Geochemical Evolution within the Tonga-Kermadec-Lau Arc-Back-arc Systems: the Role of Varying Mantle Wedge Composition in Space and Time

Ewart, A.

doi:10.1093/petrology/39.3.331

Cited by 105 publications

(184 citation statements)

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“…The standard interpretation of extensional arc magmatism is trench rollback−coupled backarc extension and trenchward arc migration (Ewart et al, 1998). However, in the Panama arc we propose an alternative interpretation.…”

Section: Discussionmentioning

confidence: 69%

Fracturing of the Panamanian Isthmus during initial collision with South America

Farris

Jaramillo

Bayona

et al. 2011

Geology

271

284

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Tectonic collision between South America and Panama began at 23-25 Ma. The collision is signifi cant because it ultimately led to development of the Panamanian Isthmus, which in turn had wide-ranging oceanic, climatic, biologic, and tectonic implications. Within the Panama Canal Zone, volcanic activity transitioned from hydrous mantle-wedge−derived arc magmatism to localized extensional arc magmatism at 24 Ma, and overall marks a permanent change in arc evolution. We interpret the arc geochemical change to result from fracturing of the Panama block during initial collision with South America. Fracturing of the Panama block led to localized crustal extension, normal faulting, sedimentary basin formation, and extensional magmatism in the Canal Basin and Bocas del Toro. Synchronous with this change, both Panama and inboard South America experienced a broad episode of exhumation indicated by (U-Th)/He and fi ssion-track thermochronology coupled with changing geographic patterns of sedimentary deposition in the Colombian Eastern Cordillera and Llanos Basin. Such observations allow for construction of a new tectonic model of the South America-Panama collision, northern Andes uplift and Panama orocline formation. Finally, synchroneity of Panama arc chemical changes and linked uplift indicates that onset of collision and Isthmus formation began earlier than commonly assumed.

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Section: Discussionmentioning

confidence: 69%

Fracturing of the Panamanian Isthmus during initial collision with South America

Farris

Jaramillo

Bayona

et al. 2011

Geology

271

284

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“…In contrast, BASR lavas have high Y (Ͼ20 ppm), high TiO 2 (Ͼ1.0 wt%), and low Th/Yb (Ͻ 0.30). Ti, Y, Nb, Zr, Yb, and Hf are the elements thought to be minimally modified by subduction processes (Ewart et al, 1998), and their concentrations should therefore provide an indicator of the extent of source depletion. Figure 8 shows clearly that TiO 2 and Y contents progressively decrease from BASR lavas to IA lavas, which indicates that the mantle beneath the island arc is more depleted than the mantle beneath the backarc basins.…”

Section: Trace Elementsmentioning

confidence: 99%

“…The marine geology studies have shown that backarc basins such as the Mariana and Lau Troughs of the western Pacific form by rifting of island arcs (Karig, 1971;Gribble et al, 1998;Ewart et al, 1998). The eruption of felsic lavas accompanies the early stages of backarc-basin opening, and the bimodal suite of felsic and basic lavas that erupt during early backarc-basin formation is a criterion of rifting of an island arc to form a backarc basin.…”

Section: Introductionmentioning

confidence: 99%

Magmagenesis in the Ordovician backarc basins of the Northern Qilian Mountains, China

Linqi

Zuchun

2003

Geo. Society Am. Bull.

125

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This paper reports the results of a petrologic and geochemical study of lavas from early Paleozoic backarc basins in the Northern Qilian Mountains in the People's Republic of China. Petrographic and geochemical characteristics of lavas reflect the changing styles of extension: typical basic lavas due to backarc seafloor spreading are found in the north, but to the south, the lava compositions become increasingly similar to arc lavas. Glassy (devitrified now), sparsely phyric basic lavas characterize the regions of seafloor spreading. Felsic lavas and porphyritic basic lavas occur in the southern, island-arc rifting part of the study area. Geochemical compositions distinguish between mature arc rocks (Y Ͻ 20 ppm, TiO 2 Ͻ 0.60 wt%, Th/Yb Ͼ 0.60) in the north and rocks formed during backarc spreading (Y Ͼ 20 ppm, TiO 2 Ͼ 1.0 wt%, Th/Yb Ͻ 0.30) in the south. These changes reflect the changing processes of melt generation associated with an evolving backarc basin such as the Ordovician backarc basin that is preserved in the Northern Qilian Mountains. The rift axis captured the arc magmatic flux in the early island-arc rifting stage so that the lavas that erupted from this part of the rift cannot be compositionally distinguished from arc lavas. As backarc extension continued and the backarc basin widened, the rift axis moved progressively away from the arc magmatic flux. The distance between the axis of extension and the zone of subarc mantle downwelling was eventually sufficient to allow mantle upwelling to become established under the axis of extension and to generate a mid- † ocean ridge-like decompression melting system to support backarc-basin spreading.

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“…Most intraoceanic arc basalts have a relatively low Sri of ~0-7035 (e.g. Dixon & Batiza 1979;Tatsumi et al 1991;Taylor & Nesbitt 1995;Ewart et al 1998), while continental arc basalts commonly are slightly more enriched, Sri >0-704 (e.g., Kimura et al 2002). Some parts of the mantle beneath continental arcs are especially enriched.…”

Section: Characterisation Of the Mantle-derived Componentmentioning

confidence: 99%

Mafic rocks from the Ryoke Belt, southwest Japan: implications for Cretaceous Ryoke/San-yo granitic magma genesis

Nakajima

Kamiyama

Williams

et al. 2004

The Fifth Hutton Symposium on the Origin of Granites and Related Rocks

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Mafic rocks in the Ryoke belt, the Cretaceous granitic province in Southwest Japan, occur in two modes: (1) as mafic dykes and pillow-shaped enclaves, and (2) as isolated kilometresized bodies of gabbroic cumulate. The dykes and pillows have fine-grained textures with thin radiating plagioclase laths, indicative of quenching. The gabbroic cumulates are predominantly coarse-grained and commonly lithologically layered.SHRIMP zircon U-Pb ages of both types of mafic rocks are in the range 71-86 Ma, late Cretaceous. The mafic rocks become younger eastwards, matching the along-arc age trend of the associated Cretaceous granites (Nakajima et al. 1990). Both types of mafic rocks were apparently generated during the same magmatic event that produced the Ryoke/San-yo granites. The mafic dykes and pillows are aphyric basaltic-andesites to andesites (SiO 2 54-60 wt.%), with microphenocrysts of biotite and hornblende. They have a composition which is similar to mafic rocks from the northern Sierra Nevada, and also to medium-K calc-alkaline rocks from present-day arc volcanics. The gabbroic cumulates are mostly pyroxene-hornblende gabbros (SiO 2 43-52 wt.%). Their bulk-rock chemical compositions are mostly unlike any magma compositions.Both types of mafic rocks from the Ryoke belt have relatively high 87 Sr/ 86 Sr initial ratios (Sri), 0-7071-0-7097, which are similar to those of the associated granites. The granites were formed either by fractional crystallisation of the mafic magmas, or by partial melting of newly formed mafic rocks at depth. The high Sri indicates that the mafic magmas were derived from enriched mantle or mixed with enriched crustal materials. Even if the mixing occurred between primitive basaltic magma and metasedimentary rocks, then the basaltic andesite-andesite magmas must have contained more than 60% mantle-derived components. The Cretaceous magmatism in Southwest Japan represents a major episode of crustal growth by additions from the upper mantle in an arc setting.

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Geochemical Evolution within the Tonga-Kermadec-Lau Arc-Back-arc Systems: the Role of Varying Mantle Wedge Composition in Space and Time

Cited by 105 publications

References 0 publications

Fracturing of the Panamanian Isthmus during initial collision with South America

Fracturing of the Panamanian Isthmus during initial collision with South America

Magmagenesis in the Ordovician backarc basins of the Northern Qilian Mountains, China

Mafic rocks from the Ryoke Belt, southwest Japan: implications for Cretaceous Ryoke/San-yo granitic magma genesis

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