Precambrian Tectonics Research Articles

3D shear-wave velocity structure of the Eastern Indian Shield from ambient noise tomography: Ultramafic lower crust underneath the Singhbhum Craton

Singhbhum Craton (SC) in the Eastern Indian Shield (EIS) is known to have preserved Archean crust which might provide insights into the Precambrian tectonics. In this study, ambient noise cross-correlation of about 1 year of continuous data recorded in 15 broadband seismic stations across EIS is performed. Rayleigh wave group velocities at 4–22 s periods obtained by frequency-time analysis of the cross-correlograms were subjected to tomographic inversion to produce group velocity maps. The spatial resolution of these maps was found to be ∼100 km. Inverted 1D shear-wave velocity (VS) models at regular grid points of these tomographic maps were combined to construct the first 3D VSmodel of the SC and adjoining regions within the EIS. The 3D model highlights a high VS(3.6–3.8 km/s) structure in the 4–20 km depth range and an ultra-high VS(∼4.0–4.2 km/s) structure at depths ≥ 20 km within the SC only. The VS of the upper layer and its regionalisation match with the well-studied granite batholith within the SC. The ultra-high velocitylayer in the lower crust, spatially spanning ∼100 km × 150 km, is distinctly imaged for the first time and its VS indicates probable ultramafic composition. The existence of ultramafic composition at ∼800 MPa lithostatic pressure requires ultra-high temperature metamorphism, possible through mantle upwelling/melting. The previous studies of upwarped crust-lithosphere beneath the SC and the lower-crustal ultramafic composition inferred in this study probably confirm the delamination of the lithosphere beneath the SC at some point during the Precambrian eon.

Geoheritage of the Kaliningrad Region, SE Baltic Coast

The Kaliningrad Region is physiographically a mosaic and travel-attractive part of the SE Baltic coast. The Sambia Peninsula, the geomorphically most interesting, E-W-oriented extension of the mainland, has been shaped by past dynamic processes, starting with the Precambrian tectonics, the Palaeozoic and Mesozoic sea transitions, the Last Ice Age glaciations, the post-glacial riverine network formation, and the present shoreline erosion. The complex geological and palaeogeographical history generated a broad variety of geo-forms and landscapes, relicts of which are seen from the sea coast to the mainland. Rich fossils sealed in ancient, well-stratified formations of specific lithologies, with the famous Palaeogene amber beds, provide witness of past natural settings with flourishing life forms. The great geo-diversity of the peninsula underscores its scientific value as well as national and international tourism significance, adding to the historical architectural sites of this area. Some of these geomorphologically and geologically valuable places are increasingly threatened, besides anthropogenic factors, by storm surges, gravity flows and aeolian activity, causing progressing erosion along undercut cliffs, slumping and degradation of sand dune fields, among other geo-hazards. Survey, mapping and publicity of unique geo-sites are a proviso for their registration in natural heritage programmes with the implementation of appropriate geo-environmental protection strategies in balance with land-use management. This paper outlines the scientific, educational and touristic potential of the national geoheritage in the frame of the Baltic Sea coast geo-conservation initiatives.

Precambrian tectonics and metacratonization in the NW Indian shield inferred from magnetotelluric imaging across the Marwar Terrane and Aravalli-Delhi Mobile Belt

Precambrian tectonics and metacratonization in the NW Indian shield inferred from magnetotelluric imaging across the Marwar Terrane and Aravalli-Delhi Mobile Belt

Three-dimensional crustal and upper-mantle resistivity structure of Alberta, Canada: implications for Precambrian tectonics

SUMMARY This paper describes the first detailed 3-D study of the Alberta basement using the magnetotelluric (MT) method. Long-period MT data were used to generate a 3-D electrical resistivity model of the crust and upper mantle beneath Alberta. The Western Canada Sedimentary Basin was imaged as a low-resistivity layer. A number of crustal and upper-mantle conductors were imaged and include: (1) the Red Deer conductor, (2) the Kiskatinaw conductor, (3) a conductor coincident with the Kimiwan oxygen isotope anomaly, (4) the southern Alberta–British Columbia conductor, (5) the Loverna block conductor and (6) a conductor beneath the Birch Mountain kimberlite field. Conductors (3) and (6) are newly identified in this study. All of these conductors can be related to past tectonic events associated with the assembly of Laurentia and subsequent kimberlite magmatism. The depth of the lithosphere–asthenosphere boundary across Alberta varies from 150 to 300 km as defined from the 100 Ω m contour. Furthermore, the Snowbird tectonic zone in Alberta is characterized by a thick, resistive lithosphere. Similarly, the diamondiferous Buffalo Head Hills kimberlite field is imaged with a thick, resistive lithosphere, both may indicate depletion. In contrast, the Birch Mountain kimberlite field is underlain by a pronounced conductor that extends through the lithosphere and may be the result of metasomatism.

Shear Wave Splitting Across Antarctica: Implications for Upper Mantle Seismic Anisotropy

AbstractWe examine upper mantle anisotropy across the Antarctic continent using 102 new shear wave splitting measurements obtained from teleseismic SKS, SKKS, and PKS phases combined with 107 previously published results. For the new measurements, an eigenvalue technique is used to estimate the fast polarization direction and delay time for each phase arrival, and high‐quality measurements are stacked to determine the best‐fit splitting parameters at each seismic station. The ensemble of splitting measurements shows largely NE‐SW‐oriented fast polarization directions across Antarctica, with a broadly clockwise rotation in polarization directions evident moving from west to east across the continent. Although the first‐order pattern of NE‐SW‐oriented polarization directions is suggestive of a single plate‐wide source of anisotropy, we argue the observed pattern of anisotropy more likely arises from regionally variable contributions of both lithospheric and sub‐lithospheric mantle sources. Anisotropy observed in the interior of East Antarctica, a region underlain by thick lithosphere, can be attributed to relict fabrics associated with Precambrian tectonism. In contrast, anisotropy observed in coastal East Antarctica, the Transantarctic Mountains (TAM), and across much of West Antarctica likely reflects both lithospheric and sub‐lithospheric mantle fabrics. While sub‐lithospheric mantle fabrics are best associated with either plate motion‐induced asthenospheric flow or small‐scale convection, lithospheric mantle fabrics in coastal East Antarctica, the TAM, and West Antarctica generally reflect Jurassic—Cenozoic tectonic activity.

Insights into crustal architecture and tectonics across Palghat Cauvery Shear Zone, India from combined analysis of gravity and magnetic data

The Palghat Cauvery Shear Zone (PCSZ), which dissects the Southern Granulite Terrane (SGT), evoked much attention for last two‐three decades as it offers an enticing opportunity to understand Precambrian tectonics. Many studies suggest that it is a suture zone or a terrane boundary, but tectonic evolution is mainly derived from structural and geochronological evidences. The present gravity‐magnetic study provides insight into both shallow and deeper crustal architecture and addresses the issues related to validation/modification of the existing tectonic realm. A total of 3,650 gravity and magnetic measurements were made covering ~8,640 km2 area, represented by high‐grade metamorphic rocks and acid intrusives of Archean to Neoproterozoic age. Representative rock samples were also collected for determination of petrophysical properties (density and susceptibility) which have augmented the understanding of gravity‐magnetic signature. The gravity anomaly map and subsequent modelling suggest an occurrence of a high‐density batholith at mid‐crustal level at the central part of the area. The magnetic anomaly map reveals that ENE‐WSW trending linear magnetic low zone is coincident with a residual gravity high, which probably indicates the fossil of an oceanic crust. The horizontal gradient of gravity‐magnetic data reveals the shallow crust, which is bounded by Palghat Cauvery Shear Zone (PCSZ) and Dharapuram Shear Zone (DSZ), and separates two terranes in terms of density and susceptibilities. The study suggests N‐S verging compressional tectonics had led to closure of an ocean, imprints of which is well manifested in gravity and magnetic maps.

Spatiotemporal constraints on the western Cauaburi Belt tectonics – northwestern Amazon Craton, Brazil

ABSTRACT The study of Precambrian tectonics is an intricate task, demanding a holistic approach to take an accurate view of geologic history. Here we attempt to set up the overview of an Orosirian-Statherian continental arc in the northwestern Amazon Craton, the Cauaburi Belt. Field relations, petrological, geochemical, and geochronological data of calc-alkaline metagranitoids, high-grade metasedimentary rocks, and peraluminous metasyenogranites yielded new interpretations about its tectonic evolution. The record of intense and episodic calc-alkaline magmatism between ca. 1805 and 1759 Ma, assign to the Cauaburi Complex, with field evidence of magma mixing and lodgement in a compressional tectonic regime, suggest a continental arc as the tectonic setting. During the magmatic lulls, deformation and metamorphism increase, culminating with the partial fusion of the high-grade metasedimentary rocks of the Taiuaçu-Cauera Complex. This succession composes the precursor paleobasin, presenting maximum and minimum depositional ages of 1819 and 1794 Ma, and was a relevant source for the calc-alkaline magmatism. The geochronological record of a low-volume production of peraluminous crustal rocks (Igarapé Tocandira Granite), with crystallization age at ca. 1791 Ma and metamorphic age at ca. 1771 Ma, also highlights the time and effect of the magmatic lulls. The Cauaburi Belt structural framework follows a general E-W to ENE-WSW trend, expressed in the Paleoproterozoic rocks as syn-magmatic and solid-state deformation fabrics. Assuming that Columbia Supercontinent nucleus assembled in the late Orosirian, we interpret that this coeval continental arc developed at its border and followed a north-south shortening direction, at current orientation.

Geochronology and geochemistry of the palaeoproterozoic mafic dikes in the Jiaobei terrane: implications for tectonic evolution of the Jiao-Liao-Ji Belt, eastern North China Craton

ABSTRACT The palaeoproterozoic tectonic/geodynamic evolution of the Jiao-Liao-Ji Belt (JLJB), one of the three representative palaeoproterozoic tectonic units in the North China Craton (NCC), remains controversial. The palaeoproterozoic mafic dikes sampled in the Jiaobei terrane, situated in the southern segment of the JLJB, could provide significant evidence for the JLJB’s evolution. Their LA-ICP-MS zircon U-Pb dating data show that these dikes were emplaced at the period of ~2175 Ma. They have relatively low SiO2 contents and relatively high contents of Al2O3, MgO, Cr, and Ni. Further, they exhibit high field strength elements (HFSE) (e.g. Nb and Ta) depletion and weak Eu anomalies. Also, they show limited initial 87Sr/86Sr ratios (0.700478–0.705069) and low ɛNd(t) values (−2.07 to −0.09) with model ages (TDM1) of 2722–2967 Ma. The magmatic crystal zircons yielded low ɛHf(t) values of −9.22 ~ −3.82 relative to the corresponding Hf model ages of 2627–2870 Ma. These geochemical characteristics of the dikes indicate that they originated via 5–10% partial melting of the North China Craton’s enriched lithospheric mantle within the spinel stability field. In combination with contemporaneous A-type granites, mafic rocks, and other meta-volcanic associations, palaeoproterozoic Jiaobei mafic dikes formed in a back-arc extensional tectonic setting. This further indicates that the JLJB experienced back-arc extending triggered by slab rollback of subducted oceanic plate at ~2175 Ma ago. This study reports new evidence regarding the evolution of Precambrian tectonics of the North China Craton.

Origin of V. Grib pipe eclogites (Arkhangelsk region, NW Russia): geochemistry, Sm-Nd and Rb-Sr isotopes and relation to regional Precambrian tectonics

In this paper, new main and trace elements and isotopic data are presented for 14 coarse-grained eclogite xenoliths from the V. Grib kimberlite pipe in the central part of the Arkhangelsk Diamondiferous Province. Based on reconstructed whole rock MgO content, this suite is divided into high-MgO and low-MgO varieties. Eclogitic groups have a similar range of variations in the trace element compositions of garnet, clinopyroxene and reconstructed whole rock. All eclogites show positive Eu anomalies in garnet and Sr anomalies in the whole rock. The negative correlation between the Mg#, Sr/Lu ratio and HREE in a whole rock points to upper and lower oceanic crustal rocks as a protolith for eclogites with high and low whole rock HREEs, respectively. Low-MgO eclogites with higher whole rock HREEs have the basaltic upper oceanic crustal protolith, whereas the protoliths of eclogites with lower whole rock HREEs could be of gabbroic composition from the lower oceanic crust. High-MgO eclogites could represent MgO-rich portions of oceanic crustal rocks: picritic/MgO basalt portions in the upper oceanic crust and troctolite portions in the lower oceanic crust. The Sr and Nd isotope compositions suggest a complex history of eclogites during their residence in the lithospheric mantle. Similarities in the Nd isotope compositions and two-point Sm-Nd isochron ages are evidence for re-equilibration of the Sm-Nd isotope system between the eclogite garnet and clinopyroxene via a pre-kimberlite thermal event at 396 ± 24 Ma. The subset of clinopyroxenes from four eclogites has a Sr isotope composition that plots on the isochron at an age of 2.84 Ga, which reflects the time of the subduction event and emplacement into the lithosphere and corresponds to the time of the Belomorian Eclogite Province of Baltic Shield formation.

Visualizing Precambrian basement tectonics beneath a carbon capture and storage site, Illinois Basin

Characterization of Precambrian basement tectonics using 3D reflection seismology is critical for fully constraining the geology of a carbon capture and storage (CCS) site. Our study applied state-of-the-art visualization and attribute analysis to a 3D seismic volume of the basement complex that underlies the Illinois Basin-Decatur Project CCS site. The most successful interpretative techniques used include geobody analysis, [Formula: see text] (east–west, crossline)-directed amplitude change, and corendering (e.g., amplitude with semblance), integrated with gradient analysis. The 3D volume reveals a strong reflector deep within the basement complex that is interpreted to be a mafic sill, disrupted by a coherent pattern of prominent structural discontinuities. The discontinuities, which have a mutually orthogonal northwest–northeast trend, could have formed as part of the intrusion process, as tectonic faults, or a combination of both processes. Our preferred interpretation is that discontinuities are small faults with varying senses of offset. The most prominent of these is a narrow, well-defined northwest-striking crest or flexure in the igneous sill reflector. Injection-induced microseismicity describes a conspicuous pattern of northeast-trending clusters of events, some of which nucleated in the uppermost part of the basement, directly over this crest. This distribution of seismic events is proposed to be controlled, in part, by fracture zones related to the crest and associated discontinuities in the mafic sill. These fractures would be oriented in directions to be critically stressed, resulting in aligned microseismicity following pore pressure increases.

Origin and evolution of the South Carpathians basement (Romania): a zircon and monazite geochronologic study of its Alpine sedimentary cover

This study investigates the advantages of a multi-mineral approach in detrital mineral geochronology, as tracers of regional tectonic events. We present new detrital zircon and monazite ages on six sands and sandstones collected from the South Carpathians, Romania. They represent clastic sediments derived from the pre-Alpine basement and related sedimentary cover, which accumulated in distinct palaeogeographic and geotectonic environments, during the multiphase Alpine tectonic evolution. Three samples are mid-Cretaceous sandstones from different depositional settings of the syn-tectonic clastic wedge that activated during the intra-Albian thrusting phase. One is Upper Cretaceous sandstone from the South Carpathian foredeep, associated with the intra-Maastrichtian thrusting phase. Two additional samples are Quaternary fluvial deposits reworking the Upper Cretaceous hinterland basin siliciclastic deposits. Detrital zircon U–Pb ages confirm periods of zircon-producing magmatism in the Neoproterozoic (ca. 590–850 Ma), Cambrian–Ordovician (ca. 540–450 Ma), and, in one sample, Late Cretaceous (ca. 76–81 Ma). Precambrian tectonics is documented by inherited zircons (ca. 0.9–1.2 Ga, 1.8–2.2 Ga, 2.6–2.8 Ga), most likely recycled from metasedimentary rock units from the Getic basement. Zircon age distribution patterns from all samples are consistent with derivation from eroded equivalents to basement rocks of the Getic–Supragetic thrust sheets. In contrast, chemical ages on all detrital monazites document a single metamorphic event of Late Devonian to Carboniferous ages (ca. 300–400 Ma), coincident with the Variscan orogeny in central Europe. A small proportion of the zircon population is also of the same age range (ca. 380–320 Ma) – those zircons typically have high U–Th ratios, characteristic of metamorphic zircons. Detrital monazite ages are consistent with previous limited geochronological data on high-pressure metamorphic rocks from the Getic–Supragetic basement. In addition to the timing of tectonic events in the Carpathian basement, geochronology of detrital minerals brings new constraints regarding the duration of these events.

Late Mesoproterozoic to early Neoproterozoic ridge subduction along southern margin of the Jiangnan Orogen: New evidence from the Northeastern Jiangxi Ophiolite (NJO), South China

The Precambrian ophiolites in South China include the Northeastern Jiangxi Ophiolite (NJO) and the Fuchuan Ophiolite in southern Anhui. These two ophiolites contain important information on the Precambrian tectonics of South China. The NJO occurs along the southern margin of the Jiangnan Orogen, considered as the suture between Yangtze and Cathaysia Blocks in South China. Here we report new results for NJO from our field observations, U–Pb ages and Hf isotopic compositions of zircons from the cumulate and diabase units, chemical compositions of the clinopyroxene from the cumulates, and whole-rock geochemistry of the dismembered ophiolite units in an attempt to evaluate the late Mesoproterozoic to early Neoproterozoic evolution of the South China. Zircon U–Pb age data indicate that NJO formed at ∼1020Ma. Whole-rock geochemistry reveals that the tholeiitic cumulate and diabase members from the NJO have elemental compositions deviating from typical MORB- to arc-signatures. Clinopyroxene from the cumulates exhibits non-alkaline rifting-related features. Whole-rock and mineral chemistry, in combination with depleted MORB mantle (DMM)-like zircon Hf isotope composition (ɛHf(t)zircon=12–16) and whole-rock Nd isotope compositions (ɛNd(t)=4.5–7.8), argues that the cumulates and diabases share a common depleted mantle source with variable contamination by continental crust during magma ascent and/or emplacement. Elemental geochemistry and Nd isotope compositions of the serpentinites also reveal their DMM signature.Based on our new geochronological and geochemical data for NJO, as well as previous studies on the slightly younger adakites (970Ma) intruded into NJO and the Nb-enriched basalts (∼930Ma) in the northeastern section of the suture zone between Yangtze and Cathysia Blocks, we propose that NJO was a ridge-subduction type ophiolite. This new model may shed new light on the late Mesoproterozoic to early Neoproterozoic tectonic evolution of the South China.

Monazite response to ultrahigh-pressure subduction from U–Pb dating by laser ablation split stream

To assess the response of monazite during subduction of continental crust to mantle depths, U–Pb isotopic ratios and elemental abundances were measured simultaneously by laser-ablation split-stream inductively-coupled plasma mass spectrometry (LASS) in rocks from the ultrahigh-pressure Western Gneiss Region of the Scandinavian Caledonides. Nearly seventy different samples of quartzofeldspathic basement and overlying metasedimentary rocks were studied. Pre-subduction monazite (chiefly 1.6Ga and 1.0Ga) is preserved locally in the structurally lowest, basement rocks because earlier, Precambrian tectonism produced coarse-grained, high-grade rocks that were resistant to further recrystallization in spite of syn-subduction temperatures and pressures of 650–800°C and 2–3.5GPa. A few of the monazite in the metasedimentary rocks atop the basement preserve syn-subduction U–Pb dates, but the majority continued to recrystallize during post-subduction exhumation and record a general westward decrease in age related to westward-progressing exhumation. The absence of Precambrian monazite in the metasedimentary rock atop the basement suggests that sedimentation postdated the 1.0–0.9Ga high-grade metamorphism and was late Proterozoic to early Paleozoic.

Detrital zircon U–Pb ages of the Proterozoic metaclastic-sedimentary rocks in Hainan Province of South China: New constraints on the depositional time, source area, and tectonic setting of the Shilu Fe–Co–Cu ore district

The Shilu Fe–Co–Cu ore district, located at Hainan Province of South China, is well known for high-grade hematite-rich Fe ores and also two Precambrian host successions, i.e. the Shilu Group and the overlying Shihuiding Formation. This district has been interpreted as a banded iron formation (BIF) deposit-type, but its depositional time, source area and depositional setting have been in debate due to poor geochronological work. Detrital zircon U–Pb dating aided by cathodoluminescence imaging has been carried out on both the Shilu Group and Shihuiding Formation. Most of the zircon grains from both the successions are subrounded to rounded in morphology and have age spectra between 2000Ma and 900Ma with two predominant peaks at ca. 1460–1340Ma and 1070Ma, and three subordinate peaks at ca. 1740–1660Ma, 1220Ma and 970Ma. The similar age distribution suggests the same depositional system for both successions. Linked to the geological and paleontological signatures, the Shihuiding Formation is better re-interpreted as the top, i.e. Seventh member of the Shilu Group, rather than a distinct Formation. The youngest statistical zircon age peaks for both successions, i.e. ca. 1070–970Ma may define the maximum depositional time of the Shilu Group and interbedded BIFs. At least two erosional sources are required for deposition of the studied detrital zircons, with one proximal to provide the least abraded zircons and the other distal or recycled to offer the largely abraded zircons. The predominance of rounded or subrounded zircons over angular zircons probably implies a relatively stable tectonic setting during deposition. Given the Precambrian tectonics of Hainan Island, a retro-arc foreland basin is proposed for the deposition of the Shilu Group and interbedded BIFs. In comparison with those from the South China and other typical Grenvillian orogens, the detrital zircon age populations reveal that Hainan Island had crystalline basement similar to neither the Yangtze nor the Cathaysia Blocks. Combined with the tectonothermal events, we propose that Hainan Island was independent of South China at least before the late Ordovician and most likely attached or close to northwestern Laurentia before the breakup of Rodinia.

Supercomputer simulation of continental collisions in Precambrian: The effect of lithosphere thickness

Many aspects of Precambrian tectonics are still unclear due to the undetermined influence of several key physical parameters (the temperature of the mantle, the thickness of the lithosphere, etc.) on the geodynamic processes. The values of these parameters in the Precambrian are known to have been significantly different from current conditions. This work presents the results of two-dimensional (2D) numerical petrological-thermomechanical experiments that simulate the process of plate convergence at a velocity of 5 cm/year depending on the thickness of the continental lithosphere. The model continental-lithosphere thickness ranged from 100 to 200 km, the modern mantle temperature exceeded 150°C, while radiogenic heat generation in the continental crust was 1.5 times higher then that at present. The numerical simulations showed that if the lithosphere is 100–160 km thick, the subduction process (closure of an ocean) is terminated by detachment of the oceanic plate from the continental plate (slab break-off) followed by the formation of a large igneous province (an oceanic plateau) between the continents instead of orogeny. The thinner the lithosphere is, the earlier and closer to the surface the slab break-off occurs. Thus, for a model with a continental lithosphere thickness of 150 km, the slab was detached in 10.3 Ma at a depth of 150 km, whereas for a lithosphere of 100 km thick it occurred in just 5.1 Ma almost at the surface. In the latter case, the magma generation area becomes much larger due to the formation of igneous provinces on both sides of the oceanic slab instead of one side, as is proposed in other models. Collision of continents with a very thick lithosphere (200 km or more) is not accompanied by slab break-off and significant volcanic activity. Thus, the results of our modeling show that the SLAB PULL mechanism in a subduction zone contributes to the processes at a plate convergent boundary.

Anisotropic lithosphere under the Fennoscandian shield from P receiver functions and SKS waveforms of the POLENET/LAPNET array

Seismic azimuthal anisotropy is the key evidence of the past and present strains in the upper mantle. The standard analysis of shear-wave splitting with the SKS techniques is useful in mapping lateral variations but it is insensitive to depth of anisotropy and to variations of anisotropy with depth. To retrieve the depth localized anisotropy under the Fennoscandian shield, we inverted P-wave receiver functions of the POLENET/LAPNET array in northern Finland jointly with SKS recordings. Shear-wave anisotropy of ~2.5% with the fast direction of 40°–60° in a depth range from the Moho to ~110km is a robust result of the inversion. The obtained direction is nearly normal to the azimuth of the maximum horizontal compressional stress in the lithosphere, but a recent origin of this anisotropy is in doubt. This anisotropy may be frozen since the Precambrian, but it shows no clear relation with the trends of the Precambrian tectonics. The upper anisotropic layer accounts for ~40% of shear-wave splitting in SKS, and to explain the rest another anisotropic layer is required. The top of the second layer with a practically similar fast direction is found at a depth of 200–240km. This direction is close to the current APM direction of the lithosphere with implication that the inferred anisotropy may be related with the current plate motion, and the anisotropic layer belongs to the asthenosphere. The bottom of this layer is uncertain, but it is at least 320km deep. In a depth range from 160km to 200–240km the fast anisotropy direction is 110–150°. Origin of this direction is unclear.

Three-dimensional resistivity structure of Southern Alberta, Canada: implications for Precambrian tectonics

Three-dimensional resistivity structure of Southern Alberta, Canada: implications for Precambrian tectonics

Global tectonics by PhilipKearey, Keith A.Klepeis and Frederick J.Vine. Third edition. Wiley‐Blackwell, Chichester, 2009. No. of pages: xiii+482. ISBN 978‐1‐4051‐0777‐8 (paperback).

Global tectonics by PhilipKearey, Keith A.Klepeis and Frederick J.Vine. Third edition. Wiley‐Blackwell, Chichester, 2009. No. of pages: xiii+482. ISBN 978‐1‐4051‐0777‐8 (paperback).

The Main Geological Events of the Chinese Archaean and Proterozoic Eons

A systematic review and comparison of the time, sequence, nature, and characteristics of the major geological events of worldwide Archean and Chinese Precambrian and their interrelationships reveals that these events reveals the spatial-temporal pattern of the events and their significance in geological evolution. The study also touches upon relationship between Early Precambrian Era and plate tectonics. A comparison between the Precambrian major geological events and those elsewhere on the earth proves that the crustal evolution is characterized by striking irreversibility, gradualism, and synchronism. The geological events in China have their unique features, which shows that China has a relatively complete record of formation and evolution of rocks, strata, structures, and organisms spanning 3800 Ma to 540 Ma. The Archean underwent multiple-stage complex metamorphism and deformation; metamorphism is on the higher end; komatiite is absent in the greenstone belts; cratonization occurred rather late and varied between the north and the south. The research results above provide main theoretical basis for deeply systematic researching the early dynamic evolution laws of the earth and the dynamic evolution characteristics of the tectonic plates.

Workshop on Precambrian Tectonics and Related Mineralization in South India

Workshop on Precambrian Tectonics and Related Mineralization in South India