This study reconstructs the lithofacies and paleogeographic evolution of North Africa during the Cambrian to Devonian periods,emphasizing the influence of tectonic events,sea-level fluctuations,and climatic changes on...This study reconstructs the lithofacies and paleogeographic evolution of North Africa during the Cambrian to Devonian periods,emphasizing the influence of tectonic events,sea-level fluctuations,and climatic changes on the region's depositional systems and basin development.Integrating seismic,well log,and core data,we identify key depositional patterns and their implications for hydrocarbon exploration.During sedimentation of diverse stages,the source-to-sink systems underwent significant transitions under provenance variation.During the Cambrian-Ordovician periods,intracratonic sag basins dominated,with braided river systems transitioning into glacial deposits in response to climatic cooling and glaciation.Under the control of the source-to-sink system,Silurian witnessed the opening of the Paleo-Tethys Ocean,leading to extensive marine transgressions and the deposition of organic-rich shales of the Lower Silurian,a primary hydrocarbon source rock.Regression during the Late Silurian introduced deltaic and fluvial systems,influenced by tectonic uplifting.During the Devonian period,the Hercynian Orogeny significantly impacted basin architecture,facilitating the development of passive margin basins.Braided and meandering river systems transitioned into deltaic and shallow marine environments,with Late Devonian anoxic conditions fostering the formation of additional hydrocarbon source rocks.This research highlights the interplay of tectonics,climate,and sea-level changes in shaping North Africa's sedimentary history.The findings provide critical insights into the distribution of hydrocarbon source and reservoir rocks,offering valuable guidance for exploration and development in the region.展开更多
The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block.The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east an...The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block.The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east and west sides and the discontinuous marginal zone,the late-stage main body of dominant riebeckite granite,and minor aegirine granite.Studies on petrological geochemistry and LA-ICP-MS zircon U-Pb dating of the late-stage riebeckite granite,origin and evolution of the Muchang alkali granite and the relationship between the granite and the associated skarn-type Luziyuan Pb-Zn deposit are discussed in this paper.The results show that the Muchang alkali granites belong to A-type granites,which are characterized by enrichment in Al_2O_3,SiO_2,total alkali and Fe, depletion in MgO and CaO contents with high FeO_T/MgO ratios.The REE concentrations are relatively high,exhibiting highly fractionated LREE patterns with significantly Eu negative anomaly. The Muchang granites are obviously enriched in lithophile elements（e.g.,Rb,K,U and Th） and high field strength elements（e.g.,Zr,Hf,Nb,Y and Ga） with high 10000×Ga/Al ratios and depleted in Sr, Ba,Ti,Cr and Ni,which are similar to those of the A-type granites and quite different from those of S-type andⅠ-type granites.The LA-ICP-MS zircon dating results of the Muchang granite gave a weighted mean age of 266.2±5.4 Ma（2σ）,suggesting that they were formed in the stage of extension at the end of post-collision at Middle Permian and the consumption of Paleo-Tethys ocean took place before 266 Ma. It is suggested that the unexposed intermediate-acid intrusive rocks in the Luziyuan ore district,which is the ＂sister＂ rocks material of the Muchang granites and related closely to Luziyuan Pb-Zn mineralization,were the product of Middle Permian.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.92255302).
文摘This study reconstructs the lithofacies and paleogeographic evolution of North Africa during the Cambrian to Devonian periods,emphasizing the influence of tectonic events,sea-level fluctuations,and climatic changes on the region's depositional systems and basin development.Integrating seismic,well log,and core data,we identify key depositional patterns and their implications for hydrocarbon exploration.During sedimentation of diverse stages,the source-to-sink systems underwent significant transitions under provenance variation.During the Cambrian-Ordovician periods,intracratonic sag basins dominated,with braided river systems transitioning into glacial deposits in response to climatic cooling and glaciation.Under the control of the source-to-sink system,Silurian witnessed the opening of the Paleo-Tethys Ocean,leading to extensive marine transgressions and the deposition of organic-rich shales of the Lower Silurian,a primary hydrocarbon source rock.Regression during the Late Silurian introduced deltaic and fluvial systems,influenced by tectonic uplifting.During the Devonian period,the Hercynian Orogeny significantly impacted basin architecture,facilitating the development of passive margin basins.Braided and meandering river systems transitioned into deltaic and shallow marine environments,with Late Devonian anoxic conditions fostering the formation of additional hydrocarbon source rocks.This research highlights the interplay of tectonics,climate,and sea-level changes in shaping North Africa's sedimentary history.The findings provide critical insights into the distribution of hydrocarbon source and reservoir rocks,offering valuable guidance for exploration and development in the region.
基金supported by the National"973 Project"(No.2009CB421003)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No:KZCX2-YW-1 36-2,KZCX2-YW- 111-03)the Foundation of State Key Lab.Of Ore Deposit Geochemistry
文摘The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block.The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east and west sides and the discontinuous marginal zone,the late-stage main body of dominant riebeckite granite,and minor aegirine granite.Studies on petrological geochemistry and LA-ICP-MS zircon U-Pb dating of the late-stage riebeckite granite,origin and evolution of the Muchang alkali granite and the relationship between the granite and the associated skarn-type Luziyuan Pb-Zn deposit are discussed in this paper.The results show that the Muchang alkali granites belong to A-type granites,which are characterized by enrichment in Al_2O_3,SiO_2,total alkali and Fe, depletion in MgO and CaO contents with high FeO_T/MgO ratios.The REE concentrations are relatively high,exhibiting highly fractionated LREE patterns with significantly Eu negative anomaly. The Muchang granites are obviously enriched in lithophile elements（e.g.,Rb,K,U and Th） and high field strength elements（e.g.,Zr,Hf,Nb,Y and Ga） with high 10000×Ga/Al ratios and depleted in Sr, Ba,Ti,Cr and Ni,which are similar to those of the A-type granites and quite different from those of S-type andⅠ-type granites.The LA-ICP-MS zircon dating results of the Muchang granite gave a weighted mean age of 266.2±5.4 Ma（2σ）,suggesting that they were formed in the stage of extension at the end of post-collision at Middle Permian and the consumption of Paleo-Tethys ocean took place before 266 Ma. It is suggested that the unexposed intermediate-acid intrusive rocks in the Luziyuan ore district,which is the ＂sister＂ rocks material of the Muchang granites and related closely to Luziyuan Pb-Zn mineralization,were the product of Middle Permian.
