Prolonged post-rift magmatism on highly extended crust of divergent continental margins (Baiyun Sag, South China Sea)

Zhao, Fang; Alves, Tiago Marcos; Wu, Shiguo; Li, Wei; Huuse, Mads; Mi, Lijun; Sun, Qiliang; Ma, Benjun

doi:10.1016/j.epsl.2016.04.001

Cited by 134 publications

(139 citation statements)

References 40 publications

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“…Furthermore, the ages of dredged basaltic rock samples (~22–21 Ma) [ Wang et al ., ] indicate that extensive volcanism simultaneously erupted during the seafloor spreading. The volcanic activity timing was further constrained by the well BY7‐1 data, which showed two episodes of volcanism at ~35.5 Ma and ~17.6 Ma [ Zhao et al ., ]. As a corollary, we consider that the HVL in the COT was emplaced in the lower crust prior to SCS spreading and that it could not have formed after the seafloor spreading ceased [ Yan et al ., ; Wang et al ., ; Zhao et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Deep seismic structure of the northeastern South China Sea: Origin of a high‐velocity layer in the lower crust

et al. 2017

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We present a 2‐D seismic tomographic image of the crustal structure along the OBS2012 profile, which delineates the Moho morphology and magmatic features of the northeastern South China Sea margin. The image was created by forward modeling (RayInvr) and traveltime tomographic inversion (Tomo2D). Overall, the continental crust thins seaward from ~27 km to ~21 km within the continental shelf across the Zhu I Depression and Dongsha Rise, with slight local thickening beneath the Dongsha Rise accompanying the increase in the Moho depth. The Dongsha Rise is also characterized by ~4–7 km thick high‐velocity layer (HVL) (~7.0–7.6 km/s) in the lower crust and exhibits a relatively high velocity (~5.5–6.4 km/s) in the upper crust with a velocity gradient lower than those of the Zhu I Depression and Tainan Basin. Across the continental slope and continent‐ocean transition (COT), which contain the Tainan Basin, the crust sharply thins from 20 km to 10 km seaward and a ~2–3 km thick HVL is imaged in the lower crust. We observed that volcanoes are located only within the COT, but none exist in the continental shelf; the Dongsha Rise exhibits a high magnetic anomaly zone and different geochemical characteristics from the COT. Based on those observations, we conclude that the HVL underlying the COT is probably extension related resulting from the decompression melting in the Cenozoic, whereas the HVL beneath the Dongsha Rise is probably arc related and associated with the subduction of the paleo‐Pacific plate. These findings are inconsistent with those of some previous studies.

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Section: Discussionmentioning

confidence: 99%

Deep seismic structure of the northeastern South China Sea: Origin of a high‐velocity layer in the lower crust

et al. 2017

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“…We use borehole data (well loggings, core cuttings, micropaleontology) from BY7-1 to constrain the lithology and age of the volcano-bearing succession and, thus, the age of volcano emplacement (Ma et al, 2018;Qin, 2000;Zhao et al, 2016) (Figure 2). 530 km 2 , in water depths of ca.…”

Section: Methodsmentioning

confidence: 99%

“…500-1,200 m, and acquired in 2010 by a 3,000 m long streamer with 240 channels. Parts of the well loggings are also used in Qin (1996Qin ( , 2000 and Zhao et al (2016). The data are zero-phase processed and displayed with SEG (Society of Exploration Geophysicists) normal polarity, whereby a downward increase in acoustic impedance corresponds to a positive reflection (red on displayed seismic profiles).…”

Section: Methodsmentioning

confidence: 99%

Deeply buried ancient volcanoes control hydrocarbon migration in the South China Sea

et al. 2019

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Seismic reflection data image now‐buried and inactive volcanoes, both onshore and along the submarine portions of continental margins. However, the impact that these volcanoes have on later, post‐eruption fluid flow events (e.g., hydrocarbon migration and accumulation) is poorly understood. Determining how buried volcanoes and their underlying plumbing systems influence subsurface fluid or gas flow, or form traps for hydrocarbon accumulations, is critical to de‐risk hydrocarbon exploration and production. Here, we focus on evaluating how buried volcanoes affect the bulk permeability of hydrocarbon seals, and channel and focus hydrocarbons. We use high‐resolution 3D seismic reflection and borehole data from the northern South China Sea to show how ca. <10 km wide, ca. <590 m high Miocene volcanoes, buried several kilometres (ca. 1.9 km) below the seabed and fed by a sub‐volcanic plumbing system that exploited rift‐related faults: (i) acted as long‐lived migration pathways, and perhaps reservoirs, for hydrocarbons generated from even more deeply buried (ca. 8–10 km) source rocks; and (ii) instigated differential compaction and doming of the overburden during subsequent burial, producing extensional faults that breached regional seal rocks. Considering that volcanism and related deformation are both common on many magma‐rich passive margins, the interplay between the magmatic products and hydrocarbon migration documented here may be more common than currently thought. Our results demonstrate that now‐buried and inactive volcanoes can locally degrade hydrocarbon reservoir seals and control the migration of hydrocarbon‐rich fluids and gas. These fluids and gases can migrate into and be stored in shallower reservoirs, where they may then represent geohazards to drilling and impact slope stability.

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“…Neritic, deltaic, and nearshore deposits were well developed within syn-rift and transition supersequences, whereas deep-water sedimentary systems became widely developed within post-rift supersequences, in response to a prominent shelf-slope-basin physiography (Zhu et al, 2010;Franke et al, 2011;Franke, 2013;Zhao et al, 2016). Sandy turbidites in the transition and post-rift supersequences are the focus of the present case study.…”

Section: Geological and Oceanographic Settingsmentioning

confidence: 97%

“…Accordingly, the basin infill of the Pearl River Mouth Basin can be divided into three main supersequences, namely a syn-rift supersequence from Paleocene to early Oligocene, a transition supersequence of late Oligocene, and a post-rift supersequence from early Miocene to Quanternary (e.g., Gong et al, 2013;Zhao et al, 2016). Neritic, deltaic, and nearshore deposits were well developed within syn-rift and transition supersequences, whereas deep-water sedimentary systems became widely developed within post-rift supersequences, in response to a prominent shelf-slope-basin physiography (Zhu et al, 2010;Franke et al, 2011;Franke, 2013;Zhao et al, 2016).…”

Section: Geological and Oceanographic Settingsmentioning

confidence: 99%

Middle Miocene reworked turbidites in the Baiyun Sag of the Pearl River Mouth Basin, northern South China Sea margin: Processes, genesis, and implications

Gong

Wang

Zheng

et al. 2016

Journal of Asian Earth Sciences

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Prolonged post-rift magmatism on highly extended crust of divergent continental margins (Baiyun Sag, South China Sea)

Cited by 134 publications

References 40 publications

Deep seismic structure of the northeastern South China Sea: Origin of a high‐velocity layer in the lower crust

Deep seismic structure of the northeastern South China Sea: Origin of a high‐velocity layer in the lower crust

Deeply buried ancient volcanoes control hydrocarbon migration in the South China Sea

Middle Miocene reworked turbidites in the Baiyun Sag of the Pearl River Mouth Basin, northern South China Sea margin: Processes, genesis, and implications

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