab becomes stagnant in the mantle transition zone under east China. The western edge of the stagnant slab is roughly coincident with a surface topographic boundary in east China. The active Changbai and Wudalianchi intraplate volcanoes in northeast China are underlain by significant slow anomalies in the upper mantle, above the stagnant Pacific slab. These results suggest that the active intraplate volcanoes in NE China are not hot spots but a kind of back‐arc volcano associated with the deep subduction of the Pacific slab and its stagnancy in the transition zone. Under the Mariana arc, however, the Pacific slab penetrates directly down to the lower mantle. The active Tengchong volcano in southwest China is related to the eastward subduction of the Burma microplate. The subducting Indian and Philippine Sea plates are also imaged clearly. The Indian plate has subducted down to 200–300 km depth under the Tibetan Plateau with a horizontal moving distance of about 500 km. High‐velocity anomalies are revealed in the upper mantle under the Tarim basin, Ordos, and Sichuan basin, which are three stable blocks in China.

Elemental geochemistry and Nd isotopic characteristics of the metasedimentary rocks from the metamorphic belt in central Jiangxi: Provenance and tectonically environmental constraints

The metamorphic belt in central Jiangxi, located in the compound terrain within the Cathaysia, Yangtze Block and Caledonian fold zone of South China, is composed dominantly of meta-argillo-are-naceous rocks, with minor amphibolite. These rocks underwent amphibolite-facies metamorphism. The meta-argillo-arenaceous rocks show large variations in major element composition, but have similar REE patterns and trace element composition, incompatible element and LIE enrichments [high Th/Sc (0.57−3.59), La/Sc (1.46−12.4), La/Yb (5.84−19.0)] and variable Th/U ratios, with ΣREE=129−296µg/g, δEu=0.51−0.86, and (La/Yb)N=3.95−12.9. The Nd isotopic model agest DM of these rocks vary from 1597 to 2124 Ma. Their143Nd/144Nd values are low [ɛNd(0)=−11.4 to −15.8]. Some conclusions have been drawn as follows: (1) The metamorphic rocks in central Jiangxi Province are likely formed in a tectonic environment at the passive continental margin of the Cathaysia massif. (2) The metamorphosed argillo-arenaceous rocks are composed dominantly of upper crustal-source rocks (Al- and K-rich granitic or/and sedimentary rocks of Early Proterozoic), which experienced good sorting, slow deposition and more intense chemical weathering. (3) According to the whole-rock Sm-Nd isochron ages (1113±49 to 1199±26 Ma) of plagioclase-amphibole (schist) and Nd isotopic model aget DM (1597−2124 Ma) of meta-argillo-arenaceous rocks, the metamorphic belt in central Jiangxi Province was formed during the Middle Proterozoic (1100−1600 Ma).

Present-Day crustal deformation field in China continent inverted from GPS observations, earthquake moment tensor and quaternary fault slip rates

Based on the bi-cubic Bessel spline function method, we have inverted the present-day crustal horizontal velocity field and deformation field in China continent by combining with 410 GPS observations, 327 seismic moment tensors of earthquakes and fault slip rates in China and its neighboring areas, and considered the geological and geophysical parameters at the same time. The results reveal that the crustal movement mostly takes on compression in SN-NE direction and extension in EW-NW direction in China continent. The continent is rotating southeast and takes on a clockwise rotation image from the west to the east, particularly in the southeast of Tibet and Chuan-dian area. Different blocks have different deformation in China continent. The south China, Ordos and Northeast block have good integrity. The deformation in the western part of China is obviously stronger than that in the eastern part. The strong strains are focused on the Himalaya, east Tibet, west Tian Shan and Chuandian block etc. The deformation at the joint of blocks is stronger than that within the blocks. The China continent deformation not only has the strike-slip faulting and extrusion feature but also has the crustal shortening and thickening feature.

Crustal Velocity Structure of the Deep Continental Subduction Zone — A Wide Angle Reflection/Refraction Seismic Study on the Eastern Dabie Orogen

AbstractSix two‐dimensional crustal structure profiles in the eastern Dabie, Anhui Province, have been obtained by wide‐angle seismic reflection/refraction exploration. The results reveal that the crust of the eastern Dabie orogen presents a high‐velocity dome, the middle‐ and lower‐crust's metamorphic rocks exposed on the surface in the core of the dome, where the velocity approaches to 5.0 km/s. A low velocity layer (body) about 6.1 km/s has developed in the upper‐middle crust on it's both side wings. The depth of the Moho discontinuity varies greatly from about 41km in the core to 32–34km in the surrounding area, and a 4km Moho‐offset is observed beneath the Xiaotian–Mozitan Fault. We recognize that the eastern Dabie orogen shows a typical velocity‐pattern of continent‐continent deep subduction/ collision. The Moho offset should be related with the deep subduction of the Yangtze block and represents the suture zone between the Yangtze/North China Blocks. Therefore, the high‐velocity dome may be a result of collision/extrusion between the two continental blocks and the low‐velocity layers (bodies) mentioned above may play an important role in the post‐collisional crust extension and exhumation of the ultra‐high pressure metamorphic rocks.

Present-day crustal deformation in China relative to ITRF97 kinematic plate model

A global plate motion model is established based on the ITRF97 velocity fields and geological model NUVEL1. Sub-plate models are estimated by using the velocity fields derived from 45 global positioning system (GPS) sites under the ITRF97 reference frame in China. Comparisons between space geodesy and geological models are given. It is found that the Euler vector of the AFRC–EURA pair has an obvious discrepancy between space geodetic and geological models. The motion patterns of tectonic blocks in China predicted by GPS are consistent with those of geological data on the whole.

Are post-seismic effects of theM= 8.4 Bolnay earthquake (1905 July 23) still influencing GPS velocities in the Mongolia-Baikal area?

SUMMARY GPS measurement campaigns in the Mongolia‐Baikal area show that: (1) the Baikal rift zone is currently opening at 4‐5 mm yr −1 in a NW‐SE direction and (2) the western part of the Amurian‐north China block is moving eastward relative to Eurasia at 5‐7 mm yr −1 . These results are consistent with recent geodetic studies in Asia, and indicate that crustal motions in Mongolia and north China derived from geodetic measurements are significantly faster than those proposed by most deformation models of Asia. Using a numerical model, we test whether post-seismic deformation caused by viscoelastic relaxation in the lower crust following the Tsetserleg‐Bolnay earthquake sequence (Mw = 7.9 and 8.4, 1905 July) can explain this discrepancy. We find that surface velocities at the GPS sites presented here for the 1997‐ 2000 time period can reach 4 mm yr −1 , depending on the earthquake source parameters and the rheology used in the models. Using a model based on our best current knowledge of lithospheric structure and rheology in the Mongolia‐Baikal area, we find that the contribution of post-seismic effects to the GPS velocities presented here is less than 2 mm yr −1 for the Mongolian sites and less than 1 mm yr −1 for the Baikal sites. We therefore conclude that the post-seismic effects of the Mw = 8.4, 1905 Bolnay earthquake cannot explain why the GPS-derived crustal motions in Mongolia and the Baikal rift zone are significantly larger than those proposed by deformation models of Asia. This discrepancy must therefore be sought in processes not accounted for in most of these deformation models, such as the farfield contribution of the Pacific subduction zones and/or the effect of gravitational forces on intracontinental deformation.

Contemporary crustal movement of continental China obtained by global positioning system (GPS) measurements

We obtain a unified horizontal velocity field of continental China and vicinity through measurements at 81 GPS stations provided by the National Key Infrastructure Project, Crustal Movement Observation Network of China. The velocity field delineates patterns of movements and deformation of active crustal blocks in continental China under the Eurasia-fixed reference frame. The space-based geodesy also clearly shows for the first time the horizontal movement and deformation of continental China induced by indentation of the Indian plate. The data provide kinematic constraints for simulating dynamic process of continental lithospheric deformation.

Seismic tomography beneath the orogenic belts and adjacent basins of northwestern China

Three-dimensional velocity images of the crust and upper mantle beneath orogenic belts and adjacent basins of the northwestern continent of China are reconstructed by seismic tomography, based on arrival data of P wave recorded in seismic networks in Xinjiang, Qinghai, Gansu of China and Kyrgyzstan. The velocity images of upper crust demonstrate the tectonic framework on the ground surface. High velocities are observed beneath orogenic belts, and low velocities are observed in the basins and depressions that are obviously related to unconsolidated sediments. The velocity image in mid-crust maintains the above features, and in addition low velocities appear in some earthquake regions and a low velocity boundary separates the western Tianshan Mts. from eastern Tianshan Mts. The orogenic belts and the northern Tibetan plateau have a Moho depth over 50 km, whereas the depths of the Moho in basins and depressions are smaller than 50 km. The velocity images of upper mantle clearly reveal the colliding relationship and location of deep boundaries of the continental blocks in northwestern China, indicating a weakness of the upper mantle structure of orogenic belts. The top depth of upper mantle asthenosphere varies from place to place. It seems shallower under the northern Tibetan plateau, Altay and Qilian Mts., and deeper under the Tarim and Tianshan regions. Hot mantle probably rose to the bottom of some orogenic belts along tectonic boundaries when continental blocks collided to each other. Therefore their dynamic features are closely correlated to the formation and evolution of orogenic belts in northwestern China.

Preliminary division of active block boundary in Chinese mainland based on recent vertical crustal movement

The characteristics of vertical crustal movement in Chinese mainland are studied, and the ideas and principles for dividing active blocks according to the map of recent vertical crustal deformation rate in China is proposed. As a result, Chinese mainland is divided into 2 first-grade blocks, the east and west block, 6 second-grade blocks, the Northeast China, North China, East China, Xizang (Tibet), Gansu-Qinghai-Xizang (Gan-Qing-Zang) and Xinjiang block, and 16 third-grade blocks. The boundaries of active blocks divided in this paper are generally consistent with the pattern of neotectonic movement with some local difference. It shows that the recent crustal activity in Chinese mainland inherits the neotectonic movement occurred since the Quaternary, while some new activity tendencies appear.

Crustal motion of Chinese mainland monitored by GPS

To measure and monitor the crustal motion in China, a GPS network has been established with an average side length of 1 000 km and with more than 20 points on the margins of each major tectonic block and fault zone in China. Three campaigns were carried out in 1992,1994 and 1996, respectively by this network. Here we present, for the first time, the horizontal displacement rates of 22 GPS monitoring stations distributed over the whole China and global IGS stations surrounding China, based on these GPS repeated measurements. From these results by GPS, we have obtained the sketch of crustal motion in China.

New constraints on current deformation in Asia from continuous GPS measurements at Ulan Baatar, Mongolia

On the basis of 3 years of continuous GPS measurements (1995–1998) show a velocity of 6.4±1.6 mm/yr in a N125±30° azimuth with respect to Eurasia at a permanent site in Ulan Baatar, Mongolia. Together with recent GPS results in Asia, this result indicates motion of the Amurian/North China block at 6–10 mm/yr to the east to southeast relative to Eurasia, 0 to 5mm/yr slower than south China (10–11 mm/yr eastward). The small differential motion between these two blocks is in agreement with deformation models of Asia where crustal thickening dominates lateral extrusion. The fact that the velocity of the Amurian/North China block is significantly faster than the predictions of models based on the hypothesis that deformation in Asia is enterely driven by the India/Eurasia collision suggests that other mechanisms, such as far‐field effects of subduction processes and gravitational forces could significantly contribute to intracontinental deformation.

The Global Geoscience Transect from Altay, China to the Philippine Sea and Taiwan

The geoscience transect from Altay to Taiwan has a total length of ∼4,334 km. The transect begins along the northwestern border of China and ends in the Philippine Sea basin to the east of Taiwan. Systematic seismic soundings, magnetotelluric soundings, and heat-flow, gravity, aeromagnetic, and geological studies were conducted along the transect. The main tectonic features that are suggested by geological and geophysical data collected along the transect can be understood in the context of the tectonic history of the craton. The tectonic evolution of China can be divided into three stages— (1) development of continental crust during the Archean era with separate cratonic blocks (the West China and the East Asia cratons) that subsequently were juxtaposed to form the Old China craton; (2) remobilization and breakup of the continental land mass during the Paleozoic period, forming the Northern and the Southern China plates; and (3) development of three tectonic domains (the eastern extensional domain, the Qinghai-Tibet compressional domain, and the relatively stable tectonic domain between them) of continental China during the Mesozoic to Cenozoic period, subject to the effects of Pacific and Indian plate motions. The convergence between cratonic blocks in China resulted in wedge structures. The deformation of lithosphere began with the mantle lithosphere, followed by the crust. Where cratonic lithosphere was compressed, such as in the West China craton, the mantle lithosphere folded and the crust was imbricated along thrusts forming major nappe structures along zones of weakness. Where a relatively weak accreting lithosphere, such as Tibet, was compressed, the mantle lithosphere shortened and thickened, with decoupling between the crust and the mantle lithosphere. Where cratonic lithosphere was extended, such as in the East Asian craton, tectonic thinning resulted in formation of a rhombochasm basin or rift. The inhomogeneity of mantle material has exerted an important effect on surface structure, with the stable region at the surface frequently coinciding with mantle structure. The boundaries of mantle features coincide with zones of mineralization that contain deposits with economic potential.

A preliminary research establishing the present-time intraplate blocks movement model on the Chinese mainland based on GPS data

The Chinese mainland is regarded as the best area for studying the continental crustal movement and dynamics. In the past, based on the ground surface observation, it was very difficult to study the movement of the intraplate blocks within a range of larger space and a time scale of several years quantitatively. In this paper, a method of calculating the Euler vectors of present-time motion among blocks by using Cardan angles has been given completely based on two periods of GPS repetition measurement data of the National Ascending Plan of China (NAPC) — the study and application of current crustal movement and geodynamics in 1994 and 1996. A present-time blocks movement model on the Chinese mainland (PBMC-1), which describes the motion of seven blocks—Tibet, Chuan-Dian, Gan-Qing, Xinjiang, South China, North China and Heilongjiang block, is established preliminarily. The velocity field of the relative motion among the intraplate blocks and boundary motion in the Chinese mainland are firstly given within several years time scale. It is shown by the results calculated with the model that the velocity-rate of each block is reduced gradually from the south to north and from the west to east, and the motion direction changes gradually from NNE to E, even SEE or SE. The collision of Indian plate plays a leading role in the movement of the intraplate blocks in the Chinese mainland, while the motion manner and velocity-rate of block boundary zone (fracture zone) depend on the motion of every block again. The present-time motion of a time scale of several years computed with the model is not only largely consistent with the average motion of a time scale of several million years derived from geology, but also very coincident with the results of geophysical and astronomic observation. It is shown preliminarily that the observed results of space geodesy techniques such as GPS etc. are capable of discovering the crustal movement at present.

Geodynamic models and palaeomagnetic constraints on the evolution of the North West Shelf : Klootwijk C., AGSO Research Newsletter, 1997, 26/- (22–24)

During the Neoproterozoic and Palaeozoic the two continents of Baltica and Laurentia witnessed the break-up of one supercontinent, Rodinia, and the formation of another, but less long-lived, Pangea. Baltica and Laurentia played central roles in a tectonic menage a trois that included major orogenic events, a redistribution of palaeogeography and a brief involvement of both with Gondwana. Many of these plate re-organisations took place over a short time interval and invite a re-evaluation of earlier geodynamic models which limited the speeds at which large continental plates could move to an arbitrarily low value.Baltica and Laurentia probably shared a common drift history for the time interval 750 – 600 Ma as they rotated clockwise and drifted southward from an equatorial position during the opening of the Proto-Pacific between Laurentia and East Gondwana (initial break-up of Rodinia). On their combined approach toward the south pole, Baltica and Laurentia were glaciated during the Varanger glaciations. Although the two continents drifted toward the south pole during the Late Proterozoic, they began to separate at around 600 Ma (rift to drift) to form the Iapetus Ocean through asymmetric rifting and relative rotations of up to 180°. Initiation of rifting on the Baltic margin is marked by the 650 Ma Egersund tholeiitic dykes (SW Norway) which contain abundant lower crustal zenoliths, and the tholeiitic magma was probably derived from a mantle plume.In latest Precambrian time, the final redistribution of Rodinia is characterised by high plate velocities. In particular, Laurentia began a rapid, up to 20 cm/yr, ascent to equatorial latitudes and essentially stayed in low latitudes throughout most of the Palaeozoic. The high velocities suggest either that Laurentia was pushed off a lower mantle heat anomaly originating from supercontinental mantle insulation or that Laurentia was pulled toward a subduction-generated cold spot in the proto-Pacific. Baltica, except for a short and rapid excursion to lower latitudes in the Late Vendian, remained mostly in intermediate to high southerly latitudes and closer to the Gondwana margin until Early Ordovician times.In Early Ordovician times, Arenig-Llanvirn platform trilobites show a broad distinction between the continents of Laurentia/Siberia/North China Block (Bathyurid), Baltica (Ptychopygine/ Megalaspid) and the areas of NW Gondwana/Avalonia/Armorica (Calymenacean-Dalmanitacean). During the Ordovician, Baltica rotated and moved northward, approaching close enough to Laurentia by the late Caradoc for trilobite and brachiopod spat to cross the intervening Iapetus Ocean. Docking appears to have been irregular both in time and manner: the collision between Scotland/Greenland and western Norway resulted in the early Scandian Orogeny in the Silurian (c. 425 Ma), but further south, there is evidence of late Silurian impingement with subduction of Avalonian continental crust (in England and Ireland) below the eastern edge of Laurentia until the Emsian. In the northern Appalachians the main time of collision appears to have been during the Emsian/Eifellian Acadian Orogeny.Recent analyses invalidates the traditional concept of a sustained orthogonal relationship between Baltica and Laurentia across a single Iapetus Ocean throughout the Caledonide evolution. The active margin of Baltica (Scandinavian Caledonides) faced Siberia during the Late Cambrian and Early Ordovician with oceanic separation between these landmasses in the order of 1200–1500 km. This may explain the local occureences of Siberia-Laurentian type Bathyarid tribobite faunas in Central Norwegian Caledonian nappes, earlier interpreted as Laurentia-Baltica trilobite mixing. Subsequent counterclockwise rotation of Baltica transferred the Caledonian margin in the direction of Laurentia by Silurian times, when the two continents once again started to collide to form Euramerica. This rotation, along with the strongly asymmetric opening of the Iapetus at around 600 Ma, demonstrates a complexity in Precambrian-Palaeozoic plate tectonics, i.e. a collage of metastable plate boundaries which have perhaps too often been simplified to an orthagonal Wilson cycle tectonic scenario.