 | | Journal (article/letter/editorial) | | and Okenyenyaigneous complexes, north-western Namibia Received: 10 August 1993/Accepted: 15 January...units of the Brandberg and Okenyenya igneous complexes, northwestern Namibia, confirm the Early Cretaceous...rocks of Okenyenya, 133.3 _+ 1.4 to 129.2 _+ 0.7 Ma. The mean K - A r age of the Okenyenya complex is essentially...dating of this complex (129.1-123.4Ma). K - A r chronology for the Brandberg complex is in conflict with...layered intrusion yields the oldest age from the complex, 135.2 4- 1.4 Ma. The concordancy of age measurements |  | | Journal (article/letter/editorial) | | felsic magmatism in the Cretaceous Paresis ring complex, Namibia: evidence for mixing of crust and mantle-derived...subordinate intrusions of quartz syenite and alkali-feldspar syenite. These felsic units are accompanied...the farthest inland of any felsic complex in the Cretaceous ring complex group. The other ring complexes...comprise metaluminous feldspar rhyolites and peraluminous, more differentiated quartz-feldspar rhyolites. Both...the Congo craton and related inliers in northern Namibia. The comendites are peralkaline, highly differentiated |  | | Journal (article/letter/editorial) | | extensive crustal contamination in the Okenyenya igneous complex, Namibia I13MA A. MARTINEZ,J CHRIS HARRIS...Energy, Geological Survey, P.O. Box 2168, Windhoek, Namibia (Received August 9, 1995; accepted in revised...rock types from the 130 Ma Okenyenya igneous complex of northwestern Namibia. These rock types include...the difference in 6~80 values between coexisting feldspar, pyroxene, and biotite are consistent with equilibrium...monzodioritic body was the earliest to crystallize in the complex and this was followed by relatively uncontaminated |  | | Journal (article/letter/editorial) | | Gross Spitzkoppe topaz granite, central western Namibia: a geochemical and Nd–Sr–Pb isotope study Stephen...igneous complexes that formed in the Damaraland of Namibia during an episode of continental rifting and magmatism...of the GSS yield an age for emplacement of the complex at 125 F 1 Ma. Initial 87Sr/86Sr ratios vary from...from 5.6 to 6.4. The Pb isotopic ratios (K-feldspar or age-corrected whole rock) fall in the range...melting is by basaltic underplating of the source region in the lower crust. The range in initial Nd and |  | | Journal (article/letter/editorial) | | of the Alkaline Core of the Messum Igneous Complex, Namibia: Evidence for the Progressively Decreasing...3 GEOLOGICAL SURVEY, P.O. BOX 2168, WINDHOEK, NAMIBIA RECEIVED NOVEMBER 12, 1998; REVISED TYPESCRIPT...TYPESCRIPT ACCEPTED APRIL 12, 1999 The Messum complex of NW Namibia, a part of the Paraná– Etendeka volcanic...INTRODUCTION Paraná–Etendeka volcanism; Messum complex; alkaline core; crustal contamination; Tristan...Etendeka Igneous province in the Damaraland region of northwest Namibia (Fig. 1) contains numerous anorogenic |  | | Journal (article/letter/editorial) | | lamprophyre dyke from the Okenyenya igneous complex, northwestern Namibia. Mica separates were heat-treated...lamprophyre dike from the Okenyenya igneous complex, northwestern Namibia (Lanyon and le Roex 1995)....clinopyroxene, ilmenite, and very rare alkali feldspar and zeolite. The Okenyenya ultramafic lamprophyres are interpreted...1 except TABLE 1. Chemical Analysis (wt%) of Okenyenya (OKJ) and OLA 9037 phlogopites SiO2 TiO2 Al2O3...that the Fe3+ in the natural phlogopite from Okenyenya complex occurs exclusively via the Fe-oxy mechanism |  | | Journal (issue) | | island. The eontribution of Birkenmajer deseribes a region not very familiar in literature. He gives a review...transmission of seismic energy through the tectonically complex overlying section (Fig. 3). 239 100 km Basel...ofIvrea (crossed ruling); CRL = Cremosina line complex, bounding the Ivrea-Ceneri body (narrow horizontal...Helvetic nappes and the External Massifs is similarly complex, yet did not produce a comparable effect, and that...Scientific Party, 1991; Buness, 1992). The border region of the Po plain is problematic. Here, excellent |  | | Book | | and products 209 8. Granitic rocks 241 9. Alkali rocks 291 Appendix A – Mineral identification...Chapters 6 and 8. The final chapter examines the alkali rocks, whose diversity and mineralogical complexity...act as a type mineral in another (nepheline in alkali gabbro) or be present as an accessory in a third...simplest way to visualize the chemical composition of complex silicate materials is as a mixture of oxides: silicon...SiO2 contents range from 31% to 76%, and total alkali contents vary from 1% up to 15%. (This range is |
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