A Reappraisal of the Geology, Structures and Tectonics of the Mozambique Belt in Kenya East of the Rift System

Nyamai, C. M.; Mathu, Eliud M.; Wallbrecher, E.; Opiyo-Akech, Nobert

doi:10.1016/s1342-937x(05)70517-7

Cited by 6 publications

(7 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the context of the Tertiary-Quaternary Afro-Arabian rift system, evidence for ancient (PanAfrican) mantle magmatism/metasomatism in a convergent tectonic regime comes from mafic xenoliths (granulites and pyroxenites) from the Chyulu Hills, southern Kenya (Ulianov and Kalt 2006; ). Similar to the Chyulu Hills, the crustal basement of the Marsabit volcanic field consists of Precambrian polymetamorphic rocks of the Mozambique mobile belt resulting from multiple PanAfrican accretion events (e.g., Key et al 1989;Nyamai et al 2003). The preservation of mantle rocks recording the same events would be a logical consequence, yet, has to be tested by further work.…”

Section: Origin Of the Grt Websteritesmentioning

confidence: 99%

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser

Olker

Kalt

et al. 2008

Contrib Mineral Petrol

View full text Add to dashboard Cite

Garnet-bearing and garnet-free pyroxenite xenoliths from Quaternary basanites of Marsabit, northern Kenya, were analysed for microstructures and mineral compositions (major and trace elements) to constrain the thermal and compositional evolution of the lithospheric mantle in this region. Garnet-bearing rocks are amphibolebearing websterite with *5-10 vol% orthopyroxene. Clinopyroxene is LREE-depleted and garnet has high HREE contents, in agreement with an origin as cumulates from basaltic mantle melts. Primary orthopyroxene inclusions in garnet suggest that the parental melts were orthopyroxene-saturated. Rock fabrics vary from weakly to strongly deformed. Thermobarometry indicates extensive decompression and cooling (*970-1,100°C at *2.3-2.6 GPa to *700-800°C at *0.5-1.0 GPa) during deformation, best interpreted as pyroxenite intrusion into thick Paleozoic continental lithosphere subsequently followed by continental rifting (i.e., formation of the Mesozoic Anza Graben). During continental rifting, garnet websterites were decompressed (garnet-to-spinel transition) and experienced the same P-T evolution as their host peridotites. Strongly deformed samples show compositional overlaps with cpx-rich, initially garnet-bearing lherzolite, best explained by partial re-equilibration of peridotite and pyroxenite during deformation and mechanical mingling. In contrast, garnet-free pyroxenites include undeformed, cumulate-like samples, indicating that they are younger than the garnet websterites. Major and trace element compositions of clinopyroxene and calculated equilibrium melts suggest crystallisation from alkaline basaltic melt similar to the host basanite, which suggests formation in the context of alkaline magmatism during the development of the Kenya rift.

show abstract

Section: Origin Of the Grt Websteritesmentioning

confidence: 99%

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser

Olker

Kalt

et al. 2008

Contrib Mineral Petrol

View full text Add to dashboard Cite

show abstract

“…NRZ, Nyanza rift zone. MMA, Matuu‐Masinga area exposing Neoproterozoic arc granitoids [ Nyamai et al , 1999, 2003]. The distribution of granulites, ophiolites, and ultramafics in the region are also shown [ Shackleton , 1986; Smith and Mosley , 1993].…”

Section: Introductionmentioning

confidence: 99%

“…It will be instructive to examine the audiofrequency magnetotelluric (AMT) data along this particular seismic‐gravity profile to ascertain any possible shallow‐depth signature of the LDS and ANL shear zones and their relationship with the deep basement. A recent combined geological, geochemical and isotopic study identified a Neoproterozoic magmatic arc (see MMA in Figure 1) near the Athi‐Ikutha shear zone [ Nyamai et al , 1999, 2003] raising the possibility of a concealed fossil subduction zone or hitherto unknown deep features in the region that can be imaged using the available LMT data. We posit that the reactivation of both shallow and deep systems of Precambrian shear zones and thrusts under varying stress conditions (possibly induced by lithospheric buckling) and their possible subsequent modification by fluids from the widespread Quaternary magmatism in this region should render them detectable by broadband MT conductivity imaging.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous crust and upper mantle across southern Kenya and the relationship to surface deformation as inferred from magnetotelluric imaging

Meju

Sakkas

2007

J. Geophys. Res.

View full text Add to dashboard Cite

[1] We have used magnetotelluric data imaging to determine the resistivity structure across southern Kenya and our results suggest the presence of a buckled blocky or segmented lithosphere across the region. Prominent steep conductive zones at the Oloololo (OLO) escarpment and eastern rift margin allow us to subdivide the region into three crustal domains. West of OLO, a bow-shaped conductor underlies a 10 km thick resistive upper crustal unit spatially correlating with an exposed Archaean greenstone belt. Between OLO and the eastern rift margin are found steeply dipping alternating conductive and resistive zones that appear buckled. East of this belt are found prominent, 5 to 20 km deep, subhorizontal conductors atop steep resistive blocks with flanking conductors. The main steep features in the crust appear to extend below the seismic Moho and thus suggest the presence of anomalously thick crust across the region. A 50 km-wide and 4-8 km deep w-shaped (double half-graben) structure is suggested at the position of the Kenyan rift. We show that our inferred lateral zoning is consistent with collocated gravity and seismic measurements. We propose a link between the deep resistivity heterogeneity and surface deformation pattern in the area.

show abstract

“…The geology, structures and tectonic the history of the Mozambique Belt in Kenya have been reviewed by Waswa et al [15]. Other reviewers of this belt include Mathu and Tole [16]; Mathu [17]; Mathu et al [18]; Mathu et al [19]; Gaciri et al [20]; Biyajima et al [21]; Suwa et al [22]; Opiyo-Aketch and Nyambok [23]; Hackman et al [24]; Mosley [25]; Nyamai [26]- [32]; Saggerson [33]; Walsh [34].…”

Section: Geology Of the Study Areamentioning

confidence: 99%

Application of Magnetic Survey in the Investigation of Iron Ore Deposits and Shear Zone Delineation: Case Study of Mutomo-Ikutha Area, SE Kenya

Waswa¹,

Nyamai²,

Mathu³

et al. 2015

IJG

View full text Add to dashboard Cite

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.

show abstract

A Reappraisal of the Geology, Structures and Tectonics of the Mozambique Belt in Kenya East of the Rift System

Cited by 6 publications

References 2 publications

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Heterogeneous crust and upper mantle across southern Kenya and the relationship to surface deformation as inferred from magnetotelluric imaging

Application of Magnetic Survey in the Investigation of Iron Ore Deposits and Shear Zone Delineation: Case Study of Mutomo-Ikutha Area, SE Kenya

Contact Info

Product

Resources

About