This study addresses the question of how and where arc magmas obtain their chemical and isotopic ... more This study addresses the question of how and where arc magmas obtain their chemical and isotopic characteristics. The Wooley Creek batholith and Slinkard pluton are a tilted, mid- to upper-crustal part of a vertically extensive, late-Jurassic, arc-related magmatic system in the Klamath Mountains, northern California. The main stage of the system is divided into an older lower zone (c. 159 Ma) emplaced as multiple sheet-like bodies, a younger upper zone (c. 158–156 Ma), which is gradationally zoned upward from mafic tonalite to granite, and a complex central zone, which represents the transition between the lower and upper zones. Xenoliths are common and locally abundant in the lower and central zones and preserve a ghost stratigraphy of the three host terranes. Bulk-rock Nd isotope data along with ages and Hf and oxygen isotope data on zircons were used to assess the location and timing of differentiation and assimilation. Xenoliths display a wide range of εNd (whole-rock) and εHf (...
The 1800 Ma Raftsund intrusion covering area of 75x35 km is the largest intrusion in the Vesterål... more The 1800 Ma Raftsund intrusion covering area of 75x35 km is the largest intrusion in the Vesterålen-Lofoten AMCG suite in Northern Norway. It consists of monzonite to syenite containing scattered Fe-Ti-P mineralizations which vary from mm-size Fe-rich mineral clusters and apatite +/zircon, to up to 200 m x 50 m-large lenses. Although the Raftsund has suffered from medium to high-pressure metamorphism subsequent to crystallization of the intrusion, primary igneous minerals and textures are generally well preserved. A prominent feature in undeformed monzonites and syenites, is the common texture of stringer-like clusters of mafic minerals (inverted pigeonite or Fe-rich olivine, iron-rich augite, Fe-Ti oxides and minute grains of apatite and zircon) around larger areas of alkali feldspar and smaller amounts of plagioclase and small random mafic minerals. According to Philpotts (1981) such mafic clustering is best explained by crystallization from droplet of immiscible Fe-rich melt trap...
The Scandinavian Caledonides consist of disparate nappes of Baltican and exotic heritage, thrust ... more The Scandinavian Caledonides consist of disparate nappes of Baltican and exotic heritage, thrust southeastwards onto Baltica during the Mid-Silurian Scandian continent–continent collision, with structurally higher nappes inferred to have originated at increasingly distal positions to Baltica. New U–Pb zircon geochronological and whole-rock geochemical and Sm–Nd isotopic data from the Rödingsfjället Nappe Complex reveal 623 Ma high-grade metamorphism followed by continental rifting and emplacement of the Umbukta gabbro at 578 Ma, followed by intermittent magmatic activity at 541, 510, 501, 484 and 465 Ma. Geochemical data from the 501 Ma Mofjellet Group is indicative of arc magmatism at this time. Syntectonic pegmatites document pre-Scandian thrusting at 515 and 475 Ma, and Scandian thrusting at 429 Ma. These results document a tectonic history that is compatible with correlation with peri-Laurentian and/or peri-Gondwanan terranes. The data allow correlation with nappes at higher and...
The 1800 Ma monzonitic to syenitic Raftsund intrusion is the largest intrusive body of the Lofote... more The 1800 Ma monzonitic to syenitic Raftsund intrusion is the largest intrusive body of the Lofoten–Vesterålen anorthosite–mangerite–charnockite–granite (AMCG) suite. It is composed of three units that can be differentiated based on their textures. This study focuses on the most voluminous, predominantly equigranular, unit consisting of a pigeonite–augite syenite and a fayalite–augite monzonite. The pigeonite–augite syenite is associated with centimeter-scale to hundred-meter scale occurrences of Fe–Ti–P-rich rocks that display sharp to gradational contacts with the surrounding syenite. Iron–Ti–P-rich rocks consist of augite, Fe-rich olivine ± partly inverted pigeonite, apatite, ilmenite, titanomagnetite and sparse pyrrhotite, hornblende and biotite. Partly resorbed ternary feldspar crystals are common toward the contact with the syenite. Microtextures, such as symplectites, encountered at the contact between the syenite and the Fe–Ti–P-rich rocks indicate local disequilibrium betwee...
The Wooley Creek batholith (WCb) is a tilted plutonic complex that intrudes three host terranes: ... more The Wooley Creek batholith (WCb) is a tilted plutonic complex that intrudes three host terranes: a structurally lower ophiolitic mélange of the Rattlesnake Creek terrane (RCt) is overlain by volcanogenic metasediments of the western Hayfork arc sequence (wHt), which is in turn overlain by chert-argillite mélange of the eastern Hayfork terrane (eHt). Xenoliths and screen-like zones are widespread and encompass metaperidotite, amphibolite, semipelitic migmatitic schist and gneiss, quartz-rich rock types, and calc-silicate rocks (some migmatitic). Because the batholith is tilted, identification of xenolith sources is important in reconstructing the magmatic system and interpreting modes of emplacement. However, aside from ultramafic rocks (from the RCt), lithologic discrimination of xenolith sources is complicated by the presence of argillitic rocks in all three terranes and mafic (meta) volcanic and volcaniclastic rocks in the RCt and wHt. On a geochemical basis, the mafic host rock t...
The Wooley Creek batholith is part of a tilted magmatic system that was emplaced between 156 and ... more The Wooley Creek batholith is part of a tilted magmatic system that was emplaced between 156 and 159 Ma through three different host rock terranes. The eastern Hayfork terrane is an argillite matrix mélange that bounds much of the southern, upper part of the intrusion, and is separated from the two other host units by a major thrust fault. A serpentine matrix mélange, the Rattlesnake Creek terrane, is overlain by the western Hayfork terrane, which consists of volcaniclastic deposits. These terranes host the lower and middle parts of the intrusion. The eastern Hayfork terrane is the only host terrane containing blocks with detrital Proterozoic zircon (Ernst et al., 2008), however, no Paleozoic or Mesozoic zircons have been found in this terrane. The composition of the intrusion ranges from structurally low pyroxene gabbro to structurally high granodiorite. Zircons were separated from different parts of the intrusion, as well as from xenoliths and dated by U-Pb at the Stanford SHRIMP-...
The volume of interconnected melt capable of chemically and physically interacting within batholi... more The volume of interconnected melt capable of chemically and physically interacting within batholiths emplaced in the middle to upper crust is still debated. In this study, we take an alternative and/or complementary approach to geochronology and use the trace element record in minerals crystallizing early in magmatic systems to reconstruct the assembly history of a batholith. The Wooley Creek batholith (WCb) is a tilted calc-alkaline pluton situated in the Klamath Mountains, northern California, USA. The intrusion can be divided in three main units. The lower WCb ranges from two pyroxene biotite hornblende diorite to quartz-diorite. Trace elements in augite suggest that each sample analyzed belongs to a different magma batch and that individual batches underwent various extents of fractional crystallization. The upper WCb (80km2), ranging from hornblende biotite tonalite to granite, is zoned upward with more felsic rocks toward the structurally highest levels. The REE patterns of ho...
This study addresses the question of how and where arc magmas obtain their chemical and isotopic ... more This study addresses the question of how and where arc magmas obtain their chemical and isotopic characteristics. The Wooley Creek batholith and Slinkard pluton are a tilted, mid- to upper-crustal part of a vertically extensive, late-Jurassic, arc-related magmatic system in the Klamath Mountains, northern California. The main stage of the system is divided into an older lower zone (c. 159 Ma) emplaced as multiple sheet-like bodies, a younger upper zone (c. 158–156 Ma), which is gradationally zoned upward from mafic tonalite to granite, and a complex central zone, which represents the transition between the lower and upper zones. Xenoliths are common and locally abundant in the lower and central zones and preserve a ghost stratigraphy of the three host terranes. Bulk-rock Nd isotope data along with ages and Hf and oxygen isotope data on zircons were used to assess the location and timing of differentiation and assimilation. Xenoliths display a wide range of εNd (whole-rock) and εHf (...
The 1800 Ma Raftsund intrusion covering area of 75x35 km is the largest intrusion in the Vesterål... more The 1800 Ma Raftsund intrusion covering area of 75x35 km is the largest intrusion in the Vesterålen-Lofoten AMCG suite in Northern Norway. It consists of monzonite to syenite containing scattered Fe-Ti-P mineralizations which vary from mm-size Fe-rich mineral clusters and apatite +/zircon, to up to 200 m x 50 m-large lenses. Although the Raftsund has suffered from medium to high-pressure metamorphism subsequent to crystallization of the intrusion, primary igneous minerals and textures are generally well preserved. A prominent feature in undeformed monzonites and syenites, is the common texture of stringer-like clusters of mafic minerals (inverted pigeonite or Fe-rich olivine, iron-rich augite, Fe-Ti oxides and minute grains of apatite and zircon) around larger areas of alkali feldspar and smaller amounts of plagioclase and small random mafic minerals. According to Philpotts (1981) such mafic clustering is best explained by crystallization from droplet of immiscible Fe-rich melt trap...
The Scandinavian Caledonides consist of disparate nappes of Baltican and exotic heritage, thrust ... more The Scandinavian Caledonides consist of disparate nappes of Baltican and exotic heritage, thrust southeastwards onto Baltica during the Mid-Silurian Scandian continent–continent collision, with structurally higher nappes inferred to have originated at increasingly distal positions to Baltica. New U–Pb zircon geochronological and whole-rock geochemical and Sm–Nd isotopic data from the Rödingsfjället Nappe Complex reveal 623 Ma high-grade metamorphism followed by continental rifting and emplacement of the Umbukta gabbro at 578 Ma, followed by intermittent magmatic activity at 541, 510, 501, 484 and 465 Ma. Geochemical data from the 501 Ma Mofjellet Group is indicative of arc magmatism at this time. Syntectonic pegmatites document pre-Scandian thrusting at 515 and 475 Ma, and Scandian thrusting at 429 Ma. These results document a tectonic history that is compatible with correlation with peri-Laurentian and/or peri-Gondwanan terranes. The data allow correlation with nappes at higher and...
The 1800 Ma monzonitic to syenitic Raftsund intrusion is the largest intrusive body of the Lofote... more The 1800 Ma monzonitic to syenitic Raftsund intrusion is the largest intrusive body of the Lofoten–Vesterålen anorthosite–mangerite–charnockite–granite (AMCG) suite. It is composed of three units that can be differentiated based on their textures. This study focuses on the most voluminous, predominantly equigranular, unit consisting of a pigeonite–augite syenite and a fayalite–augite monzonite. The pigeonite–augite syenite is associated with centimeter-scale to hundred-meter scale occurrences of Fe–Ti–P-rich rocks that display sharp to gradational contacts with the surrounding syenite. Iron–Ti–P-rich rocks consist of augite, Fe-rich olivine ± partly inverted pigeonite, apatite, ilmenite, titanomagnetite and sparse pyrrhotite, hornblende and biotite. Partly resorbed ternary feldspar crystals are common toward the contact with the syenite. Microtextures, such as symplectites, encountered at the contact between the syenite and the Fe–Ti–P-rich rocks indicate local disequilibrium betwee...
The Wooley Creek batholith (WCb) is a tilted plutonic complex that intrudes three host terranes: ... more The Wooley Creek batholith (WCb) is a tilted plutonic complex that intrudes three host terranes: a structurally lower ophiolitic mélange of the Rattlesnake Creek terrane (RCt) is overlain by volcanogenic metasediments of the western Hayfork arc sequence (wHt), which is in turn overlain by chert-argillite mélange of the eastern Hayfork terrane (eHt). Xenoliths and screen-like zones are widespread and encompass metaperidotite, amphibolite, semipelitic migmatitic schist and gneiss, quartz-rich rock types, and calc-silicate rocks (some migmatitic). Because the batholith is tilted, identification of xenolith sources is important in reconstructing the magmatic system and interpreting modes of emplacement. However, aside from ultramafic rocks (from the RCt), lithologic discrimination of xenolith sources is complicated by the presence of argillitic rocks in all three terranes and mafic (meta) volcanic and volcaniclastic rocks in the RCt and wHt. On a geochemical basis, the mafic host rock t...
The Wooley Creek batholith is part of a tilted magmatic system that was emplaced between 156 and ... more The Wooley Creek batholith is part of a tilted magmatic system that was emplaced between 156 and 159 Ma through three different host rock terranes. The eastern Hayfork terrane is an argillite matrix mélange that bounds much of the southern, upper part of the intrusion, and is separated from the two other host units by a major thrust fault. A serpentine matrix mélange, the Rattlesnake Creek terrane, is overlain by the western Hayfork terrane, which consists of volcaniclastic deposits. These terranes host the lower and middle parts of the intrusion. The eastern Hayfork terrane is the only host terrane containing blocks with detrital Proterozoic zircon (Ernst et al., 2008), however, no Paleozoic or Mesozoic zircons have been found in this terrane. The composition of the intrusion ranges from structurally low pyroxene gabbro to structurally high granodiorite. Zircons were separated from different parts of the intrusion, as well as from xenoliths and dated by U-Pb at the Stanford SHRIMP-...
The volume of interconnected melt capable of chemically and physically interacting within batholi... more The volume of interconnected melt capable of chemically and physically interacting within batholiths emplaced in the middle to upper crust is still debated. In this study, we take an alternative and/or complementary approach to geochronology and use the trace element record in minerals crystallizing early in magmatic systems to reconstruct the assembly history of a batholith. The Wooley Creek batholith (WCb) is a tilted calc-alkaline pluton situated in the Klamath Mountains, northern California, USA. The intrusion can be divided in three main units. The lower WCb ranges from two pyroxene biotite hornblende diorite to quartz-diorite. Trace elements in augite suggest that each sample analyzed belongs to a different magma batch and that individual batches underwent various extents of fractional crystallization. The upper WCb (80km2), ranging from hornblende biotite tonalite to granite, is zoned upward with more felsic rocks toward the structurally highest levels. The REE patterns of ho...
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