Showing papers in "Tectonics in 2004"
TL;DR: In this article, the authors describe the evolution of the western Mediterranean subduction zone (WMSZ) during the last 35 Myr by combining new and previous geological data, new tomographic images of the Western Mediterranean mantle, and plate kinematics.
Abstract: [1] The western Mediterranean subduction zone (WMSZ) extends from the northern Apennine to southern Spain and turns around forming the narrow and tight Calabrian and Gibraltar Arcs. The evolution of the WMSZ is characterized by a first phase of orogenic wedging followed, from 30 Ma on, by trench retreat and back-arc extension. Combining new and previous geological data, new tomographic images of the western Mediterranean mantle, and plate kinematics, we describe the evolution of the WMSZ during the last 35 Myr. Our reconstruction shows that the two arcs form by fragmentation of the 1500 km long WMSZ in small, narrow slabs. Once formed, these two narrow slabs retreat outward, producing back-arc extension and large scale rotation of the flanks, shaping the arcs. The Gibraltar Arc first formed during the middle Miocene, while the Calabrian Arc formed later, during the late Miocene-Pliocene. Despite the different paleogeographic settings, the mechanism of rupture and backward migration of the narrow slabs presents similarities on both sides of the western Mediterranean, suggesting that the slab deformation is also driven by lateral mantle flow that is particularly efficient in a restricted (upper mantle) style of mantle convection.
884 citations
TL;DR: In this article, a regional compilation of the drainage history in southeastern Tibet suggests that modern rivers draining the plateau margin were once tributaries to a single, southward flowing system which drained into the South China Sea.
Abstract: [1] A new regional compilation of the drainage history in southeastern Tibet suggests that the modern rivers draining the plateau margin were once tributaries to a single, southward flowing system which drained into the South China Sea. Disruption of the paleo-drainage occurred by river capture and reversal prior to or coeval with the initiation of Miocene (?) uplift in eastern Tibet, including ∼2000 m of surface uplift of the lower plateau margin since reversal of the flow direction of the Yangtze River. Despite lateral changes in course due to capture and reversal, the superposition of eastward and southward draining rivers that cross the southeastern plateau margin suggests that uplift has occurred over long wavelengths (>1000 km), mimicking the present low-gradient topographic slope. Thus reorganization of drainage lines by capture and reversal events explains most of the peculiar patterns of the eastern plateau rivers, without having to appeal to large-magnitude tectonic shear.
688 citations
TL;DR: In this paper, the authors extrapolate the present day slip rates of many active fault systems for ∼3-7 million years to account for their total displacement, which means that the present kinematics of the Arabia-Eurasia collision are unlikely be the same as at its start, which was probably in the early Miocene (16-23 Ma) or earlier.
Abstract: The Arabia-Eurasia collision deforms an area of ∼3,000,000 km2 of continental crust, making it one of the largest regions of convergent deformation on Earth. There are now estimates for the active slip rates, total convergence and timing of collision-related deformation of regions from western Turkey to eastern Iran. This paper shows that extrapolating the present day slip rates of many active fault systems for ∼3–7 million years accounts for their total displacement. This result means that the present kinematics of the Arabia-Eurasia collision are unlikely be the same as at its start, which was probably in the early Miocene (16–23 Ma) or earlier. In some, but not all, active fault systems, short-term (∼10 year) and long-term (∼5 million year) average deformation rates are consistent. There is little active thickening across the Turkish-Iranian plateau and, possibly, the interior of the Greater Caucasus. These are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening, and where there are structural and/or stratigraphic data for pre-late Miocene deformation. We suggest that once thick crust (up to 60 km) built up in the Turkish-Iranian plateau and the Greater Caucasus, convergence took place more easily by crustal shortening in less elevated regions, such as the Zagros Simple Folded Zone, the South Caspian region and foothills of the Greater Caucasus, or in other ways, such as westward transport of Turkey between the North and East Anatolian faults. The time and duration of this changeover are not known for certain and are likely be diachronous, although deformation started or intensified in many of the currently active fault systems at ∼5 ± 2 Ma.
515 citations
TL;DR: In this article, the authors reconstruct the evolution of the Tyrrhenian Sea and show that the major stage of rifting associated with the opening of this basin began at similar to 10 Ma.
Abstract: Reconstruction of the evolution of the Tyrrhenian Sea shows that the major stage of rifting associated with the opening of this basin began at similar to10 Ma. It involved two episodes of back arc extension, which were induced by the rollback of a west dipping subducting slab. The first period of extension (10-6 Ma) was prominent in the northern Tyrrhenian Sea and in the western part of the southern Tyrrhenian Sea. The second period of extension, mainly affected the southern Tyrrhenian Sea, began in the latest Messinian (6-5 Ma) and has been accompanied by subduction rollback at rates of 60-100 km Myr(-1). Slab reconstruction, combined with paleomagnetic and paleogeographic constraints, indicates that in the central Apennines, the latest Messinian (6-5 Ma) arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike-slip faults. These processes resulted in the formation of a narrow subducting slab beneath the Ionian Sea that has undergone faster subduction rollback and induced extreme rates of back arc extension.
396 citations
TL;DR: In this article, the authors present new geochronological and structural data that indicate a continuation of the Dharwar Craton into the Southern Granulite Terrain as far south as a newly identified Neoproterozoic shear zone, here named the Karur-Kamban-Painavu-Trichur Shear Zone (KKPTSZ).
Abstract: [1] The high-grade rocks of the Southern Granulite Terrain (SGT) of Peninsular India are bounded to the north by the Archean Dharwar Craton. Another high-grade terrane, the Mesoproterozoic Eastern Ghats, occurs to the northeast of the SGT. The tectonic relationship between these crustal domains is complex. We present new geochronological and structural data that indicate a continuation of the Dharwar Craton into the Southern Granulite Terrain as far south as a newly identified Neoproterozoic shear zone, here named the Karur-Kamban-Painavu-Trichur Shear Zone (KKPTSZ). South of the KKPTSZ, Mesoproterozoic dates of the SGT are similar to those recorded in the Eastern Ghats, and the two domains may have been conterminous. Thirty-three new U/Pb/Th single zircon and monazite dates of samples from six structural transects across the regional shear zones indicate that the SGT has experienced at least seven thermo-tectonic events at 2.5 Ga, ∼2.0 Ga, ∼1.6 Ga, ∼1.0 Ga, ∼800 Ma, ∼600 Ma, and ∼550 Ma, and two distinct episodes of metasomatism/charnockitization between 2.50–2.53 and between 0.55–0.53 Ga. Deformation along a number of major shear zones in the SGT is Neoproterozoic to earliest Paleozoic in age, with an early phase (D2) concentrated between 700–800 Ma, and a later phase (D3) between 550 and 600 Ma. Major charnockitization (530–550 Ma) post dates D3, and is, in turn, overprinted by granitization, retrogression, and uplift between 525 and 480 Ma. The KKPTSZ, active between 560 and 570 Ma, is either a terrane boundary, or a tectonized decollement between cover and Archean basement rocks represented by predominantly paragneisses to the south and orthogneisses to the north, respectively. Other regional Neoproterozoic shear zones do not appear to separate allochthonous terranes as previously suggested on the basis of Nd model ages and Rb/Sr biotite/whole rock dates. The Neoproterozoic-Cambrian tectonothermal history of the SGT and Eastern Ghats is similar to that recorded in parts of Madagascar, East Africa, and Antarctica, and is used to reconstruct parts of central Gondwana, here named the Deccan Continent, with more robust confidence.
304 citations
TL;DR: In this article, a relatively simple crustal structure for the Pamirs and Tibet has been proposed, which suggests that the metamorphic rocks in these domes are equivalent to the Karakul-Mazar-Songpan-Garze system.
Abstract: [1] Magmatic rocks and depositional setting of associated volcaniclastic strata along a north-south traverse spanning the southern Tien Shan and eastern Pamirs of Kyrgyzstan and Tajikistan constrain the tectonics of the Pamirs and Tibet The northern Pamirs and northwestern Tibet contain the north facing Kunlun suture, the south facing Jinsha suture, and the intervening Carboniferous to Triassic Karakul–Mazar subduction accretion system; the latter is correlated with the Songpan-Garze–Hoh Xi system of Tibet The Kunlun arc is a composite early Paleozoic to late Paleozoic-Triassic arc Arc formation in the Pamirs is characterized by ∼370–320 Ma volcanism that probably continued until the Triassic The cryptic Tanymas suture of the southern northern Pamirs is part of the Jinsha suture A massive ∼≤227 Ma batholith stitches the Karakul–Mazar complex in the Pamirs There are striking similarities between the Qiangtang block in the Pamirs and Tibet Like Tibet, the regional structure of the Pamirs is an anticlinorium that includes the Muskol and Sares domes Like Tibet, the metamorphic rocks in these domes are equivalents to the Karakul–Mazar–Songpan-Garze system Granitoids intruding the Qiangtang block yield ∼200–230 Ma ages in the Pamirs and in central Tibet The stratigraphy of the eastern Pshart area in the Pamirs is similar to the Bangong-Nujiang suture zone in the Amdo region of eastern central Tibet, but a Triassic ocean basin sequence is preserved in the Pamirs Arc-type granitoids that intruded into the eastern Pshart oceanic-basin–arc sequence (∼190–160 Ma) and granitoids that cut the southern Qiangtang block (∼170–160 Ma) constitute the Rushan-Pshart arc Cretaceous plutons that intruded the central and southern Pamirs record a long-lasting magmatic history Their zircons and those from late Miocene xenoliths show that the most distinct magmatic events were Cambro-Ordovician (∼410–575 Ma), Triassic (∼210–250 Ma; likely due to subduction along the Jinsha suture), Middle Jurassic (∼147–195 Ma; subduction along Rushan-Pshart suture), and mainly Cretaceous Middle and Late Cretaceous magmatism may reflect arc activity in Asia prior to the accretion of the Karakoram block and flat-slab subduction along the Shyok suture north of the Kohistan-Ladakh arc, respectively Before India and Asia collided, the Pamir region from the Indus-Yarlung to the Jinsha suture was an Andean-style plate margin Our analysis suggests a relatively simple crustal structure for the Pamirs and Tibet From the Kunlun arc in the north to the southern Qiangtang block in the south the Pamirs and Tibet likely have a dominantly sedimentary crust, characterized by Karakul–Mazar–Songpan-Garze accretionary wedge rocks The crust south of the southern Qiangtang block is likely of granodioritic composition, reflecting long-lived subduction, arc formation, and Cretaceous-Cenozoic underthrusting
301 citations
TL;DR: The Himalayan crystalline core zone exposed along the Sutlej valley (India) is composed of two high-grade metamorphic gneiss sheets that were successively underthrusted and tectonically extruded, as a consequence of the foreland-directed propagation of crustal deformation in the Indian plate margin this article.
Abstract: The Himalayan crystalline core zone exposed along the Sutlej Valley (India) is composed of two high-grade metamorphic gneiss sheets that were successively underthrusted and tectonically extruded, as a consequence of the foreland-directed propagation of crustal deformation in the Indian plate margin. The High Himalayan Crystalline Sequence (HHCS) is composed of amphibolite facies to migmatitic paragneisses, metamorphosed at temperatures up to 750°C at 30 km depth between Eocene and early Miocene. During early Miocene, combined thrusting along the Main Central Thrust (MCT) and extension along the Sangla Detachment induced the rapid exhumation and cooling of the HHCS, whereas exhumation was mainly controlled by erosion since middle Miocene. The Lesser Himalayan Crystalline Sequence (LHCS) is composed of amphibolite facies para- and orthogneisses, metamorphosed at temperatures up to 700°C during underthrusting down to 30 km depth beneath the MCT. The LHCS cooled very rapidly since late Miocene, as a consequence of exhumation controlled by thrusting along the Munsiari Thrust and extension in the MCT hanging wall. This renewed phase of tectonic extrusion at the Himalayan front is still active, as indicated by the present-day regional seismicity, and by hydrothermal circulation linked to elevated near-surface geothermal gradients in the LHCS. As recently evidenced in the Himalayan syntaxes, active exhumation of deep crustal rocks along the Sutlej Valley is spatially correlated with the high erosional potential of this major trans-Himalayan river. This correlation supports the emerging view of a positive feedback during continental collision between crustal-scale tectono-thermal reworking and efficient erosion along major river systems.
279 citations
TL;DR: In this article, the authors used satellite imagery to identify displaced geological and geomorphological markers, which were used in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right-lateral shear.
Abstract: [1] Right-lateral shear between central Iran and Afghanistan is accommodated on N–S right-lateral strike-slip faults surrounding the aseismic Dasht-e-Lut. North of ∼34°N, the right-lateral shear is accommodated on left-lateral faults that rotate clockwise about vertical axes. Little is known of the late Tertiary and younger offsets and slip rates on the active fault systems, results that are important for understanding the regional tectonics. We use observations from satellite imagery to identify displaced geological and geomorphological markers, which we use in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right-lateral shear. Estimates of cumulative fault movements from offset features and inferred vertical axis rotation of fault-bounded blocks suggest that the late Cenozoic strain is concentrated toward the eastern margin of Iran, along the Sistan shear zone, where bedrock offsets of at least 70 km are observed across the active faults. The geomorphology of the Deh Shir, Anar, and Great Kavir strike-slip faults in central Iran suggest that although little shortening is accommodated across this region, they might still be active, and hence capable of producing earthquakes. Present-day activity on these faults in central Iran would not be expected from distributions of instrumental and historical earthquakes. Although speculative, the late Tertiary strain distribution described in this paper is consistent with what we know of the present-day rates of shear in eastern Iran and provides a framework to which later, more detailed, work can be added.
270 citations
TL;DR: The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr as mentioned in this paper.
Abstract: The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520°–550°C below the Main Central Thrust zone down to less than 330°C. These temperatures describe structurally a 20°–50°C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3–4 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m^2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units.
206 citations
TL;DR: The Alpine Oligocene plutons are spatially and temporally associated with the activity of the Periadriatic Fault System (PFS), an orogen-parallel, crustal-scale transpressive mylonitic belt as discussed by the authors.
Abstract: [1] The Alpine Oligocene plutons are spatially and temporally associated with the activity of the Periadriatic Fault System (PFS), an orogen-parallel, crustal-scale transpressive mylonitic belt. Excellent three-dimensional exposure, combined with a wealth of structural, seismic, petrological, geochronological, geochemical, and paleomagnetic data collected over the last decades help to constrain the relationships between deformation, ascent, and emplacement of the plutons. Magmas were channeled from the base of the thickened continental crust into the narrow mylonitic belt of the Periadriatic Fault System, which was used as ascent pathway to cover vertical lengths of 20 to 40 km. Therefore the linear alignment of the plutons at the surface is not the expression of a linear source region at depth. Ascent of the melts is controlled by the mylonitic foliation of the PFS, which forms the only steep anisotropy, continuously traversing the entire Alpine crust. In contrast, the flow direction is not influenced by the specific kinematics of the faults. Final emplacement of the plutons occurred by extrusion from the Periadriatic Fault System into the adjacent country rocks. The transition from ascent to final emplacement is favored by partitioning of transpressive deformation.
203 citations
TL;DR: In this article, the authors proposed that all HP/UHP events in the Scandinavian Caledonides occurred through the subduction of crustal slabs into the mantle and their subsequent buoyancy-enhanced exhumation toward the surface (eduction).
Abstract: [1] The evolution of the Caledonides of Scandinavia included at least four events that resulted in high-pressure (HP) and ultrahigh-pressure (UHP) eclogite facies metamorphism and the introduction of peridotite from the mantle into the crust. Two are the classic Finnmarkian orogeny at ∼500 Ma and the Scandian orogeny between 400 and 425 Ma. We have dated a third HP metamorphism in the Seve Nappe Complex in Jamtland, central Sweden, at ∼454 Ma. Identical Upper Ordovician ages from eclogite of the Troms region, northern Norway, date a simultaneous fourth HP event that occurred in a different tectonic setting, probably western Iapetus. Recently reported Late Silurian ages from eclogite of the Bergen Arcs District, southern Norway, suggest a possible fifth event. We propose that all HP/UHP events in the Scandinavian Caledonides occurred through the subduction of crustal slabs into the mantle and their subsequent buoyancy-enhanced exhumation toward the surface (eduction). The slabs are recognized as intensely deformed, high-grade (eclogite and HP granulite facies) metamorphic rocks although HP metamorphism is not necessarily penetrative and retrogression to medium grade assemblages is common. The HP/UHP metamorphic terranes are bounded by thrust faults at the base and low-angle normal detachments at the top and are separated by these shear zones from less deformed terranes of lower pressure metamorphic grade. The peridotite bodies were introduced from the overlying mantle wedge during subduction or eduction. The evolution of metamorphic terranes in other orogens might be better understood through successive subduction/eduction events, a process we provisionally call “dunk” tectonics.
TL;DR: In this paper, the authors systematically traced established central Himalayan tectonostratigraphy around the western Himalayan syntaxis and across Pakistan, and revealed the following stratigraphic and structural relationships: (1) there is a westward decrease in Neogene shortening across the Himalayan fold and thrust belt such that there is no age equivalent thrust in Pakistan with displacement and metamorphic juxtaposition equivalent to the central mountainous MCT.
Abstract: [1] Indian plate rocks in the central Himalaya have traditionally been divided into orogen-parallel, fault-bound tectonostratigraphic zones. A straightforward westward extrapolation of these zones has proved problematic in part because of a lack of consensus on the existence or significance of major faults within the metamorphic zone of the Indian plate in Pakistan where more than 10 locations for the Main Central thrust (MCT) have been proposed. We address this ambiguity by systematically tracing established central Himalayan tectonostratigraphy around the western Himalayan syntaxis and across Pakistan. This exercise reveals the following stratigraphic and structural relationships: (1) There is a westward decrease in Neogene shortening across the Himalayan fold and thrust belt such that there is no age equivalent thrust in Pakistan with displacement and metamorphic juxtaposition equivalent to the central Himalayan MCT. (2) Shortening across the fold and thrust belt in western Pakistan is concentrated in the unmetamorphosed foreland as opposed to the metamorphic zone in the central Himalaya. (3) Lesser Himalayan, Higher Himalayan, and Tethyan rocks are in stratigraphic order within the metamorphic zone of Pakistan which appears to be the metamorphic equivalent of Kashmir Tethyan stratigraphy. (4) The combination of early Paleozoic and late Paleozoic tectonism in Pakistan has locally eliminated Upper Proterozoic Higher Himalayan rock and lower to middle Paleozoic Tethyan rock from the metamorphic zone of Pakistan. (5) Late Cretaceous and/or early Paleocene proto-Himalayan deformation in the Pakistan foreland telescoped and eroded stratigraphy prior to the main phase of Himalayan orogeny. (6) Tectonostratigraphic zones are offset in eastern Pakistan by the transverse Jhelum-Balakot fault. (7) There is no evidence within the Indian plate of Pakistan for a large-scale normal fault system comparable to the South Tibetan detachment system. (8) Stratigraphy, as well as the age and tectonic setting of deformation and metamorphism, must be taken into account when drawing tectonostratigraphic zones.
TL;DR: Tohver and van der Pluijm as mentioned in this paper showed that the NBMB marks the Mesoproterozoic limit of the SW Amazon craton and the Aguapeo´ belt, in contrast, seems to record only limited deformation internal to the Paragua craton.
Abstract: (� 910 Ma). The NBMB marks the Mesoproterozoic limit of the SW Amazon craton. The discordance of the NBMB to the NNW structural trend of the younger Aguapeo´ belt (200 km SE of NBMB), together with marked differences between the two belts in sedimentary environment, metamorphic grade, and timing of deformation, signify that these two belts are not geologically continuous. The ‘‘Grenvillian’’ deformation recorded by the NBMB belt marks the final docking of the Amazon craton and Paragua craton within the Rodinia framework. The Aguapeo´ belt, in contrast, seems to record only limited deformation internal to the Paragua craton. INDEX TERMS: 8102 Tectonophysics: Continental contractional orogenic belts; 3660 Mineralogy and Petrology: Metamorphic petrology; 1035 Geochemistry: Geochronology; 8025 Structural Geology: Mesoscopic fabrics; 9360 Information Related to Geographic Region: South America; KEYWORDS: Rodinia, Grenville mobile belt, Amazon craton, Paragua craton, geochronology, P-T path. Citation: Tohver, E., B. van der Pluijm, K. Mezger, E. Essene, J. Scandolara, and G. Rizzotto (2004), Significance of the Nova ...
TL;DR: In this paper, the authors investigated the NNW striking transition zone that connects Zagros and Makran: the Minab-Zendan fault system and found evidence for active deformation that is not localized but distributed across a wide domain.
Abstract: [1] At Iranian longitude, the Arabian plate is moving northward relative to Eurasia (∼20 mm yr−1 according to GPS). To the east, this relative motion is accommodated by northward subduction under the E-W Makran emerged accretionary prism. To the west, it is accommodated partly by the Zagros fold-and-thrust belt and partly by the Alborz/Kopet Dagh deforming zones further north. This work investigates the NNW striking transition zone that connects Zagros and Makran: the Minab-Zendan fault system. Satellite images, and structural and geomorphic field observations show a distributed deformation pattern covering a wide domain. Five north to NW trending major faults were identified. They exhibit evidence for late Quaternary reverse right-lateral slip, and correspond to two distinct fault systems: the western one transferring the Zagros deformation to the Makran prism, and the eastern one northward transferring the deformation to the Alborz/Kopet Dagh. Tectonic study and fault slip vector analyses indicate that two distinct tectonic regimes have occurred successively since the Miocene within a consistent regional NE trending compression: (1) an upper Miocene to Pliocene tectonic regime characterized by partitioned deformation, between reverse faulting and en echelon folding; (2) a NE trending σ1 axis transpressional regime homogeneously affecting the region since upper Pliocene. The change is contemporaneous with major tectonic reorganization regionally recorded. Therefore this study provides evidence for active deformation that is not localized, but distributed across a wide zone. It accommodates the convergence and transfers it from collision to subduction by transpressional tectonics without any partitioning process in the present-day period.
TL;DR: In this article, the authors showed that coherent Baltica crust at 60-70 km depth experienced subvertical and horizontal shortening while extending toward the foreland during a top-southeast thrusting parallel to plate motion.
Abstract: [1] Well-preserved eclogite-facies structural features in metamorphosed gabbro and diorite gneiss in Baltica crust, formed at a minimum depth of 60–70 km during the Scandian orogeny, allow direct inferences to be made regarding the geometry of folds, kinematics, and original structural orientations related to production and exhumation of high-pressure rocks Folds associated with eclogite-facies fabrics are isoclinal to tubular with axes parallel to the trend of a stretching lineation Strain estimates and L > S or L ≫ S fabrics indicate that these structures were formed in a constrictional strain field Locally, they are well preserved in eclogite-facies mylonite zones at least 40 m thick that cut Proterozoic gabbro and adjacent gneiss Where steeply dipping, they show a north-side-up shear sense across a younger, northeast trending, shallowly plunging, amphibolite-facies anticlinorium formed in a constrictional, noncoaxial strain field Where original structural facing direction can be inferred, small-circle rotation of the eclogite-facies lineation about the anticline axis indicates that the relative motion vector of Baltica with respect to overlying imbricated crust and Laurentia was oriented 320° in a present-day reference frame This result is identical to the orientation of the relative motion vector estimated from paleomagnetic plate reconstructions and consistent with Late Silurian to Early Devonian oblique sinistral convergence between Baltica and Laurentia Results of this study indicate that coherent Baltica crust at 60–70 km depth experienced subvertical and horizontal shortening while extending toward the foreland during tops-southeast thrusting parallel to plate motion High-pressure rocks were progressively imbricated and stacked along eclogite-facies mylonite zones, with the deforming zone separating coherent Baltica crust from imbricated basement above The constrictional strains under eclogite-facies conditions are interpreted to have resulted from stretching associated with sinking of the cool dense mantle lithosphere
TL;DR: In this article, the authors explore the available database, together with the coseismic observations from the region, to further understand the nature of faulting, and identify the northern boundary fault as a major seismic source.
Abstract: [1] The 1897 Shillong (Assam), northeast India, earthquake is considered to be one of the largest in the modern history Although Oldham's [1899] classic memoir on this event opened new vistas in observational seismology, many questions on its style of faulting remain unresolved Most previous studies considered this as a detachment earthquake that occurred on a gently north dipping fault, extending from the Himalayan front A recent model proposed an alternate geometry governed by high-angle faults to the north and south of the plateau, and it suggested that the 1897 earthquake occurred on a south dipping reverse fault, coinciding with the northern plateau margin In this paper, we explore the available database, together with the coseismic observations from the region, to further understand the nature of faulting The geophysical and geological data examined in this paper conform to a south dipping structure, but its location is inferred to be in the Brahmaputra basin, further north of the present plateau front Our analyses of paleoseismic data suggest a 1200-year interval between the 1897 event and its predecessor, and we identify the northern boundary fault as a major seismic source The Shillong Plateau bounded by major faults behaves as an independent tectonic entity, with its own style of faulting, seismic productivity, and hazard potential, distinct from the Himalayan thrust front, a point that provides fresh insight into the regional geodynamics
TL;DR: In this article, a quantitative reconstruction of uplift of the western flank of the Altiplano plateau (central Andes), one of the largest monoclines on the Earth, was presented based on an analysis of tectonic structures, syntectonic deposits, and geophysical data.
Abstract: [1] We present a quantitative reconstruction of uplift of the western flank of the Altiplano plateau (central Andes), one of the largest monoclines on the Earth, on the basis of an analysis of tectonic structures, syntectonic deposits, and geophysical data. Uplift occurred on a west vergent, slowly propagating system of high-angle reverse faults merging into a joint detachment that ramps down to midcrustal levels below the plateau edge. The upper ramps determine local fold geometries while the lower ramp controls large-scale surface tilting and uplift. At 20°S, this fault system was active between ∼30 Ma and 5–10 Ma, with maximum shortening rates of 0.22 mm/yr between 17 and 10 Ma. It generated some 2600 m of surface uplift with only minor shortening of ∼3000 m. Its activity was largely synchronous to eruption of large-volume ignimbrites from a midcrustal source. Geophysical data indicate that the fault system localized deformation at the boundary between a cool, strong forearc crust and a presumably fluid-rich and/or partially molten zone underneath the plateau area. The systematic relation between crustal melting and shortening with uplift at the western plateau margin can be traced along most of the plateau flank, with a stepwise decrease in age of deformation and magmatism toward the south indicating discontinuous addition of plateau segments. Crustal thickening to as much as 70 km from westward underthrusting in the back arc parts of the plateau isostatically compensated the tectonic surface uplift and monocline formation with respect to a stable forearc, which only reacted with minor tilting.
TL;DR: In this paper, the authors derived a slip rate for a thrust at the central Qilian Shan mountain front by combining structural investigations, satellite imagery, topographic profiling, luminescence dating, and 10Be exposure dating.
Abstract: [1] We derive a slip rate for a thrust at the central Qilian Shan mountain front by combining structural investigations, satellite imagery, topographic profiling, luminescence dating, and 10Be exposure dating. The seismically active Zhangye thrust transects late Pleistocene alluvial fan deposits and forms a prominent north facing scarp. The fault consists of two segments that differ in orientation, scarp height, and age. A series of loess-covered terraces records the uplift history of the western thrust segment. Loess accumulation on all terraces started at 8.5 ± 1.5 kyr and postdates terrace formation. Gravels from the highest terrace yielded a 10Be exposure age of 90 ± 11 kyr, which dates the onset of faulting. With a displacement of 55–60 m derived from fault scarp profiles, this yields a vertical slip rate of 0.64 ± 0.08 mm yr−1. Along the eastern thrust segment, three 10Be ages from the uplifted alluvial fan constrain that faulting started at ∼31 ± 5 kyr. Together with a displacement of 25–30 m this leads to a vertical faulting rate of 0.88 ± 0.16 mm yr−1. A dip estimate of 40° to 60° for the fault plane combined with lower and upper limits of ∼0.6 and ∼0.9 mm yr−1 for the vertical slip rate gives minimum and maximum horizontal shortening rates of 0.4 and 1.1 mm yr−1 across the Zhangye thrust. Our results are consistent with geologic and GPS constraints, which suggest that NNE directed shortening across the northeastern Tibetan Plateau is distributed on several active faults with a total shortening rate of 4 to 10 mm yr−1.
TL;DR: In this article, the exhumation process of the ultra-high pressure Tso Morari dome (NW-Himalaya) was investigated using structural, petrological and geochronological data.
Abstract: Exhumation processes of the ultra-high pressure (UHP) Tso Morari dome (NW-Himalaya) are investigated using structural, petrological and geochronological data. The UHP Tso Morari unit is bounded by the low-grade metamorphic Indus Suture Zone to the NE and Mata unit to the SW. Three deformation phases (D1, D2 and D3) are observed. Only D3 is common to the UHP unit and the surrounding units. In the UHP unit, the first deformation phase (D1) produced upright folds, under eclogitic conditions (> 20 kbar; 580 ± 60 °C). D1 is overprinted by D2 structures related to a NW-SE trending open anticline. This phase is characterized by blueschist mineral associations, and corresponds to the quasi-isothermal decompression from a depth of 90 km (eclogitic conditions) up to 30-40 km. The final exhumation phase of the Tso Morari unit is dominated by tectonic denudation and erosion (D3), associated with a slight temperature increase. Radiochronological analyses indicate that the UHP exhumation process began during the Eocene. Exhumation was fast during D1-D2 and slowed down through D3 in Oligocene time. The change in the deformation style from D1-D2 to D3 in the Tso Morari unit coincides with changes in the exhumation rates and in the metamorphic conditions. These changes may reflect the transition from an exhumation along the subduction plane in a serpentinized wedge, to the vertical uplift of the Tso Morari unit across the upper crust.
TL;DR: In this article, the authors show that the Cordillera in northern Canada is underlain by westward tapering layers that can be followed from outcrops of Proterozoic strata in the Foreland belt to the lowermost crust of the orogenic interior, a distance of as much as 500 km across strike.
Abstract: [1] The Cordillera in northern Canada is underlain by westward tapering layers that can be followed from outcrops of Proterozoic strata in the Foreland belt to the lowermost crust of the orogenic interior, a distance of as much as 500 km across strike. They are interpreted as stratified Proterozoic rocks, including ∼1.8–0.7 Ga supracrustal rocks and their basement. The layering was discovered on two new deep seismic reflection profiles in the Yukon (Line 3; ∼650 km) and northern British Columbia (Line 2; ∼1245 km in two segments) that were acquired as part of the Lithoprobe Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) transect. In the Mackenzie Mountains of the eastern Yukon, the layering in Line 3 is visible between 5.0 and 12.0 s (∼15 to 36 km depth). It is followed southwestward for nearly 650 km (∼500 km across strike) and thins to less than 1.0 s (∼3.0–3.5 km thickness) near the Moho at the Yukon-Alaska international boundary. In the northern Rocky Mountains of British Columbia, the upper part of the layering on Line 2 correlates with outcrops of Proterozoic (1.76–1.0 Ga) strata in the Muskwa anticlinorium. At this location, the layering is at least 15 km thick and is followed westward then southward into the middle and lower crust for ∼700 km (∼300 km across strike). It disappears as a thin taper at the base of the crust ∼150 km east of the coast of the Alaskan panhandle. The only significant disruption in the layering occurs at the Tintina fault zone, a late to postorogenic strike-slip fault with up to 800 km of displacement, which appears as a vertical zone of little reflectivity that disrupts the continuity of the deep layering on both profiles (∼300 km apart). The base of the layered reflection zone coincides with the Moho, which exhibits variable character and undulates in a series of broad arches with widths of ∼150 km. In general, the mantle appears to have few reflections. However, at the southwest end of Line 3 near the Alaska-British Columbia border, a reflection dips eastward from ∼14.0 s to ∼21.0 s (∼45 to 73 km depth) beneath exposed Eocene magmatic rocks. It is interpreted as a relict subduction surface of the Kula plate. Our interpretation of Proterozoic layered rocks beneath most of the northern Cordillera suggests a much different crustal structure than previously considered: (1) Ancient North American crust comprising up to 25 km of metamorphosed Proterozoic to Paleozoic sediments plus 5–10 km of pre-1.8 Ga crystalline basement projects westward beneath most of the northern Canadian Cordillera. (2) The lateral (500 km by at least 1000 km) and vertical (up to 25 km) extent of the Proterozoic layers and their internal deformation are consistent with a long-lived margin for northwestern North America with alternating episodes of extension and contraction. (3) The detachments that carry deformed rocks of the Mackenzie Mountains and northern Rocky Mountains are largely confined to the upper crustal region above the layering. (4) Accreted terranes include thin klippen that were thrust over North American pericratonic strata (e.g., Yukon-Tanana), and terranes such as Nisling and Stikinia that thicken westward as the underlying Proterozoic layers taper and disappear. (5) The ages of exposed rocks are not necessarily indicative of the ages of underlying crust, a frequent observation in Lithoprobe interpretations, so that estimates of crustal growth based on surface geology may not be representative.
TL;DR: In this article, the authors reconstruct the nappe-structured belt of Calabria through a multidisciplinary approach which integrates structural investigations with metamorphic thermobarometry and 40Ar/39Ar geochronology.
Abstract: [1] The nappe-structured belt of Calabria constitutes the eastward termination of the southern branch of the Alpine Mediterranean belt that delimits the northern edge of the Africa plate Contrasting hypotheses for the origin and tectonic significance of the north Calabrian nappe edifice have been proposed, and kinematic data from north Calabria have been used to support different interpretations of the Alps-Apennines linkage and the polarity of the Tethyan subduction in the Apennine region We reconstruct the architecture of the north Calabria nappe edifice through a multidisciplinary approach which integrates structural investigations with metamorphic thermobarometry and 40Ar/39Ar geochronology Results from this study indicate that north Calabria consists of a Tertiary nappe stack, resulting from superimposed top-to-the-west extensional shearing (late Oligocene to middle Miocene in age) onto a previously structured top-to-the-east compressional belt (Eocene to Oligocene in age) This study also documents that the top-to-the-west extensional tectonics was achieved by means of regionally sized extensional detachment fault systems, stretching apart and translating as allochthonous fragments the previously accreted units Thinning operated by top-to-the-west extensional detachment tectonics also resulted in the direct juxtaposition of non-Alpine or slightly Alpine metamorphosed units (upper plate complex) onto the previously exhumed deep-seated portions of the orogenic wedge, metamorphosed under blueschist facies metamorphic conditions (lower plate complex) These findings support a new tectonic scenario for the orogenic history of north Calabria, which may be adequately framed within the Tertiary Apennine-Tyrrhenian system evolution
TL;DR: In this paper, an east vergent fold-thrust belt (EVFTB) involving a major angular unconformity between Early and Middle Ordovician rocks, a highly deformed volcano-sedimentary belt, and a ductile shear zone affecting Famatinian granites is described.
Abstract: [1] The Famatina belt, southern central Andes, records a circa 470 m.y. shortening episode (Ocloyic orogeny) affecting the peri-Gondwanan back arc basin in response to the accretion of the Precordillera terrane. Collision created distinct features across and along the margin, some of which persisted into the present Andean structure. From east to west, the Ocloyic deformation is recorded across the telescoped region of Famatina, represented by (1) an east vergent fold-thrust belt (EVFTB) involving a major angular unconformity between Early and Middle Ordovician rocks, (2) a highly deformed volcano-sedimentary belt, and (3) an east vergent ductile shear zone affecting Famatinian granites. Axis attitudes of Ordovician refolded anticlines in the EVFTB show west-east tectonic transport, in agreement with kinematics of Ocloyic high-strain belts, indicating shortening orthogonal to the present Pacific margin. Eastward displacement of the Ordovician volcanic arc at ∼27°S latitude together with a documented sinistral slip zone across the proto-Andean margin suggests tectonic indentation.
TL;DR: In this paper, a large-scale visco-plasto-elastic thermomechanical model was used to model the evolution of a continent-continent collision and draw some parallels with the tectonic evolution of the Himalaya.
Abstract: We model evolution of a continent-continent collision and draw some parallels with the tectonic evolution of the Himalaya. We use a large-scale visco-plasto-elastic thermomechanical model that has a free upper surface, accounts for erosion and deposition and allows for all modes of lithospheric deformation. For quartz/olivine rheology and 60 mm/yr convergence rate, the continental subduction is stable, and the model predicts three distinct phases. During the phase 1 (120 km or 6% of shortening), deformation is characterized by back thrusting around the suture zone. Some amount of delaminated lower crust accumulates at depth. During phase 2 (120 km–420 km or 6%–22% of shortening), this crustal root is exhumed (medium- to high-grade rocks) along a newly formed major thrust fault. This stage bears similarities with the period of coeval activity of the Main Central thrust and of the South Tibetan Detachment between 20–16 Myr ago. During phase 3 (>420 km or 22% of shortening), the crust is scraped off from the mantle lithosphere and is incorporated into large crustal wedge. Deformation is localized around frontal thrust faults. This kinematics should produce only low- to medium-grade exhumation. This stage might be compared with the tectonics that has prevailed in the Himalaya over the last 15 Myr allowing for the formation of the Lesser Himalaya. The experiment is conducted at constant convergence rate, which implies increasing compressive force. Considering that this force is constant in nature, this result may be equivalent to a slowing down of the convergence rate as was observed during the India-Asia collision.
TL;DR: The first evidence for ultra-high pressure metamorphism in the Eastern Alps is reported from kyanite eclogites of the Pohorje Mountains in Slovenia as discussed by the authors.
Abstract: [1] The first evidence for ultrahigh-pressure (UHP) metamorphism in the Eastern Alps is reported from kyanite eclogites of the Pohorje Mountains in Slovenia. Polycrystalline quartz inclusions surrounded by radial fractures in garnet, omphacite, and kyanite are interpreted to be pseudomorphs after coesite. Abundant quartz rods and needles in omphacite indicate an exsolution from a preexisting supersilicic clinopyroxene that contained a Ca-Eskola component. Geothermobarometry on the mineral assemblage garnet + omphacite + kyanite + phengite + quartz/or coesite yields peak pressure and temperature conditions of 3.0–3.1 GPa and 760°–825°C, well within the stability field of coesite, thus supporting the microtextural evidence for UHP metamorphism. This records the highest-pressure conditions of Eo-Alpine metamorphism during the Cretaceous orogeny in the Alps, implying a very deep subduction of the continental crust to at least 90–100 km depths. The new data are evidence for a regional southeastward increase of peak pressures in the Lower Central Austroalpine, indicating a south- to eastward dip of the subduction zone. Subduction was intracontinental; northwestern parts of the Austroalpine (Lower Central Austroalpine) were subducted under southeastern parts (Upper Central Austroalpine). The subduction zone formed in the Early Cretaceous in the northwestern foreland of the Meliata suture after Late Jurassic closure of the Meliata Ocean and the resulting collision, by a forward subduction shift to a Permian rift.
TL;DR: In this article, small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement and found that surface deformation, which reflects the weakness zone geometry, exerts a major control on patterns of magnetite migration.
Abstract: [1] Small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement. Experiments considered the reactivation of weakness zones in the lower crust and the presence of magma at Moho depths. Results suggest that surface deformation, which reflects the weakness zone geometry, exerts a major control on patterns of magma migration. In the case of a single rift segment, the experimental lower crust and magma were both transferred in an extension-parallel direction toward the rift flanks. This lateral migration reflected the dominance of far-field stresses over extension-induced buoyancy forces. Local pressure gradients favored the raise of experimental magma in correspondence of marginal grabens. The lateral migration gave rise to major accumulations below the footwall of major boundary faults, providing the magma source able to feed off-axis volcanoes in nature, as inferred for the Main Ethiopian Rift. In the case of two offset rift segments, a major transfer zone developed. This transfer zone was characterized by prominent experimental lower crust doming and strong magma accumulation. Dynamic analysis showed that the transfer zone development caused a strong pressure difference in a rift-parallel direction, which dominated over the far-field thinning. Owing to this pressure gradient, almost all the underplated experimental magma collected below the lower crust dome, suggesting a rift-parallel (extension-orthogonal) migration. This process has a direct relevance for the localization of magmatic activity at transfer zones in natural continental rifts, such as in the Western Branch of the East African Rift System.
TL;DR: This paper examined the last 3 m.y. of this collision through an analysis of Euler poles for motion of the Yakutat microplate with respect to North America and the Pacific.
Abstract: [1] Oblique convergence in the St. Elias orogen of southern Alaska and northwestern Canada has constructed the world's highest coastal mountain range and is the principal driver constructing all of the high topography in northern North America. The orogen originated when the Yakutat terrane was excised from the Cordilleran margin and was transported along margin-parallel strike-slip faults into the subduction-transform transition at the eastern end of the Aleutian trench. We examine the last 3 m.y. of this collision through an analysis of Euler poles for motion of the Yakutat microplate with respect to North America and the Pacific. This analysis indicates a Yakutat-Pacific pole near the present southern triple junction of the microplate and predicts convergence to dextral-oblique convergence across the offshore Transition fault, onland structures adjacent to the Yakutat foreland, or both, with plate speeds increasing from 10 to 30 mm/yr from southeast to northwest. Reconstructions based on these poles show that NNW transport of the collided block into the NE trending subduction zone forced contraction of EW line elements as the collided block was driven into the subduction-transform transition. This suggests the collided block was constricted as it was driven into the transition. Constriction provides an explanation for observed vertical axis refolding of both earlier formed fold-thrust systems and the collisional suture at the top of the fold-thrust stack. We also suggest that this motion was partially accommodated by lateral extrusion of the western portion of the orogen toward the Aleutian trench. Important questions remain regarding which structures accommodated parts of this motion. The Transition fault may have accommodated much of the Yakutat-Pacific convergence on the basis of our analysis and previous interpretations of GPS-based geodetic data. Nonetheless, it is locally overlapped by up to 800 m of undeformed sediment, yet elsewhere shows evidence of young deformation. This contradiction could be produced if the overlapping sediments are too young to have accumulated significant deformation, or GPS motions may be deflected by transient strains or strains from poorly understood fault interactions. In either case, more data are needed to resolve the paradox.
TL;DR: In this article, the authors use a thermomechanical model to quantify how an inherited weak nappe influences the development of fault patterns resulting from postorogenic extension, and apply this model to the case of the Gulf of Corinth (Greece).
Abstract: [1] Orogenic building leaves a complex heritage consisting of a stack of nappes that may have contrasting lithologic structures resulting in heterogeneous mechanical behavior of the system during the postorogenic stages. While the thermal state of the region is reequilibrating, strong lateral variations of the depth to the brittle-ductile transition develop as a consequence of these preexisting heterogeneities. We use a thermomechanical model to quantify how an inherited weak nappe influences the development of fault patterns resulting from postorogenic extension. The competence contrast between the nappe and the rest of the upper crust as well as the strength of the crust itself are the principal variable parameters of our experiments. The results suggest that a dipping weak nappe introduces a lateral velocity discontinuity and serves as a localization factor for deformation. The presence of a preexisting nappe with a low competence contrast is sufficient to localize strain along the nappe leading to the formation of a flexural rolling hinge. In this case, the migration of the basin is slow, continuous, and limited by gravity driven processes that lead to the rise of hot (weak) material under the subsiding basin. In case of a high competence contrast, overall crustal strength is reduced by a “dipping pie” effect. Assuming overall high crustal strength, the presence of a contrasting nappe leads to a bimodal fault pattern governed by two types of faults: crustal-scale planar faults rooting on the brittle ductile transition of the crust and thin-skinned listric faults rooting on the nappe itself. This bimodality results in a jump-like migration of the basin downward along the dipping weak nappe. Applying this model to the case of the Gulf of Corinth (Greece) allows us to explain, in the case of assumed high competence contrast, the observed microseismicity patterns, the asymmetry of the Gulf, and the kinematics of fault migration within the basin.
TL;DR: The Antinir-Copahue Fault Zone (ACFZ) as discussed by the authors is formed by an east vergent fan of high-angle dextral transpressive and transtensive faults, which invert a Paleogene intra-arc rift system in an out-sequence order with respect to the Cretaceous to Miocene fold and thrust belt.
Abstract: [1] The Antinir-Copahue fault zone (ACFZ) is the eastern orogenic front of the Andes between 38° and 37°S. It is formed by an east vergent fan of high-angle dextral transpressive and transtensive faults, which invert a Paleogene intra-arc rift system in an out of sequence order with respect to the Cretaceous to Miocene fold and thrust belt. 3.1–1.7 Ma volcanic rocks are folded and fractured through this belt, and recent indicators of fault activity in unconsolidated deposits suggest an ongoing deformation. In spite of the absence of substantial shallow seismicity associated with the orogenic front, neotectonic studies show the existence of active faults in the present mountain front. The low shallow seismicity could be linked to the high volumes of retroarc-derived volcanic rocks erupted through this fault system during Pliocene and Quaternary times. This thermally weakened basement accommodates the strain of the Antinir-Copahue fault zone, absorbing the present convergence between the South America and Nazca plates.
TL;DR: The O'Higgins Seamount Group is a cluster of volcanic domes located 120 km west of the central Chilean Trench on the crest of the Juan Fernandez Ridge.
Abstract: The O'Higgins Seamount Group is a cluster of volcanic domes located 120 km west of the central Chilean Trench on the crest of the Juan Fernandez Ridge. This aseismic hot spot track is subducting under South America triggering a belt of intraslab earthquake hypocenters extending about 700 km inland. The Juan Fernandez Ridge marks the southern boundary of a shallow subduction segment. Subduction of oceanic basement relief has been suggested as a cause for the “flat” slab segments characterizing the Andean trench system. The Juan Fernandez Ridge, however, shows only moderate crustal thickening, inadequate to cause significant buoyancy. In 2001, wide-angle seismic data were collected along two perpendicular profiles crossing the O'Higgins Group. We present tomographic images of the volcanic edifices and adjacent outer rise-trench environment, which indicate a magmatic origin of the seamounts dominated by extrusive processes. High-resolution bathymetric data yield a detailed image of a network of syngenetic structures reactivated in the outer rise setting. A pervasive fault pattern restricted to the hot spot modified lithosphere coincides with anomalous low upper mantle velocities gained from a tomographic inversion of seismic mantle phases. Reduced uppermost mantle velocities are solely found underneath the Juan Fernandez Ridge and may indicate mineral alterations. Enhanced buoyancy due to crustal and upper mantle hydration may contribute an additional mechanism for shallow subduction, which prevails to the north after the southward migration of the Juan Fernandez Ridge.
TL;DR: In this article, the authors show that the burial of 3470-3430 Ma granitoid-rich crust beneath the Euro Basalt and its precursors led to long-term crustal temperature increases of 170-234°C at 35 km depth, with a corresponding reduction in effective viscosity of 2-5 orders of magnitude.
Abstract: [1] The Archean East Pilbara Granite-Greenstone Terrane (EPGGT) of the Pilbara Craton in Western Australia preserves a prolonged record of voluminous mafic-dominated volcanism and felsic plutonism, commencing at circa 3515 Ma and ultimately resulting in the development of spectacular “dome-and-keel” structures. Early crustal growth was dominated by basaltic magmatism and the regional development of a 12–18 km thick greenstone sequence by circa 3335 Ma, overlying widespread 3470–3430 Ma tonalite-trondhjemite-granodiorite (TTG) suites emplaced into the middle crust. Stratigraphic and structural relationships imply that voluminous granitoid plutonism and crustal-scale dome-and-keel formation in the southeastern EPGGT was not initiated until circa 3325 Ma but proceeded rapidly over the interval 3325–3308 Ma. This scenario is consistent with a “conductive incubation” period of 10–100 Myr duration, following the burial of radiogenic granitic crust beneath the accumulated greenstone pile. For heat production parameters appropriate to the 3515–3308 Ma EPGGT, we show that the burial of 3470–3430 Ma granitoid-rich crust beneath the ≥3335 Ma Euro Basalt and its precursors led to long-term crustal temperature increases of 170–234°C at 35 km depth, with a corresponding reduction in effective viscosity of 2–5 orders of magnitude. In combination with the greenstone-over-granitoid density inversion, the changes in effective viscosity of the mid to deep crust due to the burial of heat sources may have provided the crucial trigger for the initiation of dome-and-keel formation. Similarly, cooling and strengthening of the crust during syndoming exhumation of the heat production potentially terminated large-scale dome-and-keel amplification.