scholarly journals Geochronology and Geochemistry of the Zengudi and Tuobake Granite Porphyries in the Sanjiang Region, SW China: Petrogenesis and Tectonic Significance

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 404
Author(s):  
Mao-Jun Tian ◽  
Huan Li ◽  
Landry Soh Tamehe ◽  
Zhen Xi
Keyword(s):  
Basaltic Magma ◽  
Volcanic Rocks ◽  
Isotopic Data ◽  
Tectonic Significance ◽  
Gondwana Margin ◽  
Granite Porphyries ◽  
Tethys Ocean ◽  
T Values ◽  
Crust Shortening ◽  
Representative Samples

The boundary between the Gondwana and Yangtze plate is still controversial. In southwest China, the Sanjiang region marks the collision zone which accreted several blocks coming from the northern Gondwana margin. In this region, subduction of the Paleo-Tethys Ocean and associated continental blocks during the Triassic Period led to the formation of an N–S trending complex involving intrusive and volcanic rocks. The intrusive rocks are important for constraining the evolution of the Paleo-Tethyan in southwestern China. This study presents new geochronological, geochemical, and Sr-Nd-Hf isotopic data of granite porphyries from northern Lancangjiang, in order to discuss the origin of these granites and their tectonic significance. Representative samples of the Zengudi and the Tuobake granite porphyries from the Yezhi area yielded weighted mean 206Pb/238U ages of 247–254 Ma and 246 Ma, respectively. The Zengudi granite porphyries display zircon ԐHf(t) values of −12.94 to −2.63, ԐNd(t) values of −14.5 to −9.35, and initial 87Sr/86Sr ratios of 0.708 to 0.716. The Tuobake granite porphyries have zircon ԐHf(t) values of −14.06 to −6.55, ԐNd(t) values of −10.9 to −9.41, and initial 87Sr/86Sr ratios of 0.716 to 0.731. Both the Zengudi and Tuobake granite porphyries exhibit strongly peraluminous signatures with high A/CNK nAl2O3/(K2O + Na2O + K2O) ratios (1.07–1.86 and 0.83–1.33, respectively). These granites are enriched in Rb and Th, and depleted in Ti, Nb, Ta, Sr, and P, with negative Eu anomalies (Eu/Eu* < 0.61). These geochemical and isotopic data indicate that the primary magma of the granite porphyries originated from partial melting of ancient continental crust as a result of basaltic magma underplating and underwent fractionation crystallization during their emplacement. We propose that the Triassic subduction of the Paleo-Tethys Ocean led to crust shortening and thickening in the Sanjiang region, while the northern Lancangjiang area was involved in the continental collision after the subduction of the Paleo-Tethys Ocean before 254 Ma.

Cenozoic high Sr/Y volcanic rocks in the Qiangtang terrane, northern Tibet: geochemical and isotopic evidence for the origin of delaminated lower continental melts

2008 ◽  
Vol 145 (4) ◽  
pp. 463-474 ◽  
Author(s):  
SHEN LIU ◽  
RUI-ZHONG HU ◽  
CAI-XIA FENG ◽  
HAI-BO ZOU ◽  
CAI LI ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Volcanic Rocks ◽  
Mantle Peridotite ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Slab Melting ◽  
Northern Tibet ◽  
High K ◽  
T Values ◽  
Qiangtang Terrane

AbstractGeochemical and Sr–Nd–Pb isotopic data are presented for volcanic rocks from Zougouyouchaco (30.5 Ma) and Dogai Coring (39.7 Ma) of the southern and middle Qiangtang block in northern Tibet. The volcanic rocks are high-K calc-alkaline trachyandesites and dacites, with SiO2 contents ranging from 58.5 to 67.1 wt % The rocks are enriched in light REE (LREE) and contain high Sr (649 to 986 ppm) and relatively low Yb (0.8 to 1.2 ppm) and Y (9.5 to 16.6 ppm) contents, resulting in high La/Yb (29–58) and Sr/Y (43–92) ratios, as well as relatively high MgO contents and Mg no., similar to the compositions of adakites formed by slab melting in subduction zones. However, the adakitic rocks in the Qiangtang block are characterized by relatively low εNd(t) values (−3.8 to −5.0) and highly radiogenic Sr ((87Sr/86Sr)i=0.706–0.708), which are inconsistent with an origin by slab melting. The geochemistry and tectonics indicate that the adakitic volcanic rocks were most likely derived from partial melting of delaminated lower continental crust. As the pristine adakitic melts rose, they interacted with the surrounding mantle peridotite, elevating their MgO values and Mg numbers.

Supplemental Material: Tectonic origin of the Bainaimiao arc terrane in the southern Central Asian orogenic belt: Evidence from sedimentary and magmatic rocks in the Damao region

2020 ◽  
Author(s):  
Hai Zhou ◽  
Guochun Zhao ◽  
et al.
Keyword(s):  
Volcanic Rocks ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Isotopic Data ◽  
Magmatic Rocks ◽  
Central Asian ◽  
Southern Central ◽  
Samples And Sampling ◽  
Tectonic Origin

Table S1: Summary of the samples and sampling positions in this study (sampling sites are marked in Fig. 3); Table S2: U-Pb age data for zircons of (meta-)sedimentary and volcanic rocks in this study; Table S3: Lu-Hf isotopic data for zircons of (meta-)sedimentary and volcanic rocks in this study.

Nd isotopic characteristics of metamorphic and plutonic rocks of the Coast Mountains near Prince Rupert, British Columbia

1998 ◽  
Vol 35 (5) ◽  
pp. 556-561 ◽  
Author(s):  
P J Patchett ◽  
G E Gehrels ◽  
C E Isachsen
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Published Data ◽  
Isotopic Data ◽  
Crustal Component ◽  
Coast Mountains ◽  
Crustal Rocks ◽  
Metasedimentary Rocks ◽  
Plutonic Rocks

Nd isotopic data are presented for a suite of metamorphic and plutonic rocks from a traverse across the Coast Mountains between Terrace and Prince Rupert, British Columbia, and for three contrasting batholiths in the Omineca Belt of southern Yukon. A presumed metamorphic equivalent of Jurassic volcanic rocks of the Stikine terrane gives epsilon Nd = +6, and a number of other metaigneous and metasedimentary rocks in the core of the Coast Mountains give epsilon Nd values from +3 to +7. A single metasedimentary rock approximately 3 km east of the Work Channel shear zone gives a epsilon Nd value of -9. Coast Belt plutons in the traverse yield epsilon Nd from -1 to +2. The Omineca Belt plutons give epsilon Nd from -10 to -17. All results are consistent with published data in demonstrating that (i) juvenile origins for both igneous and metamorphic rocks are common in the Coast Belt; (ii) representatives of a continental-margin sedimentary sequence with Precambrian crustal Nd are tectonically interleaved in the Coast Mountains; (iii) Coast Mountains plutons can be interpreted as derived from a blend of metamorphic rocks like those seen at the surface, or as arc-type melts contaminated with the older crustal component; and (iv) Omineca Belt plutons are dominated by remelted Precambrian crustal rocks.

Ultramafic mantle xenoliths in the Late Cenozoic Volcanic rocks of the Antarctic Peninsula and Jones Mountains, West Antarctica

2021 ◽  
pp. M56-2019-44
Author(s):  
Philip T. Leat ◽  
Aidan J. Ross ◽  
Sally A. Gibson
Keyword(s):  
Antarctic Peninsula ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Incompatible Trace Element ◽  
Mantle Xenoliths ◽  
South Shetland Islands ◽  
West Antarctica ◽  
Gondwana Margin

AbstractAbundant mantle-derived ultramafic xenoliths occur in Cenozoic (7.7-1.5 Ma) mafic alkaline volcanic rocks along the former active margin of West Antarctica, that extends from the northern Antarctic Peninsula to Jones Mountains. The xenoliths are restricted to post-subduction volcanic rocks that were emplaced in fore-arc or back-arc positions relative to the Mesozoic-Cenozoic Antarctic Peninsula volcanic arc. The xenoliths are spinel-bearing, include harzburgites, lherzolites, wehrlites and pyroxenites, and provide the only direct evidence of the composition of the lithospheric mantle underlying most of the margin. The harzburgites may be residues of melt extraction from the upper mantle (in a mid-ocean ridge type setting), that accreted to form oceanic lithosphere, which was then subsequently tectonically emplaced along the active Gondwana margin. An exposed highly-depleted dunite-serpentinite upper mantle complex on Gibbs Island, South Shetland Islands, supports this interpretation. In contrast, pyroxenites, wehrlites and lherzolites reflect percolation of mafic alkaline melts through the lithospheric mantle. Volatile and incompatible trace element compositions imply that these interacting melts were related to the post-subduction magmatism which hosts the xenoliths. The scattered distribution of such magmatism and the history of accretion suggest that the dominant composition of sub-Antarctic Peninsula lithospheric mantle is likely to be harzburgitic.

The Duck Pond and Boundary Cu–Zn deposits, Newfoundland: new insights into the ages of host rocks and the timing of VHMS mineralization

2010 ◽  
Vol 47 (12) ◽  
pp. 1481-1506 ◽  
Author(s):  
Vicki McNicoll ◽  
Gerry Squires ◽  
Andrew Kerr ◽  
Paul Moore
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Isotopic Data ◽  
Sulphide Ores ◽  
Intrusive Rocks ◽  
Felsic Volcanic ◽  
Host Rocks ◽  
Felsic Volcanic Rocks

The Duck Pond Cu–Zn–Pb–Ag–Au deposit in Newfoundland is hosted by volcanic rocks of the Cambrian Tally Pond group in the Victoria Lake supergroup. In conjunction with the nearby Boundary deposit, it contains 4.1 million tonnes of ore at 3.3% Cu, 5.7% Zn, 0.9% Pb, 59 g/t Ag, and 0.9 g/t Au. The deposits are hosted by altered felsic flows, tuffs, and volcaniclastic sedimentary rocks, and the sulphide ores formed in part by pervasive replacement of unconsolidated host rocks. U–Pb geochronological studies confirm a long-suspected correlation between the Duck Pond and Boundary deposits, which appear to be structurally displaced portions of a much larger mineralizing system developed at 509 ± 3 Ma. Altered aphyric flows in the immediate footwall of the Duck Pond deposit contained no zircon for dating, but footwall stringer-style and disseminated mineralization affects rocks as old as 514 ± 3 Ma at greater depths below the ore sequence. Unaltered mafic to felsic volcanic rocks that occur structurally above the orebodies were dated at 514 ± 2 Ma, and hypabyssal intrusive rocks that cut these were dated at 512 ± 2 Ma. Some felsic samples contain inherited (xenocrystic) zircons with ages of ca. 563 Ma. In conjunction with Sm–Nd isotopic data, these results suggest that the Tally Pond group was developed upon older continental or thickened arc crust, rather than in the ensimatic (oceanic) setting suggested by previous studies.

Petrogenesis of Early Cambrian granitoids in the western Kunlun orogenic belt, Northwest Tibet: Insight into early stage subduction of the Proto-Tethys Ocean

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2221-2240 ◽  
Author(s):  
Jiyuan Yin ◽  
Wenjiao Xiao ◽  
Min Sun ◽  
Wen Chen ◽  
Chao Yuan ◽  
...  
Keyword(s):  
Partial Melting ◽  
Orogenic Belt ◽  
Early Cambrian ◽  
The South ◽  
The West ◽  
Juvenile Material ◽  
Tethys Ocean ◽  
West Kunlun ◽  
T Values ◽  
Oceanic Slab

Abstract The west Kunlun orogenic belt, located on the northwest margin of the Tibetan Plateau, represents a crucial tectonic junction between the central Asia and Tethys domains. Its evolution was closely related to the Paleozoic subduction and closure of the Proto-Tethys Ocean, which was formed by the breakup of the Rodinia supercontinent following the Neoproterozoic. However, the early evolution of Proto-Tethys oceanic subduction (e.g., subduction initiation timing, polarity, and process) remains controversial. The source of the Early Cambrian granitoids is also unclear. To explore these questions, four Cambrian plutons (i.e., two Tianshuihai monzogranites and south Kunlun diorite and monzogranite) were chosen for geochronological and geochemical studies. Zircon U-Pb dating reveals that these plutons formed at ca. 533–513 Ma and thus represent the oldest arc-related magmatism in the west Kunlun orogenic belt. The Tianshuihai monzogranites have positive εNd(t) values (+0.76 to +1.34) and zircon εHf(t) values of +0.25 to +6.42, with low δ18Ozrn values of +5.11‰ to +7.38‰, suggesting that their source includes juvenile material. These rocks are weakly peraluminous and have relatively old Hf model ages of 1.09–1.48 Ga. Mass balance calculations show that the Tianshuihai monzogranites were derived from partial melting of Mesoproterozoic meta-igneous rocks with the addition of 22% of juvenile material. The south Kunlun monzogranites in this study are weakly peraluminous, and their lowest εNd(t) values are –9.24 to –9.27 and zircon εHf(t) values are –7.80 to –11.2. The oldest Hf model ages are 1.97–2.18 Ga, and the highest zircon δ18Ozrn values are +8.11 to +9.73‰. Their isotopic compositions are different from those of the magmas derived from partial melting of just Paleoproterozoic and Mesoproterozoic basement rocks but can be produced by a mixing source of 32% meta-igneous rock and 68% meta-sedimentary rock. The south Kunlun diorites are characterized by high Sr contents and relatively high Sr/Y (52–63) ratios but low Y, Yb, Cr, and Ni contents, like those of the thickened continental crust-derived adakites. Their Sr-Nd–Hf-O isotopic compositions indicate that their parental magma was derived from a Mesoproterozoic metaigneous basement in the garnet stability field. Based on the newly identified, oldest island arc magmatic records in the west Kunlun orogenic belt, the subduction initiation of the Proto-Tethys oceanic slab must have occurred prior to the Early Cambrian (&gt;533 Ma). Our results, with previously published data, show that the west Kunlun orogenic belt was in an extensional setting during the Early Cambrian and that the magmatism migrated northeastward along the axis of the south Kunlun terrane between 533 Ma and 513 Ma. Therefore, considering the spatial and temporal distribution and petrogenesis of the Early–Middle Cambrian plutons in the west Kunlun orogenic belt, we propose that the Early Cambrian magmatism was most plausibly triggered by asthenospheric upwelling in response to the rollback of southward-subducted Proto-Tethys oceanic slab.

Early Devonian (415–400 Ma) A-type granitoids and diabases in the Wuyishan, eastern Cathaysia: A signal of crustal extension coeval with the separation of South China from Gondwana

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2295-2317 ◽  
Author(s):  
Yujia Xin ◽  
Jianhua Li ◽  
Lothar Ratschbacher ◽  
Guochun Zhao ◽  
Yueqiao Zhang ◽  
...  
Keyword(s):  
Partial Melting ◽  
South China ◽  
Crustal Extension ◽  
Eastern Asia ◽  
The South ◽  
Early Devonian ◽  
Enriched Mantle ◽  
Key Issues ◽  
Tethys Ocean ◽  
T Values

Abstract The evolution of the South China continental crust and its linkage to the assembly and rifting of eastern Gondwana are key issues in the understanding of the early Paleozoic evolution of eastern Asia. We report U-Pb zircon ages and geochemical and Lu-Hf isotopic data for the South Fufang and Yingshang granitoids and the Mayuan diabases from the Wuyishan of eastern South China. The zircons yielded U-Pb ages of ca. 414–404 and ca. 409–401 Ma for the granitoids and diabases, respectively. Petrographic and geochemical features indicate that the granitoids are peraluminous A-type granites, expressed by high Ga/Al ratios and high Zr, Nb, Ce, Y, and rare earth element contents. They show negative zircon εHf(t) values (–15.4 to –5.8), consistent with the derivation from a crustal source. The granitoids likely originated from partial melting of dry granulite residues in the lower crust. The diabases show depletion in Ti, and negative correlations between FeOt and Mg#, and SiO2 and TiO2/FeOt, reflecting clinopyroxene, olivine, and Fe-Ti oxide fractionation. Their negative zircon εHf(t) values (–4.5 to –0.4) indicate an ancient enriched-mantle origin. The diabases likely originated from partial melting of a sub-continental lithospheric mantle. We interpret these A-type granitoids and diabases as post-orogenic, formed during extensional collapse of thickened crust. Their generation indicates that South China experienced crustal extension during the Early Devonian. The extension occurred coevally with global rifting that led to the separation of the continental blocks of eastern Asia from eastern Gondwana, which was associated with the Early Devonian opening of the paleo–Tethys Ocean.

scholarly journals Genesis of Volcanic Rocks in the Zijinshan Ore District, SE China: Implications for Porphyry-Epithermal Mineralization

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 200 ◽  
Author(s):  
Zheng-Zheng Feng ◽  
Zhong-Jie Bai ◽  
Hong Zhong ◽  
Wei-Guang Zhu ◽  
Shi-Ji Zheng
Keyword(s):  
Oxygen Fugacity ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Parental Magma ◽  
High Oxygen ◽  
Magma Source ◽  
High Water Content ◽  
High Oxygen Fugacity ◽  
Epithermal Mineralization ◽  
T Values

Volcanic rocks, as the extrusive counterparts of the mineralized intrusions, can provide important information on the magma source, petrogenesis, and metallogenic conditions of the coeval porphyry-epithermal system. Shanghang Basin volcanic rocks are spatially and temporally related to a series of adjacent porphyry-epithermal Cu–Au deposits, and they can be used as a window to study the related deposits. Two laser-ablation–inductively coupled plasma–mass spectrometry zircon U–Pb analyses of the volcanic rocks yield weighted mean ages of ~105 Ma, identical to the age of the coeval porphyry-epithermal mineralization. Rocks have SiO2 contents of 55.4 to 74.8 wt % and belong to the high-K to shoshonitic series, characterized by strong differentiation of light rare-earth elements (REEs) relative to heavy REEs (mean LaN/YbN = 16.88); enrichment in light REEs, Rb, Th, and U; and depletion in Nb, Ta, Zr, Hf, and Ti. The volcanic rocks display (87Sr/86Sr)i values of 0.709341 to 0.711610, εNd(t) values of −6.9 to −3.3 εHf(t) values of −3.95 to −0.30, and δ18O values of 6.07‰–6.79‰, suggesting that the parental magmas were derived from a mantle source enriched by subduction-related progress. SiO2 content shows a strong negative correlation with the contents of some major and trace elements, indicating that fractional crystallization played an important role in the generation of these rocks. A binary mixing model of Hf–O isotopes gives an estimated degree of crustal contamination of 30%. In addition, magnetite crystallized early, and the samples showed high zircon EuN/EuN* values (0.48–0.68), indicating that the parental magma had a high oxygen fugacity. The inferred suppression of plagioclase crystallization and increasing hornblende crystallization during magma evolution suggest that the magma was water rich. The high-water content and high oxygen fugacity of the magma promoted the dissolving of sulfides containing Cu and Au in the source area and contributed to the migration of ore-forming elements.

Gabbro in Wanning, Hainan Island: LA-ICP-MS Chronometry and its Geological Significance

2011 ◽  
Vol 137 ◽  
pp. 307-311
Author(s):  
Li Mei Tang
Keyword(s):  
Tectonic Setting ◽  
Research Work ◽  
Hainan Island ◽  
Major And Trace Elements ◽  
Ocean Basin ◽  
Age Dating ◽  
Icp Ms ◽  
Tethys Ocean ◽  
T Values ◽  
Made In

Gabbro is mostly the result of partly melting from mantle rock, and its formation is usually related with extension tectonic, the research work on Triassic gabbro from Hainan island has important instruction significance to its tectonic background. System chronometry and geochemistry research on hornblende gabbro in Wanning area was made in this paper, and its tectonic significance is to be discussed. The LA-ICP-MS zircon U-Pb age dating result shows that the gabbro in Wanning area was formed in 241±1.7Ma. The major and trace elements characteristic shows that the rocks belong to alkaline series, enrichment in light REE (LREE/HREE＝7.22-8.5) and LILE Rb, Th, and Sr, Ba while depleted in HFSE Nb, Ta and Zr, Hf. The Wanning gabbro exhibits a narrow range of εNd(t) values (1.59-1.76), and a broad rang 87Sr/86Sr initial ratios(0.70633-0.70964). The tectonic background of Wanning gabbro is intracontinental extensional setting, and its geochemistry characteristic declare that there was an ancient ocean basin existed, and maybe one branch of the ancient eastern Tethys ocean. The formation age and tectonic setting declare that the ancient ocean basin was disappeared at least before 241Ma.

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