contrasting styles of mineralization in the chinese altai and east junggar nw china implications for the accretionary history of the southern altaids abstract the chinese altai east junggar collage in the southern altaids hosts three metallogenic belts which are from north to south 1 a volcanogenic massive sulphide vms cu pb zn belt 2 a belt of shear zone related gold deposits 3 a porphyry cu au mo belt the vms deposits formed in two pulses c 405 ma and c 375 ma in the chinese altai arc the porphyry deposits developed in three pulses in the east junggar arc the first two synchronous with the vms mineralization and the third at c 330 ma the shear zone related gold deposits developed in the late carboniferous to permian at the contact between the chinese altai and east junggar arcs time space distributions of diverse ore deposits across the altai east junggar collage indicate that the collage developed from two independent arcs the chinese altai and the east junggar the vms and porphyry deposits developed in the chinese altai and east junggar arcs respectively the chinese altai arc is interpreted to be a japanese type arc and the east junggar arc a mariana type arc during the latest palaeozoic the two arcs were juxtaposed by the erqis fault when many shear zone related lode gold deposits were emplaced these metallogenic distributions were a likely response to spatially localized mechanisms of crust growth and to the tectonic evolution of the altai east junggar collage and they are consistent with interpretation of the altaids as a multiple subduction accretion collage

detrital zircon reference for the north china block abstract u pb analyses of 250 single detrital zircons from upper proterozoic to ordovician strata collected from the zhuozi shan in north central china provide a detrital zircon reference for the north china block a major crustal entity in the asian tectonic collage the results which range in age from 1 72 to 2 97 ga shed new light on the age of the crystalline basement in north china much of which is covered by younger sedimentary units in addition this detrital zircon reference can be used to help determine the provenance of clastic sedimentary units and for assessing validity of paleogeographic and regional tectonic models that include the complex history of asian continental amalgamation terrane accretion and subsequent translation that is ongoing today

a review of the western part of the altaids a key to understanding the architecture of accretionary orogens abstract the altaids is one of the largest accretionary collages in the world and the tectonic styles of the accretionary processes have been interpreted in several ways including as an amalgamation of multiple terranes as a result of oroclinal bending of a long single arc or as a caledonian continental collision based on recent tectonostratigraphic analyses together with paleomagnetic data the tectonic styles of the neoproterozoic to paleozoic accretionary processes of the altaids are discussed the western altaids is the main focus of the study which was mainly composed of several independent linear components such as arcs and microcontinents with proterozoic basement and cover rocks various kinds of arcs existed in the paleo asian ocean including a complicated type of arc alaskan type which is a combination of the japan and mariana type intra oceanic arcs and the cordillera type continental arcs these linear components rotated and collided with each other with multiple subduction polarities which could have been an important result of multiple linear element amalgamation and which has contributed greatly to the architecture of the eurasian continent the basic tectonic styles of the altaids can be summarized as arc arc collision oroclinal bending and large scale rotation and multiple subductions with a complicated archipelago paleogeography these basic features of accretionary orogens in general can be attributed to the amalgamation of complicated multiple linear elements some mesozoic to cenozoic accretionary orogens in the world are also characterized by processes of multiple linear element amalgamation more attention should be paid to the multiple linear element amalgamation of ancient accretionary orogens which will shed light on lateral and vertical continental growth

radiation and extinction patterns in permian floras from north china as indicators for environmental and climate change abstract permian continental sequences from north china contain previously unrecognized episodes of plant radiation and elevated extinction the earliest extinction in the lower shihhotse formation roadian guadalupian records a 45 floral species loss and is tentatively correlated with global extinctions amongst dinocephalian reptiles two younger extinctions are dated by correlating the illawara reversal and palaeomagnetic polarity sequences from shanxi province against global palaeomagnetic history missing data from the shanxi sequence are evaluated using a novel approach estimating likely maximum and minimum sequence changes that provide age estimates for post illawara events in north china the second extinction in the middle upper shihhotse formation is more significant and is dated to the mid capitanian with a loss of 56 of plant species coinciding with two phases of volcanism of the emeishan large igneous province in south china previously linked to the mid capitanian marine mass extinction the youngest extinction in the upper upper shihhotse formation late capitanian to mid wuchapingian is catastrophic and represents the end of range in the sequence changes in sedimentary facies suggest it to be related to global climatic warming and drying other viable causal mechanisms for the extinction episodes include plate motion and collision global climate change volcanism and biological competition

paleozoic multiple accretionary and collisional processes of the beishan orogenic collage in the paper by xiao and others american journal of science v 310 p 1553 1594 1 please substitute figure 16 reproduced here for figure 16 that appears between pages 1573 and 1574 the original figure 16 2 was printed at an improper size figure 3 1 lookup volpage 310

late devonian early permian a type granites in the southern altay range northwest china petrogenesis and implications for tectonic setting of a 2 type granites abstract the altay range is an important part of the central asian orogenic belt caob that contains a type granites that have been attributed to a post collisional setting during the late carboniferous permian however our new la icp ms zircon u pb age data demonstrates that there were two episodes of a type granite magmatism in the southern altay range a late carboniferous to early permian 308 291 ma suite does occur in the vicinity of qiakuerte but a distinct late devonian 382 367 ma suite is present in the kouan area the early kouan a type granites are mainly composed of alkali feldspar granites which are approximately synchronous with adakites boninites high ti basalts picrites ophiolitic rocks and high temperature low pressure metamorphic rocks whereas the late qiakuerte a type granites mainly consist of arfvedsonite and aegirine bearing granites which are approximately coeval with some mafic ultramafic rocks in the southern altay range a type granites are commonly classified as a1 and a2 sub types which are considered to be generated in anorogenic rift or plume related or post collisional settings respectively both suites of the southern altay range are geochemically similar to typical a2 type granites e g high k2o na2o feo mgo and ga al and y nb values and low cao ba sr and eu contents the kouan a type granites have relatively low la yb n 2 7 5 9 high end t 6 7 to 7 7 and nb la 0 59 1 67 and variable ehf t 5 0 to 14 1 values whereas the qiakuerte a type granites have comparatively high la yb n 4 2 9 2 low end t 5 3 to 6 0 and nb la 0 33 0 74 and variable ehf t 10 0 to 18 7 values the early kouan a type granites may have been generated by partial melting of a mafic source containing more depleted mantle derived components than the late qiakuerte a type granites we suggest that the late carboniferous to early permian qiakuerte granites were formed in a post collisional extensional setting as is typical of a2 type granites however the late devonian kouan a type granites were more plausibly generated in an extensional setting as a result of slab window caused by a ridge subduction in this case the upwelling of asthenosphere through the slab window provided the source of parental magmas or the heat for the generation of devonian magmas therefore our results suggest that a2 type granites can also form in a ridge subduction related extensional setting

the dynamic evolution of the palaeozoic geography of eastern asia abstract new palaeogeographical reconstructions are presented for eleven time intervals through the palaeozoic of the eastern asia region from the middle cambrian at 510 ma to the end of the permian at 250 ma they centre on the continental blocks of north china south china and annamia indochina and their relationships with northeastern gondwana which was united to form part of pangea from the late carboniferous onwards also shown is the continent of tarim during the lower palaeozoic as well as the hutag uul songliao and khanka jiamasu bureya terranes both of which straddle the russian mongolian and chinese borders today from silurian times onwards we conclude that annamia and south china were united as a single continent throughout the lower palaeozoic and early devonian and were translocated by major strike slip faulting along the northeastern gondwana margin during that period from off afghanistan to outboard of the sibumasu and australian sectors of the superterrane they left the gondwana marginal area together during the lower devonian opening of the palaeotethys ocean but very shortly afterwards they themselves divided into the two separate continental blocks that we recognise today not to reunite until the triassic the various cambrian to permian rocks found in japan largely represent active volcanic arcs which originally lay to the southeast of south china although the carboniferous was more quiescent there the neotethys ocean opened during the permian dividing sibumasu and the tibetan terranes from gondwana and the palaeotethys ocean started to close progressively in the upper palaeozoic as most of the east asian continents and smaller terranes moved towards siberia the positions of the various continents and terranes have been deduced from a mixture of palaeomagnetic and faunal data the positions of large igneous provinces and kimberlites and the need to provide kinematic continuity between maps of successive ages however many uncertainties remain

tectonic significance of the xilin gol complex inner mongolia china petrological geochemical and u pb zircon age constraints abstract the xilin gol complex consisting of strongly deformed and metamorphosed rocks is exposed as a large tectonic unit within the central asian orogenic belt caob it is located on the xilinhot sonidzuoqi north dipping thrust belt and near the solonker suture zone that is widely regarded to record the terminal evolution of the caob its genesis and tectonic origin are a key to test the existing tectonic models as to whether there was a single arc chain by successive accretion or multiple amalgamation involving some microcontinents this study reports petrological geochemical and zircon u pb age data of biotite plagioclase gneisses from the complex as migmatization is common in the gneiss restitic and magmatic components are identified in the gneiss by their petrographic features mineral chemistry indicates that the xilin gol complex was subjected to amphibolite facies metamorphism three groups of zircons are identified by cathodoluminescence cl images and th u ratios 1 the first and most abundant group is of magmatic origin and yields a weighted mean 206 pb 238 u age of 452 5 ma 2 the second scarcest group is of metamorphic origin and yields a weighted mean 206 pb 238 u age of 339 4 ma 3 the third group is minor of apparent detrital origin and yields 207 pb 206 pb ages from 1902 11 to 886 54 ma for the cores with a peak at 1150 to 900 ma whole rock major and trace element contents are representative for the upper continental crust with rb pb u th k lree enrichment and nb ta sr depletion this suggests the gneisses are sourced in the upper continental crust with some old sediment contamination the protolith of the biotite plagioclase gneiss is a sedimentary rock with detrital source ages between 1902 11 ma and 886 54 ma that was deposited at the southern active continental margin of the siberia craton during the amalgamation of the rodinia supercontinent partial melting and migmatization occurred at 452 5 ma in response to north dipping oceanic subduction in the sonidzuoqi xilinhot area many new magmatic materials formed in the xilin gol complex during this time while it resided in a continental marginal arc tectonic setting oceanic subduction started at 490 8 ma and lasted at least to 440 4 ma in the early paleozoic the caob was an advancing accretionary orogen the complex was mildly affected by a 320 310 ma magmatic event in the xilinhot sonidzuoqi area therefore the xilin gol complex recorded a long lived successive accretion along the southern margin of the siberia craton

evolution of a permian intraoceanic arc trench system in the solonker suture zone central asian orogenic belt china and mongolia abstract the identification of a fossil arc trench system from the ophiolite decorated solonker suture zone in the southernmost central asian orogenic belt caob enables us to constrain the timing of pre subduction extension ca 299 290 ma subduction initiation ca 294 280 ma ridge trench collision ca 281 273 ma and slab break off ca 255 248 ma in the permian a fraction of proto arc crust ca 45 km long up to 8 km wide is preserved as a volcanic plutonic sequence and is juxtaposed against a wide ca 30 80 km forearc melange this proto arc crust comprises two distinct magma series island arc tholeiite iat and mid ocean ridge basalt morb both of which have strong supra subduction zone ssz geochemical signatures zircons from a gabbro and a plagiogranite yielded weighted mean 206pb 238u ages of 284 0 4 0 and 288 0 6 0 ma the forearc melange consists of numerous ophiolite fragments and continental margin derived olistoliths blocks that predate the ophiolite the olistoliths are best represented by a gabbroic block 291 8 2 3 ma that contains granite xenoliths 312 6 1 8 and 313 6 3 1 ma other dated blocks include a trondhjemite 323 9 2 7 ma a gabbro 296 6 1 7 ma and a tonalite 294 9 2 4 ma small bodies of diabase andesite and diorite in the forearc melange exhibit a wide variety of geochemical signatures we dated zircons from an n morb like diabase 274 4 2 5 ma an e morb like diabase 252 5 2 3 ma a transitional sanukitoid adakite andesite 250 2 2 4 ma a sanukitoid high mg diorite 251 8 1 1 ma and an anorthosite 252 2 1 7 ma the n morb like diabase contains ca 301 394 ma zircon xenocrysts suggesting assimilation of trench sediments when a spreading ridge intersected a trench the other dated rocks simultaneously formed near the permian triassic boundary and captured abundant zircon xenocrysts ca 269 295 ma ca 301 495 ma and ca 923 2501 ma our new formation ages constrain a magmatic episode in response to slab break off beneath a fossil forearc in a young post collisional setting and the youngest xenocryst ages ca 269 273 ma may define the maximum depositional age of trench sediments

a review of lower and middle palaeozoic biostratigraphy in west peninsular malaysia and southern thailand in its context within the sibumasu terrane abstract fossils from the cambrian to devonian rocks of southern thailand the langkawi islands mainland kedah perlis north perak and central west peninsular malaysia are listed and reviewed and their stratigraphy and correlation reassessed the hitherto anomalous record of the trilobite dalmanitina from malaysia is reviewed and found to be of latest ordovician hirnantian age rather than lower silurian age as previously reported and is considered a probable synonym of the widespread mucronaspis mucronata a new stratigraphical nomenclature is erected for part of the langkawi mainland kedah and perlis area successions in which the term setul limestone which stretched from the ordovician to the devonian is abandoned and replaced by the middle ordovician kaki bukit limestone the late ordovician and early silurian tanjong dendang formation the silurian mempelam limestone and the early devonian timah tasoh formation all underlying the paraconformity with the late devonian langgun red beds there was a single depositional basin in the generally shallow water and cratonic areas of southern thailand langkawi and mainland kedah and perlis in contrast to the deeper water basin of north perak only silurian rocks are dated with certainty within another basin in central west malaysia near kuala lumpur which were also cratonic and shallow water although to the east in west pahang there are basal devonian deeper water sediments with graptolites the area is reviewed in its position within the sibumasu terrane which in the palaeozoic also included central and northern thailand burma myanmar and southwest china part of yunnan province

the phuket terrane a late palaeozoic rift at the margin of sibumasu abstract it is widely accepted that sibumasu rifted from gondwana in the late palaeozoic but the rifts themselves have not previously been documented in southeast asia this paper identifies the pre middle permian kaeng krachan group of upper peninsular thailand as the infill of one such rift which is given the name phuket terrane indirect evidence suggests the rift infill is several kilometres thick and glacially influenced diamictites are conspicuous in the succession there are significant similarities with the 3 km thick pre middle permian rift infill of the carnarvon basin of western australia east of the khlong marui fault belt the succession is thinner and diamictites are a minor component a tectono stratigraphic model is proposed involving gondwana glaciers dropping their load at the present western margin of the phuket terrane from where it was re sedimented in the rapidly subsiding marine rift basin it is suggested that the khlong marui fault formed part of the eastern boundary of the rift system the three pagodas fault belt similarly juxtaposes different pre middle permian successions rifting ceased in the early permian and a passive margin formed as the mesotethys ocean widened the upper part of the kaeng krachan group and the overlying ratburi limestone representing the post rift sequence

mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy 1 tectonic and metamorphic data for the central alps switzerland italy are used to discuss this classic example of a barrovian metamorphic terrain notably the evolution of its thermal structure in space and time available p t t data indicate variable contributions of advective and conductive heat transport during collision and subsequent cooling and exhumation some areas experienced a prolonged period of partial melting while other areas at the same time show but moderate heating the barrow type metamorphic field gradient observed in the final orogen is the result of two distinct tectonic processes with their related advective and conductive heat transport processes the two tectonic processes are 1 accretion of material within a subduction channel related to decompression and emplacement of high pressure units in the middle crust and 2 wedging and related nappe formation in the continental lower plate the second process postdates the first one wedging and underthrusting of continental lower plate material produces heat input into lower crustal levels and this process is responsible for predominantly conductive heat transport in the overlying units the interacting processes lead to different maximum temperatures at different times producing the final barrovian metamorphic field gradient the south experienced rapid cooling whereas the north shows moderate cooling rates this discrepancy principally reflects differences in the temperature distribution in the deeper crust prior to cooling differences in the local thermal gradient that prevailed before the cooling also determined the relationships between cooling rate and exhumation rate in the different areas citation berger a s m schmid m engi r bousquet and m wiederkehr 2011 mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy tectonics 30 tc1007 doi 10 1029 2009tc002622

geology of the giant sudbury polymetallic mining camp ontario canada a new 1 100 000 scale compilation bedrock geology map provided with this issue presents a geologic synthesis of canada s most prolific mining camp the world class sudbury structure with total past production and current reserves of over 1 7 billion tonnes of ni cu co pt pd au ag ore lydon 2007 the polymetallic ore is hosted within one of earth s largest preserved impact craters the new map of the ni cu pge sudbury district after ames et al 2005 is included in a pocket at the back of this issue map 1 and is linked to mineral deposit commodity and geochronology data in tables 1 and 2 of this paper view this table table 1 list of mineral deposits and occurrences of the sudbury map area map 1 view this table table 2 u pb isotope data across the map area since 1891 six compilation maps of the geology of sudbury have been published bell 1891 collins 1937 cooke 1946 card 1969 dressler 1984 ames et al 2005 fig 1 some of the ni cu pge mines have operated for over a century whereas new ore deposits discovered as recently as 2004 are already in production or are in the process of being developed i e advanced prospects in the last 15 years sudbury has been the training ground for 60 postgraduate geoscience students in north america fig 1 from 1903 to 1990 only 23 graduate theses were completed on sudbury related topics eight of them in the 1970s after the discovery of shatter cones dietz 1964 fig 1 number of graduate theses of north american geoscientists trained on sudbury geology per decade showing the minor peak in training after the discovery of shatter cones and the recent education boom with over 50 geoscience graduate theses completed since 1990 the dashed lines represent the regional geologic maps of the sudbury area

new cambrian and ordovician paleomagnetic poles for the north china block and their paleogeographic implications multicomponent magnetization has been revealed in several cambrian and ordovician sedimentary units from localities in hebei and shandong provinces of the north china block ncb a well defined component with lower unblocking temperature is characterized by northerly declination and moderate to steep inclination with both polarities and postdates the late cretaceous folding the pole position derived from the overprinted directions is close to both the cretaceous pole for the ncb as well as the present north pole the overprint is not a simple thermal remanent magnetization but is probably a chemical remanent magnetization imposed at moderately elevated temperature during the major episode of regional deformation in the late mesozoic the higher unblocking temperature characteristic components pass reversal baked contact and fold tests and are internally consistent with rocks of different lithologies from widely distributed localities moreover the data exhibit an overall similarity in the magnetic polarity pattern in the stratigraphic sequence at sampled localities hence the high unblocking temperature characteristic component was probably acquired at or near the time of deposition the cambrian and ordovician paleopoles are somewhat different from the other coeval poles for the ncb which are based on much less data and do not pass as many reliability tests but all imply that the ncb was in the equatorial zone in the early paleozoic

silurian clastic sediments in the north qilian shan nw china chemical and isotopic constraints on their forearc provenance with implications for the paleozoic evolution of the tibetan plateau abstract the north qilian shan is an accretion collision orogenic belt in the northeastern margin of the tibetan plateau that connects the north china plate to the north with the tethyan orogenic assemblage to the south its early paleozoic temporal spatial tectonic evolution has been extensively studied but the nature and tectonic setting of its silurian deposition is poorly understood our new petrological analysis suggests that the clast composition of fan conglomerates is complex in the danbanshan and zhongdabanshan sections abundant lenticular conglomerate beds contain mainly subrounded rounded metamorphic clasts whereas the tongziba and haichaoba sections contain volcanic chert limestone ultramafic and granitoid clasts however in the sunan area clast types are relatively simple dominated by basalt and granitoids and at tongziba gabbro and basalt clasts are subrounded and angular indicating two different types of provenance ultramafic limestone and abundant chert clasts in the haichaoba and tonghe conglomerates indicate an ophiolitic source whereas subrounded rounded quartzite and granitoid gneiss clasts were probably derived from the central qilian basement geochemical data from the volcanic and granitoid clasts suggest an arc related source and their zircon u pb ages of 515 429 ma suggest that the arc magmatism did not end in the mid silurian sandstone petrology and detrital modes suggest that the silurian sediments were deposited in a forearc basin paleogeographic reconstructions inferred from nnw nne paleocurrent data indicate that an island arc was present off the southern margin of the silurian basin and that southward subduction of oceanic crust between north china and the qilian shan was active or continued in the silurian

further shrimp geochronology on the early cambrian of south china zircon 206pb 238u ages are reported for bentonites from two cambrian sections in south china the meishucun and the fandian the analyzed zircons vary widely in age because of the presence of detrital and altered grains spot ages were corrected for calibration drift during analysis and the age of reference zircon sl13 was calibrated as 580 ma against other standards using sims use of mixture modeling was essential to resolve the different age components and to identify the volcanic ages two age groups occur within the meishucun bed 5 bentonite of which the larger at 518 7 2 5 ma is interpreted as a post depositional zircon growth event and the other at 539 4 2 9 ma as the volcanic age bentonites from the meishucun bed 9 and its fandian equivalent have two age groups 526 5 1 1 ma and 540 2 1 0 ma we interpret the younger of these as the tuff magmatic age and the older as detrital small shelly fossils indicate meischucunian bed 5 is an equivalent of the late nemakit daldynian and its 539 4 2 9 ma age both closely times the base of the cambrian and is a maximum for the basal tommotian the 526 5 1 1 ma for bed 9 and its equivalents approximates the close of the tommotian

structure of the mobile south flank of kilauea volcano hawaii how do huge landslides occur in hawaii we can begin to address this question by examining an incipient landslide structure on the mobile south flank of kilauea volcano between 1970 and 1989 this part of the south flank moved in a southeast direction seaward by 4 m on its eastern end and by 10 m on its western end parallel to the western boundary of a large oifshore topographic bench we show that abrupt decreases in cumulative flank movement correspond to abrupt decreases in hypocenter concentration most of the earthquakes occur in a 7 to 10 km deep band beneath the south flank and relative relocation of a subset of these events shows that they are derived from a single horizontal plane which appears to be a decollement focal mechanisms for this deep seismicity are dominated by thrust fault mechanisms with the overlying block moving seaward a comparison of south flank bathymetry with decollement structures on other volcanoes suggests that the distal end of this decollement coincides with the distal end of the offshore topographic bench 30 50 km from shore and 5 km below sea level the fault system forming the hilina pali is connected with this decollement so that slip on the hilina pali s normal faults coincides with slip of the decollement and with reverse faulting of the distal end of the bench this interpretation is supported by studies of the events associated with the m7 2 kalapana earthquake in 1975 when the hilina pali is connected to the outer bench with a decollement inferred from seismicity a wedge 8 km thick adjacent to kilauea s magma system and 1 2 km thick along the edge of the outer bench an area over 3000 km2 is defined the thickness adjacent to the magma system decreases eastward along kilauea s east rift zone and southwestward from kilauea caldera whereas the thickness of the lip of the outer bench decreases only eastward geologic observations and geophysical studies of the subaerial flank reveal an extensive magma system beneath the koae fault system as well as beneath kilauea caldera and its east rift zone we infer that the boundary of the proximal end of the mobile flank is the southern boundary of this magma system and that this boundary coincides with the southern boundaries of both the koae fault system and kilauea s east rift zone

permian geodynamic setting of northeast china and adjacent regions closure of the paleo asian ocean and subduction of the paleo pacific plate abstract northeast china and adjacent regions are located in the central east asian continent and consist tectonically of both the paleo asian and paleo pacific orogens between the siberian platform and sino korean north china block this paper discusses some hotly debated issues concerning the permian geodynamic setting of these regions based on a comprehensive analysis of available geological geochemical paleobiogeographical and paleomagnetic data spatial and temporal distribution of ophiolites and associated continental marginal sequences permian sedimentary sequences spatial distribution and geochemistry of permian magmatic rocks and the evolution of paleobiogeographical realms imply 1 that the permian marine basins in northeast china and adjacent regions include remnants of the paleo asian ocean in southeastern inner mongolia and central jilin province and active continental margins of the paleo pacific ocean 2 that the suture between the siberian and sino korean paleoplates was finally emplaced in the permian and is located in areas from suolunshan solonker eastwards through regions north to the xar moron river in southeastern inner mongolia and then central jilin province to the yanji area and 3 that the permian crustal evolution of northeast china and adjacent regions as well as parts of the siberian paleoplate was influenced by subduction of the paleo pacific oceanic plate finally the permian tectonic framework and paleogeography of northeast china and adjacent regions in central east asia are discussed briefly and early and late permian palinspastic reconstruction maps are provided

tectonic framework and phanerozoic evolution of sundaland abstract sundaland comprises a heterogeneous collage of continental blocks derived from the india australian margin of eastern gondwana and assembled by the closure of multiple tethyan and back arc ocean basins now represented by suture zones the continental core of sundaland comprises a western sibumasu block and an eastern indochina east malaya block with an island arc terrane the sukhothai island arc system comprising the linchang sukhothai and chanthaburi blocks sandwiched between this island arc formed on the margin of indochina east malaya and then separated by back arc spreading in the permian the jinghong nan uttaradit and sra kaeo sutures represent this closed back arc basin the palaeo tethys is represented to the west by the changning menglian chiang mai inthanon and bentong raub suture zones the west sumatra block and possibly the west burma block rifted and separated from gondwana along with indochina and east malaya in the devonian and were accreted to the sundaland core in the triassic west burma is now considered to be probably cathaysian in nature and similar to west sumatra from which it was separated by opening of the andaman sea basin south west borneo and or east java west sulawesi are now tentatively identified as the missing argoland which must have separated from nw australia in the jurassic and these were accreted to se sundaland in the cretaceous revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of sundaland and adjacent regions are presented