Neoproterozoic boninite-series rocks in South China: A depleted mantle source modified by sediment-derived melt

Zhao, Jun‐Hong; Asimow, Paul D.

doi:10.1016/j.chemgeo.2014.09.004

Cited by 67 publications

(32 citation statements)

References 107 publications

(104 reference statements)

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“…More specifically, they contain moderate SiO 2 contents (47.7–57.6 wt %), high MgO (8.5–12.6 wt %), and CaO (5.4–21.2 wt %) contents, high (Th/Nb) N ratios (3.0–4.8), low TiO 2 (0.27–0.58 wt %), Al 2 O 3 (11.1–14.4 wt %), Zr (11.6–43.8 ppm), and Y (9.01–15.1 ppm) contents, ΣREE contents of 10.0–27.4 ppm, and low Ti/V ratios (7.8–14.1). These are atypical features of back‐arc basin, and are analogous to boninites derived from an ultra‐depleted source [ Stern et al ., ; Xia et al ., ; Zhao and Asimow , ]. This sequence of mafic rocks reflects a magma source that underwent a change in composition through the combined influences of melt depletion and subduction‐related metasomatism.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, the Lanong ophiolite contains both typical OIB-type and N-MORB-type mafic rocks, the latter containing arc-type geochemical signatures that deviate from the mantle-OIB array (supporting information Figure S3c). More specifically, they contain moderate SiO 2 contents (47.7-57.6 wt %), high [Stern et al, 2012;Xia et al, 2012;Zhao and Asimow, 2014]. This sequence of mafic rocks reflects a magma source that underwent a change in composition through the combined influences of melt depletion and subduction-related metasomatism.…”

Section: Implications For Fore-arc Ophiolite Evolutionmentioning

confidence: 94%

“…However, sediments may undergo partial melting more readily than underlying crust, especially in continental margin settings, where a thick sedimentary cover occurs on the subducting slab [ Nichols et al ., ; Peacock et al ., 1994, ; Hanyu et al ., ]. Although the participation of sediment melts in the petrogenesis of some boninites has been recognized [ Xia et al ., ; Zhao and Asimow , ; Hasse et al ., 2015], direct observations of these melts in ophiolites, especially in the presence of boninite, are rare, with the exception of a plagiogranite in the Oman ophiolite, although its petrogenesis is still hotly debated [ Rollison , ; Hasse et al ., 2015].…”

Section: Introductionmentioning

confidence: 99%

“…However, sediments may undergo partial melting more readily than underlying crust, especially in continental margin settings, where a thick sedimentary cover occurs on the subducting slab [Nichols et al, 1994;Peacock et al, 1994Peacock et al, , 2005Hanyu et al, 2006]. Although the participation of sediment melts in the petrogenesis of some boninites has been recognized [Xia et al, 2012;Zhao and Asimow, 2014;Hasse et al, 2015], direct observations of these melts in Jurassic Xihu Group (J 1-2X ), the Muggar Kangri Group (J MG ), the Middle-Upper Jurassic Jienu Group (J 2-3 Jn), the Lower Cretaceous Qushenla Formation (K 2 q), and the Upper Cretaceous Jingzhushan Formation (K 2 j) ( Figure 1c). With the exception of the Qushenla Formation, the ages of the strata have been assessed on the basis of fossils or field relationships, and there is a lack of reliable U-Pb zircon ages from volcanic layers within these formations.…”

Section: Introductionmentioning

confidence: 99%

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Sediment melting during subduction initiation: Geochronological and geochemical evidence from the Darutso high‐Mg andesites within ophiolite melange, central Tibet

Zeng

Chen

et al. 2016

Geochem Geophys Geosyst

110

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In addition to fluids, the concept of sediment‐derived melts infiltrating the fore‐arc mantle during subduction initiation has been proposed based on studies of modern subduction zones and ophiolite mélange. However, outcrops that contain the products of such melts are rare, especially in conjunction with boninite. New U‐Pb zircon dating reveals that the Darutso volcanic rocks (DVRs) within ophiolitic mélange in the Beila area, central Tibet, crystallized at ∼164–162 Ma. This is the first recognition of Jurassic volcanic rocks in the middle section of the Bangong‐Nujiang Suture Zone. Geochemically, the DVRs are high‐Mg andesites with moderate SiO2 (59.03–63.62 wt %) and high MgO (3.74–6.53 wt %), Cr (up to 395 ppm), and Mg# (50.3–67.9). They also have high Th contents, (La/Sm)N ratios, and (87Sr/86Sr)i values (0.7085–0.7147); low Ba/Th, U/Th, and Sr/Y ratios; and negative values of εNd(t) (−8.7 to −9.8) and zircon εHf(t) (−7.4 to −9.9). The εNd(t) values of the DVRs overlap those of regional sediments. Detailed analyses of these geochemical characteristics indicate that the DVRs were derived from partial melting of subducted sediments and subsequent interaction with overlying mantle peridotite in a shallow and hot setting. In combination with the regional geology, in particular adjacent ophiolites that contain MORB‐like and boninite mafic lavas, these rocks collectively recorded the evolution of a fore‐arc setting during the initiation of the northward subduction of the south branch of the Bangong‐Nujiang Ocean. Therefore, the results provide direct evidence for sediment melting during subduction initiation and constrain the Jurassic tectonic evolution of the Lhasa terrane.

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Section: Discussionmentioning

confidence: 99%

Section: Implications For Fore-arc Ophiolite Evolutionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

“…However, sediments may undergo partial melting more readily than underlying crust, especially in continental margin settings, where a thick sedimentary cover occurs on the subducting slab [Nichols et al, 1994;Peacock et al, 1994Peacock et al, , 2005Hanyu et al, 2006]. Although the participation of sediment melts in the petrogenesis of some boninites has been recognized [Xia et al, 2012;Zhao and Asimow, 2014;Hasse et al, 2015], direct observations of these melts in Jurassic Xihu Group (J 1-2X ), the Muggar Kangri Group (J MG ), the Middle-Upper Jurassic Jienu Group (J 2-3 Jn), the Lower Cretaceous Qushenla Formation (K 2 q), and the Upper Cretaceous Jingzhushan Formation (K 2 j) ( Figure 1c). With the exception of the Qushenla Formation, the ages of the strata have been assessed on the basis of fossils or field relationships, and there is a lack of reliable U-Pb zircon ages from volcanic layers within these formations.…”

Section: Introductionmentioning

confidence: 99%

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Sediment melting during subduction initiation: Geochronological and geochemical evidence from the Darutso high‐Mg andesites within ophiolite melange, central Tibet

Zeng

Chen

et al. 2016

Geochem Geophys Geosyst

110

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“…4). Due to the lack of comprehensive geochemical data for Oman boninites, we cannot assess this further, but sedimentary melts have been suggested to contribute to boninite source mantle in the Cretaceous Troodos ophiolite (Cyprus) (König et al, 2010), in the Ordovician Betts Cove ophiolite (Canada) (Bédard, 1999), and in the Neoproterozoic of southern China (Zhao and Asimow, 2014). We suggest that hydrous sedimentary melts formed from the subducting plate beneath the Oman ophiolite, and these melts intruded both the cold shallow part and the hotter interior of the mantle wedge, yielding the incompatible element signature of boninite magmas (Fig.…”

Section: Implications For Sediment Recycling In Subduction Zonesmentioning

confidence: 98%

Melts of sediments in the mantle wedge of the Oman ophiolite

Haase

Freund

Koepke

et al. 2015

Geology

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The rocks in the crustal section of the Oman ophiolite show an increasing input of a subduction component with time, most likely reflecting the generation of the ophiolite above a subducting slab. Field relations, new geochemical data, and Nd-Hf isotope data for felsic to mafic intrusive rocks in the mantle harzburgite from the Haylayn block in the Oman ophiolite suggest late magmatic events in a mantle wedge shortly before obduction of the ophiolite. Incompatible element contents and low e Nd and e Hf of the felsic rocks exclude differentiation from mafic magmas, but are consistent with an origin by partial melting of pelagic sediments similar to leucogranites in continental collision zones. These melts apparently mixed with mafic magmas resembling enriched late-stage lavas from the ophiolite. The leucogranitic intrusions into the mantle wedge confirm the transfer of melts of sediments from the subducted plate into the mantle at subduction zones. We suggest that the enrichment of Rb, K, and Pb observed in the Oman boninites is caused by addition of melts of sediments similar to those from the Haylayn block to the boninite source in the mantle wedge.

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Geochronology and geochemistry of basalts from the Yingchuan Formation, eastern Jiangnan Orogen: Implications for the Neoproterozoic tectonic evolution of the South China Block

Chen

Wang

et al. 2023

Geological Journal

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The Neoproterozoic magmatism along the Jiangnan Orogen preserves significant information for understanding the tectonic evolution of the South China Block (SCB). We conducted a systematic zircon U–Pb geochronological and whole‐rock geochemical study on the basalts from the Yingchuan Formation in the eastern Jiangnan Orogen, SCB. The basalts yielded a weighted mean 206Pb/238U age of 817 ± 13 Ma, enriched in Rb, Th, U, LREE and HFSE (e.g., Zr and Ti). The basalts have positive εNd(t) (+1.9 to +2.1) and high (87Sr/86Sr)i (0.69853–0.70737), indicating a slightly depleted mantle source. The high La/Nb (2.14–2.35) and La/Ta (28.6–33.3) ratios indicate a lithospheric mantle source for the basalts. Their high Ba/Yb (7.85–44.3) and Th/Yb (0.59–0.74) ratios and high absolute Nb contents (7.64–11.6 ug/g) indicate that the lithospheric mantle source has been metasomatized by melts and fluids derived from a subducted slab. The basalts are characterized by (La/Yb) N ratios (3.0–3.5) and Sm/Nd ratios (0.24–0.26), comparable to intra‐continental back arc basin basalts (BABBs). Their Ta/Yb (0.14–0.16) and Th/Yb (0.59–0.74) ratios are similar to those of Okinawa Trough basalts and contemporary mafic rocks formed in the back‐arc basin in the Jiangnan Orogen. Combined with their source features, we propose that the basalts were formed in a back‐arc basin setting. The identification of BABBs from the Yingchuan Formation shows that there were Neoproterozoic back‐arc basins in the south‐eastern Yangtze Block, indicating that the final assembly between the Yangtze and Cathaysia blocks did not occur before ca. 817 Ma.

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Neoproterozoic boninite-series rocks in South China: A depleted mantle source modified by sediment-derived melt

Cited by 67 publications

References 107 publications

Sediment melting during subduction initiation: Geochronological and geochemical evidence from the Darutso high‐Mg andesites within ophiolite melange, central Tibet

Sediment melting during subduction initiation: Geochronological and geochemical evidence from the Darutso high‐Mg andesites within ophiolite melange, central Tibet

Melts of sediments in the mantle wedge of the Oman ophiolite

Geochronology and geochemistry of basalts from the Yingchuan Formation, eastern Jiangnan Orogen: Implications for the Neoproterozoic tectonic evolution of the South China Block

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