Geology,Geochemistry,and Genesis of the Tongcun Reduced Porphyry Mo(Cu) Deposit,NW Zhejiang Province,China

The Tongcun Mo（Cu） deposit in Kaihua city of Zhejiang Province,eastern China,occurs in and adjacent to the Songjiazhuang granodiorite porphyry and is a medium-sized and important porphyry type ore deposit.Two irregular Mo（Cu） orebodies consist of various types of hydrothermal veinlets.Intensive hydrothermal alteration contains skarnization,chloritization,carbonatization,silicification and sericitization.Based on mineral assemblages and crosscutting relationships,the oreforming processes are divided into five stages,i.e.,the early stage of garnet ＋ epidote ± chlorite associated with skarnization and K-feldspar ＋ quartz ± molybdenite veins associated with potassicsilicic alteration,the quartz-sulfides stage of quartz ＋ molybdenite ± chalcopyrite ± pyrite veins,the carbonatization stage of calcite veinlets or stockworks,the sericite ＋ chalcopyrite ± pyrite stage,and the late calcite ＋ quartz stage.Only the quartz-bearing samples in the early stage and in the quartzsulfides stage are suitable for fluid inclusions（FIs） study.Four types of FIs were observed,including1） CO2-CH4 single phase FIs,2） CO2-bearing two- or three-phase FIs,3） Aqueous two-phase FIs,and4） Aqueous single phase FIs.FIs of the early stages are predominantly CO2- and CH4-rich FIs of the CO2-CH4-H2O-NaCl system,whereas minerals in the quartz-sulfides stage contain CO2-rich FIs of the CO2-H2O-NaCl system and liquid-rich FIs of the H2O-NaCl system.For the CO2-CH4 single phase FIs of the early mineralization stage,the homogenization temperatures of the CO2 phase range from 15.4 ℃ to 25.3 ℃（to liquid）,and the fluid density varies from 0.7 g/cm^3 to 0.8 g/cm^3;for two- or three-phase FIs of the CO2-CH4-H2O-NaCl system,the homogenization temperatures,salinities and densities range from 312℃ to 412℃,7.7 wt%NaCl eqv.to 10.9 wt%NaCl eqv.,and 0.9 g/cm^3 to 1.0 g/cm^3,respectively.For CO2-H2O-NaCI two- or threephase FIs of the quartz-sulfides stage,the homogenization temperatures and salinities range from255℃ to 418℃,4.8 wt%NaCl eqv.to 12.4 wt%NaCl eqv.,respectively;for H2O-NaCl two-phase FIs,the homogenization temperatures range from 230 ℃ to 368 ℃,salinities from 11.7 wt%NaCl eqv.to16.9 wt%NaCl eqv.,and densities from 0.7 g/cm^3 to 1.0 g/cm^3.Microthermometric measurements and Laser Raman spectroscopy analyses indicate that CO2 and CH4 contents and reducibility（indicated by the presence of CH4） of the fluid inclusions trapped in quartz-sulfides stage minerals are lower than those in the early stage.Twelve molybdenite separates yield a Re-Os isochron age of 163 ± 2.4 Ma,which is consistent with the emplacement age of the Tongcun,Songjiazhuang,Dayutang and Huangbaikeng granodiorite porphyries.The 〈S18OSMow values of fluids calculated from quartz of the quartz-sulfides stage range from 5.6‰ to 8.6‰,and the 〈JDSMOw values of fluid inclusions in quartz of this stage range from-71.8‰ to-88.9‰,indicating a primary magmatic fluid source.〈534SV-cdt values of sulfides range from＋1.6‰ to ＋3.8‰,which indicate that the sulfur in the ores was sourced from magmatic origins.Phase separation is inferred to have occurred from the early stage to the quartz-sulfides stage and resulted in ore mineral precipitation.The characteristics of alteration and mineralization,fluid inclusion,sulfur and hydrogen-oxygen isotope data,and molybdenite Re-Os ages all suggest that the Tongcun Mo（Cu） deposit is likely to be a reduced porphyry Mo（Cu） deposit associated with the granodiorite porphyry in the Tongcun area.

Impact of Land-Use Changes on Sediment Load and Capacity Reduction of Lake Ziway, Ethiopia

Land-use change has been a factor that alters the hydrologic response of the watersheds leading to influencing on sediment yield changes. This study is mainly focusing on the assessment of the impacts of the land-use changes on sediment load and lake depth reduction on Lake Ziway, Ethiopia using an integrated approach of Remote Sensing (RS), GIS and SWAT model. ERDAS IMAGINE 14 model was used to generate land-use maps from Landsat TM, ETM+, and Ls8 acquired, in 1988, 2002 and 2015 as representative for the periods of (1988-1998), (1998-2008) and (2008-2018), respectively. The maximum likelihood algorithm of supervised classification applied to classify the basin land-use into seven land-use classes. The SWAT hydrological model with ArcGIS interface setup for the basin to evaluate the flow and sediment load with calibration and validation performance of the model range R2 (0.71 - 0.89) and NSE (0.57 - 0.87). As a result, the total average annual sediment yield from the sub-basins estimated as 3.59 t/ha/yr, 4.36 t/ha/yr, and 4.89 t/ha/yr for three consecutive decadal periods 1988-1998, 1998-2008, and 2008-2018 respectively. The increasing trend of sediment yield in the Lake Ziway watershed through one period to another justified as due to land-use. Similarly, the net sediment volume deposited in the lake also showed incremental trained with the land-use changes as 1.5 mcm/yr, 1.81 mcm/yr, and 2.033 mcm/yr for the period of 1988-1998, 1999-2008, and 2009-2018, respectively. The depth and water holding capacity of the lake reduced by 4.3 m and 25.76 mcm, respectively, from the depth and capacity recorded on the 2006 bathymetric survey, which was the effect of deposited sediment over the last 12 years.

Alleviating Water Scarcity in the Central Rift Valley Lakes through an Inter-Basin Water Transfer, Ethiopia

Demand for fresh water, as one of the major natural resources, is increasing rapidly with increasing development and environmental degradation. The continued abstraction of water from Lake Ziway and its main feeder rivers Meki and Katar for irrigation indicates that the water demand may soon exceed the supply. To illustrate disparities in spatial distribution of water resources, the Upper Awash sub-basin, which shares a water-divide with the CRVL sub-basin, has large flow volumes particularly in the rainy season and suffers with seasonal flooding. The rationale behind regaining the water in CRVL relies on this non-uniform spatial distribution of fresh water, calling for a balance between water surplus and deficit regions. For this reason, Inter Basin Water Transfer (IBWT) is suggested as a viable option to augment utilizable water resources of the Upper Awash sub-basin to reduce the significant pressure on the water supply of the rapidly developing urban and irrigation areas in the CRVL sub-basin. A water evaluation and planning (WEAP) model was used to quantify the amount of surplus water in the donor basin, when examining the hydrological dynamics of the basins. Furthermore, optimal flow diversion scenarios were generated by maintaining two baseline scenario constraints. The estimated surplus water in the rainy season is expected to contribute 18 million cubic meters (mcm), 88 mcm and 192 mcm in months June, July and August respectively under average conditions. The optimal amount of diverted water could potentially stabilize the environmental degradation of Lake Ziway and Lake Abijata by compensating for development-driven abstraction and surface water evaporation respectively.

A High Performance Multifrontal Code for Linear Solution of Structures Using Multi-Core Microprocessors

A multifrontal code is introduced for the efficient solution of the linear system of equations arising from the analysis of structures. The factorization phase is reduced into a series of interleaved element assembly and dense matrix operations for which the BLAS3 kernels are used. A similar approach is generalized for the forward and back substitution phases for the efficient solution of structures having multiple load conditions. The program performs all assembly and solution steps in parallel. Examples are presented which demonstrate the code’s performance on single and dual core processor computers.