Layered intrusion

Layered intrusions. Chlorine isotope studies of the Stillwater Complex of Montana, USA (e.g., Stewart et al. 1996 Boudreau et al. 1997), and the Bushveld Complex in the Republic of South Africa (e.g., Willmore et al. 2002) show that both intrusions are anomalously rich in chlorine (e.g., Boudreau et al. 1986 Willmore et al. 2000), but that, their chlorine-isotopic compositions are distinct from one another (Fig. 1). The 8 Cl values of Stillwater samples range from -0.93%o to 0.27%o with all but one value below 0.1 %o (Fig. 1). In contrast the... 

Schoenberg et al. (2008) presented the first set of Cr isotope data for rocks and Cr(ll) rich ores. Mantle derived rocks and chromite ores from layered intrusions have a uniform Cr/ Cr isotope ratio very close to the certified Cr standard NIST SRM 979. The Cr isotope composition of hydrothermal lead chromates is substantially heavier (S Cr from 0.6 to 1.0%o) than the rocks from which the chromium was leached. 

U-Pb analytical data of igneous zircon samples from a silicic dike intruded into the Dufek layered intrusion are as follows (Minor and Mukasa, 1997), °" Pb/... 

Dike A layered intrusive igneous rock or magma that cuts across layers and other structures in its host rocks. 

Irvine, T. N. (1975) Crystallization sequences in the Muskox intrusion and other layered intrusions. II. Origin of chromitite layers and similar deposits of other magmatic ores. Geochim. Cosmochim. Acta, 39,991-1020. 

Wiebe R. A. (1996) Mafic-sihcic layered intrusions the role of basaltic injections on magmatic processes and the evolution of silicic magma chambers. Trans. Roy. Soc. Edinburgh Earth Sci. 87, 233 -242. 

Figure 2 Major element variations of eclogites and associated ultramafic rocks from the Su-Lu and Dabie terranes of east-central China (Jahn, 1998). Eclogites are generally basaltic and quartz-normative, with some showing the cumulate nature of their protoliths. Type 1 is gneiss-hosted, type II, marble-associated. Type III are members of layered intrusions or associated with ultramafic rocks. Also plotted are data from peridotites (Perid.),...

Rich accumulations of both rare and common metallic elements make Proterozoic rocks a significant source of mineral wealth for North America, as on other continents. Chromium, nickel, copper, tin, titanium, vanadium, and platinum ores are found together in the onionlike layers of crystallized igneous rocks called layered intrusions. Greenstone belts are mined for copper, lead, and zinc, each of which is mixed with sulfur to form a... 

Hatton, C. J. von Gruenewaldt, G. 1990. Early Precambrian layered intrusions. In Hall, R. P. Hughes, D. J. (eds) Early Precambrian Basic Mag-matism. Chapman and Hall, New York, 56-82. 

Phinney, W. C. 1982. Petrogenesis of Archean anorthosites. In Walker, D. McCallum, I. S. (eds) Workshop on Magmatic Processes of Early Plcmetary Crusts Magma Oceans and Stratiform Layered Intrusions. Lunar and Planetary Institute Technical Report, 82-01, 121-124. 

Deterministic permeability models. Application of the above principles to high temperature stable isotopes was pioneered by Norton and Taylor (1979) in their models of isotopic alteration of the Skaergaard layered intrusion and its host rocks. They used discreet zones and layers to which they assigned individual permeability values. Cartwright (1997) presented two-dimensional cases in which he modeled individual high permeability networks (fractures). Cook et al. (1997) used multiple, constant permeability zones to model the distribution of lithologies in the Alta stock area (see detailed discussion below). The advantage of this approach is that the calculated stable isotope patterns can be compared directly with measured patterns provided the permeability structure is adequately known. Permeability is also a function of time. Bolton et al. 

Boudreau AE (1993) Chlorine as an exploration guide for the platinum-group elements in layered intrusions. J Geochem Explor 48 21-37... 

Sr/ Sr with height up the intrusion and that there is a marked increase in initial ratio in the central part of the layered intrusion — the Main Zone (Figure 6.23). The gradual change in Sr/ Sr from 0.7065 at the base of the intrusion to 0.7073 at the top is interpreted as magma addition and mixing. The high initial ratio of the Main Zone (0.7085) represents a different liquid layer (probably contaminated with... 

Pokrovskite, Mg2(C03)(0H)2- 0-5HjO, a new mineral from the Zlatogorskaya layered intrusive, 413 ... 

Cawthorn RG (1996) Layered intrusions. Elsevier, Amsterdam, The Netherlands... 

Ford AB (1970) Development of the layered series tmd capping granophyre of the Dufek intrusion of Antarctica. In sser DJL, von Gruenewaldt G (eds) Symposium on the Bushveld igneous complex and other layered intrusion. Geol Soc South Africa, Spec Pub 1 492-510... 

Marsh BD, Philipp JR (1996) Three-dimensional magmatic filling of Basement sill revealed by unusual crystal concentrations. Antarctic J US 31(2) 39-40 Marsh BD, Zieg MJ (1997) The Dais layered intrusion A new discovery in the Basement sfil of the McMurdo dry valleys. Antarctic J US 32(5) 18-20... 

Alkali syenite or granite U,Th,P,Zr,S,REE Refractory minerals, uraninite or uranothorite associated with dykes and apophyses or layered intrusions Illmaussaq, Greenland Baker Lake, Canada... 

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