Subduction transitioning from beneath oceanic crust to beneath continental crust, northern Peninsular Ranges batholith: Structural and thermal imprint on prebatholithic rocks

2014 ◽  
Author(s):  
Douglas M. Morton ◽  
Rachel M. Alvarez ◽  
Alison Alcott ◽  
Fred K. Miller ◽  
Pamela M. Cossette
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Peninsular Ranges

scholarly journals Towards understanding how surface life can affect interior geological processes: a non-equilibrium thermodynamics approach

2011 ◽  
Vol 2 (1) ◽  
pp. 139-160 ◽  
Author(s):  
J. G. Dyke ◽  
F. Gans ◽  
A. Kleidon
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Mantle Convection ◽  
Dynamical Models ◽  
Geological Processes ◽  
The Earth ◽  
Uplift And Erosion ◽  
Life On Earth ◽  
Mantle Temperature ◽  
Non Equilibrium

Abstract. Life has significantly altered the Earth's atmosphere, oceans and crust. To what extent has it also affected interior geological processes? To address this question, three models of geological processes are formulated: mantle convection, continental crust uplift and erosion and oceanic crust recycling. These processes are characterised as non-equilibrium thermodynamic systems. Their states of disequilibrium are maintained by the power generated from the dissipation of energy from the interior of the Earth. Altering the thickness of continental crust via weathering and erosion affects the upper mantle temperature which leads to changes in rates of oceanic crust recycling and consequently rates of outgassing of carbon dioxide into the atmosphere. Estimates for the power generated by various elements in the Earth system are shown. This includes, inter alia, surface life generation of 264 TW of power, much greater than those of geological processes such as mantle convection at 12 TW. This high power results from life's ability to harvest energy directly from the sun. Life need only utilise a small fraction of the generated free chemical energy for geochemical transformations at the surface, such as affecting rates of weathering and erosion of continental rocks, in order to affect interior, geological processes. Consequently when assessing the effects of life on Earth, and potentially any planet with a significant biosphere, dynamical models may be required that better capture the coupled nature of biologically-mediated surface and interior processes.

General discussion

1987 ◽  
Vol 321 (1557) ◽  
pp. 271-273
Keyword(s):  
Mathematical Models ◽  
Continental Crust ◽  
Oceanic Crust ◽  
Continuous Medium ◽  
The Urals ◽  
The Earth ◽  
Scandinavian Caledonides ◽  
Fold Belts ◽  
Normal Thickness

E. V. Artyushkov ( Institute of Physics of the Earth, Moscow, U.S.S.R .). Shortening of the crust has been modelled by compression of a continuous medium. It has also been supposed that compression can start in continental crust of normal thickness. Mathematical models of the same type have recently been used by some other authors. It should be noted that an intense shortening of the crust in fold belts never occurred in such a way. In the main Phanerozoic fold belts (the Urals, Appalachians, Scandinavian Caledonides, the Alpine and Verkhoyansk belts, and others) no era tonic block with a normal continental crust and lithosphere was shortened (Artyushkov & Baer 1983, 1984, 1986). An intense compression took place only in deep basins on oceanic or continental crust. Most oceanic crust disappeared from the surface in the process of subduction. Now the fold belts are mainly built up of a strongly compressed crust of deep basins on continental crust. How can it be proven that this crust was really thin?

3D structures and sedimentary infill across the continent-ocean transition of the northern South China Sea: constraint by the drilling results from IODP Expeditions 367, 368 and 368X

2020 ◽  
Author(s):  
Chao Lei ◽  
Jianye Ren ◽  
Geoffroy Mohn ◽  
Michael Nirrengarten ◽  
Xiong Pang ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Crust ◽  
Oceanic Crust ◽  
South China ◽  
Lower Boundary ◽  
Seismic Survey ◽  
High Angle ◽  
Seismic Profiles ◽  
Continental Breakup ◽  
China Sea

<p>Apart from the Iberia-Newfoundland margins, the South China Sea (SCS) represents  another passive margin where continent-ocean transition basement was sampled by deep drilling. Drilling data from IODP Expedition 367-368 and 368X combined with seismic profiles revealed a narrow continent-ocean transition (COT) between the Distal High sampled at Site U1501 and the Ridge B sampled at Site U1500. Results suggested that major Eocene lithospheric thinning triggered Mid-Ocean Ridge type melt production which emplaced within hyperextended continental crust leading eventually to continental breakup.  </p><p>Because of available dense seismic survey consisting of deep-penetrated seismic data imaging as deep as 12 s TWT, as well as drilling results from IODP Expeditions 367-368 and 368X, the COT in the northern SCS enables us to investigate the 3D propagation of continental breakup and the interactions between tectonic extension and magmatism. The top of acoustic basement can be consistently interpreted through all of our seismic survey and reveal various types of reliefs and nature from hyperextended continental crust to oceanic crust. In the basement, deep-penetrated seismic profiles present series of densely sub-parallel high-amplitude reflections that occurred within the lower crust. The lower boundary of these reflections is often characterized by double continual and high reflections interpreted as the Moho. Across the COT, the basement structure is characterized by: 1) Series of tilted blocks bounded by high angle faults on the Distal High and filled by syn-tectonic sedimentary wedges, 2) Rounded mounds of the basement with chaotic seismic reflection and sedimentary onlaps on these structures, 3) Series of ridges delimited by high-angle normal faults with no sedimentary wedge on the first oceanic crust.</p><p>Based on the detail stratigraphic framework constraint by drilling results from IODP Expeditions, the nature and timing of formation of these basement highs can be investigated. Some of these highs are limited by extensional faults while the nature of mounded structures located on the thinnest continental crust remain mysterious.  Our detailed analyses emphasize the occurrence and local control of syn-rift magmatism in order to build such structures. At larger scale, the hyperextended continental crust is characterized by significant 3D morphological variations both observed on dip and strike profiles. In contrast, the initial oceanic crust is characterized by a more homogenous structure and consistently juxtaposed to continental crust over a sharp and narrow zone.</p><p> </p>

scholarly journals Bien Dong seafloor spreading and its influence to formation & development of sedimentary basins

2014 ◽  
Vol 17 (3) ◽  
pp. 132-138
Author(s):  
Hung Nguyen Manh ◽  
Tieng Hoang Dinh
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Sedimentary Basins ◽  
Seafloor Spreading ◽  
Fault System ◽  
Basalt Magma ◽  
Deep Fault ◽  
Thermal Anomalies ◽  
South West ◽  
Favorable Conditions

The paper presents the characteristics of Bien Dong seafloor spreading which including two parts: The Eastern part is quite large, in which developed by Eastern- Western orientation (spreading on N-S). The Southern- Western part gradually changed its orientation from E-W into East- North and in to South- West at the end (spreading SE- NW). There are two main dynamic resources created the spreading and deformation: The appearance of thermal abnormality by mantle plume occurred 36 M.a. until 14 M.a. The Eastern thermal anomalies continued to develop follow this orientation. In the SW- part the thermal anomalies changed it orientation from E-W into NE- SW 26 M.a and gradually developing toward S-W. Since 14 M.a, both two these trends been stopped, began to cooling and shrinkage. The abnormal existence caused pinchout and rifting the continental crust in Bien Dong Center and generating new oceanic crust as well. The uplift and variation of thermal abnormality (basalt magma) raised up the favorable conditions to forming, developing and varying the axis of Bien Dong spreading seafloor. The all above synthetic activities created favorable conditions for generation and development a series of deep fault systems with E-W direction in Eastern part and NE- SW direction in Southern-Western direction in remain part, and created and evolved the sedimentary basins in margins of Bien Dong with along the main deep fault system.

U-Pb dating, oxygen and hafnium isotopic ratios of zircon from rocks of oceanic core complexes at Mid-Atlantic Ridge: evidence for an interaction of young and ancient crusts at spreading of the ocean floor

2019 ◽  
Vol 489 (5) ◽  
pp. 483-489
Author(s):  
N. S. Bortnikov ◽  
S. А. Silantiev ◽  
F. Bea ◽  
P. Montero ◽  
T. F. Zinger ◽  
...  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Isotopic Ratio ◽  
Ocean Floor ◽  
Isotopic Ratios ◽  
Icp Ms ◽  
Different Ages ◽  
Mid Atlantic Ridge ◽  
Slow Spreading ◽  
Central Atlantic

U-Pb age, oxygen and hafnium isotopic ratios in zircon from rocks of ocean core complexes at Mid-Atlantic Ridge have been studied using SHRIMP and MC-LA-ICP-MS techniques. U-Pb dating revealed four group of zircons: 1) 0,6-1,7 Ma, 2) 6,7-11,2 Ma, 3) 12,9-17,6 Ma, 4) 200 to 2044 Ma. The 18O values range from 4,74 to 7,2 and are distinct for zircon grains of different ages. Hafnium isotopic ratio for zircon aged from 0,6 to 17,6 Ma corresponds or is close to that of MORB from Central Atlantic. The oxygen and hafnium isotopic compositions of zircon elder than 280 Ma correspond to those of the sialic continental crust. A hypothesis of involvement of the ancient pre-Atlantic sialic (280 млн лет) and old Atlantic (7-17 Ma) crusts in a generation of the contemporary (young) oceanic crust during formation of the slow-spreading Mid-Atlantic Ridge has been proposed.

Crustal contamination and hybridization of an embryonic oceanic crust during the Red Sea rifting: An example from the Tihama Asir igneous complex, Saudi Arabia

2021 ◽  
Author(s):  
Valentin Basch ◽  
Alessio Sanfilippo ◽  
Luigi Vigliotti ◽  
Antonio Langone ◽  
Najeeb Rasul ◽  
...  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Red Sea ◽  
Crustal Contamination ◽  
Seafloor Spreading ◽  
Rift System ◽  
Continental Rifting ◽  
Igneous Complex ◽  
Early Stages ◽  
Incompatible Elements

<p>The Red Sea rift system represents the best case study of the rift-to-drift history, i.e., the transition from a continental to an oceanic rift and the formation of passive margins. Although the onset of seafloor spreading has been constrained by geophysical observations to 5 Ma in the southern Red Sea, recent studies have suggested that MORB-type melts were intruded within the extended continental crust already during the early stages of rifting. We present here a petro-geochemical investigation of gabbroic bodies and associated basaltic intrusions from the Tihama Asir igneous complex, which formed as part of the intense magmatism that occurred during early Red Sea continental rifting. The most primitive olivine gabbros present modal, bulk and mineral compositions consistent with formation from MORB-type parental melts, but more evolved gabbros and oxide gabbros show saturation of phlogopite and define a geochemical evolution that progressively diverges from that of lower oceanic crust at mid-ocean ridges. Indeed, the Tihama Asir evolved gabbros are characterized by enrichments in LREE and highly incompatible elements (Rb, Ba, U, Th, Nb, Sr, K), suggesting hybridization of a MORB-type parental melt through a process of progressive assimilation of continental crust during the emplacement of gabbroic bodies. Additionally, the gabbros are associated with basaltic dike swarms intruded into the extending continental crust. The basalts show enrichments in LREE and highly incompatible elements similar to the gabbros, suggesting that they formed from melts extracted from the hybridized gabbroic crystal mush. This indicates that the Red Sea oceanization started before the onset of seafloor spreading, and that the cold continental crust was partially assimilated and replaced by hot gabbroic bodies since the early stages of continental rifting.</p>

Partial melting of subducted oceanic crust and isolation of its residual eclogitic lithology

1991 ◽  
Vol 335 (1638) ◽  
pp. 407-418 ◽  
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Oceanic Crust ◽  
Significant Proportion ◽  
Oceanic Lithosphere ◽  
Rutile Phase ◽  
Island Arc ◽  
Plate Boundaries ◽  
Water Release ◽  
Depleted Mantle

Oceanic lithosphere is produced at mid-ocean ridges and reinjected into the mantle at convergent plate boundaries. During subduction, this lithosphere goes through a series of progressive dehydration and melting events. Initial dehydration of the slab occurs during low pressure metamorphism of the oceanic crust and involves significant dewatering and loss of labile elements. At depths of 80-120 km water release by the slab is believed to lead to partial melting of the oceanic crust. These melts, enriched in incompatible elements (excepting Nb, Ta and Ti), fertilize the overlying mantle wedge and produce the enriched peridotitic sources of island arc basalts. Retention of Nb, Ta and Ti by a residual mineral (e.g. in a rutile phase) in a refractory eclogitic lithology within the sinking slab are considered to cause their characteristic depletions in island arc basalts. These refractory eclogitic lithologies, enriched in Nb, Ta and Ti, accumulate at depth in the mantle. The continued isolation of this eclogitic residuum in the deep mantle over Earth ’s history produces a reservoir which contains a significant proportion of the Earth’s Ti, Nb and Ta budget. Both the continental crust and depleted mantle have subchondritic Nb /La and Ti/Zr ratios and thus they cannot be viewed strictly as complementary geochemical reservoirs. This lack of complementarity between the continental crust and depleted mantle can be balanced by a refractory eclogitic reservoir deep in the mantle, which is enriched in Nb, Ta and Ti. A refractory eclogitic reservoir amounting to ca . 2% of the mass of the silicate Earth would also contain significant amounts of Ca and Al and may explain the superchondritic Ca/Al value of the depleted mantle.

Some remarks on the continental margins in the Aquitaine and French Pyrenees

1984 ◽  
Vol 121 (5) ◽  
pp. 407-412 ◽  
Author(s):  
G. Boillot
Keyword(s):  
Iberian Peninsula ◽  
Continental Crust ◽  
Oceanic Crust ◽  
Late Eocene ◽  
Continental Margins ◽  
Bay Of Biscay ◽  
Transform Faults ◽  
The North ◽  
Transform Zone ◽  
Aquitaine Basin

AbstractFrom the Triassic to the Late Eocene, the Iberian Peninsula underwent three successive rotations with respect to the stable European plate, (a) Prior to the Late Aptian, a nearly 150 km southwestward motion resulted in stretching and thinning of the continental crust beneath the North Pyrenean zone, the Aquitaine Basin and the Bay of Biscay continental margins (rifting). Distensive structures trended 90° N to 130° N, and were shifted by 30° N to 50° N transform faults. (b) During the Late Aptian to Santonian interval, an approximately 400 km southeastward motion resulted in the opening of the Bay of Biscay and sinistral slipping of Iberia along the North Pyrenean transform zone (drifting), (c) During palaeocene–Eocene time, a 150 km northwestward convergent motion resulted in limited subduction of the oceanic crust of the Bay of Biscay beneath the Iberian plate, and folding of the Pyrenean chain. The folded belt resulted from squeezing of the former European and Iberian margins (rifted or transform margins, depending on the segment considered).

Mapping the continent-ocean transition in the Eastern Black Sea Basin

2020 ◽  
Author(s):  
Tim Minshull ◽  
Vanessa Monteleone ◽  
Hector Marin Moreno ◽  
Donna Shillington
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Black Sea ◽  
Seismic Data ◽  
Wide Angle ◽  
Seismic Velocities ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Rifted Margins ◽  
Geodynamic Processes

<p>The transition from continental to oceanic crust at rifted margins is characterised by changes in a variety of parameters including crustal thickness, basement morphology and magnetisation. Rifted margins also vary significantly in the degree of magmatism that is associated with breakup. The Eastern Black Sea Basin formed by backarc extension in late Cretaceous to early Cenozoic times, by the rotation of Shatsky Ridge relative to the Mid Black Sea High. Wide-angle seismic data show that anomalously thick oceanic crust is present in the southeast of the basin, while further to the northwest the crust is thinner in the centre of the basin. This thinner crust has seismic velocities that are anomalously low for oceanic crust, but is significantly magnetised and has a similar basement morphology to the thicker crust to the southeast. We synthesise constraints from wide-angle seismic data, magnetic anomaly data and new long-offset seismic reflection data into an integrated interpretation of the location and nature of the continent-ocean transition within the basin. Northwest to southeast along the axis of the basin, we infer a series of transitions from mildly stretched continental crust at the Mid Black Sea High to hyper-thinned continental crust, then to thin oceanic crust, and finally to anomalously thick oceanic crust. We explore the geodynamic processes that may have led to this configuration.</p>

Temperature-dependent Rutile Solubility in Garnet and Clinopyroxene from Mantle Eclogite: Implications for Continental Crust Formation and V-based Oxybarometry

2020 ◽  
Vol 61 (6) ◽  
Author(s):  
Sonja Aulbach
Keyword(s):  
Low Temperature ◽  
Continental Crust ◽  
Oxygen Fugacity ◽  
Oceanic Crust ◽  
Tetrahedral Site ◽  
Bulk Composition ◽  
Distribution Coefficients ◽  
Accessory Mineral ◽  
Stability Field ◽  
Increasing Temperature

Abstract Despite its accessory mineral status in metabasaltic rocks, rutile controls the whole-rock Ti, Nb and Ta budget. These are key elements used to trace fluid- and melt-mediated mass transfer across the mantle–crust boundary. Rutile also contains significant amounts of the redox-sensitive element V, which is increasingly used to estimate oxygen fugacity. Kimberlite-borne mantle eclogite xenoliths, which are frequently rutile-bearing, have been interpreted as residues from the extraction of silicic partial melt similar in composition to the average continental crust. Published mineral compositions for eclogite xenoliths from various cratons combined with geothermobarometrical calculations show that TiO2 contents in garnet and clinopyroxene increase with increasing temperature of last residence in the lithospheric mantle, whereas apparent clinopyroxene–garnet distribution coefficients decrease. This implies that (1) increasing TiO2 contents in eclogitic garnet or clinopyroxene are not a signature of increasing metasomatism with depth, (2) whole-rock eclogites reconstructed without rutile will increasingly underestimate TiO2, Nb and Ta contents with decreasing temperature, and (3) low-temperature eclogites are more likely to contain free rutile. Only about a third of the ∼250 samples considered here would have whole-rock TiO2 contents (reconstructed with calculated rutile modes) required for rutile saturation during subduction and partial melting. If there is a role for subducting oceanic crust now sampled as mantle eclogite, the characteristic Ti–Nb–Ta depletion in continental crust may require fluid-dominated processes, where these elements are not efficiently mobilised. In garnet, Ti uptake on the octahedral site is accommodated primarily by coupled substitution with Na and subordinately with a divalent metal cation, and there is no evidence for substitution on the tetrahedral site. For samples equilibrated to the conductive geotherm, Ti in addition to Na enrichment may be indicative of equilibration in the diamond stability field. The jadeite component in clinopyroxene as a function of temperature is a good indicator of the geotherm to which the various samples equilibrated, and can be used to reveal samples within each suite that have been affected by isobaric heating. The distribution of V in eclogitic garnet, clinopyroxene and rutile is affected by bulk composition, temperature and oxygen fugacity. In carefully vetted, low-temperature samples with TiO2 contents >0·8 wt%, V-based oxybarometry may monitor redox conditions prevailing during metamorphism of oceanic crust or, at lower TiO2, during (secular) cooling-related exsolution of rutile from garnet or clinopyroxene, whereas in higher-temperature ilmenite-bearing samples metasomatic conditions may be recorded.

Sign in / Sign up

Export Citation Format

Share Document