Most basaltic shergottites are too Mg-rich to represent parent melt compositions because they contain some cumulus pyroxenes. However, basaltic shergottite Northwest Africa(NWA) 8656 with subophitic texture can be use...Most basaltic shergottites are too Mg-rich to represent parent melt compositions because they contain some cumulus pyroxenes. However, basaltic shergottite Northwest Africa(NWA) 8656 with subophitic texture can be used as the parent melt composition in petrogenetic studies because it contains no or rare cumulus pyroxenes. Its pyroxene cores(Mg# 66-68, the most magnesian) are in equilibrium with the bulk rock composition based on major(Fe-Mg) and trace elements(REE—rare earth elements).The patchy zoning of pyroxenes has been interpreted as reflecting a two-stage crystallization history: 1) crystallization of Mg-rich pyroxene cores at depth(50 km, the base of Martian crust), 2) crystallization of Fe-rich pyroxene rims at the shallow depth near the Martian surface with a fast cooling history. The crystallization of Fe-rich pyroxenes and the existence of different symplectites indicate that NWA 8656 underwent eruption. The oxygen fugacity of NWA 8656(QFM –0.9±0.5) suggests an oxidized condition at the late-stage crystallization process, and the CI-normalized REE patterns of different minerals show enrichment in LREE, compared to that of depleted shergottites. Both of these observations suggest a relatively ITE(incompatible trace elements)-enriched signature of NWA 8656, similar to those of other enriched shergottites. The REE compositions of augite core and rim and plagioclase can be successfully reproduced by progressive crystallization without exogenous components, which indicates a closed magmatic system for NWA 8656. Consequently, we conclude that the ITE-enriched signature of NWA 8656 is inherited from an enriched mantle source rather than caused by crustal assimilation. Moreover, partial melting of depleted Martian mantle could not directly yield magmas that have geochemical characteristics similar to enriched shergottite parent magmas, so the enriched and depleted shergottites are derived from distinct mantle sources, and the mantle source of enriched shergottites would be expected to contain ilmenite.展开更多
Theoretically, a system is anything that is made up of various parts. Theses parts are known as subsystems. At every point in time, these parts should work in harmony so that objectives could be achieved successfully....Theoretically, a system is anything that is made up of various parts. Theses parts are known as subsystems. At every point in time, these parts should work in harmony so that objectives could be achieved successfully. A system could be inanimate or animate item. Examples of inanimate systems include vehicles, households, computer and institution. Examples of animate systems are human being, animal and insect. Both inanimate and animate systems are made up of various subsystems. Such subsystems are required to co-operate, collaborate and work together so that set objectives could be achieved successfully. From practical managerial point of view, business organizations are equally systems that are made up of subsystems which may take the form of departments, sections and/or units. It is supposed to be collaborations among the managers and other members in these departments, sections and/or units so that organizational objectives could be achieved. All the managers in various departments, sections and/or units are required to work together as a team to make the system coherent and closely-knit to make disintegration impossible. Closely related to the systems approach to management is managerial decision-making. Decision-making is a very important function of every manager＇s job. The success and failure stories of many organizations are the result of the quality of decisions made. Many organizations have survived turbulent conditions. Others have also collapsed in spite of favourable conditions. These varying conditions are the result of the quality of decisions made by managers at positions of authority and responsibility. Therefore the systems approach to management enjoins top managers in particular to be very circumspect and cautious in certain decision-making activities. This is because, the quality of decision a manager makes can go a long way to determine the success or failure story of an organization as exemplified in the case study in this paper.展开更多
文摘Most basaltic shergottites are too Mg-rich to represent parent melt compositions because they contain some cumulus pyroxenes. However, basaltic shergottite Northwest Africa(NWA) 8656 with subophitic texture can be used as the parent melt composition in petrogenetic studies because it contains no or rare cumulus pyroxenes. Its pyroxene cores(Mg# 66-68, the most magnesian) are in equilibrium with the bulk rock composition based on major(Fe-Mg) and trace elements(REE—rare earth elements).The patchy zoning of pyroxenes has been interpreted as reflecting a two-stage crystallization history: 1) crystallization of Mg-rich pyroxene cores at depth(50 km, the base of Martian crust), 2) crystallization of Fe-rich pyroxene rims at the shallow depth near the Martian surface with a fast cooling history. The crystallization of Fe-rich pyroxenes and the existence of different symplectites indicate that NWA 8656 underwent eruption. The oxygen fugacity of NWA 8656(QFM –0.9±0.5) suggests an oxidized condition at the late-stage crystallization process, and the CI-normalized REE patterns of different minerals show enrichment in LREE, compared to that of depleted shergottites. Both of these observations suggest a relatively ITE(incompatible trace elements)-enriched signature of NWA 8656, similar to those of other enriched shergottites. The REE compositions of augite core and rim and plagioclase can be successfully reproduced by progressive crystallization without exogenous components, which indicates a closed magmatic system for NWA 8656. Consequently, we conclude that the ITE-enriched signature of NWA 8656 is inherited from an enriched mantle source rather than caused by crustal assimilation. Moreover, partial melting of depleted Martian mantle could not directly yield magmas that have geochemical characteristics similar to enriched shergottite parent magmas, so the enriched and depleted shergottites are derived from distinct mantle sources, and the mantle source of enriched shergottites would be expected to contain ilmenite.
文摘Theoretically, a system is anything that is made up of various parts. Theses parts are known as subsystems. At every point in time, these parts should work in harmony so that objectives could be achieved successfully. A system could be inanimate or animate item. Examples of inanimate systems include vehicles, households, computer and institution. Examples of animate systems are human being, animal and insect. Both inanimate and animate systems are made up of various subsystems. Such subsystems are required to co-operate, collaborate and work together so that set objectives could be achieved successfully. From practical managerial point of view, business organizations are equally systems that are made up of subsystems which may take the form of departments, sections and/or units. It is supposed to be collaborations among the managers and other members in these departments, sections and/or units so that organizational objectives could be achieved. All the managers in various departments, sections and/or units are required to work together as a team to make the system coherent and closely-knit to make disintegration impossible. Closely related to the systems approach to management is managerial decision-making. Decision-making is a very important function of every manager＇s job. The success and failure stories of many organizations are the result of the quality of decisions made. Many organizations have survived turbulent conditions. Others have also collapsed in spite of favourable conditions. These varying conditions are the result of the quality of decisions made by managers at positions of authority and responsibility. Therefore the systems approach to management enjoins top managers in particular to be very circumspect and cautious in certain decision-making activities. This is because, the quality of decision a manager makes can go a long way to determine the success or failure story of an organization as exemplified in the case study in this paper.
