Contribution of an Eastern Indochina-derived fragment to the formation of island arc systems in the Philippine Mobile Belt

2021 ◽  
Author(s):  
Lin Gong ◽  
Pete Hollings ◽  
Yu Zhang ◽  
Jing Tian ◽  
Dengfeng Li ◽  
...  
Keyword(s):  
Middle Eocene ◽  
Plate Boundary ◽  
Philippine Sea Plate ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Potential Contribution ◽  
Northern Margin ◽  
Early Oligocene ◽  
Arc Setting ◽  
T Values

The Philippine Mobile Belt is a complex plate boundary with multiple terranes in Southeast Asia, yet its early tectonic evolution is still not fully understood due to a scarcity of solid evidence. Here we report new whole rock geochemical, Sr-Nd isotopic, and zircon U-Pb-Hf isotopic data for Cretaceous-Miocene arc magmatic rocks from the Cebu and Bohol Islands, Philippine Mobile Belt. Bulk geochemical data display arc affinities with enriched large ion lithophile elements (e.g., Sr and Ba) and depleted high field strength elements (e.g., Nb, Ta, and Ti). The high positive εNd(t) (+4.6 to +9.1) values and low initial 87Sr/86Sr ratios (0.7032−0.7048) suggest that these igneous rocks were generated by partial melting of mantle wedge in an arc setting. U-Pb dating of zircons revealed Cretaceous (ca. 120−90 Ma), middle Eocene to early Oligocene (ca. 43−30 Ma), and middle Miocene (ca. 14 Ma) crystallization ages for the arc magmatism with abundant Permian-Triassic zircon xenocrysts clustering at ca. 250 Ma. The Permian-Triassic grains show dominantly negative εHf(t) values ranging from −16.2 to −6.6, which are similar to those of coeval rocks in Eastern Indochina. Combined with previous paleomagnetic studies, we propose that an Eastern Indochina-derived continental fragment was involved during the formation of arcs in the Cebu and Bohol Islands, which highlights the potential contribution of ancient continental materials in the formation of intra-oceanic arcs. This scenario does not support the previously proposed model that the Cretaceous arc in the Philippine Mobile Belt formed in the northern margin of the proto-Philippine Sea Plate and Australian margin.

scholarly journals The Cenozoic Malaguide Basin from Sierra Espuña (Murcia, S Spain): An Example of Geological Heritage

Geosciences ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Santiago Moliner-Aznar ◽  
Manuel Martín-Martín ◽  
Tomás Rodríguez-Estrella ◽  
Gregorio Romero-Sánchez
Keyword(s):  
Middle Eocene ◽  
Geological Heritage ◽  
Passive Margin ◽  
Early Miocene ◽  
Late Oligocene ◽  
Deep Basin ◽  
Sedimentary Evolution ◽  
Early Oligocene ◽  
Upper Oligocene ◽  
Very High

The Cenozoic Malaguide Basin from Sierra Espuña (Internal Betic Zone, S Spain) due to the quality of outcropping, areal representation, and continuity in the sedimentation can be considered a key-basin. In the last 30 years, a large number of studies with very different methodological approaches have been done in the area. Models indicate an evolution from passive margin to wedge-top basin from Late Cretaceous to Early Miocene. Sedimentation changes from limestone platforms with scarce terrigenous inputs, during the Paleocene to Early Oligocene, to the deep basin with huge supplies of turbidite sandstones and conglomerates during the Late Oligocene to Early Miocene. The area now appears structured as an antiformal stack with evidence of synsedimentary tectonics. The Cenozoic tectono-sedimentary basin evolution is related to three phases: (1) flexural tectonics during most of the Paleogene times to create the basin; (2) fault and fold compartmentation of the basin with the creation of structural highs and subsiding areas related to blind-fault-propagation folds, deforming the basin from south to north during Late Oligocene to Early Aquitanian times; (3) thin-skin thrusting tectonics when the basin began to be eroded during the Late Aquitanian-Burdigalian. In recent times some works on the geological heritage of the area have been performed trying to diffuse different geological aspects of the sector to the general public. A review of the studies performed and the revisiting of the area allow proposing different key-outcrops to follow the tectono-sedimentary evolution of the Cenozoic basin from this area. Eight sites of geological interest have been selected (Cretaceous-Cenozoic boundary, Paleocene Mula Fm, Lower Eocene Espuña-Valdelaparra Fms, Middle Eocene Malvariche-Cánovas Fms, Lowermost Oligocene As Fm, Upper Oligocene-Lower Aquitanian Bosque Fm, Upper Oligocene-Aquitanian Río Pliego Fm, Burdigalian El Niño Fm) and an evaluation has been performed to obtain four parameters: the scientific value, the educational and touristic potential, and the degradation risk. The firsts three parameters obtained values above 50 being considered of “high” or “very high” interest (“very high” in most of the cases). The last parameter shows always values below 50 indicating a “moderate” or “low” risk of degradation. The obtained values allow us considering the tectono-sedimentary evolution of this basin worthy of being proposed as a geological heritage.

scholarly journals Late oligocene–early miocene shortening in the Thrace Basin, northern Aegean

2021 ◽  
Author(s):  
Ümitcan Erbil ◽  
Aral I. Okay ◽  
Aynur Hakyemez
Keyword(s):  
Large Scale ◽  
Middle Eocene ◽  
Early Miocene ◽  
Fold Axis ◽  
Late Oligocene ◽  
The Balkans ◽  
Sedimentary Sequences ◽  
The North ◽  
Early Oligocene ◽  
Thrace Basin

AbstractLate Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.

Constraints on the formation of the giant Daheishan porphyry Mo deposit (NE China) from whole-rock and accessory mineral geochemistry

2021 ◽  
Author(s):  
Kai Xing ◽  
Qihai Shu ◽  
David R Lentz
Keyword(s):  
High Water ◽  
Accessory Mineral ◽  
Ne China ◽  
Accessory Minerals ◽  
Slab Rollback ◽  
Continental Arc ◽  
Arc Setting ◽  
Porphyry Mo Deposit ◽  
T Values ◽  
Water Contents

Abstract There are more than 90 porphyry (or skarn) Mo deposits in northeastern China with Jurassic or Cretaceous ages. These are thought to have formed mainly in a continental arc setting related to the subduction of the Paleo-Pacific oceanic plate in the Jurassic and subsequent slab rollback in the early Cretaceous. The Jurassic Daheishan porphyry Mo deposit is one of the largest Mo deposits in NE China, which contains 1.09 Mt Mo with an average Mo grade of 0.07%. To better understand the factors that could have controlled Mo mineralization at Daheishan, and potentially in other similar porphyry Mo deposits in NE China, the geochemical and isotopic compositions of the ore-related granite porphyry and biotite granodiorite, and the magmatic accessory minerals apatite, titanite and zircon from the Daheishan intrusions, were investigated so as to evaluate the potential roles that magma oxidation states, water contents, sulfur and metal concentrations could have played in the formation of the deposit. Magmatic apatite and titanite from the causative intrusions show similar εNd(t) values from -1.1 to 1.4, corresponding to TDM2 ages ranging from 1040 to 840 Ma, which could be accounted for by a mixing model through the interaction of mantle-derived basaltic melts with the Precambrian lower crust. The Ce and Eu anomalies of the magmatic accessory minerals have been used as proxies for magma redox state, and the results suggest that the ore-forming magmas are highly oxidized, with an estimated ΔFMQ range of + 1.8 to + 4.1 (+2.7 in average). This is also consistent with the high whole-rock Fe2O3/FeO ratios (1.3–26.4). The Daheishan intrusions display negligible Eu anomalies (Eu/Eu* = 0.7–1.1) and have relatively high Sr/Y ratios (40–94) with adakitic signatures; they also have relatively high Sr/Y ratios in apatite and titanite. These suggest that the fractionation of amphibole rather than plagioclase is dominant during the crystallization of the ore-related magmas, which further indicates a high magmatic water content (e.g., >5 wt%). The magmatic sulfur concentrations were calculated using available partitioning models for apatite from granitoids, and the results (9–125 ppm) are indistinguishable from other mineralized, subeconomic and barren intrusions. Furthermore, Monte Carlo modelling has been conducted to simulate the magmatic processes associated with the formation of the Daheishan Mo deposit, and the result reveals that a magma volume of ∼280 km3 with ∼10 ppm Mo was required to form the Mo ores containing 1.09 Mt Mo in Daheishan. The present study suggests that a relatively large volume of parental magmas with high oxygen fugacities and high water contents is essential for the generation of a giant porphyry Mo deposit like Daheishan, whereas a specific magma composition (e.g., with unusually high Mo and/or S concentrations), might be less critical.

Geochemistry and original nature of Precambrian khondalites in the Eastern Ghats, Orissa: a discussion

1991 ◽  
Vol 82 (1) ◽  
pp. 87-88 ◽  
Author(s):  
J. K. Nanda ◽  
U. C. Pati
Keyword(s):  
Major Part ◽  
Eastern Ghats ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Indian Peninsula ◽  
Eastern Ghats Mobile Belt

While congratulating the authors for the wealth of geochemical data on a very important Precambrian lithological assemblage of India, known commonly as khondalites, which constitute a major part of the Eastern Ghats mobile belt bordering the eastern fringes of the Indian Peninsula, we have a few comments to offer on the hypothesis propounded by the authors (Dash et al. 1987).

Falcatifolium (Podocarpaceae) macrofossils from paleogene sediments in south-eastern Australia: a reassessment

1998 ◽  
Vol 11 (6) ◽  
pp. 711 ◽  
Author(s):  
Robert S. Hill ◽  
Leonie J. Scriven
Keyword(s):  
Leaf Morphology ◽  
Middle Eocene ◽  
Late Eocene ◽  
South Eastern ◽  
Early Oligocene ◽  
Extant Species ◽  
Eastern Australia ◽  
South Eastern Australia

A re-investigation of macrofossils previously referred to the extantpodocarpaceous genus Falcatifolium Laubenfels shows thatno records can be sustained. Falcatifolium australisD.R.Greenwood from Middle Eocene sediments in Victoria bears littleresemblance to extant species in the genus and is transferred to the newfossil genus Sigmaphyllum R.S.Hill & L.J.Scriven.Specimens from Early Oligocene sediments in Tasmania previously assigned toFalcatifolium are described as a second species ofSigmaphyllum, S. tasmanensisR.S.Hill & L.J.Scriven, and specimens from mid to late Eocene sediments inTasmania previously assigned to Falcatifolium do notbelong to that genus, although their true generic affinities are uncertain.Dispersed cuticle specimens from Late Eocene–Oligocene sediments inSouth Australia referred to Falcatifolium are notreliable records of the genus and require further investigation. However,Dacrycarpus eocenica D.R.Greenwood, from Middle Eocenesediments in Victoria is transferred to Falcatifolium,and is similar to the extant species F. angustumLaubenfels, which has a leaf morphology unusual for the genus.Falcatifolium eocenica (D.R.Greenwood) R.S.Hill & L.J.Scriven is the only reliable record of the genus in the Australian fossilrecord to date.

Paleogeographic evolution of the United States Pacific Northwest during Paleogene time

1987 ◽  
Vol 24 (8) ◽  
pp. 1652-1667 ◽  
Author(s):  
Paul L. Heller ◽  
Rowland W. Tabor ◽  
Christopher A. Suczek
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Middle Eocene ◽  
The United States ◽  
Oceanic Islands ◽  
Local Source ◽  
Second Phase ◽  
Early Oligocene ◽  
Basin Development ◽  
Major Transition

Paleogeographic reconstructions for Oregon and Washington during Paleogene time illustrate a major transition from a dominantly compressional (prior to middle Eocene time) to an extensional tectonic regime. This transition resulted in the development of three phases of Paleogene basin evolution in the United States Pacific Northwest. During the initial phase, basins formed along the continental margin during collision of oceanic islands. Sediments in these basins were derived from nearby orogenic highlands. The second phase of basin development began in middle Eocene time and consisted of rapid subsidence of individual basins that formed within a broad forearc region. Nonmarine basins that formed during this phase were caused by extension possibly associated with transcurrent faulting. Rapid sedimentation in both marine and nonmarine basins during this time consisted dominantly of sandstone derived from Cretaceous plutonic sources far to the east. The final stage of basin development was the modification of previous basin configurations by the growth of the Cascade volcanic arc, which was initiated in early Oligocene time. The rising Cascade Range diverted streams carrying eastern-derived material, thereby reducing overall sedimentation rates in the coastal basins and providing a local source of volcanic detritus.

Paleolake salinity evolution in the Qaidam Basin (NE Tibetan Plateau) between ~42 and 29 Ma: Links to global cooling and Paratethys sea incursions

2021 ◽  
Author(s):  
Chengcheng Ye ◽  
Yibo Yang ◽  
Xiaomin Fang ◽  
Weilin Zhang ◽  
Chunhui Song ◽  
...  
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Middle Eocene ◽  
Qaidam Basin ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Driving Mechanism ◽  
The Tibetan Plateau ◽  
Early Oligocene ◽  
Global Cooling

<p>Global cooling, the early uplift of the Tibetan Plateau, and the retreat of the Paratethys are three main factors that regulate long-term climate change in the Asian interior during the Cenozoic. However, the debated elevation history of the Tibetan Plateau and the overlapping climate effects of the Tibetan Plateau uplift and Paratethys retreat makes it difficult to assess the driving mechanism on regional climate change in a particular period. Some recent progress suggests that precisely dated Paratethys transgression/regression cycles appear to have fluctuated over broad regions with low relief in the northern Tibetan Plateau in the middle Eocene–early Oligocene, when the global climate was characterized by generally continuous cooling followed by the rapid Eocene–Oligocene climate transition (EOT). Therefore, a middle Eocene–early Oligocene record from the Asian interior with unambiguous paleoclimatic implications offers an opportunity to distinguish between the climatic effects of the Paratethys retreat and those of global cooling.</p><p>Here, we present a complete paleolake salinity record from middle Eocene to early Miocene (~42-29 Ma) in the Qaidam Basin using detailed clay boron content and clay mineralogical investigations. Two independent paleosalimeters, equivalent boron and Couch’s salinity, collectively present a three-staged salinity evolution, from an oligohaline–mesohaline environment in the middle Eocene (42-~34 Ma) to a mesosaline environment in late Eocene-early Oligocene (~34-~29 Ma). This clay boron-derived salinity evolution is further supported by the published chloride-based and ostracod-based paleosalinity estimates in the Qaidam Basin. Our quantitative paleolake reconstruction between ~42 and 29 Ma in the Qaidam Basin resembles the hydroclimate change in the neighboring Xining Basin, of which both present good agreement with changes of marine benthic oxygen isotope compositions. We thus speculated that the secular trend of clay boron-derived paleolake salinity in ~42-29 Ma is primarily controlled by global cooling, which regulates regional climate change by influencing the evaporation capacity in the moisture source of Qaidam Basin. Superimposed on this trend, the Paratethys transgression/regression cycles served as an important factor regulating wet/dry fluctuations in the Asian interior between ~42 and ~34 Ma.</p>

Genesis of the Wuxing Pt–Pd-rich Cu–Ni sulfide deposit in the eastern Central Asian Orogenic Belt: evidences from geochronology, elemental geochemistry, and Sr–Nd–Hf isotopic data

2019 ◽  
Vol 56 (4) ◽  
pp. 380-398 ◽  
Author(s):  
Jing-gui Sun ◽  
Yun-peng He ◽  
Ji-long Han ◽  
Zhong-yu Wang
Keyword(s):  
Crustal Contamination ◽  
Early Period ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Geochemical Data ◽  
Sulfide Deposit ◽  
Late Period ◽  
Enriched Mantle ◽  
Central Asian ◽  
T Values

The Wuxing Pt–Pd-rich Cu–Ni sulfide deposit in Heilongjiang Province, Northeast China, is located to the northeast of the Dunhua–Mishan fracture of the eastern Central Asian Orogenic Belt. The mafic–ultramafic complex consist of early-period hornblende–olivine pyroxenite, diopsidite, and hornblende pyroxenite and late-period gabbro and diabase units. An early-period hornblende pyroxenite yielded a zircon U–Pb age of 208.2 ± 2.6 Ma and a late-period diabase yielded a U–Pb age of 205.6 ± 1.1 Ma, with zircon εHf(t) values of +1.24 to +8.13. The early- and late-period lithofacies are relatively enriched in LILE (Rb, Ba, and Sr) and LREE, and variably depleted in HFSE (Nb, Ta). The whole-rock and single-mineral analyses of the early-period lithofacies yield (87Sr/86Sr)i ratios of 0.7055–0.7083 and εNd(t) ratios of −7.98–+3.10. These geochemical data suggest that the parental magmas of the Wuxing complex are high-Mg subalkaline basaltic in nature and were derived from an enriched mantle source. The magmas chamber formed after the injection of magma into the crust along with crustal contamination, producing early crystalline minerals and ore-bearing magmas. The rupturing of the magma chamber released evolved magmas, which then ascended and generated Pt–Pd-bearing lithofacies and Cu–Ni sulfide orebodies by fractional crystallization, accumulation, and liquation. During the late period, the residual magma invaded the early lithofacies and Cu–Ni orebodies. The fluids exsolved from the gabbroic magmas concentrated the mineralized metal elements and enhanced the precipitation of Pt–Pd-bearing veinlet-disseminated orebodies and Pt–Pd–Cu–Ni orebodies.

scholarly journals Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins

2018 ◽  
Author(s):  
Americus Perez ◽  
Susumu Umino ◽  
Graciano P. Yumul Jr. ◽  
Osamu Ishizuka
Keyword(s):  
Middle Eocene ◽  
Pillow Lava ◽  
Philippine Sea Plate ◽  
Volcanic Stratigraphy ◽  
Subduction Initiation ◽  
Philippine Sea ◽  
High Silica ◽  
Magnesium Andesite ◽  
Trench Slope ◽  
Fall Deposits

Abstract. A key component of subduction initiation rock suites is boninite, a high-magnesium andesite that is uniquely predominant in Western Pacific forearc terranes and in select Tethyan ophiolites such as Oman and Troodos. We report the discovery of low-calcium, high-silica boninite in the middle Eocene Zambales ophiolite (Luzon island, Philippines). Olivine-orthopyroxene microphyric high-silica boninite, olivine-clinopyroxene-phyric low-silica boninite and boninitic basalt occur as lapilli fall deposits and pillow lava flows in the upper volcanic unit of the juvenile arc section (Barlo locality, Acoje Block) of Zambales ophiolite. This upper volcanic unit in turn overlies a lower volcanic unit consisting of basaltic andesite, andesite to dacitic lavas and explosive eruptives (subaqueous pahoehoe and lobate sheet flows, agglutinate, and spatter deposits) forming a low-silica boninite series. The overall volcanic stratigraphy of the extrusive sequence at Barlo resembles Holes U1439 and U1442 drilled by IODP Expedition 352 in the Izu-Ogasawara (Bonin) trench slope. The presence of proto-arc basalts in Coto Block (45 Ma), boninite and boninite series volcanics in Barlo, Acoje Block (44 Ma) and simultaneous and post-boninite moderate-Fe arc tholeiites in Sual and Subic, Acoje Block (44–43 Ma) indicate that the observed subduction initiation stratigraphy in the Izu-Ogasawara-Mariana forearc is present in Zambales ophiolite as well. Paleolatitudes derived from tilt-corrected sites in the Acoje Block place the juvenile arc of northern Zambales ophiolite in the western margin of the Philippine Sea Plate. In this scenario, the origin of Philippine Sea Plate boninites (IBM and Zambales) would be in a doubly-vergent subduction initiation setting.

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