Plate Tectonic Models Research Articles

The Neogene–Quaternary volcanism of the Carpathian–Pannonian region: from initial plate tectonic models to quantitative petrogenetic explanations

A wide range of volcanic rocks formed in the Carpathian–Pannonian region during the last 20 Myr, closely associated with the tectonic evolution of the area: (1) high-SiO 2 rhyolites and rhyodacites; (2) calc-alkaline-type volcanic suites (basalt–andesite–dacite–rhyolite and adakitic rocks); (3) potassic–ultrapotassic volcanic rocks (shoshonites, latites, leucitites and lamproites); and (4) alkali sodic volcanic rocks (basalts, trachyandesites and trachytes). During the 18.1–14.4 Ma silicic ignimbrite flare-up volcanism, explosive eruptions produced large volume of tephras, which covered extended areas of Europe. Calc-alkaline-type volcanism took place in syn-extensional and post-collisional settings. There is no classic volcanic arc in the Carpathian–Pannonian Region, and so the term ‘back-arc basin’ should be used for the Pannonian Basin only in a structural geology sense. Alkali basalt volcanism occurred mostly in the peripheral areas of the Pannonian Basin primarily owing to edge-driven convective upwelling of heterogeneous asthenospheric mantle. The youngest eruptions took place 100–30 ka ago, mostly in the geodynamically still active southeast Carpathians. After 50 years of intense research, there are still many open questions to be solved. Interdisciplinary understanding of the results of different disciplines is crucial to better constrain the evolution of this tectonically complex area, to reveal its geoenergy and to assess potential natural hazards.

A new reconstruction of Phanerozoic Earth evolution: Toward a big-data approach to global paleogeography

Reliable reconstruction of global paleogeography through deep geologic time provides a key surface boundary condition for investigating many first-order Earth system and geodynamic processes such as climate change, geomagnetic field stability, regional geological and tectonic history, and biological evolution. Over the past decade, the development of the GPlates software led to a resurgence of community efforts in creating state-of-the-art plate tectonic models that integrate paleomagnetic, geological, and paleontological datasets, resulting in a plethora of reconstruction models. In this paper, we briefly review the strengths and weaknesses of existing global models, which depict alternative and sometimes contradictory tectonic scenarios. We then provide an overview of the general procedure in our construction of a revised Phanerozoic global paleogeographic model, including (1) evaluation of the paleomagnetic data that quantitatively dictate continental paleolatitudes and orientations, (2) selection of reference frames in which continents were positioned, and (3) calibration of continental longitudes in deep time. We update the apparent polar wander paths (APWPs) of the major continents using a recently developed weighted running mean approach, which rectifies two major issues with the conventional running mean approach regarding missing paleopoles in age windows and the enforced assumption of the Fisherian distribution. We re-evaluate the Phanerozoic continental reconstructions in a paleomagnetic framework using the updated APWPs, and calibrate continental paleolongitudes following the extended orthoversion hypothesis by placing the centroids of supercontinents Rodinia and Pangea 90° apart, with that of Rodinia at ∼90°E. We emphasize that the resulting global model is not intended to provide solutions to all global tectonic issues throughout the entire Phanerozoic Eon. Rather, we present our results as one viable model of Phanerozoic tectonic history which, like many existing interpretations, is built upon our understanding of the paleomagnetic, geological, and paleontological observations. Our goals are for this study to highlight the fundamental differences between reconstruction models and to serve as a starting point for future studies to fill key data gaps and test alternative hypotheses and tectonic scenarios.

Influence of plate reference frames on deep-time climate simulations

Deep-time paleogeographic maps can be constructed on plate tectonic models that utilize mantle or paleomagnetic reference frames. Different reference frames result in divergence in plate positions, which are important boundary conditions in deep-time paleoclimate simulations. Here, using three early Eocene paleogeographic maps, we demonstrate the impact of reference frames on the simulated atmospheric circulations with the Norwegian Earth System Model. With these three maps, one using the paleomagnetic and the other two using the mantle reference frame, our simulations show significant differences in the simulated general climatic characteristics, especially in the Pacific region. The paleomagnetic reference frame leads to a narrower and stronger Pacific Walker Circulation, more asymmetrical Hadley Circulations, and a stronger subtropical high in the North Pacific, compared to the mantle reference frame.

Geochemical mapping of lithospheric architecture disproves Archean terrane accretion in the Yilgarn craton

Abstract The basement of Mesoarchean to Neoarchean greenstone basins in the Yilgarn craton is composed of fragments of evolved crust up to 3.7 Ga old. New cratonwide geochemical and isotopic data with unparalleled spatial resolution image a NE- to ENE-trending architecture in pre–2.73 Ga crust. These trends cannot be reconciled with plate-tectonic models, as they persist across younger NNW-striking structural fabrics, including a proposed suture previously interpreted to result from exotic terrane accretion. Our results suggest that, in spite of their substantial strike length, the NNW-trending structures have limited horizontal displacement and, although important for understanding regional geology, may be a geodynamically insignificant overprint of the primary ENE-trending architecture. We propose that these greenstone provinces or belts include individual basins formed in rifts with location, size, and orientation influenced by the interaction between basement fragments and regional crustal extension.

Landscape dynamics and the Phanerozoic diversification of the biosphere

The long-term diversification of the biosphere responds to changes in the physical environment. Yet, over the continents, the nearly monotonic expansion of life started later in the early part of the Phanerozoic eon1 than the expansion in the marine realm, where instead the number of genera waxed and waned over time2. A comprehensive evaluation of the changes in the geodynamic and climatic forcing fails to provide a unified theory for the long-term pattern of evolution of life on Earth. Here we couple climate and plate tectonics models to numerically reconstruct the evolution of the Earth’s landscape over the entire Phanerozoic eon, which we then compare to palaeo-diversity datasets from marine animal and land plant genera. Our results indicate that biodiversity is strongly reliant on landscape dynamics, which at all times determine the carrying capacity of both the continental domain and the oceanic domain. In the oceans, diversity closely adjusted to the riverine sedimentary flux that provides nutrients for primary production. On land, plant expansion was hampered by poor edaphic conditions until widespread endorheic basins resurfaced continents with a sedimentary cover that facilitated the development of soil-dependent rooted flora, and the increasing variety of the landscape additionally promoted their development.

Zircon U–Pb ages and Hf and O isotope systematics of crustal zircons from Mesoproterozoic kimberlites of the Dharwar craton, India: Implications for Neoarchean craton assembly

Plate tectonic models for the amalgamation of the dominantly Paleo-Mesoarchean Western Dharwar Craton (WDC) and Neoarchean Eastern Dharwar Craton (EDC) remain inconclusive on the polarity of Neoarchean subduction. Here we present insitu U-Pb age and Hf-O isotopic compositions of xenocrystic zircons in ca. 1.4-1.1 Ga kimberlites and lamproites emplaced within the ca. 2.8-2.5 Ga EDC as deep probes of the crustal architecture across the WDC-EDC boundary. The different zircon populations yield wide range of ages extending back to ca. 3.6 Ga, including distinctly ‘kimberlitic zircons’ with a mean 206Pb/238U age of 1112 ± 42 Ma, consistent with previous age estimates for kimberlite magmatism. The presence of zircons with ages >3.33 Ga is surprising as this age group of zircons is atypical of magmatic rocks in the EDC, but wide-spread in the WDC. Also, the highest concentration of zircons with ages >3.0 Ga is found in the kimberlites closest to the notional boundary shear zone between the WDC and EDC. The Hf isotope systematics of a majority of magmatic zircons with ages between 2.75-2.50 Ga require melting of older (3.6-3.3 Ga) source rocks. O-isotope data for these Neoarchean zircons show a wide scatter, lie both above (δ18O to 13.5 ‰) and well below mantle values (δ18O to <2 ‰). δ18O values outside the mantle range are closely associated with low εHf. The data are interpreted as evidence for transportation of older upper crustal rocks to lower crust and mantle depths consistent with tectonic models invoking collisional under thrusting of WDC beneath EDC.

Models of plate tectonics with the Lattice Boltzmann Method

Modern geodynamics is based on the study of a large set of models, with the variation of many parameters, whose analysis in the future will require Machine Learning to be analyzed. We introduce here for the first time how a formulation of the Lattice Boltzmann Method capable of modeling plate tectonics, with the introduction of plastic non-linear rheology, is able to reproduce the breaking of the upper boundary layer of the convecting mantle in plates. Numerical simulation of the earth’s mantle and lithospheric plates is a challenging task for traditional methods of numerical solution to partial differential equations (PDE’s) due to the need to model sharp and large viscosity contrasts, temperature dependent viscosity and highly nonlinear rheologies. Nonlinear rheologies such as plastic or dislocation creep are important in giving mantle convection a past history. We present a thermal Lattice Boltzmann Method (LBM) as an alternative to PDE-based solutions for simulating time-dependent mantle dynamics, and demonstrate that the LBM is capable of modeling an extremely nonlinear plastic rheology. This nonlinear rheology leads to the emergence plate tectonic like behavior and history from a two layer viscosity model. These results demonstrate that the LBM offers a means to study the effect of highly nonlinear rheologies on earth and exoplanet dynamics and evolution.

MIDDLE EOCENE IN THE ALPINE RETROFORELAND BASIN (NORTHERN ITALY): SEDIMENTARY RECORD OF A “MESO-ALPINE” ARC-TRENCH SYSTEM IN THE ALPS

The middle Eocene Cibrone Formation of Brianza (central-western Lombardy) represents an important stratigraphic record to understand a key step of the tectonic evolution of the Alpine range poorly recorded elsewhere. Quantitative petrographic analysis of turbidite arenites, well-constrained in age by the biostratigraphy of interlayered marlstones based on calcareous foraminifera and nannoplankton, allowed us to identify a possible vertical compositional trend within the Cibrone Fm. and to document the NP17 nannofossil Zone (Bartonian) in central Lombardy exposures, east of the Ternate Formation outcrop area. Variable arenite compositions are interpreted to reflect contributions from different source areas, i.e., recycled orogen, island arc, and starved continental shelf. In a paleogeographic scenario still open to different interpretations, the proposed reconstruction supports a classical plate tectonics model for arc-trench systems. The stratigraphic gap, recorded everywhere in Lombardy, between the Eocene succession and the base of the Gonfolite Lombarda Group (upper NP24 nannofossil Zone, early Chattian), corresponds to the earliest stage of continental collision, uplift and erosion that climaxed in the Neo-Alpine Phase.

The provenance of Avalonia and its tectonic implications: a critical reappraisal

Abstract The late Neoproterozoic–Cambrian interval is characterized by global-scale orogenesis, rapid continental growth and profound changes in Earth systems. Orogenic activity involved continental collisions spanning more than 100 myr, culminating in Gondwana amalgamation. Avalonia is an example of arc magmatism and accretionary tectonics as subduction zones re-located to Gondwana's periphery in the aftermath of those collisions, and its evolution provides significant constraints for global reconstructions. Comprising late Neoproterozoic ( c. 650–570 Ma) arc-related magmatic and metasedimentary rocks, Avalonia is defined as a composite terrane by its latest Ediacaran–Ordovician overstep sequence: a distinctive, siliciclastic-dominated cover bearing ‘Acado-Baltic’ fauna. This definition implies that Neoproterozoic Avalonia may consist of several terranes, and so precise palaeomagnetic or provenance determination in one locality need not apply to all. On the basis of detrital zircon and Nd isotopic data, Avalonia and other lithotectonically related terranes, such as Cadomia, have long been thought to have resided along the Amazonian–West African margin of Gondwana between c. 650 and 500 Ma – Avalonia connected to Amazonia, and Cadomia to West Africa. These interpretations have constrained Paleozoic reconstructions, many of which imply that the departure of several peri-Gondwanan terranes led to the Early Paleozoic development of the Rheic Ocean whose subsequent demise in the Late Paleozoic led to Pangaea's amalgamation. Since these ideas were proposed, several new lines of evidence have challenged the Amazonian affinity of Avalonia. First, there is evidence that some Avalonian terranes may have been ‘peri-Baltican’ during the Neoproterozoic. Baltica was originally excluded as a potential source for Avalonia because, unlike Amazonia, arc-related Neoproterozoic rocks were not documented. However, subsequent recognition of Ediacaran arc-related sequences in the Timanides of northeastern Baltica invalidates this assumption. Second, detailed palaeontological and lithostratigraphic studies have been interpreted to reflect an insular Avalonia, well removed from either Gondwana or Baltica during the Ediacaran and early Cambrian. Third, recent palaeomagnetic data have raised the possibility of an ocean (Clymene Ocean) between Amazonia and West Africa in the late Neoproterozoic, thereby challenging conventional reconstructions that show the ‘peri-Gondwanan’ terranes as a contiguous belt straddling the suture zone between these cratons. In this contribution, we critically re-evaluate the provenance of the so-called ‘peri-Gondwanan’ terranes, the contiguity of the so-called ‘Avalonian–Cadomian’ belt and the validity of the various plate tectonic models based on the traditional interpretation of these terranes. In addition, we draw attention to critical uncertainties and the challenges that lie ahead.

The role of the Ebro Block on the deformation experienced within the Pyrenean realm: Insights from deformable plate tectonic models

Plate kinematic models of the Pyrenees have been extensively debated due to discrepancies between plate kinematic constraints for the Iberian plate and Atlantic/Tethyan related plate motions. Recently, the morphology of the Iberian plate and its partitioning into several continental blocks has been proposed as a solution towards reconciling discrepancies between previously published reconstructions that treat Iberia as a single, rigid, tectonic plate. Herein, the first deformable plate tectonic modeling study of the Pyrenean realm is presented using previously published and newly presented reconstructions of Iberia. Special emphasis is given to the kinematics of the Ebro Block, a continental block situated between the Pyrenees and Iberian Ranges, whose kinematics are considered to play a key role in the extensional deformation experienced within the Pyrenean realm. Temporal variations in strain rate and crustal thickness calculated by deformable plate models provide insights regarding the pre-orogenic template of the Pyrenees and the variability in regional stress directions along the Iberia-Eurasia plate boundary from the Triassic to Cenomanian. Models that propose transtensional rift phases within the Pyrenean realm induced by the Landes High and Ebro Block kinematics since the Triassic are successful in deriving crustal thicknesses indicative of a pre-orogenic hyperextended rifted margin within the Pyrenean realm. The results of this study demonstrate the importance of continental block kinematics during rift-related deformation and their impact on the evolution and partitioning of rift domains. Furthermore, this study also highlights potential avenues to consider for improving future plate kinematic models of Iberia, and regions elsewhere.

Innovation, Integration Enable Success in Guyana-Suriname Basin

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30946, “Innovation and Integration: Exploration History, ExxonMobil, and the Guyana-Suriname Basin,” by Audrey L. Varga, Matthew R. Chandler, and Worth B. Cotton, ExxonMobil, et al. The paper has not been peer reviewed. Copyright 2021 Offshore Technology Conference. Reproduced by permission. _ Exploration in the Guyana-Suriname Basin has been a decades-long endeavor, including technical challenges and a lengthy history of drilling with no offshore success before the 2015 Liza discovery. The collection of extensive seismic data has been leveraged to enable successful exploration of multiple play types across the basin. Further data collection has enabled the operator to adopt interpretation techniques that are applied across the entire basin to characterize and understand the subsurface better. Historical Context The first wells drilled in the Guyana-Suriname Basin were onshore; the Rose Hall well in Guyana in 1941 first found oil shows. Rumors of oil in the region, and hopes that the prolific hydrocarbon systems present in Venezuela extended into Guyana and Suriname, led geologists from the Standard Oil Company to conduct initial reconnaissance and seismic and geochemical studies. Despite hints—in retrospect—of a favorable basin configuration and hydrocarbon presence, the decision was made to discontinue exploration activities. Through the 1950s and early 1960s, the region saw relatively low levels of activity. In 1960, the first well was drilled offshore Guyana, and, in 1964, the first offshore well was drilled in Suriname; both were dry. In 1965, the Geological and Mining Service of Suriname found heavy oil near the present-day Calcutta Field. This led to the discovery of the Calcutta, Tambaredjo, and Weg naar Zee heavy-oil accumulations, but only a thin reservoir and heavy oil were encountered. In 1975, Esso participated in the North Coronie-1 well in Suriname. The well found oil and gas shows, confirming the presence of immature but rich source rock that was age-equivalent to the prolific La Luna source in Venezuela. A reconnaissance 2D seismic program followed, and, in 1978, Esso drilled the first deepwater well at Demerara A2-1. This well also was dry but did find high-quality, immature source rock and weak oil and gas shows. After another disappointing well at FG-1 in French Guyana in 1978, Esso ultimately relinquished its licenses but noted the presence of excellent-quality source rocks and reservoirs. The onshore Tambaredjo field, discovered in the 1960s, did not start production until 1982. All in all, before the Liza discovery, more than 300 wells were drilled in the basin, with more than 200 of these dry. Of these, all 60 offshore wells were dry. Why, then, did exploration continue? Data Evolution In the mid- to late-1990s, the Guyana deepwater acreage was completely open. The data available to the operator’s geoscientists consisted of one or two seismic lines, approximately four offshore wells, and a Suriname onshore oil sample. At that time, a major change in global coverage and quality of satellite free-air gravity data occurred with the declassification of US military data. An internal project by the operator merged the Sandwell and Smith free-air gravity grid, available in the public domain, with Getech onshore Bouguer gravity grids to create a global gravity compilation. The operator’s researchers recognized the applicability of these data as a key technology enabler to update plate tectonic models and genetic basin analysis.

An overview of Early Paleozoic arc systems in New Brunswick, Canada, and eastern Maine, USA

A plate tectonic model involving northwesterly retreat of an Iapetan subducting slab has been developed over the last three decades to explain the time span of volcanism recorded within the development of Early Paleozoic arc systems preserved in New Brunswick. These arc systems are referred as the Penobscot arc-backarc (514–482 Ma), and Popelogan–Meductic arc (478–460 Ma). Opening of the Tetagouche backarc basin associated with the Popelogan–Meductic arc was diachronous and heterogeneous and involved volcanism associated mainly with the crustal extension and rifting between 472–455 Ma. The complex evolution of the Tetagouche backarc basin is examined in respect to six sub-basins, containing relatively well documented stratigraphic sections in New Brunswick: namely from northeast to southwest the Fournier, California Lake, Bathurst, Sheephouse Brook, Napadogan, and Becaguimec sub-basins. Recently, alternate plate tectonic models have been proposed for the northern Appalachians based on newly acquired geochronological data from northern Maine. We integrate these new data with existing stratigraphic, structural, paleontological, and geochemical evidence to support and refine the previously proposed migrating-arc model for New Brunswick and Maine.

An early Miocene (∼20 Ma) paleogeographic reconstruction for paleoclimate modelling

The current Asian monsoon system is considered to have formed in the late Oligocene–early Miocene, but the mechanisms of the monsoonal system are not fully understood. A knowledge of paleogeography is essential for understanding past climatic change. A reliable paleogeographic reconstruction for the early Miocene is essential to provide key boundary conditions for early Miocene climate modelling studies. However, the temporal–spatial distribution of key geographic features such as seaways and mountain belts that control climate change differ for various published early Miocene paleogeographic reconstructions, which thus require updating with new geological data. Here we present a new reconstruction of global paleogeography for the early Miocene (∼20 Ma). We used a four-step methodology and integrated various types of geological data into a coherent plate tectonic model using GPlates and ArcGIS to reconstruct the paleogeography. Based on previous paleogeographic reconstructions and our compiled geological data, we further constrained and revised the land–sea distribution in several key regions (i.e., the Paratethys Sea, Sunda Shelf, Bohai Sea–Yellow Sea, Barents Sea–Kara Sea, and Hudson Bay); the paleodepths of the Paratethys Sea, Mediterranean Sea, and key seaways (i.e., the Atlantic–Mediterranean Gateway, eastern Tethys Seaway, Indonesian Gateway, Panama Seaway, Fram Strait, and Greenland–Scotland Ridge); and paleoelevations of high mountains and plateaus (i.e., the Tibetan Plateau, North American Cordillera, Andes, East Africa, and Antarctica). The new and improved early Miocene paleogeographic reconstruction is available for use in climate models to facilitate early Miocene climate modelling studies.

Austral and Subtropical Gyre Radiolaria – latest Jurassic to Early Cretaceous Leg 123, Site 765, Argo Abyssal Plain revisited: Southern Hemisphere paleobiogeography and global climate change

The aim of this report is to 1) to formally describe Austral and Subtropical Gyre Radiolaria recovered from ODP Hole 123-765C), 2) to compare them with published records of Southern Hemisphere “non-Tethyan” assemblages and 3) to discuss radiolarian paleobiogeography of the Southern Hemisphere and its implications for global climate change during the Jurassic–Cretaceous transition. The Tithonian to Aptian/early Albian radiolarian record recovered from Hole 765C, Cores -62R to -36R in the Argo Abyssal Plain (AAP) is unique in its density of well-preserved samples and in its faunal contents. Radiolaria recovered from claystones yielded the low diversity, ecologically tolerant “Crypto-Archaeo” Assemblage, (chiefly cryptocephalic and cryptothoracic nassellarians and Archeodictyomitra spp.) interpreted herein as originated in the Subtropical Gyre (STG). In contrast, assemblages extracted from radiolarite layers, interpreted as pelagic turbidites derived from the deeper Australian margin, are dominated by Austral taxa. Neotethyan taxa are very rare to absent before the late Hauterivian/Barremian, when they gradually gain in diversity and abundance. Described Austral and STG taxa include 10 families, of which Fusitanellidae n. fam. and Windaliinae n. subfam. are new. Of 18 genera 7 are new (Nodosphaera, Praewindalia, Pachycingula, Archaeotanella, Morchella, Fusitanella, Argofusus) and of 55 species 30 new ones are formally described and 14 new ones are left in open nomenclature. The southern hemisphere Late Jurassic to Early Cretaceous radiolarian biogeography is defined from low- to high latitude: 1. the Neotethyan (NT) and 2. the Central Panthalassan (CP) realms, 3. Eastern Boundary Current (EBC) realm, 4. the Subtropical Gyre (STG) and the Austral (A) circum south-polar realm. Radiolarian biogeography and plate tectonic models support a scenario of palaeoceanographic and global climatic change during the Jurassic–Cretaceous transition related to progressive Pangea break-up with the following consequences: 1. an increased heat transfer to the Southern hemisphere which caused cooling of Neotethyan regions during the Late Tithonian dry event. 2. A northward shift of the southern summer Intertropical Conve nience Zone reduced the Neotethyan monsoon area and allowed the establishment of a southern Neotethyan subtropical gyre documented by the “Crypo-Archaeo” Assemblage. 3. The south-polar West Wind Drift may have forced a circum Antarctic-Australian cold current through the epicontinental rift between India and Antarctica-Australia since the Berriasian (140 my), transporting Austral Radiolaria into the AAP where they accumulated in radiolarite layers.

Arctic sediment routing during the Triassic: sinking the Arctic Atlantis

Opening of the Arctic Ocean has been the subject of much debate, and the placement of terranes in the Early Mesozoic remains a crucial part of this important discussion. Several continental terranes complicate the palaeogeographical reconstruction. One such terrane is Crockerland, which has been inferred to explain sediment distribution in the Arctic throughout the Mesozoic. However, Triassic successions throughout the Arctic basins bear many similarities, and a common sedimentary source could offer a simpler explanation with fewer complications for the past configuration of the Arctic. The study's goal is to test the hypothesis of long-distance sediment transport from a common source in present-day Russia to all Arctic basins in the Triassic, and to demonstrate how estimates of sediment routing distances can improve pre-break-up plate-tectonic reconstructions. Results confirm that (1) the Arctic basins were closely connected prior to break-up in the Mesozoic, (2) based on regional facies distribution, sediment budgets, sediment modelling and detrital zircon age spectra, the Crockerland terrane is unlikely to have existed as a major sediment supplying area, (3) the reconstructed Arctic sediment routing system can help to constrain plate-tectonic models, and (4) statistical estimation of sediment transport is a novel and potentially important tool for improving plate-tectonic and palaeogeographical reconstructions. Supplementary material : A database for provenance study, detrital zircon age spectra and the sedimentary length calculations method are available at https://doi.org/10.6084/m9.figshare.c.6086468

NeoKinema Deformation Model for the 2023 Update to the U.S. National Seismic Hazard Model

Abstract We develop a crustal deformation model of the western conterminous United States for the 2023 update of the National Seismic Hazard Model (NSHM). The kinematic finite-element code NeoKinema is used to describe crustal deformation, including long-term slip on faults and off-fault strains (both elastic and permanent). Three different data sets—Global Positioning System (GPS) velocities, geological fault offset rates, and crustal stress orientations—are used to constrain the model, and the plate tectonic rotation of Pacific relative to North America is also imposed on some boundaries. Compared to the last NSHM model update in 2014, the GPS and geological fault data are substantially updated, and new corrections are implemented in both the data and modeling approach, including the correction of the “ghost transient” effect due to postseismic deformation following large historic earthquakes, and correction for shallow creep on faults estimated from independent data. Based on these modeling results and a plate tectonic model of the Cascadia subduction zone, a long-term seismicity rate map is also computed for the western United States; this map is independent of the local seismic catalog and can, therefore, be tested retrospectively as well as prospectively. We find good success in most of the region, except in Cascadia, where the 45 yr instrumental seismicity record is much quieter than the forecast of our long-term model.

PLATE TECTONICS AS A TOOL FOR GLOBAL SCREENING OF MAGMATIC ARCS AND PREDICTIONS FOR RELATED PORPHYRY DEPOSITS

Abstract The formation of most mineral deposits is closely linked to a geodynamic context—for example, the association of porphyry Cu-Au-Mo deposits with subduction and development of volcanic arcs. This paper proposes a new approach to the global screening of volcanic arcs and their duration, as a predictive method for a mineral systems-based approach (e.g., discovery of potential porphyry occurrences). The method utilizes geospatial and temporal analytics run on a combination of large global data sets and a global plate tectonic model (covering the time period 600 Ma to present) containing plate boundaries. The method involves (1) calculating present-day arc volcano-to-trench distances and obtaining average volcanic-arc widths in both continental and intraoceanic settings, (2) applying these values to the paleotrenches contained in the plate tectonic model on 53 time intervals spread throughout the Phanerozoic, (3) unreconstructing the results back to present day, and (4) summing up all magmatic arc occurrences using their cumulative durations. This results in a spatiotemporal model of the total cumulative duration of magmatic arc activity at the global scale, back to 600 Ma, that is updatable and can serve as a proxy to predict porphyry deposit likelihood. The model output is tested against a porphyry copper occurrence data set to validate the approach as a predictive proxy for arc-related porphyry deposits. The alignment of the model results with data control is high for most geologic time periods throughout the Phanerozoic—up to 90% in the case of buffered (1σ) magmatic arcs and up to 100% in the case of buffered magmatic arcs with an additional search distance (2σ). Recent advances in plate tectonic model quality and detail now offer a higher level of precision and confidence than ever before and enable tools for the prediction and screening of porphyry deposit locations, as well as opening the potential to screen for other geodynamic context-dependent commodities (e.g., orogenic gold, volcanogenic massive sulfide, or Ni and platinum group element-sulfide deposits), particularly in the search for poorly exposed or subsurface orebodies.

On the enigmatic mid-Proterozoic: Single-lid versus plate tectonics

The mid-Proterozoic (ca. 1850–850 Ma) is a peculiar period of Earth history in many respects: ophiolites and passive margins of this age are rare, whereas anorthosite and A-type granite suites are abundant; metamorphic rocks typically record high thermobaric (temperature/pressure) ratios, whereas ultrahigh pressure (UHP) rocks are rare; and the abundance of economic mineral deposits features rare porphyry Cu-Au and abundant Ni-Cu and Fe-oxide Cu-Ag (IOCG) deposit types. These collective observations have been used to propose that a stagnant-lid, or single-lid, tectonic regime operated at this time, between periods of plate tectonics in the Paleoproterozoic and Neoproterozoic. In our reappraisal of the mid-Proterozoic geological record, we not only assess the viability of the single-lid hypothesis for each line of evidence, but also that of the plate tectonic alternative. We find that evidence for the single-lid hypothesis is equivocal in all cases, whereas for plate tectonics the evidence is equivocal or supporting. We therefore find no reason to abandon a plate tectonic model for the mid-Proterozoic time period. Instead, we propose that the peculiarities of this enigmatic interval can be reconciled through the combination of two processes working in tandem: secular mantle cooling and the exceptionally long tenure and incomplete breakup of Earth's first supercontinent, where both of these phenomena had a dramatic effect on lithospheric behaviour and its resulting imprint in the geological record.

Advances in Deformable Plate Tectonic Models: 1. Reconstructing Deformable Continental Blocks and Crustal Thicknesses Back Through Time

AbstractDeformable plate tectonic models have been demonstrated to be a useful technique for quantifying temporal variations in strain rate and crustal thickness within recent plate kinematic studies. Using the GPlates software, deformable plate models offer an approach to visualize and assess the interplay of plate kinematics and deformation. However, several assumptions are imposed in previous studies that limit their ability to explain the crustal evolution of various tectonic regimes. Examples of these assumptions include, but are not limited to, the rigid nature of continental blocks and boundaries used to define deformable regions, and uniform crustal thickness assumptions at model start times. In this study, we address these assumptions with newly presented applications using the interplay of GPlates and its python programming library, pyGPlates. In particular, we demonstrate the ability to create deformable continental blocks, reconstruct present day crustal thickness estimates back through time, and how the landward extent of present day crustal thickness estimates can be used to define the limits of deformable plate models and rift domain boundaries a priori. To demonstrate their application and validity, these concepts are evaluated using a previously published deformable plate model of the southern North Atlantic that is tested using 4 modeling scenarios herein to assess the impact of variable model inputs. These models provide insight regarding the pre‐Jurassic (200 Ma) crustal thickness template of the southern North Atlantic, the evolution of continental blocks during rift‐related deformation, and the potential impact of ancient orogenic terranes during subsequent rifting within the North Atlantic.

Re-examination of the Base Miocene Unconformity in west Sabah, Malaysia, and stratigraphic evidence against a slab-pull subduction model

This review chiefly examines data on the regionally important Base Miocene Unconformity , confirming its age and expression in west Sabah, then integrates this with data on the tectono-stratigraphic development of the broader Sabah to Palawan region. The two unconformities described (the Base Miocene Unconformity and the younger Deep Regional Unconformity) were both produced when deformation abruptly stopped, leaving erosional surfaces that were then transgressed. The ages of these two events are c. 24 and 12–13 Ma respectively, and the areas affected by the prior uplift and erosion can be mapped. The results are incompatible with widely cited plate tectonic models that describe closure of a postulated Proto-South China Sea [PSCS]. These prior models had assumed plate drift ended with collision at plate docking over a PSCS suture in about mid Early Miocene times. However, stratigraphic data shows that Early Miocene times were a period of quiescence across Sabah, with mostly mild subsidence . It is therefore proposed that plate drift in the SCS could not have been linked to any type of subduction process anywhere around western Sabah. The absence of any plate docking or any Oligocene through Middle Miocene compression around northern Palawan is a further anomaly to the old subduction based tectonic model.