Petrogenesis of anhydrous clinopyroxenite xenoliths and clinopyroxene megacrysts in alkali basalts from the Ganseong area of South Korea     

SUNG HI CHOI  NAK KYU KIM 《Island Arc》2012,21(2):101-117

Late Cenozoic alkali basalts in the Ganseong area of South Korea contain abundant ultramafic xenoliths and clinopyroxene megacrysts. Anhydrous clinopyroxene‐rich wehrlite–clinopyroxenites make up the majority of the xenolith population and range from wehrlite through olivine clinopyroxenite to clinopyroxenite. This study investigates the petrogenesis of wehrlite–clinopyroxenite xenoliths and clinopyroxene megacrysts on the basis of petrography and mineral and whole‐rock chemistry. Observations such as an absence of carbonate or apatite, high Ti/Eu ratio, and clinopyroxene‐dominated mineralogy lead us to rule out peridotite–melt reactions as the origin of the Ganseong wehrlites– olivine clinopyroxenites. The whole‐rock compositions (e.g. high abundance of CaO at a given MgO content and low abundance of incompatible elements, such as U, K, P, and Ti compared with mafic melts) indicate that the pyroxenites do not represent crystallized magma itself, but are rather cumulates with a small amount of residual liquid. Anhydrous and orthopyroxene‐free mineral assemblages, crystallization sequence of olivine→clinopyroxene→plagioclase, and mineral chemistries (e.g. low Cr# and high TiO₂ abundances in spinels and high TiO₂ and Na₂O abundances in clinopyroxenes at a given Mg#) suggest that relatively anhydrous intraplate alkaline basalt is the most likely candidate for the parent magma. Texture and compositions of the clinopyroxene megacrysts preclude a cognate origin via high‐pressure crystallization of the host magma. The clinopyroxene megacrysts occupy the Fe‐rich end of the compositional trends defined by wehrlite–pyroxenite clinopyroxenes. Progressive decreases in Mg# and an absence of significant compositional gaps between pyroxenite xenoliths and clinopyroxene megacrysts indicate fractionation and differentiation of a similar parental magma. We suggest that the clinopyroxene megacrysts represent fragments of pegmatitic clinopyroxenites crystallized from more advanced fractionation stages of the evolution of a series of magmatic liquids formed Ganseong wehrlite–clinopyroxenites.  相似文献   

The role of United Nations Educational, Scientific and Cultural Organization–International Hydrological Programme in sustainable water resources management in East Asian countries     

Ramasamy JAYAKUMAR  DUAN Xiaoli  Eunah KIM  LIU Ke 《地理学报》2009,19(3):259-272

For over 30 years, IHP (International Hydrological Programme) has been actively operating as a UNESCO’s (United Nations Educational, Scientific and Cultural Organization) international scientific cooperative programme in water research, water resources management, education and capacity-building, and the only broadly-based science programme of the UN (United Nations) system in this region. By a number of initiatives and networks, the IHP has progressively carried out activities on the quantity and quality of global/regional water resources, transboundary water resources management, mitigation of water related hazards, and water education. While addressing comprehensive areas over water challenges, greater emphasis has been placed on the role of water resources management for sustainable development and with respect to the expected changes in climate and environmental conditions. WWAP (World Water Assessment Programme) and its major product WWDR (World Water Development Report) in East Asia are under the framework of IHP which supports field oriented activities on monitoring freshwater, developing case studies, enhancing national assessment capacity, and facilitating decision making processes. In light of transboundary waters in IHP, RSC (Regional Steering Committee) plays a focal role for facilitating regional cooperation in the Southeast and East Asia and Pacific States. Furthermore, ISI (International Sediment Initiative) and IFI (International Flood Initiative) have significant roles, respectively, for the management of erosion and sedimentation in line with river system or reservoir management, and for the flood management focusing on capacity building of each country in East Asia. There are other major areas of concern under UNESCO’s IHP programme in East Asia, specifically in aspects including, mitigating water conflicts on transboundary aquifers through ISARM (International Shared Aquifer Resources Management), water management of arid areas through Water and Development Information for Arid Lands- A Global Network (Asian G-WADI), and sustainable management of groundwater by UNESCO Water Chair, as well as water education through the programme of Sustainable Water Integrated Management- Educational Component.  相似文献