Petrogenesis of Late Cenozoic basaltic rocks from southern Vietnam

An, A-Rim; Choi, Sung Hi; Yu, Yongjae; Lee, Der-Chuen

doi:10.1016/j.lithos.2016.12.008

Cited by 71 publications

(126 citation statements)

References 115 publications

Supporting

Mentioning

103

Contrasting

Unclassified

Order By: Relevance

“…The retrograded eclogites plot in the field of within‐plate basalts (WPT)–E‐MORB in the Hf/3–Th–Ta (Figure d). The Hf/Yb values (1.65–2.28) are slightly lower than those of OIB (>2.0; Frey et al., ; Sun & McDonough, ), suggesting relatively shallower melt sources than that of OIB (An, Choi, Yu, & Lee, ). All of the studied samples fall very close to, but under, the spinel‐garnet lherzolite line in the La/Sm versus Sm/Yb diagram, with a 10–20% degree of partial melting (Figure e).…”

Section: Discussionmentioning

confidence: 97%

Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Wang

Liu

Li³

et al. 2018

Journal Metamorphic Geology

View full text Add to dashboard Cite

The Changning–Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau, is considered as the main suture zone marking the closure of the Palaeo‐Tethys Ocean between the Indochina and Sibumasu blocks. Here, we investigate the recently discovered retrograded eclogites from this suture zone in terms of their petrological, geochemical and geochronological features, with the aim of constraining the metamorphic evolution and protolith signature. Two types of metabasites are identified: retrograded eclogites and mafic schists. The igneous precursors of the retrograded eclogites exhibit rare earth element distribution patterns and trace element abundance similar to those of ocean island basalts, and are inferred to have been derived from a basaltic seamount in an intra‐oceanic tectonic setting. In contrast, the mafic schists show geochemical affinity to arc‐related volcanics with the enrichment of Rb, Th and U, and depletion of Nb, Ta, Zr, Hf and Ti, and their protoliths possibly formed at an active continental margin tectonic setting. Retrograded eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, white mica, lawsonite and rutile, and underwent five‐stage metamorphic evolution, including pre‐peak prograde stage (M1) at 18–19 kbar and 400–420°C, peak lawsonite‐eclogite facies (M2) at 24–26 kbar and 520–530°C, post‐peak epidote–eclogite facies decompression stage (M3) at 13–18 kbar and 530–560°C, subsequent amphibolite facies retrogressive stage (M4) at 8–10 kbar and 530–600°C, and late greenschist facies cooling stage (M5) at 5–8 kbar and 480–490°C. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb spot analyses of zircon show two distinct age groups. The magmatic zircon from both the retrograded eclogite and mafic schist yielded protolith ages of 451 ± 3 Ma, which is consistent with the ages of Early Palaeozoic ophiolitic complexes and ocean island sequences in the CMOB reported in previous studies. In contrast, metamorphic zircon from the retrograded eclogite samples yielded consistent Triassic metamorphic ages of 246 ± 2 and 245 ± 2 Ma, which can be interpreted as the timing of closure of the Palaeo‐Tethys Ocean. The compatible peak metamorphic mineral assemblages, P–T–t paths and metamorphic ages, as well as the similar protolith signatures for the eclogites in the CMOB and Longmu Co–Shuanghu suture (LCSS) suggest that the two belts formed part of a cold oceanic subduction system in the Triassic. The main suture zone of the Palaeo‐Tethyan domain extends at least 1,500 km in length from the CMOB to the LCSS in the Tibetan Plateau. The identification of lawsonite‐bearing retrograded eclogites in the CMOB provides important insights into the tectonic framework and complex geological evolution of the Palaeo‐Tethys.

show abstract

Section: Discussionmentioning

confidence: 97%

Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Wang

Liu

Li³

et al. 2018

Journal Metamorphic Geology

View full text Add to dashboard Cite

show abstract

“…Basalts in Hainan Island, Leizhou Peninsula, and SE Vietnam are mainly alkali ocean island basalts (OIBs) with EM2‐type (enriched mantle end‐member from an enriched mantle source (e.g., Zou & Fan, ). The OIB‐type intraplate volcanism with an EM2‐like enriched mantle source end‐member could have been originated from the Hainan plume (An et al, ; Xu et al, ). 40 Ar/ 39 Ar dating indicates that the Cenozoic volcanism in Hainan Island and Leizhou Peninsula started in the late Miocene (∼13 Ma; Wang et al, ).…”

Section: Mechanism Of Postspreading Volcanism In the South China Seamentioning

confidence: 99%

“…40 Ar/ 39 Ar dating indicates that the Cenozoic volcanism in Hainan Island and Leizhou Peninsula started in the late Miocene (∼13 Ma; Wang et al, ). In south Vietnam, 40 Ar/ 39 Ar dating on 41 samples show that the first stage of igneous activity is from the very beginning of middle Miocene (16 Ma; Lee et al, ), began ∼17 Ma ago and continues until today, mostly along the offshore margin (Hoàng et al, ), but is restricted in another study to an age range from 13.8 to 4.1 Myr (An et al, ). Thus, these basaltic samples are all younger than 17 Myr, suggesting that the influence of the Hainan plume might have started ∼17 Ma ago.…”

Section: Mechanism Of Postspreading Volcanism In the South China Seamentioning

confidence: 99%

Postseafloor Spreading Volcanism in the Central East South China Sea and Its Formation Through an Extremely Thin Oceanic Crust

Zhao

Sibuet

et al. 2018

Geochem Geophys Geosyst

View full text Add to dashboard Cite

P wave velocity models were obtained by forward and inverse modeling from 38 ocean bottom seismometers deployed in the central East subbasin of the South China Sea (SCS). Four types of crust have been defined: (a) thin oceanic crust (<5 km), (b) typical oceanic crust (5–6 km), (c) thick oceanic crust hosting postspreading volcanoes (>6 km) with significant intrusive roots, and (d) thick oceanic crust with enhanced spreading features (>6 km) but without significant roots. Within the central East subbasin, the thin oceanic crust, only identified inside an 80 km wide zone, is located within an overall 150 km wide domain characterized by N055° seafloor spreading trends. The postspreading volcanoes were formed during a N‐S tensional episode around 6–10 Ma, several millions of years after seafloor spreading ceased in the SCS. Seafloor spreading (N055° and N145°) and postspreading (N000° and N090°) features are observed in the morphology of some of these volcanoes. The rupture of the brittle thin oceanic crust was focused where the crust was the weakest, i.e., at the intersection of the extinct spreading ridge with former fracture zones. From geological and geophysical arguments, we suggest that the postspreading volcanism might have been influenced by the Hainan plume activity through a buoyancy‐driven partial melting mechanism.

show abstract

“…It seems that the basaltic rocks from Well CK-2 could be considered to have formed in an intraplate tectonic setting environment. Recently, more and more geophysical and geochemical evidence indicates the existence of the mantle plume [9,10,13,14,[82][83][84][85][86]. A virtually vertical low velocity cylinder extends beneath the Hainan Island and the SCS, from shallow depths to the 1900 km discontinuity [82].…”

Section: Tectonic Setting Discriminationmentioning

confidence: 99%

“…As a petroprobe for most geological processes, igneous activity plays an important role in the study of petrology and tectonics. However, previous studies mainly focus on the petrology and geochemistry of the Cenozoic basalts [3,[7][8][9][10][11][12][13][14][15]. There are few studies on the rock-forming minerals of basalt from the SCS and its adjacent areas [2,16,17], which seriously restricts research on the magma evolution and physicochemical conditions of Cenozoic basic rocks in the SCS and its adjacent areas.…”

Section: Introductionmentioning

confidence: 99%

LA-ICP-MS Analysis of Clinopyroxenes in Basaltic Pyroclastic Rocks from the Xisha Islands, Northwestern South China Sea

Zhang

Qian

2018

Minerals

View full text Add to dashboard Cite

Cenozoic volcanic rocks were recently discovered during full-coring kilometer-scale major scientific drilling in the Xisha Islands, northwestern South China Sea. A systematic mineralogical study of these samples was performed for this paper. The results show that the volcanic rock samples are basaltic pyroclastic. The major elements demonstrate that the clinopyroxenes are diopside and fassaite, which contain high Al 2 O 3 (5.33-11.2 wt. %), TiO 2 (2.13-4.78 wt. %) and wt. %). Clinopyroxenes have high REE abundances (104-215 ppm) and are strongly enriched in LREE (LREE/HREE = 3.56-5.14, La/Yb N = 2.61-5.1). Large-ion lithophile elements show depleted characteristics. Nb/Ta shows obvious fractionation features: Nb is lightly enriched, relative to primitive mantle, but Ta is heavily depleted, relative to primitive mantle. The parental magma of the basaltic pyroclastic rocks belongs to a silica-undersaturated alkaline series, characterized by a high temperature, low pressure, and low oxygen fugacity. The Al IV content increases with decreasing Si concentration. The Si-unsaturated state causes Si-Al isomorphic replacement during the formation of clinopyroxene. The electric charge imbalance caused by the replacement of Si by Al is mainly compensated by Fe 3+ . The clinopyroxene discrimination diagrams show that the parental magma formed in an intraplate tectonic setting environment.The mineral composition of igneous rocks depends on the chemical composition and crystallization environment of magma. Changes in mineral composition and structure are direct evidence of changes in the diagenetic environment and material composition. Therefore, the characteristics of mineral composition can be used to explore mineral petrogenesis and the magma evolution mechanism [18]. Clinopyroxene is one of the main rock-forming minerals of mafic-ultramafic rocks and plays a major role in the generation and subsequent differentiation of magma [16,[19][20][21][22][23][24]. Clinopyroxene composition mainly depends on primary magma characteristics, the crystallization environment, and the tectonic setting of magmatism [25][26][27][28][29][30][31][32]. Relative to other minerals in mafic-ultramafic rocks, clinopyroxene is considered to be the main carrier for most trace elements and holds a unique further record of magma history [33,34]. The mineral chemistry of relict clinopyroxene in igneous rocks can reflect the characteristics of the primary magma well and has been widely used to study the nature of the original magma and complicated processes that have affected the lithospheric mantle [21,[35][36][37][38][39][40][41][42]. Furthermore, clinopyroxenes in altered basalts are of interest, because they often survive in a relatively pristine form, after the matrix and other minerals have been converted to secondary minerals. The major-and minor-element geochemistry of clinopyroxene is varied and provides a filtered view of the composition of the magma from which the clinopyroxene crystallized, lending it the potential to provide insight into t...

show abstract

Petrogenesis of Late Cenozoic basaltic rocks from southern Vietnam

Cited by 71 publications

References 115 publications

Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Postseafloor Spreading Volcanism in the Central East South China Sea and Its Formation Through an Extremely Thin Oceanic Crust

LA-ICP-MS Analysis of Clinopyroxenes in Basaltic Pyroclastic Rocks from the Xisha Islands, Northwestern South China Sea

Contact Info

Product

Resources

About