Bio

Publications


2017

Nyamai, C, Wamunyu A, Daniel Ichang'i, Martelat J-E, Paquette J-L, et al.  2017.  Chronological Constraints On Tsavorite Mineralizations and Related Metamorphic Episodes In Southeast Kenya. The Canadian Mineralogist. 55(5):845-865. AbstractFull Text

Tsavorite is exclusively hosted in the Neoproterozoic Metamorphic Mozambique Belt (NMMB). The gemstone mines, widespread between Kalalani (Tanzania) and Mgama Ridge (Kenya), define a continuous corridor over a hundred kilometers in length. The tsavorite is hosted by a metasedimentary sequence defined as the Kurase tsavorite-bearing metasediments (Kurase-TB metasediments) that also hosts rubies. These metasediments underwent amphibolite-facies metamorphism and are surrounded by granulitic gneisses that are also of sedimentary origin (the Kurase high-temperature gneisses). All these rocks lie below the Kasigau Group, a unit dominated by granulite-facies metamagmatic rocks.

To constrain the timing of events that led to this peculiar occurrence of tsavorite, we have performed geochronological analyses of thin sections and of separated grains of zircon, monazite, and rutile using LA-ICP-MS and ID-TIMS, as well as 40Ar/39Ar of muscovite and phlogopite from various lithologies. The results show that the different terranes were metamorphosed synchronously between 620–580 Ma but under different P-T strain conditions. The Kurase-HT gneisses and the rocks from the Kasigau Group are highly strained and underwent granulite-facies metamorphism with abundant partial melting and emplacement of felsic melts between 620 and 600 Ma. Textural observations also underlined a late regional water flux controlling the occurrence of V-free muscovite and monazite mineralizations at 585 Ma. The latter event can be related to the activity of the Galana shear zone, in the east. The Kurase-TB metasediments escaped strain and partial melting. They record amphibolite-facies conditions with static heating, since initial sedimentary structures were locally preserved. The age of the tsavorite mineralization was inferred at 600 Ma from metamorphic zircon rims and monazite from the closest host-rocks, sampled in the mines. Hence, tsavorite crystallization occurred statically at the end of the metamorphic event, probably when the temperature and the amount of volatiles were at maximum levels.

Conversely, the ruby formed by local metasomatism of felsic dikes and isolated ultramafic bodies. The rubies are older and zircons and monazites from a ruby-bearing felsic dike (plumasite) were dated at 615 Ma. Finally, data from rutile and micas indicate a global cooling below 430°C of the whole region between 510 and 500 Ma.

Nyamai, C, Daniel Ichang'i, Wamunyu AW, Feneyrol J, Giuliani G, et al.  2017.  Age and origin of the tsavorite and tanzanite mineralizing fluids in the Neoproterozoic Mozambique Metamorphic Belt. The Canadian Mineralogist. 55(4):763-786. AbstractFull Text

The genetic model previously proposed for tsavorite- (and tanzanite-) bearing mineralization hosted in the Neoproterozoic Metamorphic Mozambique Belt (stretching from Kenya through Tanzania to Madagascar) is refined on the basis of new Sm-Nd age determinations and detailed Sr-O-S isotope and fluid-inclusion studies. The deposits are hosted within meta-sedimentary series composed of quartzites, graphitic gneisses, calc-silicate rocks intercalated with meta-evaporites, and marbles. Tsavorite occurs either in nodules (also called “boudins”) oriented parallel to the metamorphic foliation in all of the deposits in the metamorphic belt or in quartz veins and lenses located at the hinges of anticlinal folds (Lelatema fold belt and Ruangwa deposits, Tanzania). Gem tanzanite occurs in pockets and lenses in the Lelatema fold belt of northern Tanzania.

The Sm-Nd isotopic data for tsavorites and tanzanites hosted in quartz veins and lenses from Merelani demonstrate that they formed at 600 Ma, during the retrograde metamorphic episode associated with the East African Orogeny. The tsavorites hosted in nodules do not provide reliable ages: their sedimentary protoliths had heterogeneous compositions and their Sm-Nd system was not completely rehomogenized, even at the local scale, by the fluid-absent metamorphic recrystallization.

The initial 87Sr/86Sr isotopic ratios of calcite from marble and tanzanites from Merelani fit with the strontium isotopic composition of Neoproterozoic marine carbonates. Seawater sediment deposition in the Mozambique Ocean took place around 720 Ma.

The quartz-zoisite O-isotopic thermometer indicates a temperature of formation for zoisite between 385 and 448 °C.

The sulfur isotopic composition of pyrite (between –7.8 and –1.3‰ V-CDT) associated with tsavorite in the Lelatema fold belt deposits suggests the contribution of reduced marine sulfate. The sulfur in pyrite in the marbles was likely derived from bacterial sulfate reduction which produced H2S. Fluid inclusion data from tsavorite and tanzanite samples from the Merelani mine indicate the presence of a dominant H2S-S8±(CH4)±(N2)±(H2O)-bearing fluid. In the deposits in Kenya and Madagascar, the replacement of sulfate by tsavorite in the nodules and the boron isotopic composition of tourmaline associated with tsavorite are strong arguments in favor of the participation of evaporites in garnet formation.

2016

Wamalwa, RN, Nyamai CM, Ambusso WJ, Mulwa J, WASWA AARONK.  2016.  Structural Controls on the Geochemistry and Output of the Wells in the Olkaria Geothermal Field of the Kenyan Rift Valley. International Journal of Geosciences. 7(11):1299. AbstractFull Text

The Olkaria geothermal field is located in the Kenya Rift valley, about 120 km from Nairobi. Geothermal activity is widespread in this rift with 14 major geothermal prospects being identified. Structures in the Greater Olkaria volcanic complex include: the ring structure, the Ol’Njorowa gorge, the ENE-WSW Olkaria fault and N-S, NNE-SSW, NW-SE and WNW-ESE trending faults. The faults are more prominent in the East, Northeast and West Olkaria fields but are scarce in the Olkaria Domes area, possibly due to the thick pyroclastics cover. The NW-SE and WNW- ESE faults are thought to be the oldest and are associated with the development of the rift. The most prominent of these faults is the Gorge Farm fault, which bounds the geothermal fields in the northeastern part and extends to the Olkaria Domes area. The most recent structures are the N-S and the NNE-SSW faults. The geochemistry and output of the wells cut by these faults have a distinct characteristic that is the N-S, NW-SE and WNW-ESE faults are characterized by wells that have high Cl contents, temperatures and are good producers whereas the NE-SW faults, the Ring Structure and the Ol’Njorowa gorge appear to carry cool dilute waters with less chloride concentration and thus low performing wells. Though the impacts of these faults are apparent, there exists a gap in knowledge on how wide is the impact of these faults on the chemistry and performance of the wells. This paper therefore seeks to bridge this gap by analysis of the chemical trends of both old wells and newly drilled ones to evaluate the impacts of individual faults and then using buffering technique of ArcGis estimate how far and wide the influence of the faults is. The data was obtained after the sampling and analysis of discharge fluids of wells located on six profiles along the structures cutting through the field. Steam samples were collected with a stainless steel Webre separator connected between the wellhead and an atmospheric silencer on the discharging wells whereas the analysis was done in house in the KenGen geochemistry laboratory. The results indicates that Olkaria field has three categories of faults that control fluid flow that is the NW-SE trending faults that bring in high temperature and Cl rich waters, and the NE-SW trending Olkaria fracture tend to carry cool temperature waters that have led to decline in enthalpies of the wells it cuts through. The faults within the Ol Njorowa gorge act to carry cool, less mineralized water. Though initially, these effects were thought to be in shallow depths, an indication in OW-901 which is a deeper at 2200 m compared to 1600 m of OW-23 well that proves otherwise. This is, however, to be proved later as much deeper wells have been sited.

Waswa, AK, Nyamai CM.  2016.  THE GEOLOGY AND MINERAL RESOURCES POTENTIAL OF KENYA. Symposium on Capacity Building in Sustainable Resource Development in Africa.

2015

WASWA, AARONK, Nyamai CM, MATHU ELIUDM, Ichang’i DW.  2015.  Integration of Geological Mapping and Remote Sensed Studies for the Discovery of Iron–Ore Mineralization in Mutomo–Ikutha Area, SE Kenya. Universal Journal of Geoscience. 3(2):39-50. AbstractWebsite

This research integrates geology with remote sensing techniques to establish characteristic features that can be used to discover iron ore mineralization within the Neoproterozoic rocks of Mutomo – Ikutha area in south eastern Kenya. The association of hornblende gneiss and shearing as well as alteration processes near the mineralized regions appear to play an important role in the distribution and localization of the iron mineralization The methods used in this research include Image processing techniques applied on the digital subset ETM+ data that cover Mutomo – Ikutha area and geological field mapping. These techniques generated several products of enhanced satellite imagery, such as colour composite images, ratio images and principal component images. These techniques have been successfully used in the lithological discrimination of iron ore bearing sheared hornblende gneisses. The capabilities of remote sensing data to characterize the iron ore bearing gneisses, in addition to characterization and mapping the hydrothermal alteration zones helped in identification of iron mineralization regions. Extensive field geologic and geochemical investigations to the pronounced zones delineated by the image processing technique, led to discovery of four locations of high iron anomalies with some iron mineralization, mainly connected to the studied Neoproterozoic hornblende gneisses. Chemical studies were carried out using atomic absorption spectrophotometer (AAS) and X-Ray florescence, for some selected mineralized samples. Petrographic analysis and physical properties of the iron minerals were carried out as well. These investigations confirm the present iron mineral to be magnetite ore enriched with phosphates. The magnetite is found in close association with apatite chalcopyrite, quartz, and chlorite. Relics of corroded magnetite grains are occur along the Tiva river bed as well as along the road sides.

GithinjI, TW, Nyamai CM, Kutukhulu AW.  2015.  Overview of mineral processing and beneficiation in Kenya. Mineral processing and beneficiation.
Martelat, JE, G G, D O, Bosse V, Omito E, D I’i, Nyamai CM, Wamunyu A, Monie P.  2015.  U/Pb Ages of zircon and monazite from the tsavorite-bearing Neoproterozic rocks of southeastern Kenya, and the significance of static crystallisation of the tsavorite, August 2015. 13th SGA Biennial Meeting 2015. , Nancy, France Abstract

Tsavorite, the vanadian variety of green grossular, is hosted exclusively in metasedimentary formations in the Neoproterozoic Metamorphic Mozambique Belt. In order to understand the origin of tsavorite in southeastern Kenya we integrated field investigations, geochemical studies, and dating. Two units are seen in outcrop: 1) a metasedimentary sequence, and 2) a quartz-feldspar migmatitic group. This second group of rocks shows classic "Pan-african geometry" with vertical and horizontal foliation planes. The metamorphism attains granulite facies. The metasedimentary sequence is different and recorded lower metamorphism (high-amphibolite facies, 680 °C), and if static recrystallization occurs, few traces of melting was observed. Landslide with sediment deformation structures of the sedimentary deposition are preserved. Systematic LA-ICPMS U/Pb dating was done on monazite and zircon. The migmatitic rocks recorded ages from 615 Ma to 585 Ma. The metasedimentary rocks recorded ages from 600 Ma to 595 Ma. Older ages of 850-720 Ma seems to be inherited ages from magmatic minerals. The formation of tsavorite is the result of a sedimentary sequence preserved from strain but heated by surrounding granulitic rocks between 600 to 595 Ma. The regional associated tectonic process is unclear but efficient for vertical displacement. We suggest that it is a peculiar event and process, and was unable to completely recrystallize the sedimentary rocks. These last are exceptionally preserved from strain and melt, a case that may be unique in the world.

Nyamai, CM, MATHU ELIUDM, Ichang’i DW, WASWA AARONK.  2015.  Application of magnetic survey in the investigation of iron ore deposits and shear zone delineation: case study of Mutomo-Ikutha area, SE Kenya. International Journal of Geosciences,. 6(7) AbstractFull Text

The main objective of this research was to use ground magnetic survey to delineate shear zone and iron ore deposit within the Neoproterozoic rocks of Mutomo-Ikutha area of south eastern Kenya. Total field magnetic data was recorded by using high resolution proton precision geometric magnetometer which recorded total components of the ground magnetic anomaly data running through sixteen traverses. The field data was qualitatively and quantitatively interpreted and the results gave values for the total component measurements of ground magnetic anomaly that varied between a minimum negative peak value of about 250 nanoTesla and a maximum of about 1000 nanoTesla. 550 nanoTesla was considered to be threshold of the iron mineralization within the area. The results indicated that the western part of Mutomo-Ikutha was sheared, faulted and contained iron ore mineralization trending in the north-south direction. Areas with high anomalous values were geochemically proven to contain magnetite.

Nyamai, C, Rollion C, Feneyrol J, Martelat J-E, Omito E, Daniel Ichang'i, Wamunyu A.  2015.  The boron isotopic composition of tourmaline from tsavorite deposits in the Neoproterozoic Mozambique metamorphic belt, with a special focus on the mining districts in Kenya, August 2015. 13th SGA Biennial Meeting. , Nancy, France Abstractgiulianietal.boronsga-2015.pdf

The dravitic tourmalines associated with different types of rock from the tsavorite-bearing
metasedimentary Neoproterozoic sequence in Kenya, Tanzania, and Madagascar show two
ranges of boron isotopic compositions:(1) Tourmalines associated with tsavorite nodules
have homogenous 8113 values of-19.8 1 1.2 'llm that clearly involve continental evaporitic
material;(2) Tourrnalines from unmineralized rocks (elastic metasediments, metapegmatite,
and marble) have 8118 values between 45.9 and 40.356 “, which reflect a magmatic source
for the elastic tourmaline and probably an evaporitic one for tourmaline in marble.

2014

Onyancha, C, Nyamai C.  2014.  Lithology and Geological Structures as Controls in the Quality of Groundwater in Kilifi County, Kenya. British Journal of Applied Science & Technology. 4(25):3631. AbstractFull Text

Aims: Saline and brackish water has been encountered in more than half of the boreholes
across Kilifi County. The purpose of this study was to analyze the relationship between
lithology and structural geology and the quality of water encountered in boreholes in the
study area. Study Design: The study involved field observation of boreholes and collection of
hydrogeological data and analysis of geological and structural setting and water quality.
Place and Duration of Study: Borehole data was collected between January and June 2012.
Field observation of boreholes was carried out between June and September 2012. Data
analysis was carried out between October 2012 and July 2013 at Masinde Muliro University
and University of Nairobi.

2013

Nyamai, C.M. in Feneyrol J., GOFMLGPISGDAE.  2013.  New aspects and perspectives on Tsavorite Deposits. Ore Geology Reviews 53 (2013) pp 1–25.. Ore Geology Reviews . 53 (2013):pp1–25.. Abstractsciencedirect

ABSTRACT

Tsavorite, the vanadian variety of green grossular, is a high value economic gemstone. It is hosted exclusively in the metasedimentary formations from the Neoproterozoic Metamorphic Mozambique Belt. The deposits are mined in Kenya, Tanzania and Madagascar and other occurrences are located in Pakistan and East Antarctica.

They are located within metasomatized graphitic rocks such as graphitic gneiss and calc-silicates, intercalated with meta-evaporites. Tsavorite is found as primary deposits either in nodule (type I) or in quartz vein (type II), and in placers (type III). The primary mineralizations (types I and II) are controlled by lithostratigraphy and/or structure. For the African occurrences, the protoliths of the host-rocks were deposited at the beginning of the Neoproterozoic within a marine coastal sabkha environment, located at the margin of the Congo–Kalahari cratons in the Mozambique Ocean. During the East African–Antarctican Orogeny, the rocks underwent high amphibolite to granulite facies metamorphism and the formation of tsavorite deposits occurred between 650 and 550 Ma. The nodules of tsavorite were formed during prograde metamorphism, calcium coming from sulphates and carbonates, whereas alumina, silicates, vanadium and chromium probably came from clays and chlorite. The veins were formed during the deformation of the metasedimentary platform units which experienced shearing, leading to the formation of fault-filled veins.

Metasomatism developed during retrograde metamorphism. The metasedimentary sequences are characterized by the presence of evaporitic minerals such as gypsum and anhydrite, and scapolite. Evaporites are essential as they provide calcium and permit the mobilization of all the chemical elements for tsavorite formation. The H2S–S8 metamorphic fluids characterized in primary fluid inclusions of tsavorites and the δ11B values of coeval dravite confirm the evaporitic origin of the fluids. The V2O3 and Cr2O3 contents of tsavorite range respectively from 0.05 to 7.5 wt.%, while their δ18O values are in the range of 9.5–21.1‰.

The genetic model proposed for tsavorite is metamorphic, based on chemical reactions developed between an initial assemblage composed of gypsum and anhydrite, carbonates and organic matter deposited in a sabkha-like sedimentary basin.

2010

Nyamai, C.M., Ngecu WM, Kianji G.  2010.  SGL 308: Introduction to Geological Mapping (Lecture series).

2009

MUNYAO, DRNYAMAICHRISTOPHER.  2009.  Nyamai, C.M., Mingala, O.J., and Phillips, C. 2009. Sub-regional/Regional Organizations and Popular Social Engineering in Africa: Empowering young people and the spirit of volunteerism (civic service). In: A. Amuwo, H. Pul and I.O. Adadevoh (Eds.) Civil S. Proceedings of the XIIth International Anatomical Congress: London 764 A.. Abstract

One of the critical issues for Community Development, Civil Society action and Governance anywhere and specifically in Africa is to create leaders at the fastest possible rate, at all levels of the society/ community. Such levels of leadership revolve round - skilled, ethical, effective and unifying leadership. Young people are most eager to play a leadership role in these efforts. The values/ benefits of the African young people involvement in Civil Society in the African states will bring energy, catalyze other group members to rethink their priorities, commitment and remove invisible barriers that have kept them from moving forward. Typically and traditionally in many cultures, young people have been excluded from efforts to rebuild their communities. This marginalization of our youth not only harms them and endangers our future, but it also cheats the world of a valuable resource. If we are to function effectively as local and even global communities then we must incorporate all significant voices. This paper argues that an enduring and positive community renewal is possible only if all members are involved and feel a sense of ownership. On the other hand, the spirit of volunteerism by young people helps to create a stable and cohesive society and as a result add value to the services that governments provide. Voluntary action creates bonds of trust and encourages cooperation; in other words it creates social capital. Volunteerism draws people of different ethnic origins, religion and economic status. This compositional aspect enhances social harmony. Voluntary participation in public affairs can also help to create a politically literate public, which is important for the preservation of democratic principles. Volunteer effort is essential to Civil Society action as a way that would enhance community policing and conflict resolution. Service For Peace (SFP) Kenya Chapter as an organization, through its young people empowerment program has the aim to integrate service learning and volunteerism in the processes of capacity development/ building, creating appropriate awareness, dissemination and networking of the youth in the sub-regional and region areas. The Kenyan Chapter serves as a knowledge resource base for periodic value-based training programs on volunteerism.

2008

MUNYAO, DRNYAMAICHRISTOPHER.  2008.  SGL 308: Introduction to Geological Mapping, Lecture series. Proceedings of the XIIth International Anatomical Congress: London 764 A.. , Nairobi: Nairobi University Press. Abstract

One of the critical issues for Community Development, Civil Society action and Governance anywhere and specifically in Africa is to create leaders at the fastest possible rate, at all levels of the society/ community. Such levels of leadership revolve round - skilled, ethical, effective and unifying leadership. Young people are most eager to play a leadership role in these efforts. The values/ benefits of the African young people involvement in Civil Society in the African states will bring energy, catalyze other group members to rethink their priorities, commitment and remove invisible barriers that have kept them from moving forward. Typically and traditionally in many cultures, young people have been excluded from efforts to rebuild their communities. This marginalization of our youth not only harms them and endangers our future, but it also cheats the world of a valuable resource. If we are to function effectively as local and even global communities then we must incorporate all significant voices. This paper argues that an enduring and positive community renewal is possible only if all members are involved and feel a sense of ownership. On the other hand, the spirit of volunteerism by young people helps to create a stable and cohesive society and as a result add value to the services that governments provide. Voluntary action creates bonds of trust and encourages cooperation; in other words it creates social capital. Volunteerism draws people of different ethnic origins, religion and economic status. This compositional aspect enhances social harmony. Voluntary participation in public affairs can also help to create a politically literate public, which is important for the preservation of democratic principles. Volunteer effort is essential to Civil Society action as a way that would enhance community policing and conflict resolution. Service For Peace (SFP) Kenya Chapter as an organization, through its young people empowerment program has the aim to integrate service learning and volunteerism in the processes of capacity development/ building, creating appropriate awareness, dissemination and networking of the youth in the sub-regional and region areas. The Kenyan Chapter serves as a knowledge resource base for periodic value-based training programs on volunteerism.

2007

MUNYAO, DRNYAMAICHRISTOPHER, Ambrose SH, MATHU ELIUDM, Williams MAJ.  2007.  GEOLOGY, GEOCHEMISTRY, AND STRATIGRAPHY OF THE LEMUDONG’O FORMATION, KENYA RIFT VALLEY, December. Kitlandia Vol.56:53-64. : The Cleveland Museum of Natural History Abstract

ABSTRACT
The Lemudong’o Formation is defined here as part of a late Miocene to Late Pleistocene sequence of stratified lavas, air-fall and waterlain tuffs, lacustrine, alluvial, and fluvial sediments, and paleosols, that crop out over an approximately 25*50 km area on the western margin of the southern Kenyan Rift Valley, approximately 100 km west of Nairobi. The study area is deeply incised by three major permanent river systems that expose sediments of three late Neogene lake basins. The Lemudong’o Formation comprises deposits of the second paleolake basin, which formed during the late Miocene. Stratigraphic sections in several localities are described and correlated in this report, the Lemudong’o Formation is defined, and a basin sedimentary history and environmental reconstruction is proposed.

The Lemudong’o Formation has three main phases of sedimentation with a total thickness of 135 m. Phase 1 is represented by predominantly lacustrine and lake-margin siltstones, mudstones,and sandstones. Phase 2 comprises paleosols in the basin center, and fluvial and alluvial sediments on the eastern basin margin. Phase 3 comprises mainly waterlain tuffs and silts, capped by a welded tuff. Phase 2 may reflect a more arid climate, or a lower basin-overflow elevation. Four tuffs in upper phase-1 mudstones in Lemudong’o Gorge are dated to 6.12 – 6.08 Ma. The main fossil-bearing horizons at Lemudong’o Gorge Locality 1 lie between, and immediately above, the dated tuffs. Fossils are associated with beach and/or deltaic sands and fine gravels, and silty and sandy claystones representative of an intermittently flooded lake margin

MUNYAO, DRNYAMAICHRISTOPHER.  2007.  Nyamai C.M. et al. 2007. The Paleoecology and Paleogeographic Context of Lemudong. Kirtlandia Vol. 56:38-52. : The Cleveland Museum of Natural History

2005

MUNYAO, DRNYAMAICHRISTOPHER.  2005.  E.M Mathu and C.M Nyamai - Recent Findings of the geology, tectonics and economic resources of the Neoproterozoic Mozambique Belt in East African and the way forward. - 2005. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History

2004

MUNYAO, DRNYAMAICHRISTOPHER.  2004.  Nyamai, C.M. 2004. SGL 201: Principles of Mineralogy, Lecture series. Nairobi University Press, pp 119.. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  2004.  Ngecu, W.M., Nyamai, C.M. and Erima, G. 2004. The extent and Significance of mass-movements in Eastern Africa: Case studies of some major landslides in Uganda and Kenya. Environmental Geology, Vol. 46, pp 1123-1133.. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History

2003

MUNYAO, DRNYAMAICHRISTOPHER.  2003.  Nyamai, C.M., Mathu, E.M., Wallbrecher, E. and Opiyo-Akech. 2003. A reappraisal of the geology, structures and tectonics of the Mozambique Belt in Kenya, east of the rift system. African Journal of Science and Technology (AJST), Vol. 4, No.2, pp 51-71. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  2003.  Nyamai, C.M. 2003. SGL 101: Materials of the Earth, Lecture series. Nairobi University Press, pp 110.. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History

2002

Nyamai, CM, Surapunt S, Itagaki K.  2002.  Phase relations in the Cu2S-FeS-ZnS and Cu2S-PbS-ZnS Ternary Systems at 1473 K: Extraction of Zinc from sulfide ore using liquid copper as a reagent. AbstractPhase relations in the Cu2S-FeS-ZnS and Cu2S-PbS-ZnS Ternary Systems at 1473 K: Extraction of Zinc from sulfide ore using liquid

The use of liquid copper as a medium for zinc extraction has been used in the Warner Process as a method of processing zinc-lead sulphide ore. The recovery of zinc metal is based on the reaction: ZnS(s) + 2Cu(l) = Zn(g) + Cu2S(l) In this method, thermodynamic and phase equilibria investigations of the Cu2S-FeS-ZnS and Cu2S-PbS-ZnS systems are of importance and form the basis for the liquid sulphide phase which appears as a product and is used as a solvent in the Warner Process. Phase relations in the Cu2S-FeS-ZnS and Cu2S-PbS-ZnS ternary systems were determined experimentally at 1473°K to provide a fundamental basis for the new zinc smelting process. The results show that the solid solubility of ZnS in the two systems is very small (2 wt% to 3 wt% ZnS in FeS, 4 wt% ZnS in Cu2S for the Cu2S-FeS-ZnS system; less than 0.5 wt% ZnS in both PbS and Cu2S for the Cu2S-PbS-ZnS system). The Raoultian Activity Coefficient of ZnS in the liquid mixtures and the vapour pressure of zinc over the matte in both systems is relatively large (γ° = 7.7 - 15.8, Pzn(atm) = 0.088 - 1.026 for the Cu2S-FeS-ZnS system; γ° = 8.9 - 12.9, PZn(atm) = 0.075 - 0.214 for the Cu2S-PbS-ZnS system). On the FeS-ZnS join, the only phases detected are FeS and iron-rich sphalerite (Zn, Fe)S. The binary join mixture occurs at about 92 wt% FeS-8 wt% ZnS at 1473°K. Electron microprobe examination of the quenched samples indicate about 47 wt% to 48 wt% FeS in sphalerite and about 2 wt% to 3 wt% ZnS in the iron sulphide phase. On the Cu2S-ZnS join, microprobe analysis reveals that the maximum solubility is 4 wt% Zn in liquid Cu2S and 3.6 wt% Cu in solid ZnS. In the Cu2S-PbS-ZnS ternary system, microprobe analysis of the quenched samples indicate on average, 5 wt% ZnS in the liquid phase region. The only phases detected on the PbS- ZnS join are ZnS and PbS. The eutectic phase contains, on average, 13 wt% ZnS. The phase relationships, very low solid solubilities of zinc sulphide in the liquid mixtures of both Cu2S-FeS-ZnS and Cu2S-PbS-ZnS systems, coupled with the high Raoultian Activity Coefficient of ZnS as well as the high vapour pressure of zinc over matte all favour the partitioning of zinc metal into the vapour phase. This new process is cost effective and bypasses the expensive and tedious conventional technique of zinc production involving oxidation of the sulphide ore by roasting followed by a reduction process to extract the zinc. The results indicate that a new zinc smelting technology using the Warner Process would be more efficient and preferable over the traditional methods of zinc extraction.

MUNYAO, DRNYAMAICHRISTOPHER.  2002.  Nyamai, C.M 2002. University-Industry Collaboration: a strategy for Rapid Development. In: L. Vasconcelos (Ed.) Regional workshop on Tertiary Sector Geoscience Education in Southern Africa. Building Regional Networks on local expertise. University Press o. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  2002.  Mathu, E.M., Nyamai, C.M. and W.M. Ngecu. 2002. Environmental degradation through quarrying: a case study in Tala-Kangaundo area, central Kenya. Africa Geoscience Review, Vol. 9, No. 4, pp. 385-395.. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  2002.  Phase relations in the Cu2S-FeS-ZnS and Cu2S-PbS-ZnS Ternary Systems at 1473 K: Extraction of Zinc from sulfide ore using liquid copper as a reagent. Canadian Mining and Metallurgical Bulletin (CIM) Vol, 95 pp. 129-132.. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History

2001

Nyamai, CM, Mathu EM, Wallbrecher E, Opiyo-Akech..  2001.  A Reappraisal of the Geology, Structures and Tectonics of the Mozambique Belt in Kenya East of the Rift System. Gondwana Research. Vol. 4(No.4)CLICK HERE FOR THE ABSTRACT
MUNYAO, DRNYAMAICHRISTOPHER, MATHU PROFMUTHUMBIELIUD.  2001.  New fossilferous sites in Gatarakwa, central Kenya : Their geological setting, stratigraphy, and contribution to palaeontological research in East Africa. Journal of The Geoscience Society of Camerron, Vo. 1, No.1A, pp. 80-81. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  2001.  A comparison of the uncomphagrite and turjaite mineralogy (phlogopite, melilite, etc.) of the south Nyanza district, western Kenya with similar rock complexes in Asia, Australia and America. Gondwana Research, Vol. 4, No.4, p.719. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History

2000

Nyamai, CM, Njenga FG.  2000.  Post-traumatic stress disorder: Case report. AbstractPost-traumatic stress disorder: Case report

Following exposure to a major traumatic event like the August seventh 1998 Nairobi bomb blast various reactions occur, some of which result in stress-related psychiatric disorders. We have described one such case, and used it to illustrate the salient features of posttraumatic stress disorder. We have outlined the diagnostic categories of the post-traumatic disorders and discussed the different treatment modalities applicable

MUNYAO, DRNYAMAICHRISTOPHER, OPIYO PROFAKECHNOBERT.  2000.  Structures, Metamorphism and Geochronology of the Mozambique belt metamorphic and intrusive rocks from Matuu-Masinga area, central Kenya. African Journal of Science and Technology (AJST), Science and Engineering Series, Vol. 1, No.1, pp 47-55.. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  2000.  Petrography, mineral chemistry and thermobarometry of the Neoporoterozoic Mozambique belt rocks of Matuu-Masinga area, central Kenya. Proceedings of the International seminar UNESCO-IUGS-IGCP-368, Geological Survey of India Special Publication No. 57,pp.2. Ist intern. Geol. Field conf. on Oban-Odudu Massif, S.E Nigeria Calabar Univer., Scientific Programme and Abstracts pp17-18. : The Cleveland Museum of Natural History

1999

MUNYAO, DRNYAMAICHRISTOPHER, OPIYO PROFAKECHNOBERT.  1999.  Geochemistry and Tectonomagmatic affinities of the Mozambique belt intrusive rocks in Matuu-Masinga area, central Kenya. Gondwana Research, Vol.2, pp. 387-399.. Ph.D Degree Thesis, University of Nairobi Kenya. : The Cleveland Museum of Natural History
MUNYAO, DRNYAMAICHRISTOPHER.  1999.  Crustal evolution of the Neoproterozoic Mozambique belt rocks in Matuu-Masinga area, central Kenya: Implications to their tectonic setting and potential mineralization.. Ph.D Degree Thesis, University of Nairobi Kenya. : The Cleveland Museum of Natural History

1995

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