From subduction initiation to hot subduction: Life of a Neoarchean subduction zone from the Dengfeng Greenstone Belt, North China Craton

2021 ◽  
Author(s):  
Hao Deng ◽  
Ning Jia ◽  
Timothy Kusky ◽  
Ali Polat ◽  
Guanglei Peng ◽  
...  
Keyword(s):  
Rare Earth ◽  
Subduction Zone ◽  
Rare Earth Element ◽  
Mantle Source ◽  
North China Craton ◽  
Greenstone Belt ◽  
Earth Element ◽  
North China ◽  
Subduction Initiation ◽  
Magmatic Association

We report a spatially and temporally linked arc magmatic association of 2.55−2.50 Ga mid-ocean ridge basalt (MORB)-affinity gabbros, arc-affinity basalts, high-Mg basalts/basaltic andesites (HMBA), Nb-enriched basalts (NEB), and a tonalite-trondhjemite-granodiorite (TTG)-like granodiorite from the Dengfeng greenstone belt (DFGB), North China Craton. These are identical to arc magmatic rock suites from hot subduction in the present plate mosaic, and resemble suites formed during subduction initiation. Laser ablation−inductively coupled plasma−mass spectrometry zircon U-Pb dating indicates that gabbros and granodiorites intruded at ca. 2.55 Ga and the HMBAs formed at ca. 2.50 Ga, indicating a long duration of subduction zone magmatic activity of at least 50 m.y. in the DFGB. The gabbros are characterized by flat light-rare earth element (LREE) patterns without negative Nb and Zr anomalies, showing a MORB-like geochemical affinity. Combined with previously reported normal-MORB-type basalts, we suggest that they may represent magmatic products during intraoceanic subduction initiation where their mantle source was slightly metasomatized by subduction-derived fluids during the initiation stage. The arc-affinity basalts are characterized by slightly enriched LREE patterns with negative Nb and Zr anomalies. The HMBAs have higher contents of MgO, Ni, and Cr and display more fractionated rare earth element (REE) patterns and large negative Nb and Zr anomalies than the arc-affinity basalts. The NEBs are characterized by high absolute contents of Nb (9.9−14 ppm) and high ratios of Nb/Laprimitive mantle (pm) (0.40−0.46) and Nb/Thpm (0.44−0.54), and moderately fractionated REE and minor negative Nb anomalies with no Zr anomalies. One granodiorite sample is characterized by a highly fractionated REE pattern and negative Nb and Zr anomalies. Geochemical modeling suggests that the association of the normal arc-affinity basalt (NAB)-HMBA-NEB can be interpreted to be generated by hybridization of mantle wedge peridotites by slab-derived TTG-like melts. Positive values of whole-rock εNd (t) and zircon εHf (t) of the 2.55−2.50 Ga magmatic associations are consistent with a long-term depleted mantle source for the mafic assemblage. The 2.55−2.50 Ga magmatic association from MORB-affinity gabbros and basalts to arc-affinity NAB-HMBA-NEB may record a continuous Neoarchean geodynamic process from intraoceanic subduction initiation to mature arc magmatism. The NAB-HMBA-NEB association with regional sanukitoids and high-Al TTGs indicates that hot subduction may have played an important role in the production of arc-related magmatism during the Archean.

Geochemical evolution in the Blake River Group, Abitibi Greenstone Belt, Superior Province

1980 ◽  
Vol 17 (9) ◽  
pp. 1292-1299 ◽  
Author(s):  
I. E. M. Smith
Keyword(s):  
Rare Earth ◽  
Volcanic Rock ◽  
Rare Earth Element ◽  
Greenstone Belt ◽  
Earth Element ◽  
Superior Province ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
Rock Types ◽  
Element Fractionation

In well exposed, well developed greenstone belts of the Superior Province there is a clear progression from stratigraphically lower, geochemically primitive volcanic rock types (komatiites, tholeiites) to overlying geochemically evolved calc-alkaline volcanic rock types. In the western Blake River Group of the Abitibi Greenstone Belt the change from tholeiitic to calc-alkaline volcanics represents a geochemical discontinuity defined by an increase in incompatible elements and light/heavy rare-earth element fractionation in the overlying rocks. Quantitative modelling of the parameters of the discontinuity indicates that it can be explained by a change to very small amounts of melting of unmodified mantle lherzolite, although this is not a unique solution. In calc-alkaline suites showing high degrees of rare-earth element fractionation the calculated melt fraction required of unmodified mantle becomes unrealistically low and models involving a geochemically evolved source may have to be considered.

A rare earth element-rich carbonatite dyke at Bayan Obo, Inner Mongolia, North China

2003 ◽  
Vol 78 (1-2) ◽  
pp. 93-110 ◽  
Author(s):  
X.-M. Yang ◽  
X.-Y. Yang ◽  
Y.-F. Zheng ◽  
M. J. Le Bas
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Inner Mongolia ◽  
Earth Element ◽  
North China ◽  
Bayan Obo

Stable isotope and Rare Earth Element evidence for recent ironstone pods within the Archean Barberton greenstone belt, South Africa

2006 ◽  
Vol 70 (6) ◽  
pp. 1457-1470 ◽  
Author(s):  
Michael T. Hren ◽  
Donald R. Lowe ◽  
Michael M. Tice ◽  
Gary Byerly ◽  
C. Page Chamberlain
Keyword(s):  
South Africa ◽  
Rare Earth ◽  
Stable Isotope ◽  
Rare Earth Element ◽  
Greenstone Belt ◽  
Earth Element ◽  
Barberton Greenstone Belt

Pontiac metavolcanic rocks within the Cadillac tectonic zone, McWatters, Abitibi Belt, Quebec

1993 ◽  
Vol 30 (7) ◽  
pp. 1521-1531 ◽  
Author(s):  
David Morin ◽  
Michel Jébrak ◽  
Marc Bardoux ◽  
Normand Goulet
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Rare Earth Element ◽  
Greenstone Belt ◽  
Earth Element ◽  
Calc Alkaline ◽  
Tectonic Zone ◽  
Southern Boundary ◽  
Abitibi Greenstone Belt ◽  
Metavolcanic Rocks

The McWatters metavolcanic rocks are structurally bounded lenses within the Cadillac tectonic zone on the southern boundary of the Abitibi greenstone belt. They comprise komatiite, tholeiitic basalt and gabbro, and calc-alkaline andesitic lavas and volcaniclastic rocks cut by calc-alkaline dioritic and lamprophyric dykes. The McWatters basalts are mid-ocean-ridge basalt type tholeiites exhibiting low incompatible trace element contents and [La/Yb]N < 1. They may have formed via relatively high degree partial melting of a rare-earth element depleted mantle source. The andesites exhibit chondrite-normalized trace-element patterns with light-rare-earth and large-ion lithophile element enrichments and negative Nb and Ti anomalies, comparable to those of subduction-related calc-alkaline andesites. McWatters units are distinct from nearby Blake River Group rocks, despite comparable lithological assemblages and some common geochemical characteristics. The McWatters basalts exhibit lower Ti/Y, Zr/Y, and La/Yb than the Blake River tholeiites, whereas the McWatters andesites display lower Ti/Zr and higher Zr/Y than the Blake River calc-alkaline units. The McWatters tholeiites can be correlated with northern Pontiac Group tholeiitic units based on similar trace-element ratios and parallel rare-earth-element patterns. Thus, the McWatters tholeiites represent Pontiac rocks, underthrust beneath the southern Abitibi belt and appearing as isolated and retrograded lenses in the Cadillac tectonic zone. They may represent the remnants of an ocean basin that once separated the southern Abitibi greenstone belt from the Pontiac Subprovince.

Diopsidites from a Neoproterozoic–Cambrian suture in southern India

2010 ◽  
Vol 147 (5) ◽  
pp. 777-788 ◽  
Author(s):  
M. SANTOSH ◽  
V. J. RAJESH ◽  
T. TSUNOGAE ◽  
S. ARAI
Keyword(s):  
Rare Earth ◽  
Subduction Zone ◽  
Rare Earth Element ◽  
Earth Element ◽  
Suture Zone ◽  
Dharwar Craton ◽  
Southern India ◽  
The North ◽  
Calcic Amphibole ◽  
Gondwana Supercontinent

AbstractWe report the occurrence and characteristics of diopsidite dykes and veins from the Palghat-Cauvery Suture Zone (PCSZ) marking the boundary between the Archaean Dharwar craton to the north and the Proterozoic Madurai Block to the south, which is considered as a trace of the Cambrian Gondwana suture zone in southern India. The diopsidites are composed predominantly of coarse crystals of diopside [Mg no. (100 Mg/(Mg+Fetot)) up to 89] surrounded by retrograde calcic amphibole, plagioclase and phlogopite with accessory titanite and calcite. The major, trace and rare earth element characteristics of the diopside crystals suggest their formation in a subduction zone setting. We correlate the petrogenesis of the diopsidites with the tectonics associated with the subduction and closure of the Neoproterozoic Mozambique Ocean prior to the final collisional assembly of the Gondwana supercontinent in Cambrian.

Life cycle of an Archean subduction zone from initiation to arc–polarity reversal: Insights from the Zunhua ophiolitic mélange, North China Craton 

2021 ◽  
Author(s):  
Wenbin Ning ◽  
Timothy Kusky ◽  
Junpeng Wang ◽  
Lu Wang ◽  
Hao Deng ◽  
...  
Keyword(s):  
Life Cycle ◽  
Subduction Zone ◽  
North China Craton ◽  
Plate Tectonics ◽  
North China ◽  
Polarity Reversal ◽  
Iron Formation ◽  
Arc Magmatism ◽  
Subduction Initiation ◽  
Depleted Mantle

&lt;p&gt;Subduction initiation and arc&amp;#8211;polarity reversal have rarely been recognized in the Archean rock record. We document Neoarchean subduction initiation, fore-arc magmatism, and an arc&amp;#8211;polarity reversal event from the Zunhua structural belt along the eastern margin of the Central Orogenic Belt (COB) of the North China Craton (NCC). The Zunhua ophiolitic m&amp;#233;lange within the Zunhua structural belt is a mappable unit characterized by blocks of metamorphosed harzburgite/lherzolite, podiform chromite &amp;#8211;bearing dunite, pyroxenite, amphibolite, metabasites (basalt and diabase) with rare intermediate volcanics, chert, and tectonic lenses of banded iron formation in a strongly sheared metapelitic matrix. New geochronological and geochemical analyses of magmatic blocks within the ophiolitic m&amp;#233;lange show that the crustal magmatic rocks were produced in a fore-arc region at 2.55&amp;#8211;2.52 Ga from depletion of the harzburgitic&amp;#8211;lherzolitic mantle tectonites. Chemical, petrological, and temporal links between the depleted mantle blocks, and the suite of magmatic blocks derived from partial melting and metasomatism of these depleted mantle blocks, unequivocally shows that they represent part of the same original Neoarchean fore-arc ophiolite suite. After formation and accretion in the oceanic realm, the m&amp;#233;lange was emplaced on the continental margin of the Eastern Block between 2.52&amp;#8211;2.50 Ga, and underwent two stages of metamorphism at ca. 2.48&amp;#8211;2.46 Ga and 1.81 Ga. Metamorphosed intermediate&amp;#8211;mafic volcanic blocks exhibit systematic successive geochemical variations, from MORB-like to volcanic arc-like, and the N-MORB-like meta-basalts show remarkable similarity with the subduction initiation-related Izu&amp;#8211;Bonin&amp;#8211;Mariana (IBM) fore-arc basalts. We suggest that the Zunhua fore-arc complex records continuous geodynamic processes from subduction initiation to arc magmatism. The Zunhua ophiolitic m&amp;#233;lange is part of a ca. 2.5 Ga suture between an oceanic arc of the COB and Eastern Block of the NCC. After the arc&amp;#8211;continent collision, an arc&amp;#8211;polarity reversal event has been proposed to initiate a new eastward&amp;#8211;dipping subduction zone on the western side of the COB. This arc&amp;#8211;polarity reversal can be traced for more than 1,600 km along the length of the orogen, similar in scale, geometry, and duration between collision and polarity flip to the present-day arc&amp;#8211;polarity reversal of the Sunda&amp;#8211;Banda arc during its ongoing collision with the Australia continent. This indicates that a life cycle of an Archean subduction zone, including birth (subduction initiation), maturity (arc magmatism), death (arc-continent collision) and re-birth (arc&amp;#8211;polarity reversal), is recorded in the Zunhua ophiolitic m&amp;#233;lange, and the geodynamics of plate tectonics at the end of the Archean was similar to that of today.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Rare Earth Element Geochemistry of Late Palaeozoic Coals in North China

2010 ◽  
Vol 74 (1) ◽  
pp. 74-83 ◽  
Author(s):  
HUANG Wenhui ◽  
YANG Qi ◽  
TANG Dazhen ◽  
TANG Xiuyi ◽  
ZHAO Zhigen
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
North China ◽  
Element Geochemistry ◽  
Late Palaeozoic

Molecular modelling of rare earth element complexation in subduction zone fluids

2009 ◽  
Vol 73 (13) ◽  
pp. 3934-3947 ◽  
Author(s):  
Jelle van Sijl ◽  
Neil L. Allan ◽  
Gareth R. Davies ◽  
Wim van Westrenen
Keyword(s):  
Rare Earth ◽  
Subduction Zone ◽  
Rare Earth Element ◽  
Molecular Modelling ◽  
Earth Element
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