Reconstructing crustal thickness evolution from europium anomalies in detrital zircons

Geology ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 76-80 ◽  
Author(s):  
Ming Tang ◽  
Wei-Qiang Ji ◽  
Xu Chu ◽  
Anbin Wu ◽  
Chen Chen
Keyword(s):  
High Pressure ◽  
Crustal Thickness ◽  
Detrital Zircons ◽  
Crustal Thickening ◽  
Southern Tibet ◽  
Positive Correlation ◽  
Data Compilation ◽  
Felsic Rocks ◽  
Garnet Fractionation ◽  
The Eu

Abstract A new data compilation shows that in intermediate to felsic rocks, zircon Eu/Eu* [chondrite normalized Eu/ ] correlates with whole rock La/Yb, which has been be used to infer crustal thickness. The resultant positive correlation between zircon Eu/Eu* and crustal thickness can be explained by two processes favored during high-pressure differentiation: (1) supression of plagioclase and (2) endogenic oxidation of Eu2+ due to garnet fractionation. Here we calibrate a crustal thickness proxy based on Eu anomalies in zircons. The Eu/Eu*-in-zircon proxy makes it possible to reconstruct crustal thickness evolution in magmatic arcs and orogens using detrital zircons. To evaluate this new proxy, we analyzed detrital zircons separated from modern river sands in the Gangdese belt, southern Tibet. Our results reveal two episodes of crustal thickening (to 60–70 km) since the Cretaceous. The first thickening event occurred at 90–70 Ma, and the second at 50–30 Ma following Eurasia-India collision. These findings are temporally consistent with contractional deformation of sedimentary strata in southern Tibet.

scholarly journals Crustal thickness of the Grenville orogen: A Mesoproterozoic Tibet?

Geology ◽  
2021 ◽  
Author(s):  
Adam Brudner ◽  
Hehe Jiang ◽  
Xu Chu ◽  
Ming Tang
Keyword(s):  
Crustal Thickness ◽  
Detrital Zircons ◽  
Crustal Thickening ◽  
Geochemical Data ◽  
Geochronological Data ◽  
Grenville Province ◽  
Crustal Thinning ◽  
Paleoenvironmental Evolution ◽  
Orogenic Plateau ◽  
St Lawrence River

The Grenville Province on the eastern margin of Laurentia is a remnant of a Mesoproterozoic orogenic plateau that comprised the core of the ancient supercontinent Rodinia. As a protracted Himalayan-style orogen, its orogenic history is vital to understanding Mesoproterozoic tectonics and paleoenvironmental evolution. In this study, we compared two geochemical proxies for crustal thickness: whole-rock [La/Yb]N ratios of intermediate-to-felsic rocks and europium anomalies (Eu/Eu*) in detrital zircons. We compiled whole-rock geochemical data from 124 plutons in the Laurentian Grenville Province and collected trace-element and geochronological data from detrital zircons from the Ottawa and St. Lawrence River (Canada) watersheds. Both proxies showed several episodes of crustal thickening and thinning during Grenvillian orogenesis. The thickest crust developed in the Ottawan phase (~60 km at ca. 1080 Ma and ca. 1045 Ma), when the collision culminated, but it was still up to 20 km thinner than modern Tibet. We speculate that a hot crust and several episodes of crustal thinning prevented the Grenville hinterland from forming a high Tibet-like plateau, possibly due to enhanced asthenosphere-lithosphere interactions in response to a warm mantle beneath a long-lived supercontinent, Nuna-Rodinia.

scholarly journals Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet

Geosciences ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 209
Author(s):  
William B. Burke ◽  
Andrew K. Laskowski ◽  
Devon A. Orme ◽  
Kurt E. Sundell ◽  
Michael H. Taylor ◽  
...  
Keyword(s):  
Dynamic Models ◽  
Hanging Wall ◽  
Crustal Thickness ◽  
Suture Zone ◽  
Crustal Thickening ◽  
Southern Tibet ◽  
South Central ◽  
Crustal Thinning ◽  
Indian Lithosphere ◽  
Central Tibet

North-trending rifts throughout south-central Tibet provide an opportunity to study the dynamics of synconvergent extension in contractional orogenic belts. In this study, we present new data from the Dajiamang Tso rift, including quantitative crustal thickness estimates calculated from trace/rare earth element zircon data, U-Pb geochronology, and zircon-He thermochronology. These data constrain the timing and rates of exhumation in the Dajiamang Tso rift and provide a basis for evaluating dynamic models of synconvergent extension. Our results also provide a semi-continuous record of Mid-Cretaceous to Miocene evolution of the Himalayan-Tibetan orogenic belt along the India-Asia suture zone. We report igneous zircon U-Pb ages of ~103 Ma and 70–42 Ma for samples collected from the Xigaze forearc basin and Gangdese Batholith/Linzizong Formation, respectively. Zircon-He cooling ages of forearc rocks in the hanging wall of the Great Counter thrust are ~28 Ma, while Gangdese arc samples in the footwalls of the Dajiamang Tso rift are 16–8 Ma. These data reveal the approximate timing of the switch from contraction to extension along the India-Asia suture zone (minimum 16 Ma). Crustal-thickness trends from zircon geochemistry reveal possible crustal thinning (to ~40 km) immediately prior to India-Eurasia collision onset (58 Ma). Following initial collision, crustal thickness increases to 50 km by 40 Ma with continued thickening until the early Miocene supported by regional data from the Tibetan Magmatism Database. Current crustal thickness estimates based on geophysical observations show no evidence for crustal thinning following the onset of E–W extension (~16 Ma), suggesting that modern crustal thickness is likely facilitated by an underthrusting Indian lithosphere balanced by upper plate extension.

Quantifying the growth of continental crust through crustal thickness and zircon Hf-O isotopic signatures: A case study from the southern Central Asian Orogenic Belt

2021 ◽  
Author(s):  
Yujian Wang ◽  
Dicheng Zhu ◽  
Chengfa Lin ◽  
Fangyang Hu ◽  
Jingao Liu
Keyword(s):  
Continental Crust ◽  
Crustal Thickness ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Crustal Thickening ◽  
Crustal Growth ◽  
Isotopic Signatures ◽  
Central Asian ◽  
Southern Central ◽  
Juvenile Crust

Accretionary orogens function as major sites for the generation of continental crust, but the growth model of continental crust remains poorly constrained. The Central Asian Orogenic Belt, as one of the most important Phanerozoic accretionary orogens on Earth, has been the focus of debates regarding the proportion of juvenile crust present. Using published geochemical and zircon Hf-O isotopic data sets for three belts in the Eastern Tianshan terrane of the southern Central Asian Orogenic Belt, we first explore the variations in crustal thickness and isotopic composition in response to tectono-magmatic activity over time. Steady progression to radiogenic zircon Hf isotopic signatures associated with syn-collisional crustal thickening indicates enhanced input of mantle-derived material, which greatly contributes to the growth of the continental crust. Using the surface areas and relative increases in crustal thickness as the proxies for magma volumes, in conjunction with the calculated mantle fraction of the mixing flux, we then are able to determine that a volume of ∼14−22% of juvenile crust formed in the southern Central Asian Orogenic Belt during the Phanerozoic. This study highlights the validity of using crustal thickness and zircon isotopic signatures of magmatic rocks to quantify the volume of juvenile crust in complex accretionary orogens. With reference to the crustal growth pattern in other accretionary orogens and the Nd-Hf isotopic record at the global scale, our work reconciles the rapid crustal growth in the accretionary orogens with its episodic generation pattern in the formation of global continental crust.

Hf and Nd Isotopic Constraints on Pre‐ and Syn‐collisional Crustal Thickness of Southern Tibet

2019 ◽  
Vol 124 (11) ◽  
pp. 11038-11054 ◽  
Author(s):  
E. W. Alexander ◽  
M. M. Wielicki ◽  
T. M. Harrison ◽  
D. J. DePaolo ◽  
Z. D. Zhao ◽  
...  
Keyword(s):  
Crustal Thickness ◽  
Southern Tibet ◽  
Isotopic Constraints

Pressure Effects on the Optical Properties of LuVO4:Eu3+ Nanoparticles

2017 ◽  
Vol 75 ◽  
pp. 1-10 ◽  
Author(s):  
Brana Jovanić ◽  
Marco Bettinelli ◽  
Bozidar Radenković ◽  
Marijana Despotović-Zrakić ◽  
Fabio Piccinelli ◽  
...  
Keyword(s):  
High Pressure ◽  
Fluorescence Lifetime ◽  
Pressure Range ◽  
Room Temperature ◽  
Emission Spectra ◽  
Pressure Effects ◽  
Predicted Values ◽  
Line Positions ◽  
Effect Of Hydrostatic Pressure ◽  
The Eu

The effect of hydrostatic pressure (varying up to 110 kbar) at the room temperature on three lines at 594nm, 615nm and 619nm positions in emission spectra and fluorescence lifetime t of the Eu3+ for 0-2 line (5D0→7F2 transition) in LuVO4: Eu3+ nanoparticles was studied. The results showed that the increase of the pressure induced lines red shift towards longer wavelengths for all considered lines with different rate. Also, the fluorescence lifetime τ for 5D0 → 7F2 transition nonlinearly decreased with pressure in the considered pressure range. Line positions and fluorescence lifetime τ, were explained by a model which took into account the effect of high pressure on: refractive index of crystal; compression, polarizability of the crystal and individual ions. Satisfactory agreement between measured and theoretical predicted values with error less than 2% was obtained.

Lithoprobe line 55: integration of out-of-plane seismic results with surface structure, metamorphism, and geochronology, and the tectonic evolution of the eastern Grenville Province

2000 ◽  
Vol 37 (2-3) ◽  
pp. 341-358 ◽  
Author(s):  
Andrew Hynes ◽  
Aphrodite Indares ◽  
Toby Rivers ◽  
André Gobeil
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Good Control ◽  
Crustal Thickening ◽  
Metamorphic Rocks ◽  
Seismic Line ◽  
Grenville Province ◽  
Tectonic Model ◽  
Tectonic History ◽  
Out Of Plane

Lithoprobe line 55, in the Grenville Province of eastern Quebec, provides unusually good control on the three-dimensional (3-D) geometry and structural relationships among the major lithological units there. Archean basement underlies the exposed Proterozoic rocks, along the entire seismic line, and there is a lateral ramp in this basement immediately behind a lobate stack of thrust slices of high-pressure metamorphic rocks comprising the Manicouagan Imbricate Zone (MIZ). Integration of the 3-D geometry with P-T and geochronological data allows derivation of a tectonic model for the region. The MIZ was buried to depths >60 km at 1050 Ma. Preservation of its high-pressure assemblages, and the absence of metamorphism at 990 Ma, which is characteristic of lower pressure metamorphic rocks that tectonically overlie them, indicates the MIZ rocks were rapidly unroofed, early in the tectonic history. There were two discrete pulses of crustal thickening during the Grenvillian Orogeny in this region. The first, involving imbrication of Labradorian and Pinwarian rocks that comprised part of southeast Laurentia, culminated in the Ottawan pulse at ca. 1050 Ma, and produced the high-pressure metamorphism of the MIZ. Its effects were rapidly reversed, with extrusion of the MIZ rocks to shallow crustal levels at ca. 1020 Ma. The crust was again thickened, with the Moho subsiding to depths >60 km, in the Rigolet pulse at ca. 990 Ma. The site of extrusion of the MIZ was probably controlled by the subsurface lateral ramp. High geothermal gradients indicate that extrusion may have been aided by lithospheric delamination in the crustal-thickening zone.

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