Geochemistry and origin of the early Precambrian crust of northeastern Minnesota

Arth, Joseph G.; Hanson, Gilbert N.

doi:10.1016/0016-7037(75)90200-8

Cited by 450 publications

(85 citation statements)

References 70 publications

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“…2(B), 2(C) and 3(D)), weak negative Sr anomalies, and very low Sr/Ba (<0.30) (Fig. 7(B)) are consistent with residual plagioclase persisting in the source as well (Arth and Hanson, 1975;Barnes et al, 1996;Martin, 1999). In the (La/Yb) c -(La/Sr) c diagrams (Fig.…”

Section: and Clearly Higher Than The Experimental Melts Of Metabasasupporting

confidence: 55%

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Cretaceous high-potassium intrusive rocks in the Yueshan-Hongzhen area of east China: Adakites in an extensional tectonic regime within a continent

et al. 2004

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Adakites are generally associated with subduction zones (i.e., at convergent plate margins). This paper reports geochemical and isotopic data for early Cretaceous high-potassium adakitic intrusive rocks in the Yueshan-Hongzhen area of east China, which occur in an extensional tectonic regime within a continent. Based on petrology and geochemistry, these adakitic intrusive rocks are classified into two groups. One group (the Hongzhen adakitic granites) is characterized by high SiO 2 (69-75%) contents and K 2 O/Na 2 O (>1.0), low MgO (or Mg # ) values, Ni and V concentrations, low ε Nd (t) (-17.01~-18.13), and high ( 87 Sr/ 86 Sr) i (0.7071~0.7072). The other group (the Yueshan and Zongpu adakitic rocks) is characterized by relatively low SiO 2 (58-67%) contents and K 2 O/Na 2 O (<1.0), high MgO (Mg # ) values, Ni and V concentrations, as well as relatively high ε Nd (t) (-6.63~-9.62) and low ( 87 Sr/ 86 Sr) i (0.7064~0.7069). Both groups are associated with the contemporary Dongling metamorphic core complex, A-type granites, and some per-alkaline igneous rocks that are formed only in an extensional setting. The tectonic setting and chemical compositions suggest that: (1) the adakitic intrusive rocks in the Yueshan-Hongzhen area were formed in an extensional tectonic regime within a continental plate; (2) the Hongzhen adakitic granites were most likely derived directly from partial melting of mafic material with high potassium contents at the base of the continental crust at pressures of ~1.2 GPa, leaving residual garnet ± hornblende ± plagioclase in the source; (3) the Yueshan and Zongpu adakitic rocks were most probably derived from dehydration melting of basaltic materials delaminated into underlying mantle at pressures >1.2 GPa, leaving residual garnet + pyroxene in their sources. Both groups of adakitic rocks have high La/Yb and Sr/Y, indicating that the crustal thickness in the YueshanHongzhen area exceeded 40 km when the adakitic magmas were generated in the early Cretaceous. The present thickness of the crust in the Yueshan-Hongzhen area is only ~31 km, and therefore the crust appears to have been thinned by at least 10 km since the early Cretaceous. The relatively high MgO, Ni, and V values of the Yueshan and Zongpu adakitic rocks suggest that adakitic magmas interacted with mantle rocks, possibly concurrently with delamination of the lower crust.Keywords: adakite, delamination, lower crust, high potassium, east China geochemical similarity Drummond and Defant, 1990;Martin, 1999). However, some rocks with adakitic compositional features have been argued to be alternative origins, e.g., partial melting of mafic lower crust (Atherton and Petford, 1993;Muir et al., 1995;Petford and Atherton, 1996;Johnson et al., 1997), assimilation and fractional crystallization (AFC) processes involving basaltic magmas (Feeley and Hacker, 1995;Wareham et al., 1997;Castillo et al., 1999). Experimental studies (e.g., Rapp et al., 1991Rapp et al., , 1999Sen and Dunn, 1994;Rapp, 1995; Rapp and Waston, 1995;Springer and Seck, 19...

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Section: and Clearly Higher Than The Experimental Melts Of Metabasasupporting

confidence: 55%

“…4(A) and (C)) and moderate low K/Rb (329~357) (Fig. 7(B)) indicate that residual hornblende likely existed in the source regions (Arth and Hanson, 1975;Gromet and Silver, 1987). Low CaO, Al 2 O 3 and Sr contents (Figs.…”

Section: and Clearly Higher Than The Experimental Melts Of Metabasamentioning

confidence: 93%

Cretaceous high-potassium intrusive rocks in the Yueshan-Hongzhen area of east China: Adakites in an extensional tectonic regime within a continent

et al. 2004

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“…From the limited data available, it is not possible to determine the variation of partition coefficients in P-T-X space. The following regression lines are used to relate partition coefficient (K) for a given element between amphibole and melt to absolute temperature (T) using compilations of Arth and Hanson (1975), Pearce and Norry (1979), and Irving (1978) and additional values from Dostal et al (1983) and Irving and Frey (1984) Errors on these values are high but do not affect the principal conclusions. Comparable equations for magnetite, clinopyroxene and Plagioclase are also used, but these have little effect on the La/Sm and Zr/Sm ratios when modeling amphibolite melting.…”

Section: Theoretical Amphibolite Melt Compositionsmentioning

confidence: 99%

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

Pearce¹,

Laan²,

Arculus³

et al. 1992

Proceedings of the Ocean Drilling Program

288

265

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Holes drilled into the volcanic and ultrabasic basement of the Izu-Ogasawara and Mariana forearc terranes during Leg 125 provide data on some of the earliest lithosphere created after the start of Eocene subduction in the Western Pacific. The volcanic basement contains three boninite series and one tholeiite series. (1) Eocene low-Ca boninite and low-Ca bronzite andesite pillow lavas and dikes dominate the lowermost part of the deep crustal section through the outer-arc high at Site 786. (2) Eocene intermediate-Ca boninite and its fractionation products (bronzite andesite, andesite, dacite, and rhyolite) make up the main part of the boninitic edifice at Site 786. (3) Early Oligocene intermediate-Ca to high-Ca boninite sills or dikes intrude the edifice and perhaps feed an uppermost breccia unit at Site 786. (4) Eocene or Early Oligocene tholeiitic andesite, dacite, and rhyolite form the uppermost part of the outer-arc high at Site 782. All four groups can be explained by remelting above a subduction zone of oceanic mantle lithosphere that has been depleted by its previous episode of partial melting at an ocean ridge. We estimate that the average boninite source had lost 10-15 wt% of melt at the ridge before undergoing further melting (5-10%) shortly after subduction started. The composition of the harzburgite (<2% clinopyroxene, Fo content of about 92%) indicates that it underwent a total of about 25% melting with respect to a fertile MORB mantle. The low concentration of Nb in the boninite indicates that the oceanic lithosphere prior to subduction was not enriched by any asthenospheric (OIB) component.The subduction component is characterized by (1) high Zr and Hf contents relative to Sm, Ti, Y, and middle-heavy REE, (2) light REE-enrichment, (3) low contents of Nb and Ta relative to Th, Rb, or La, (4) high contents of Na and Al, and (5) Pb isotopes on the Northern Hemisphere Reference Line. This component is unlike any subduction component from active arc volcanoes in the Izu-Mariana region or elsewhere. Modeling suggests that these characteristics fit a trondhjemitic melt from slab fusion in amphibolite facies. The resulting metasomatized mantle may have contained about 0.15 wt% water. The overall melting regime is constrained by experimental data to shallow depths and high temperatures (1250°C and 1.5 kb for an average boninite) of boninite segregation. We thus envisage that boninites were generated by decompression melting of a diapir of metasomatized residual MORB mantle leaving the harzburgites as the uppermost, most depleted residue from this second stage of melting. Thermal constraints require that both subducted lithosphere and overlying oceanic lithosphere of the mantle wedge be very young at the time of boninite genesis. This conclusion is consistent with models in which an active transform fault offsetting two ridge axes is placed under compression or transpression following the Eocene plate reorganization in the Pacific. Comparison between Leg 125 boninites and boninites and related rocks e...

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“…Further, geophysical investigation of Dharwar craton suggests a much thinner crust in EDC (Gupta et al 2003) which precludes this possibility. Studies on Archaean TTGs by many workers (Arth and Hanson, 1975;Barker and Arth, 1976;Condie, 1981;Martin, 1994;Martin and Moyen, 2002) supported by experimental data (Rapp et al 1991;Rapp and Watson,1995) showed that TTGs were derived from a source with a broadly low K-basaltic composition, by partial melting at different depths and pressures. As described earlier, lack of a mafic endmember precludes the possibility of generation of TTGs by fractional crystallization of a basaltic magma, rather favours the partial melting as the dominant process for their genesis.…”

Section: Ttgsmentioning

confidence: 91%

Petrology and geochemistry of late archaean granitoids in the northern part of Eastern Dharwar Craton, Southern India: Implications for transitional geodynamic setting

et al. 2009

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Abstract:The results of field, petrographic and geochemical work of the granitoids of Hutti-Gurgunta area in the northern part of Eastern Dharwar Craton (EDC) is presented in this paper. This crustal section comprises polyphase banded to foliated TTG gneisses, middle amphibolite facies Gurgunta schist belt and upper greenschist facies Hutti schist belt and abundant granite plutons. The focus of the present study is mainly on basement TTG gneisses and a granite pluton (~ 240 sq km areal extent), to discuss crustal accretion processes including changing petrogenetic mechanism and geodynamic setting. The TTGs contain quartz, plagioclase, lesser K-feldspar and hornblende with minor biotite while the granite contain quartz, plagioclase, K-feldspar and hornblende. Late stage alteration (chloritisation, sericitisation and epidotisation) is wide spread in the entire area. A huge synplutonic mafic body which is dioritic to meladioritic in composition injects the granite and displays all stages of progressive mixing and hybridization. The studied TTGs and granite show distinct major and trace element patterns. The TTGs are characterized by higher SiO 2 , high Al 2 O 3 , and Na 2 O, low TiO 2 , Mg#, CaO, K 2 O and LILE, and HFS elements compared to granite. TTGs define strong trondhjemite trend whilst granite shows calc-alkaline trend. However, both TTGs and granite show characteristics of Phanerozoic high-silica adakites. The granite also shows characteristics of transitional TTGs in its high LILE, and progressive increase in K 2 O with differentiation. Both TTGs and granite define linear to sub-linear trends on variation diagrams. The TTGs show moderate total REE contents with fractionated REE patterns (La/Yb N =17.73-61.73) and slight positive or without any significant Eu anomaly implying little amount of amphibole or plagioclase in residual liquid. On the other hand, the granite displays poor to moderate fractionation of REE patterns (La/Yb N = 9.06-67.21) without any significant Eu anomaly. The TTGs have been interpreted to be produced by low-K basaltic slab melting at shallow depth, whereas the granite pluton has been formed by slab melting at depth and these melts interacted with peridotite mantle wedge. Such changing petrogenetic mechanisms and geodynamic conditions explain increase in the contents of MgO, CaO, Ni and Cr from 2700 Ma to 2500 Ma granitoids in the EDC.

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Geochemistry and origin of the early Precambrian crust of northeastern Minnesota

Cited by 450 publications

References 70 publications

Cretaceous high-potassium intrusive rocks in the Yueshan-Hongzhen area of east China: Adakites in an extensional tectonic regime within a continent

Cretaceous high-potassium intrusive rocks in the Yueshan-Hongzhen area of east China: Adakites in an extensional tectonic regime within a continent

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

Petrology and geochemistry of late archaean granitoids in the northern part of Eastern Dharwar Craton, Southern India: Implications for transitional geodynamic setting

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