Consumed tectonic plates in Southeast Asia: Markers from the Mesozoic to early Cenozoic stratigraphic units in the northern and central Philippines

Tectonic reconstruction models of Southeast Asia all invoke in the early Cenozoic the collision of Mesozoic oceanic plates, which have been fragmented, consumed along subduction zones or emplaced onto the overriding plate. However, with marked variations in these models, we reinvestigate the tectonic evolutionary landscape of Southeast Asia through the lens of Philippine geology. In particular, we present revisions to the more recent models by adopting the unique approach of integrating data that we have gathered for the past 17 years from the Upper Mesozoic to Lower Cenozoic stratigraphic formations in northern and central Philippines. These formations, which resulted mainly from submarine mass transport processes, evolved in response to early arc-related processes of oblique subduction, frontal wedge deformation, terrane accretion and strike slip faulting. Additional key constraints for the revisions include: (1) the timing of early Cenozoic magmatism in eastern Luzon; (2) the spatial distribution of the Upper Mesozoic to Lower Cenozoic sedimentary formations with respect to other key features (e.g. distribution of Mesozoic ophiolite fragment and continent-derived rocks) in the Philippine arc; (3) the paleolatitudinal position of Luzon and surrounding regions and; (4) the movement of the surrounding plates since the Late Mesozoic. In revising previous models, a subduction zone (proto-East Luzon Trough) separating Benham Plateau and the Philippine arc was placed to explain the spatial distribution of Eocene arc-related formational units and Mesozoic ophiolite materials comprising the accretionary complex east of Luzon at ~40 Ma period. During this time, Luzon was modeled at the southern margin of the East Asia Sea or the proto-Philippine Sea Plate. Mesozoic ophiolitic complexes that line the eastern Philippine arc as well as the ophiolitic and pelagic limestone and chert fragments included in the arc-derived, Eocene formations in Luzon could very well be traces of the now consumed East Asia Sea-proto-Philippine Sea Plate. Within the same period, we modified the Palawan Microcontinental Block (PCB), positioned at the trailing edge of the proto-South China Sea to include the whole Mindoro island and the Romblon Island Group in Central Philippines. Pieces of the consumed Izanagi Plate, the proto-South China Sea and continental-derived sediments from Asia mainland are reflected in the Mesozoic metamorphic rocks and the Eocene sedimentary formation in western Mindoro. Finally, we model Cebu, Bohol and Negros islands in Central Philippines as being at the leading oceanic edge of the Indo-Australian Plate during the early Cenozoic. With the northward movement of the Indo-Australian plate and the trench roll back of the southern margins of the Philippine Sea Plate, the accretion of the Cretaceous arc-related rocks of Cebu, Bohol and Negros onto the Philippine arc by the end of Eocene or early Oligocene becomes a possibility

Epithermal Mineralization of the Bonanza-Sandy Vein System, Masara Gold District, Mindanao, Philippines

The Masara Gold District in southeastern Mindanao island is an area of prolific hydrothermal copper and gold mineralization. This study documents the mineralization characteristics of the NW-trending Bonanza-Sandy epithermal veins to constrain possible hydrothermal fluid sources and ore-forming mechanisms. Epithermal mineralization in the NW veins is divided into three main stages: Stage 1 - massive quartz-sulfide; Stage 2 - massive to amorphous quartz-carbonate (calcite); and Stage 3 - colloform-cockade quartz-carbonate (bladed rhodochrosite). Stage 1 is the main gold mineralization phase, with chalcopyrite, pyrite, sphalerite and galena occurring with native gold and tellurides. Stages 2 and 3 contain invisible gold in the sphalerite, galena, pyrite and chalcopyrite. The deposit exhibits mineralization characteristics typical of intermediate sulfidation epithermal deposits based on the dominant chalcopyrite-pyrite mineral assemblage; illite-muscovite-chlorite alteration mineralogy that point to neutral pH conditions; and sphalerite composition of 2.26 to 8.72 mol% FeS in Stage 1 and 0.55 to 1.13 mol% FeS in Stage 2. The K-Ar age date of illite separates from highly altered diorite porphyry of the Lamingag Intrusive Complex yielded an Early Pliocene age (5.12 ± 0.16 Ma). Hydrothermal fluid exsolved from the magma that formed the Lamingag Intrusive Complex probably formed the ore-forming Stage 1 veins. Stages 2 and 3 involved the deposition of quartz and carbonate veins possibly by boiling hydrothermal fluids. Precious and base metal deposition was controlled by the Masara Fault Zone. Exploration markers for gold mineralization in the Masara Gold District and vicinity include the presence of Lamingag Intrusive Complex and massive sulfide veins

L'evento

Il concetto di evento \ue8 di grande rilievo per gli studiosi delle scienze storiche, anche se non \ue8 tra i pi\uf9 indagati, essendo stato, per lo pi\uf9 oggetto di interesse per i filosofi e per i metodologi delle scienze sociali. Da vari angoli disciplinari e culturali si propone una nuova tematizzazione del concetto a pi\uf9 voci, accompagnata dalla traduzione italiana di un brevissimo trattato di Plutarco di Cherone

Mesozoic rock suites along western Philippines: Exposed proto-South China Sea fragments?

An ancient oceanic crustal leading edge east of mainland Asia, the proto-South China Sea crust, must have existed during the Mesozoic based on tectonic reconstructions that accounted for the presence of subducted slabs in the lower mantle and the exposed oceanic lithospheric fragments strewn in the Philippine and Bornean regions. Along the western seaboard of the Philippine archipelago, numerous Mesozoic ophiolites and associated lithologies do not appear to be genetically associated with the younger Paleogene-Neogene ocean basins that currently surround the islands. New sedimentological, paleomagnetic, paleontological, and isotopic age data that we generated are presented here, in combination with our previous results and those of others, to reassess the geological make-up of the western Philippine island arc system. We believe that the oceanic lithospheric fragments, associated melanges, and sedimentary rocks in this region are exhumed slivers of the proto-South China Sea ocean plate

Slab rollback and microcontinent subduction in the evolution of the Zambales Ophiolite Complex (Philippines) : A review

New radiolarian ages show that the island arc-related Acoje block of the Zambales Ophiolite Complex is possibly of Late Jurassic to Early Cretaceous age. Radiometric dating of its plutonic and volcanic-hypabyssal rocks yielded middle Eocene ages. On the other hand, the paleontological dating of the sedimentary carapace of the transitional mid-ocean ridge – island arc affiliated Coto block of the ophiolite complex, together with isotopic age datings of its dikes and mafic cumulate rocks, also yielded Eocene ages. This offers the possibility that the Zambales Ophiolite Complex could have: (1) evolved from a Mesozoic arc (Acoje block) that split to form a Cenozoic back-arc basin (Coto block), (2) through faulting, structurally juxtaposed a Mesozoic oceanic crust with a younger Cenozoic lithospheric fragment or (3) through the interplay of slab rollback, slab break-off and, at a later time, collision with a microcontinent fragment, caused the formation of an island arc-related ophiolite block (Acoje) that migrated trench-ward resulting into the generation of a back-arc basin (Coto block) with a limited subduction signature. This Meso-Cenozoic ophiolite complex is compared with the other oceanic lithosphere fragments along the western seaboard of the Philippines in the context of their evolution in terms of their recognized environments of generation

Capacitação dos Enfermeiros da Atenção Básica a Respeito do Exame Citopatológico do Colo do Útero / Training of Primary Care Nurses Regarding Cervical Cytopathological Examination

Considerando que o exame de rastreamento do câncer de colo uterino (PCCU) é um processo complexo e não apenas um simples procedimento, é sabido que os enfermeiros precisam se adequar a esse procedimento, fazendo uso de todos os aspectos que possam favorecer o fim da qualidade do resultado.  Infelizmente, os profissionais ainda têm dificuldade nas etapas consideradas essenciais nesse universo.  O objetivo deste estudo é fornecer bases científicas para os enfermeiros da atenção básica da cidade de Tucurui-PA, através de treinamentos em parceria com a secretaria de saúde, no intuito de esclarecer quanto as responsabilidades gerais desses profissionais, tendo em vista a complexidade do exame. Nesse sentido, prosseguiu-se com o método de abordagem por meio da teoria da problematização, utilizando também as etapas estabelecidas e organizadas do arco de Maguerez que trouxeram como hipótese de solução uma palestra e o uso de um fluxo de atendimento para o resultado da PCCU. Dessa forma, a realização do treinamento seguiu como planejado, sendo possível visualizar durante os debates a complexidade do problema. Isso permitiu concluir que o trabalho contínuo com a equipe de enfermagem e o próprio interesse dos profissionais em buscar conhecer profundamente o conteúdo do câncer de colo uterino e o exame preventivo ainda são fundamentais para o empoderamento profissional de forma segura e eficaz.

Hemithioindigo-based histone deacetylase inhibitors induce a light-dependent anticancer effect

Photoswitchable molecules exhibit light-dependent biological activity which allow us to control the therapeutic effect of drugs with high precision. Such molecules could solve some of the limitations of anticancer drugs by providing a localised effect in the tumour. Histone deacetylase inhibitors (HDACis) constitute a promising drug class for oncology whose application is often limited by a lack of selectivity. Herein, we developed photoswitchable HDACis based on a hemithioindigo scaffold. We established synthetic routes to access them and determined the optimal conditions for isomerisation and their thermal stability. We then optimised their enzyme activity through three rounds of re-design to identify examples that are up to 6-fold more active under illumination than in the dark. We also confirmed that our best derivative reduces the viability of HeLa cells only under illumination. All in all, we disclose a series of derivatives containing an hemithioindigo moiety, which display a light-dependent effect on both HDAC inhibition and cancer cell viability

Terrane Boundary Geophysical Signatures in Northwest Panay, Philippines: Results from Gravity, Seismic Refraction and Electrical Resistivity Investigations

Northwest Panay consists of two terranes that form part of the Central Philippine collision zone: Buruanga Peninsula and Antique Range. The Buruanga Peninsula consists of a Jurassic chert-clastic-limestone sequence, typical of oceanic plate stratigraphy of the Palawan Micro-continental Block. The Antique Range is characterized by Antique Ophiolite Complex peridotites and Miocene volcanic and clastic rocks, representing obducted oceanic crust that serves as the oceanic leading edge of the collision with the Philippine Mobile Belt. The Nabas Fault is identified as the boundary between the two terranes. This study employed the gravity method to characterize the Northwest Panay subsurface structure. Results indicate higher Bouguer anomaly values for Buruanga Peninsula than those for Antique Range, separated by a sudden decrease in gravity values toward the east-southeast (ESE) direction. Forward gravity data modeling indicates the presence of an underlying basaltic subducted slab in the Buruanga Peninsula. Furthermore, the Nabas Fault is characterized as an east-dipping thrust structure formed by Buruanga Peninsula basement leading edge subduction beneath Antique Range. Additional geophysical constraints were provided by shallow seismic refraction and electrical resistivity surveys. Results from both methods delineated the shallow subsurface signature of the Nabas Fault buried beneath alluvium deposits. The gravity, seismic refraction and electrical resistivity methods were consistent in identifying the Nabas Fault as the terrane boundary between the Buruanga Peninsula and the Antique Range. The three geophysical methods helped constrain the subsurface configuration in Northwest Panay

Mineralization parameters and exploration targeting for gold- copper deposits in the Baguio (Luzon) and Pacific Cordillera (Mindanao) Mineral Districts, Philippines: A review

The Baguio Mineral District in Luzon, Philippines is known to host several world-class epithermal gold – porphyry copper deposits. The interplay of tectonic setting, magma composition, structural control and hydrothermal systems contributed to the generation of these deposits. Ridge subduction (Scarborough seamount) resulting to flat subduction and a transpressional regime could also be related to the formation of epithermal gold - porphyry copper deposits in Baguio. Subduction processes leading to the formation of calc-alkaline rocks associated with high water pressure, oxygen fugacity and late sulfur saturation are almost always associated with the gold-copper deposits in the district. Compared to the Baguio Mineral District, less exploration work, mine development and production were done in the Pacific Cordillera Mineral District, Mindanao in southern Philippines. It is worth noting, however, that both mineral districts show similarities and overlapping features in terms of geological, geophysical and geochemical characteristics. This leads one to conclude that the Pacific Cordillera Mineral District has ore deposits waiting to be discovered

Petrogenetic constraints on magma fertility in the Baguio Mineral District, Philippines: Probing the mineralization potential of the igneous host rocks in the Sangilo epithermal deposit

In the Baguio Mineral District (BMD), porphyry Cu ± Au deposition and associated epithermal mineralization are attributed to the highly evolved magmatism during the Pliocene. It has been well-documented that the interaction between silicic crustal melts and primitive mantle melts formed water-rich, oxidized magmas that resulted to hydrothermal mineralization. However, there are very few studies on the Early to Middle Miocene calc-alkaline magmatism which is considered to be barren of mineralization. This magmatic event is represented by phases of the Central Cordillera Diorite Complex (CCDC), which also serve as host rocks to the Sangilo epithermal deposit. The Sangilo quartz-carbonate veins in the BMD are hosted by an Early Miocene hornblende diorite (22.33 ± 0.63 Ma) intruded by a Middle Miocene quartz diorite (15.91 ± 0.6 Ma) which are, in turn, penetrated by Pliocene basaltic andesite dikes. The Miocene magmatic units with hybrid crust-mantle source affinity were formed from varying degrees of interaction within the MASH (mixing, assimilation, storage, and homogenization) zone during the formation of the CCDC. The basaltic andesite dikes, part of the Pliocene Mafic Dike Complex, represent direct differentiates of basaltic melts that experienced ponding at the base of the lower crust before ascending to shallow crustal levels. Based on the assessment of the physico-chemical conditions, three distinct magmatic events were identified: a barren Early Miocene event, a fertile Middle Miocene event and a fertile Pliocene event. The Middle Miocene fertile magmatism is attributed to further development of the MASH zone under the Luzon arc from the Early to Middle Miocene. On the other hand, the enhanced fertility during the Pliocene is associated with the subduction of the Scarborough Ridge. In the Baguio Mineral District (BMD), porphyry Cu __ Au deposition and associated epithermal mineralization are attributed to the highly evolved magmatism during the Pliocene. It has been well-documented that the interaction between silicic crustal melts and primitive mantle melts formed water-rich, oxidized magmas that resulted to hydrothermal mineralization. However, there are very few studies on the Early to Middle Miocene calc-alkaline magmatism which is considered to be barren of mineralization. This magmatic event is represented by phases of the Central Cordillera Diorite Complex (CCDC), which also serve as host rocks to the Sangilo epithermal deposit. The Sangilo quartz-carbonate veins in the BMD are hosted by an Early Miocene hornblende diorite (22.33 __ 0.63 Ma) intruded by a Middle Miocene quartz diorite (15.91 __ 0.6 Ma) which are, in turn, penetrated by Pliocene basaltic andesite dikes. The Miocene magmatic units with hybrid crust-mantle source affinity were formed from varying degrees of interaction within the MASH (mixing, assimilation, storage, and homogenization) zone during the formation of the CCDC. The basaltic andesite dikes, part of the Pliocene Mafic Dike Complex, represent direct differentiates of basaltic melts that experienced ponding at the base of the lower crust before ascending to shallow crustal levels. Based on the assessment of the physico-chemical conditions, three distinct magmatic events were identified: a barren Early Miocene event, a fertile Middle Miocene event and a fertile Pliocene event. The Middle Miocene fertile magmatism is attributed to further development of the MASH zone under the Luzon arc from the Early to Middle Miocene. On the other hand, the enhanced fertility during the Pliocene is associated with the subduction of the Scarborough Ridge