scholarly journals LINGKUNGAN DAN EVOLUSI TEKTONIK BATUAN DAN SEDIMEN BERDASARKAN UNSUR KIMIA UTAMA DI PERAIRAN BAYAH DAN SEKITARNYA, PROVINSI BANTEN

2016 ◽  
Vol 12 (3) ◽  
pp. 125
Author(s):  
Ediar Usman ◽  
Udaya Kamiludin
Keyword(s):  
Oceanic Crust ◽  
Major Elements ◽  
Igneous Rocks ◽  
Source Rocks ◽  
Calc Alkaline ◽  
Triangular Diagram ◽  
Sediment Samples ◽  
Tectonic Environment ◽  
Continental Arc ◽  
Magma Series

Pengeplotan data unsur kimia pada diagram SiO2 vs K2O untuk sampel sedimen dasar laut cenderung terjadi kenaikan SiO2 dan penurunan K2O, sehingga arah evolusi berkembang dari kalk-alkalin sedang ke kalk-alkalin rendah (toleitik). Pada sampel batuan beku dan sedimen hasil pemboran memperlihatkan pola evolusi magma sebaliknya, terjadi kenaikan SiO2 dan K2O dalam seri magma yang sama (toleitik). Kondisi ini diperkuat oleh diagram segitiga AFM (A = Na2O+K2O; F = FeOtotal ; M = MgO) yang menunjukkan sebagian besar sampel yang diplot berada antara toleitik dan kalk-alkalin sedang. Hasil ini memberi kesimpulan bahwa batuan ini bersifat transisi antara toleitik dan kalk-alkalin sedang, dan condong ke arah seri toleitik sebagai indikasi batuan berasal dari daerah samudera. Berdasarlan pengeplotan pada diagram segitiga TiO2 – 10MnO – P2O5, lingkungan tektonik batuan beku di pantai Cibobos, sedimen dasar laut dan sedimen pemboran pada umumnya berada pada lingkungan tektonik andesit kepulauan samudera dan sebagian busur benua. Hasil tersebut, maka dapat disimpulkan bahwa sedimen di daerah Bayah berhubungan dengan seri magma dengan afinitas rendah mulai toleitik hingga kalk-alkalin sedang dan batuan samudera yang menyusup ke busur kepulauan atau busur benua. Hasil ini dapat mengetahui lingkungan dan evolusi batuan sumber sehingga diharapkan bermanfaat dalam kegiatan ekplorasi sumber daya mineral dan energi di masa mendatang. Kata kunci: unsur kimia utama, lingkungan tektonik, evolusi, kerak samudera dan kontinen, perairan Bayah Plotting of major elements data of the seafloor sediment samples on diagram of SiO2 vs K2O tends to increase the SiO2 and decrease the K2O, therefore the direction of evolution develop from medium to low calc-alkaline (tholeitic). From igneous rocks and drilling sediment samples shows that the evolution magma has the opposite pattern, increasing of SiO2 and K2O in the same magma series ( tholeitic). This condition is confirmed by the triangular diagram of AFM (A = Na2O+K2O; F = FeOtotal ; M = MgO) that shows the most of plotted samples are between medium calc-alkaline and tholeitic. This result give a conclusion that these rocks are at transitional area between tholeitic and medium calc-alkaline, and tend towards tholeitic series as an indication of rocks from oceanic zone. Based on plotting on the triangular diagram of TiO2 - 10MnO - P2O5, tectonic environment of igneous rocks in the coast of Cibobos, surface and drilling sediment samples, in general these samples are in the tectonic environment of oceanic islands andesite and partial of continental arc. From this study, it can be concluded that the sediment in the Bayah area is associated with affinity magma series from low kalk-alkaline (tholeitic) to medium calc-alkaline, and oceanic crust is being subducting to continental arc. This result could recognize the environment and the evolution of source rocks, therefore it may useful in the exploration activities of mineral and energy resources in the future. Keywords: major elements, tectonic environment, evolution, continental and oceanic crust, Bayah waters.

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

scholarly journals GEOCHEMISTRY AND PETROGENESIS OF SILLS IN LAVASANAT REGION, TEHRAN, IRAN

Geosaberes ◽  
2020 ◽  
Vol 11 ◽  
pp. 480
Author(s):  
Mehdi Bina ◽  
Mohammad Ali Arian ◽  
Mohsen Pourkermani ◽  
Mohammad Hasan Bazoobandi
Keyword(s):  
Igneous Rocks ◽  
Study Region ◽  
The North ◽  
Continental Arc ◽  
Tectonic Position ◽  
Geological Map ◽  
Tehran Province ◽  
Relationship Of ◽  
The Relationship ◽  
Magma Series

The study area is located in Lavasanat region in the east of Tehran Province in the Central Alborz zone. The outcrops in this region are mainly associated with Karaj formation and belong to the upper Eocene to Oligocene periods. These outcrops consist of two intrusions: one in the north and the other in the northeast of Lavasanat. These outcrops are scattered over an area of approximately 337km2. In the study region, there are various intrusive igneous rocks, while numerous intrusive igneous rocks are scattered in the form of sills and dikes. These rocks include a range of rocks from diorite gabbro to diorite, monzonite, and syenite. The weathered colors of these rocks are black, brown and gray. The outcrops of these sills are mainly present in the middle-northern part of the quadrangle geological map of the east of Tehran. In different diagrams of the magma series, the study rocks are classified as alkaline, calc-alkaline, and shoshonite, which may indicate magma contamination. An analysis of the variations of the classical elements and trace elements, the spider plots, and interpretations of these plots confirms the relationship of these rocks with the subduction zone and continental arc. To find the tectonic position of the sills in the study area based on the geochemical diagrams, we selected samples from the within-plate (WIP) and arc zones.

Tectonic and magmatic evolution of the Aqishan-Yamansu belt: A Paleozoic arc-related basin in the Eastern Tianshan (NW China)

2020 ◽  
Author(s):  
Shuanliang Zhang ◽  
Huayong Chen ◽  
Pete Hollings ◽  
Liandang Zhao ◽  
Lin Gong
Keyword(s):  
Partial Melting ◽  
Oceanic Crust ◽  
Lower Crust ◽  
Early Carboniferous ◽  
Late Carboniferous ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Eastern Tianshan ◽  
Depleted Mantle ◽  
T Values

The Aqishan-Yamansu belt in the Chinese Eastern Tianshan represents a Paleozoic arc-related basin generally accompanied by accretionary magmatism and Fe-Cu mineralization. To characterize the tectonic evolution of such an arc-related basin and related magmatism and metallogenesis, we present a systematic study of the geochronology, whole-rock geochemistry, and Sr-Nd isotopes of igneous rocks from the belt. New zircon U-Pb ages, in combination with published data, reveal three phases of igneous activity in the Aqishan-Yamansu belt: early Carboniferous felsic igneous rocks (ca. 350−330 Ma), late Carboniferous intermediate to felsic igneous rocks (ca. 320−305 Ma), and Permian quartz diorite and diorite porphyry dikes (ca. 280−265 Ma). The early Carboniferous felsic rocks are enriched in large ion lithophile elements (LILEs) and depleted in Nb, Ta, and Ti, showing arc-related magma affinities. Their positive εNd(t) values (3.3−5.9) and corresponding depleted mantle model ages (TDM) of 0.83−0.61 Ga, as well as high MgO contents, Mg# values, and Nb/Ta ratios, suggest that they were derived from lower crust with involvement of mantle-derived magmas. The late Carboniferous intermediate igneous rocks show calc-alkaline affinities, exhibiting LILE enrichment and high field strength element (HFSE) depletion, with negative Nb and Ta anomalies. They have high MgO contents and Mg# values with positive εNd(t) values (3.9−7.9), and high Ba/La and Th/Yb ratios, implying a depleted mantle source metasomatized by slab-derived fluids and sediment or sediment-derived melts. The late Carboniferous felsic igneous rocks are metaluminous to peraluminous with characteristics of medium-K calc-alkaline I-type granites. Given the positive εNd(t) values (6.3−6.6) and TDM ages (0.56−0.53 Ga), we suggest the late Carboniferous felsic igneous rocks were produced by partial melting of a juvenile lower crust. The Permian dikes show characteristics of adakite rocks. They have relatively high MgO contents and Mg# values, and positive εNd(t) values (7.2−8.5), which suggest an origin from partial melting of a residual basaltic oceanic crust. We propose that the Aqishan-Yamansu belt was an extensional arc−related basin from ca. 350 to 330 Ma; this was followed by a relatively stable carbonate formation stage at ca. 330−320 Ma, when the Kangguer oceanic slab subducted beneath the Central Tianshan block. As the subduction continued, the Aqishan-Yamansu basin closed due to slab breakoff and rebound during ca. 320−305 Ma, which resulted in basin inversion and the emplacement of granitoids with contemporary Fe-Cu mineralization. During the Permian, the Aqishan-Yamansu belt was in postcollision extension stage, with Permian adakitic dikes formed by partial melting of a residual oceanic crust.

Constraints imposed by experimental petrology on possible and impossible magma sources and products

1984 ◽  
Vol 310 (1514) ◽  
pp. 439-456 ◽  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Basaltic Andesite ◽  
Subduction Zones ◽  
Mantle Peridotite ◽  
Experimental Petrology ◽  
Source Rocks ◽  
Calc Alkaline ◽  
Physical Constraints ◽  
Inverse Results

Experimental petrology can be used in forward and inverse approaches. The forward approach defines the compositions of liquids generated by partial melting of possible source rocks at various depths. The inverse approach determines conditions for multiple-mineral saturation at the liquidus of primitive magmas, correlates them with residual minerals of possible source rocks, and thus provides estimates of depths and temperatures required for their derivation. Review of a selection of forward and inverse results is followed by evaluation of petrological and geophysical processes in layered mantle and in subduction zones. Physical constraints imposed by solidus curves and geotherms present problems for models that derive basalts from deep mantle reservoirs, separated from overlying convecting layers. Magmas from mantle are limited to compositions less siliceous than basaltic andesite, with rare exceptions. Granite liquids cannot be generated from normal peridotite, nor from oceanic crust at mantle pressures in subduction zones. In continental crust, hydrous granite liquid is generated at depths of less than 30 km. Basaltic andesite and picritic basalt are parental magmas for the calc-alkaline series. Andesite is not primary from subcontinental depths, and can be generated as liquid in continental crust only if temperatures exceed about 1100°C. Calc-alkaline magmas may contain components from mantle peridotite, subducted oceanic crust, and continental crust.

Petrogenesis of the Ulungur Intrusive Complex, NW China, and Implications for Crustal Generation and Reworking in Accretionary Orogens

2020 ◽  
Vol 61 (2) ◽  
Author(s):  
Gong-Jian Tang ◽  
Qiang Wang ◽  
Derek A Wyman ◽  
Wei Dan ◽  
Lin Ma ◽  
...  
Keyword(s):  
Oceanic Crust ◽  
Lower Crust ◽  
Mineral Chemistry ◽  
Isotopic Signature ◽  
Source Rocks ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Depleted Mantle ◽  
Heavy Rare Earth Elements ◽  
Pressure Crystallization

Abstract Accretionary orogens are characterized by voluminous juvenile components (recently derived from the mantle) and knowing the origin(s) of such components is vital for understanding crustal generation. Here we present field and petrological observations, along with mineral chemistry, zircon U–Pb age and Hf–O isotope data, and whole rock geochemical and Sr–Nd isotopic data for the c.320 Ma Ulungur intrusive complex from the Central Asian Orogenic Belt. The complex consists of two different magmatic series: one is characterized by medium- to high-K calc-alkaline gabbro to monzogranite; the other is defined by peralkaline aegirine–arfvedsonite granitoids. The calc-alkaline and peralkaline series granitoids have similar depleted mantle-like Sr–Nd–Hf isotopic compositions, but they have different zircon δ18O values: the calc-alkaline series have mantle-like δ18O values with mean compositions ranging from 5·2 ± 0·5‰ to 6·0 ± 0·9‰ (2SD), and the peralkaline granitoids have low δ18O values ranging from 3·3 ± 0·5‰ to 3·9 ± 0·4‰ (2SD). The calc-alkaline series were derived from a hydrous sub-arc mantle wedge, based on the isotope and geochemical compositions, under garnet peridotite facies conditions. This study suggests that the magmas underwent substantial differentiation, ranging from high pressure crystallization of ultramafic cumulates in the lower crust to lower pressure crystallization dominated by amphibole, plagioclase and minor biotite in the upper crust. The peralkaline series rocks are characterized by δ18O values lower than the mantle and enrichment of high field strength elements (HFSEs) and heavy rare earth elements (HREEs). They likely originated from melting of preexisting hydrothermally altered residual oceanic crust in the lower crust of the Junggar intra-oceanic arc. Early crystallization of clinopyroxene and amphibole was inhibited owing to their low melting temperature, leading to HFSEs and HREEs enrichment in residual peralkaline melts during crystallization of a feldspar-dominated mineral assemblage. Thus, the calc-alkaline and peralkaline series represent episodes of crust generation and reworking, respectively, demonstrating that the juvenile isotopic signature in accretionary orogens can be derived from diverse source rocks. Our results show that reworking of residual oceanic crust also plays an important role in continental crust formation for accretionary orogens, which has not previously been widely recognized.

scholarly journals The Cretaceous igneous rocks in southeastern Guangxi and their implication for tectonic environment in southwestern South China Block

2020 ◽  
Vol 12 (1) ◽  
pp. 518-531
Author(s):  
Yang Liu ◽  
Nianqiao Fang ◽  
Menglin Qiang ◽  
Lei Jia ◽  
Chaojie Song
Keyword(s):  
South China ◽  
Igneous Rocks ◽  
South China Block ◽  
Calc Alkaline ◽  
Slab Melting ◽  
Late Mesozoic ◽  
Fine Grained ◽  
Tectonic Environment ◽  
High K ◽  
Cretaceous Magmatism

AbstractSoutheastern Guangxi is located in the southwestern South China Block and to the northwest of the South China Sea (SCS), with abundant records of the Cretaceous magmatism. A detailed study of igneous rocks will contribute to a better understanding of the late Mesozoic tectonic environment. Zircon U–Pb dating yields ages of 93.37 ± 0.43 Ma for Yulin andesites and 107.6 ± 1.2 Ma for Luchuan granites. Yulin andesites are hornblende andesites, of which w(MgO) is between 7.72% and 8.42%, and Mg# is between 66.7 and 68.0, belonging to high magnesian andesites (HMAs) from peridotite sources. Luchuan granites are medium- to fine-grained monzogranites. Monzogranites and clastoporphyritic lava are high-K calc-alkaline series and metaluminum to weakly peraluminous series, which belong to the I-type granites. Those are enriched in Rb, Th, K and LREEs and depleted in Nb, Ta, P and Eu, showing the geochemical characteristics related to subduction. Unlike the contemporary “bimodal igneous rock assemblages” in Zhejiang and Fujian, the intermediate-acid magmatites in the southeastern Guangxi imply the compressive tectonic environment. The assemblage of HMAs and adakitic rocks indicates that the southwestern South China Block was under the Neo-Tethyan subduction during Cretaceous, and slab melting contributed to the magma in this area.

scholarly journals Geology and Petrogenesis of Igneous Rocks from Batur Paleovolcano, Gunungkidul, Yogyakarta: Evidence from their Textures, Mineralogy, and Major Elements Geochemistry

2019 ◽  
Vol 4 (1) ◽  
pp. 32
Author(s):  
Fahmi Hakim ◽  
Yanuardi Satrio Nugroho ◽  
Cendi Diar Permata Dana ◽  
Anastasia Dewi Titisari
Keyword(s):  
Tectonic Setting ◽  
Research Area ◽  
Major Elements ◽  
Geological Mapping ◽  
Igneous Rocks ◽  
Emission Spectrometry ◽  
Geochemical Data ◽  
Geological Condition ◽  
Calc Alkaline ◽  
Andesite Lava

Batur paleovolcano is located in Wediombo Beach area, Gunungkidul Regency, Yogyakarta and is being part of Wuni Formation. Several volcanic products including lava flow, autoclastic breccia and volcanic breccia can be found associated with diorite intrusions. This research is aimed to characterize geological, mineralogical andgeochemical variations of igneous rocks from Batur paleovolcano to understand its petrogenesis. Detailed geological mapping with scale of 1:12,500 is conducted to identify geological aspects and delineate igneous rocks distributions. Igneous rocks and selected wall rocks samples were prepared for laboratory analysis including 8 samples for petrography and 5 samples for ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Several geochemical data from previous study are also added to investigate the geochemical variations. Geological condition of the research area consists of four rock units including colluvial deposit, limestone, andesite lava and diorite intrusion. Geological structures found are normal fault and shear joint where the main stress direction is north–south. Petrography analysis showed that igneous rocks in this research area consist of diorite intrusion and andesite lava with phorphyritic texture. Plagioclase become the most abundant minerals found both as phenocryst phase and groundmass. Hornblende only occur as phenocryst phase in minor amounts as accesory mineral. Major elementsgeochemistry analysis showed the rocks are characterized by intermediate silica with low alkali content. They are can be categorized as calc-alkaline series. However, some samples are fall into tholeiitic series. Major elements variation and textural study also indicate the magma is experienced differentiation process by fractional crystallization mechanism. This study suggests that igneous rocks from Batur paleovolcano is formed by two phases of formation. Earlier phase is the formation of andesite lava in island arc tholeiitic tectonic setting then at the later phase is formation of diorite intrusion in the calc-alkaline basalts tectonic setting.

Geochemistry of the Eocene clastic sediments (Suonahu Formation) in the North Qiangtang Basin, Tibet: implications for paleoclimate conditions, provenance and tectonic setting

2020 ◽  
Vol 57 (1) ◽  
pp. 40-55
Author(s):  
Lijun Shen ◽  
Jian Wang ◽  
Hualiang Shen ◽  
Xiugen Fu ◽  
Youli Wan ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Tectonic Setting ◽  
Major Elements ◽  
Climatic Conditions ◽  
Igneous Rocks ◽  
Source Rocks ◽  
Primary Control ◽  
Element Abundances ◽  
Qiangtang Basin ◽  
Clastic Sediments

The geochemistry of the clastic sedimentary units of the Suonahu Formation from the QD17 well in the northern Qiangtang basin, Tibet, was studied using various chemical analyses. SiO2/Al2O3 ratios indicated that compositional maturity and recycling of the sediments were low to moderate. The total rare earth element (∑REE) contents of the clastic sediments ranged from 29.28 to 191.92 ppm. Element abundances suggest that the studied clastic sediments in the northern Qiangtang Basin were mainly sourced from felsic rocks mixed with small amounts of intermediate rocks, and that they were mostly developed in a continental setting. The REE geochemistry of the clastic sediments suggests that these different lithological samples were derived from a similar terrigenous source and that the Eu anomaly was inherited from the source rocks. The paleoclimate index (C-value) varied from 0.01 to 0.36, reflecting generally arid to semiarid conditions. In addition, Rb/Sr (about 0.41) and Sr/Cu (about 37.02) ratios support the idea that arid conditions prevailed during the deposition of the Suonahu Formation. Sr/Ba ratios (0.48–3.23) suggest a paleoenvironment with variable salinity. The covariation among this factor and paleoclimate indicators suggests that variations in climatic conditions exerted a primary control on salinity. The chemical index of alteration (CIA), A–CN–K ternary diagram, and low Th/U ratios indicate that the parent rocks of the clastic sediments experienced weak chemical weathering. Two multidimensional tectonic discrimination diagrams based on major elements show that the Suonahu Formation was deposited in a rift-related basin. The TiO2 versus Zr, La/Th versus Hf, and Co/Th versus La/Sc bivariate diagrams and multi-major elements discrimination diagram indicate that the detritus was primarily derived from felsic igneous rocks with less contribution from intermediate igneous rocks.

Petrogenesis of the Ulungur Intrusive Complex, NW China, and Implications for Crustal Generation and Reworking in Accretionary Orogens

2020 ◽  
Author(s):  
Gong-Jian Tang ◽  
Qiang Wang ◽  
Derek Wyman ◽  
Wei Dan ◽  
Lin Ma ◽  
...  
Keyword(s):  
Oceanic Crust ◽  
Lower Crust ◽  
Mineral Chemistry ◽  
Isotopic Signature ◽  
Source Rocks ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Depleted Mantle ◽  
Heavy Rare Earth Elements ◽  
Pressure Crystallization

<p>Accretionary orogens are characterized by voluminous juvenile components (recently derived from the mantle) and knowing the origin(s) of such components is vital for understanding crustal generation. Here we present field and petrological observations, along with mineral chemistry, zircon U–Pb age and Hf-O isotope data, and whole rock geochemical and Sr-Nd isotopic data for the c. 320 Ma Ulungur intrusive complex from the Central Asian Orogenic Belt. The complex consists of two different magmatic series: one is characterized by medium-K to high-K calc-alkaline gabbro to monzogranite; the other is defined by peralkaline aegirine-arfvedsonite granitoids. The calc-alkaline and peralkaline series granitoids have similar depleted mantle-like Sr-Nd-Hf isotopic compositions, but they have different zircon δ<sup>18</sup>O values: the calc-alkaline series have mantle-like δ<sup>18</sup>O values with mean compositions ranging from 5.2 ± 0.5‰ to 6.0 ± 0.9‰ (2SD), and the peralkaline granitoids have low δ<sup>18</sup>O values ranging from 3.3 ± 0.5‰ to 3.9 ± 0.4‰ (2SD). The calc-alkaline series were derived from a hydrous sub-arc mantle wedge, based on the isotope and geochemical compositions, under garnet peridotite facies conditions. This study suggests that the magmas underwent substantial differentiation, ranging from high pressure crystallization of ultramafic cumulates in the lower crust to lower pressure crystallization dominated by amphibole, plagioclase and minor biotite in the upper crust. The peralkaline series rocks are characterized by δ<sup>18</sup>O values lower than the mantle and enrichment of high field strength elements (HFSEs) and heavy rare earth elements (HREEs). They likely originated from melting of preexisting hydrothermally altered residual oceanic crust in the lower crust of the Junggar intra-oceanic arc. Early crystallization of clinopyroxene and amphibole was inhibited owing to their low melting temperature, leading to HFSEs and HREEs enrichment in residual peralkaline melts during crystallization of a feldspar-dominated mineral assemblage. Thus, the calc-alkaline and peralkaline series represent episodes of crust generation and reworking, respectively, demonstrating that the juvenile isotopic signature in accretionary orogens can be derived from diverse source rocks. Our results show that reworking of residual oceanic crust also plays an important role in continental crust formation for accretionary orogens, which has not previously been widely recognized.</p>

Precambrian rift-related magmatism and sedimentation, south Victoria Land, Antarctica

2007 ◽  
Vol 19 (4) ◽  
pp. 471-484 ◽  
Author(s):  
Y.A. Cook
Keyword(s):  
Oceanic Crust ◽  
Volcanic Activity ◽  
Igneous Rocks ◽  
Source Rocks ◽  
Main Body ◽  
Quartz Syenite ◽  
Continental Extension ◽  
Victoria Land ◽  
First Time ◽  
Marine Basin

AbstractPrecambrian continental extension is described in detail for the first time in the Victoria Land segment of the Transantarctic Mountains and is comparable with plume related intercontinental rifting of the Afar area, Africa. The Baronick Formation comprises igneous-derived conglomerate, marble and volcanic to sub-volcanic igneous layers. Volcanic and carbonate horizons were eroded in a fluvial or marine environment and provided debris for mass flow and slump deposits which formed in a marginal marine basin in the Precambrian. Clasts in these deposits include basalt, trachyte and comendite, and along with the interbedded volcanic layers of basalt, trachyte and quartz syenite, indicate proximity and contemporaneity of volcanic activity. Igneous layers and source rocks for clasts of the Baronick Formation have an enriched MORB chemistry and underwent albitization of calcic feldspar before erosion and conglomerate deposition. The Highway Suite forms a kilometre-scale body of gabbro and dolerite plugs and is interpreted as a slice of transitional continental oceanic crust. The chemistry of all igneous rocks suggests a continental rift environment and the associated sediments are consistent with such a setting. The Baronick Formation was locally intruded by sills of the Highway Suite; however, the main body of the Highway Suite was juxtaposed against the Baronick Formation during greenschist facies shearing before c. 551 Ma.

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