Value chain analysis and small-scale fisheries management     

《Marine Policy》2017

A value chain analysis is conducted to identify upgrading, that is, improvements in quality and product design that enable producers to gain enhanced value or through diversification in the product lines served. However, a range of data and information of use to managing small-scale fisheries can be also be produced. Eight value chain studies, carried out for specific fish species in different locations around the Philippines, are examined. Policy and management lessons learned and interventions resulting from the value chain analysis for small-scale fisheries management are discussed. Recommendations for using value chain analysis in small-scale fisheries management include stricter regulation on size limits of harvest, monitoring schemes, certification processes, post-harvest facilities, seasonal closures, social enterprises, credit facilities, and habitat protection.  相似文献   

Geology and volcanic stratigraphy of the Canatuan and Malusok volcanogenic massive sulfide deposits,southwestern Mindanao,Philippines     

Ross?L.?SherlockEmail author  Timothy?J.?Barrett 《Mineralium Deposita》2004,39(1):1-20

The Canatuan and Malusok massive sulfide deposits are located near Siocon, Zamboanga del Norte, in southwestern Mindanao, Philippines. The Canatuan–Malusok area is underlain by the Jurassic–Cretaceous Tungauan schists, which form much of the Zamboanga Peninsula. The volcanic strata at Canatuan and Malusok can be traced for >7 km along strike and is host to at least three discrete massive sulfide bodies: Canatuan, Malusok and SE Malusok. Basal basaltic andesite volcanic rocks are generally chemically uniform and show only moderate alteration. The massive sulfide deposits occur in overlying rhyolitic to rhyodacitic volcanic rocks that are altered to a schistose assemblage of quartz, sericite, chlorite and pyrite. The alteration is texturally destructive but graded clastic beds are locally observed. Despite tropical saprolitic weathering, four lithogeochemical subunits of the felsic package are identified. Stratigraphic interleaving, however, has made correlation of these units over any significant distance difficult. The sulfide lenses are overlain by a few metres of felsic schists which locally contain manganese-bearing silicates and oxides that serve as a stratigraphic marker. Hangingwall andesitic volcaniclastic rocks are discontinuously preserved, although where present, they consist of regularly bedded mafic volcanic sandstones. The lateral continuity of a manganese-bearing marker and flanking felsic volcaniclastic intervals indicate that locally the volcanic strata form a homoclinal sequence. The Canatuan Au–Ag–Cu–Zn deposit consists of a gossan overlying a massive sulfide lens. The sulfides and gossan are flat lying and hosted within felsic volcanic rocks. The gossan is gold–silver-rich, and was formed by a combination of oxidation and volume collapse of the original sulfide lens. The sulfide minerals present below the current water table, are auriferous massive pyrite with base metal sulfides, with some supergene chalcocite. The transition from gossan to sulfides is very sharp, occurring at the water table. Massive sulfide deposits at Malusok are hosted in the same felsic sequence as Canatuan and they have similar base and precious metal contents. Only limited gossan has been found at Malusok. The bimodal nature of the volcanic rocks at Canatuan, together with their low HFSE contents, near-flat REE patterns and tholeiitic affinities, suggest that they formed in an intra-oceanic arc setting above a depleted mantle source. Mafic and felsic volcanic rocks of similar composition have been recovered from the Tonga-Kermadec and Izu-Bonin-Marianas island-arc systems in the western Pacific. Mafic rocks at Canatuan show no evidence for LILE enrichment that characterizes melts derived from metasomatized mantle under more mature arcs, suggesting that they are the product of a nascent, rather than a mature arc. There is no evidence from the REE, or other incompatible trace elements, that continental crust or evolved arc crust was involved in the generation of the Canatuan-Malusok volcanic rocks. Although it has been proposed that the Zamboanga metamorphic complex comprises microcontinental fragments of Eurasian affinity, our data do not support an evolved crustal setting for the Canatuan-Malusok volcanic rocks, which we suggest were derived from an intra-oceanic arc and subsequently accreted to the eastern Mindanao terrane.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00126-003-0350-7Editorial handling: R.R. Large  相似文献   

Carlin-type Gold Prospects in Surigao del Norte, Mindanao Island, Philippines: Their Geology and Mineralization Potential     

Victor B. Maglambayan    Sj Montes    Katherine Hipol    Maireen Mamitag    Rikki Pamela Pineda    Raymond Rodolfo    Noel Oliveros  Antonio Sy 《Resource Geology》2005,55(3):145-154

Abstract. Three calcareous sedimentary rock-hosted Carlin type-like gold prospects were mapped in a mineral production sharing agreement area of Philex Gold Philippines Inc. in Taganaan municipality, Surigao del Norte province in Mindanao island in the Philippines. They occur along a 20–25 km long trend of known epigenetic gold and porphyry copper deposits that lie close to several splays of the Philippine Fault Zone. The gold district forms part of the Late Cretaceous Eastern Mindanao Range that hosts early Paleogene and late Pliocene to Quaternary intrusive rocks.
Gold is invisible in the jasperoid outcrops in Lascogon, Napo, and Danao prospects. The jasperoids occur in lenses of marls belonging to the Taganaan Marl Member that is associated to a turbiditic member of the Middle Miocene Mabuhay Formation. The marl lenses include gently dipping interbedded silty limestones and calcareous shales. The "invisible gold" mineralization in silicified calcareous rocks resembles Carlin-type deposits. Based on the mapped igneous and sedimentary rocks, a possible heat source for the gold mineralization is either or both of the two main phases of intrusion, Mabuhay An-desite or Alipao Andesite Porphyry. Forty-eight rock samples, fifteen stream sediment samples, and one soil sample were critical in delineating the general features of the potential Carlin-type prospects. The gold grades of jasperoids in the three prospects range from trace amounts to 20 g/t Au. Regional studies of gold and porphyry copper mineralization in the Surigao del Norte mineral district are important in delineating ore targets for drilling in the three prospects.  相似文献   

Mass Change Calculations as Applied to the Search for Volcanogenic Massive Sulfide Deposits: An Example from Malusok, Siocon, Zamboanga del Norte, Mindanao, Philippines     

Cliff L. Querubin  Graciano P. Yumul  Jr. 《Resource Geology》2005,55(2):61-72

Abstract. The Malusok volcanogenic massive sulfide (VMS) deposits comprise two adjacent ore bodies, the Main Malusok and the Malusok Southeast ore bodies, hosted within Cretaceous metamorphic rocks. Owing to the structural and metamor-phic overprinting combined with intense hydrothermal alteration, primary textures of the Malusok volcanic rocks have been obliterated. The stratigraphic correlation of the Main Malusok and the Malusok Southeast ore bodies show that both deposits are essentially confined within a single stratigraphic interval. The lithogeochemical analysis of the Malusok samples shows that constituent lithologies have precursor compositions ranging from sub-alkaline basalts to rhyodacites. Field and mass flux data suggest that the Main Malusok VMS deposits were derived as a consequence of axial hydrothermal activity. The Malusok Southeast ore bodies represent satellite deposits generated by off-axis hydrothermal activities from vents aligned along a NW-SE trend with the Main Malusok zone. This alignment represents an ancient fissure that served as a pathway for the upwelling metalliferous hydrothermal fluids. In searching for lateral extensions of these VMS deposits, this NW-SE alignment should serve as a possible exploration guide.  相似文献   

Westward younging disposition of Philippine ophiolites and its implication for arc evolution     

Graciano P.  Yumul Jr 《Island Arc》2007,16(2):306-317

Abstract   The different ophiolite complexes in the Philippine island arc system define a progressive younging direction westward. This resulted from the clockwise rotation of the Philippine island arc system during its north-westward translation in the Eocene resulting in its western boundary colliding with the Sundaland–Eurasian margin. As a consequence of this interaction, ophiolite complexes and mélanges accreted into the Philippine island arc system along its western side. A new ophiolite zonation with four belts is proposed that takes into consideration the observed spatial and temporal relationships of the exposed oceanic lithosphere slices. With progressive younging from east to west, Belt 1 corresponds to Late Cretaceous complete ophiolite complexes with associated metamorphic soles along the eastern Philippines, whereas Belt 2 includes Early to Late Cretaceous dismembered ultramafic-mafic complexes with mélanges exposed mainly west of eastern Philippines. Belt 3 is defined by Cretaceous through Eocene to Oligocene ophiolite complexes emplaced along the collision zone between the Philippine Mobile Belt and the Sundaland–Eurasian margin. Belt 4 corresponds to the ophiolite complexes emplaced along continental margins as exposed in the Palawan and Zamboanga–Sulu areas. This proposed zonation hints that the whole Philippine Mobile Belt, except for the strike-slip fault bounded Eocene Zambales ophiolite complex in Luzon, is underlain by Cretaceous proto-Philippine Sea Plate fragments. This is contrary to the previous models that consider only the eastern margin of the Philippines to contain proto-Philippine Sea Plate materials.  相似文献   

Textural Evidence for the Chromite‐Oversaturated Character of the Melt Involved in Podiform Chromitite Formation     

Betchaida D. Payot  Shoji Arai  Graciano P. Yumul Jr 《Resource Geology》2013,63(3):313-319

Well‐preserved oval‐shaped dunite clots occur within the exceptionally fresh massive podiform chromitites from the Coto Block of the Zambales Ophiolite Complex, the Philippines. The dunite/chromitite boundary shows an interlocking texture; olivine inclusions in chromites in the podiform chromitites show the same optical extinction with larger adjacent olivines in the dunite clots. This texture was formed by the reaction between chromite‐oversaturated melt and its dunite inclusions. The existence of such type of melt was previously only hypothesized to explain the origin of layered and podiform chromitites but is now confirmed by this discovery.  相似文献   

菲律宾北甘马仁省拉惹普(Larap) 铁铜钼矿床地质特征及成因     

陈建民 《世界地质》2011,30(2):145-153

拉惹普( Larap) 铁、铜钼矿床产于菲律宾板块俯冲吕宋岛被动陆缘的岛弧造山带上,处于菲律宾中央走滑断裂带近旁。含矿层位于古近纪渐新世晚期蚀变安山岩、角砾岩和古新统的角岩、角岩化页岩的喷溢角度不整合面的追踪断裂带上。大面积的安山岩、角砾岩的褪色化和带状展布的灰绿色热液交代蚀变岩系,矿体产于蚀变带中,呈似层状、透镜状; 铁矿体在上部层位,铜钼矿体在铁矿体下部,与贫磁铁矿相伴产出; 铁矿体伴生铜、钼,铜钼矿体又伴生铁、金、银和钴等,矿石中的金属矿物以磁铁矿为主,其次有黄铁矿、黄铜矿、辉钼矿、磁黄铁矿、沥青铀矿和自然金等。元素组合除铁、铜、钼外,还有金、银、钴和铀等,与奥林匹克坝、Candelaria ( 智利) 的氧化铁型( IOCG) 铜金矿床类比,拉惹普矿床成因属于氧化铁型铜钼金矿床新类型。  相似文献   

Petrological and geochemical characteristics of the Samar Ophiolite ultramafic section: implications on the origins of the ophiolites in Samar and Leyte islands,Philippines     

J. M. R. Guotana  B. D. Payot  C. B. Dimalanta  N. T. Ramos  D. V. Faustino-Eslava  K. L. Queaño 《International Geology Review》2018,60(4):401-417

Cretaceous ophiolites and ophiolitic fragments occur in the Samar and Leyte islands in eastern central Philippines. The Samar Ophiolite is a complete crust–mantle sequence exposed in southern Samar, whereas the Tacloban and Malitbog ophiolite complexes are, respectively, located in the northeastern and southwestern portions of the nearby Leyte island. Despite the close proximity of these islands, the genetic relationship of these ophiolites and ophiolitic complexes, if any, remains to be elucidated. We present here new petrographic and geochemical data on the harzburgites and dunites of the ultramafic section of the Samar Ophiolite. These mantle peridotites are highly depleted residues which have low modal pyroxene content, high spinel Cr# (=0.62–0.79), and slightly enriched light rare earth element abundance with depletion in Zr and Ti. Such characteristics are typical of supra-subduction zone peridotites and strongly contrast with the abyssal signatures of the Tacloban and Malitbog ophiolite complexes. The absence of a structure between these adjacent ophiolite fragments initially hints that they form a single oceanic crust. However, with our new results, we suggest other possible mechanisms that could explain the relationship of these ophiolites.  相似文献   

菲律宾迪纳加特岛汇洋镍铬矿区铬铁矿成矿地质特征          下载免费PDF全文

王志刚  潘文亮  陈丹明 《地质找矿论丛》2014,29(1):72-78

菲律宾迪纳加特岛汇洋镍铬矿区发育板块碰撞成因的蛇绿岩,主要岩性为纯橄岩和方辉橄榄岩,与铬铁矿化关系密切,在纯橄岩和方辉橄榄岩的过渡带中铬铁矿化较为集中,铬铁矿多呈薄层块状或浸染状与围岩岩性条带呈"互层状"产出,块状、浸染状的铬铁矿重复出现;矿区内原生铬铁矿化非常普遍,虽然未构成原生铬铁矿体,但为次生红土型铬铁矿的成矿提供了丰富的物质来源。矿区内第四系中赋存有残坡积红土型铬铁砂矿,并与同类型镍矿共生;铁质红土层是最佳的含矿层位,松散状红土层次之;铬铁矿体呈层状、似层状,有3个铬铁砂矿化区,矿体厚度5~7m,铬铁矿品位w(Cr2O3)=2.0%~4.1%。  相似文献