Taking the Middle–Upper Cambrian Xixiangchi Group in the central–southern Sichuan Basin as an example,this study investigates the sedimentary characteristics and evolutionary history of tempestites using field outcr...Taking the Middle–Upper Cambrian Xixiangchi Group in the central–southern Sichuan Basin as an example,this study investigates the sedimentary characteristics and evolutionary history of tempestites using field outcrop,core,thin-section and logging data,and elucidates the patterns and processes by which storms have reworked grain shoal reservoirs in carbonate platforms,thereby identifying the zones with favorable reservoirs.The results indicate that:(1)The Xixiangchi Group develops massive storm deposits,with five intervals occurred in a complete storm sedimentary sequence;Xixiangchi Group exhibits six typical storm depositional sequences,with storm-related grain shoals developed in settings such as mixed tidal flats,intra-platform depressions,and margins of the intra-platform depressions.(2)During the deposition of the Xixiangchi Group,storm activities were mainly in the southeastern,central and southwestern parts of the Sichuan Basin.Overall,storm action showed an initial increase followed by a decrease.(3)The impact of storms on the reworking of grain shoal reservoirs varies across different facies zones.The intra-platform depression margins,influenced by storm centers,experienced strong reworking,leading to the vertical stacking of storm-related grain shoals and normal grain shoals,which expands the scale of the shoal complex.Furthermore,storms enhance the penecontemporaneous dissolution,favoring the development of large-scale high-quality reservoirs.The intra-platform depressions and mixed tidal flats,controlled by the storm centers,were weakly modified,possibly inducing scattered storm-related grain shoals under low-energy conditions.The degree of karst modification is generally low,and local conditions are favorable for reservoir development.(4)The Dazu-Hechuan-Guang'an area,strongly reworked by storm activities,exhibits a large scale of storm-related grain shoals with good physical properties,providing favorable conditions for the development of contiguous,high-quality grain shoal reservoirs,so it can be regarded as a key target for subsequent exploration of the Xixiangchi Group.展开更多
Iron formations are valuable archives of sedimentary conditions and post-depositional events.However,geochemical proxies commonly used to determine genetic characteristics can be variably modified during metamorphism ...Iron formations are valuable archives of sedimentary conditions and post-depositional events.However,geochemical proxies commonly used to determine genetic characteristics can be variably modified during metamorphism and deformation,hampering their use as records of regional geological events.This work focuses on strongly reworked magnetite-quartz-rich rocks from the São Josédo Campestre Massif,one of the oldest fragments of preserved crust in South America.The genetic classification of these magnetite-quartz-rich rocks is not straightforward because primary assemblages and textures were variably modified by granulite facies metamorphism during a regional Paleoproterozoic migmatization event.To address genetic ambiguities,we analyzed their magnetite and pyroxene chemistry,wholerock geochemistry,and Sm-Nd isotopes.Magnetite chemistry indicates that pyroxene-poor iron formations(Type B)are low in trace elements such as Ti,Al,V,and Mn,suggesting a chemical similarity to iron formations elsewhere.In contrast,magnetites from pyroxene-enriched Type A iron formations are rich in trace elements and more akin to magnetite crystallized from higher temperature systems,such as skarn and IOCG.The147Sm/144Nd of these rocks show substantial variation even at the outcrop scale,indicating a locally-controlled,highly heterogeneous mixture of Archean,Paleoproterozoic,and Neoproterozoic sources.Therefore,our geochemical tools point out to heterogenous signatures of these magnetitequartz rocks and proxies compatible with both low and high-temperature conditions and age of deposition spanning sources from the Archean to the Neoproterozoic.We interpret that the studied São Josédo Campestre magnetite-quartz rocks represent Archean iron formations with original magnetite chemistry and isotopic signatures variably modified by metamorphism and by at least one deformation-related hydrothermal event.These results contrast with similar examples from China and Greenland where iron formations either preserved the magnetite chemistry or the primary isotopic signatures.Our study indicates that metamorphism can selectively affect chemical proxies used to study iron formations and undermine the genetic classification of iron ores.Thus,these proxies should be carefully applied in the interpretation of syn-depositional environments of polydeformed belts.展开更多
The Economic Production Quantity (EPQ) model is commonly used by practitioners in the fields of production and inventory management to assist them in making decision on production lot size. The common assumptions in t...The Economic Production Quantity (EPQ) model is commonly used by practitioners in the fields of production and inventory management to assist them in making decision on production lot size. The common assumptions in this model are that all units produced are perfect and shortages are not allowed. But, in real situation the defective items will be produced in each cycle of production and shortages and scrap are possible. These assumptions will underestimate the actual required quantity. Hence, the defective items can not be ignored in the production process. Rework process is necessary to convert those defective into finished goods. This study proposes EPQ model that incorporates both imperfect production quality and falsely not screening out a proportion of defects, thereby passing them on to customers, resulting in defect sales returns. To active this objective a suitable mathematical model is developed and the optimal production lot size which minimizes the total cost is derived. An illustrative example is provided and numerically verified. The validation of result in this model was coded in Microsoft Visual Basic 6.0.展开更多
基金Supported by the National Natural Science Foundation of China(U22B6002)PetroChina Science and Technology Major Project(2023ZZ02)。
摘要Taking the Middle–Upper Cambrian Xixiangchi Group in the central–southern Sichuan Basin as an example,this study investigates the sedimentary characteristics and evolutionary history of tempestites using field outcrop,core,thin-section and logging data,and elucidates the patterns and processes by which storms have reworked grain shoal reservoirs in carbonate platforms,thereby identifying the zones with favorable reservoirs.The results indicate that:(1)The Xixiangchi Group develops massive storm deposits,with five intervals occurred in a complete storm sedimentary sequence;Xixiangchi Group exhibits six typical storm depositional sequences,with storm-related grain shoals developed in settings such as mixed tidal flats,intra-platform depressions,and margins of the intra-platform depressions.(2)During the deposition of the Xixiangchi Group,storm activities were mainly in the southeastern,central and southwestern parts of the Sichuan Basin.Overall,storm action showed an initial increase followed by a decrease.(3)The impact of storms on the reworking of grain shoal reservoirs varies across different facies zones.The intra-platform depression margins,influenced by storm centers,experienced strong reworking,leading to the vertical stacking of storm-related grain shoals and normal grain shoals,which expands the scale of the shoal complex.Furthermore,storms enhance the penecontemporaneous dissolution,favoring the development of large-scale high-quality reservoirs.The intra-platform depressions and mixed tidal flats,controlled by the storm centers,were weakly modified,possibly inducing scattered storm-related grain shoals under low-energy conditions.The degree of karst modification is generally low,and local conditions are favorable for reservoir development.(4)The Dazu-Hechuan-Guang'an area,strongly reworked by storm activities,exhibits a large scale of storm-related grain shoals with good physical properties,providing favorable conditions for the development of contiguous,high-quality grain shoal reservoirs,so it can be regarded as a key target for subsequent exploration of the Xixiangchi Group.
基金supported by the National Council for the Improvement of Higher Education(CAPES)the Brazilian Council for Research and Technological Development(CNPQ)。
摘要Iron formations are valuable archives of sedimentary conditions and post-depositional events.However,geochemical proxies commonly used to determine genetic characteristics can be variably modified during metamorphism and deformation,hampering their use as records of regional geological events.This work focuses on strongly reworked magnetite-quartz-rich rocks from the São Josédo Campestre Massif,one of the oldest fragments of preserved crust in South America.The genetic classification of these magnetite-quartz-rich rocks is not straightforward because primary assemblages and textures were variably modified by granulite facies metamorphism during a regional Paleoproterozoic migmatization event.To address genetic ambiguities,we analyzed their magnetite and pyroxene chemistry,wholerock geochemistry,and Sm-Nd isotopes.Magnetite chemistry indicates that pyroxene-poor iron formations(Type B)are low in trace elements such as Ti,Al,V,and Mn,suggesting a chemical similarity to iron formations elsewhere.In contrast,magnetites from pyroxene-enriched Type A iron formations are rich in trace elements and more akin to magnetite crystallized from higher temperature systems,such as skarn and IOCG.The147Sm/144Nd of these rocks show substantial variation even at the outcrop scale,indicating a locally-controlled,highly heterogeneous mixture of Archean,Paleoproterozoic,and Neoproterozoic sources.Therefore,our geochemical tools point out to heterogenous signatures of these magnetitequartz rocks and proxies compatible with both low and high-temperature conditions and age of deposition spanning sources from the Archean to the Neoproterozoic.We interpret that the studied São Josédo Campestre magnetite-quartz rocks represent Archean iron formations with original magnetite chemistry and isotopic signatures variably modified by metamorphism and by at least one deformation-related hydrothermal event.These results contrast with similar examples from China and Greenland where iron formations either preserved the magnetite chemistry or the primary isotopic signatures.Our study indicates that metamorphism can selectively affect chemical proxies used to study iron formations and undermine the genetic classification of iron ores.Thus,these proxies should be carefully applied in the interpretation of syn-depositional environments of polydeformed belts.
摘要The Economic Production Quantity (EPQ) model is commonly used by practitioners in the fields of production and inventory management to assist them in making decision on production lot size. The common assumptions in this model are that all units produced are perfect and shortages are not allowed. But, in real situation the defective items will be produced in each cycle of production and shortages and scrap are possible. These assumptions will underestimate the actual required quantity. Hence, the defective items can not be ignored in the production process. Rework process is necessary to convert those defective into finished goods. This study proposes EPQ model that incorporates both imperfect production quality and falsely not screening out a proportion of defects, thereby passing them on to customers, resulting in defect sales returns. To active this objective a suitable mathematical model is developed and the optimal production lot size which minimizes the total cost is derived. An illustrative example is provided and numerically verified. The validation of result in this model was coded in Microsoft Visual Basic 6.0.