共查询到20条相似文献，搜索用时 93 毫秒
1.
Lithology and Mineral Resources - 相似文献
2.
3.
Theodore J. Bornhorst 《Chemical Geology》1975,15(4):295-302
A small (360 × 180 m) rhyolitic intrusive body in the lower portion of the Portage Lake Lava Series of Michigan's Keweenaw peninsula was mapped and sampled in detail. The rhyolite is one of a number of similar bodies which make up less than 1% of the total volume of this thick Late-Precambrian plateau basalt pile. The rock is a low-calcium rhyolite with fine-grained homogeneous texture and sparse phenocrysts of plagioclase and quartz. Analyses of selected trace and major elements for 21 samples taken from the body reveal a chemical zonation consisting of a core zone enriched in K, Rb and Ba, and a border zone relatively poor in these elements. Little areal difference is found with respect to other elements tested (Mn, Sr, Zr, Ca, Ti, and Fe). This apparently primary zonation seems to result from the migration of K, Rb and Ba during crystallization of the shallow intrusive. Though zoned, the trace-element chemistry of the Fish Cove body is distinct from that of eight other rhyolites in the Portage Lake Lava Series, and suggests that fingerprinting by trace elements might be a fruitful method for identifying and correlating the sources of numerous rhyolitic pebbles in conglomerates interbedded with the basaltlava flows of the Portage Lake Series. 相似文献
4.
5.
6.
7.
8.
9.
The Ishpeming Greenstone Belt is an Archean belt in the southern part of the Canadian Shield in the Upper Peninsula of Michigan, U.S.A. Two volcanic cycles are preserved in it. The oldest formation, and basal to the first cycle (the Kitchi Schist), consists of mafic metavolcanics, has a major serpentinized ultramafic body near its base, and grades upward to a coarse felsic volcanic breccia at the top of the cycle. This unit in turn is overlain by a sequence of mafic flows that grades upward to interbedded mafic flows and exhalites of the Mona Schist. This sequence has been intruded by the Dead River Pluton.The Ishpeming Greenstone Belt probably represents the keel of a previously much more extensive Greenstone Belt.Gold mineralization occurs associated with mafic basaltic volcanic rocks and serpentinized ultramafics low in the succession, and with carbonate-rich quartz-chlorite-sericite schists and exhalites higher in the sequence. No mineral deposits are now being exploited here. 相似文献
10.
美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带 总被引：1，自引：0，他引：1
Stephen G. Peters Gregory C. Ferdock Maria B. Woitsekhowskay Robert Leonardson Jerry Rahn 《地质找矿论丛》2000,15(1):1-16
贝茨金矿是卡林金矿带在的卡林型矿床,由多个高品位富矿体组成。金矿体产于不纯的碳酸盐岩角砾岩和侵入体中,明显受构造控制,矿体显示出同变形热液沉淀特征。在ＮＷＷ向的ＤＤＺ剪切褶皱构造带中,贝茨金矿的富矿构成空间上的分带形式,主要的富矿类型有含金红石的硅质富矿,伊利石－粘土－黄放富矿,含雄黄、雌黄的富矿,含辉锑矿的硅质富矿和多金属富矿。研究表明,成矿溶液为弱－中等盐度,在构造活动期上升并冷却。变形时水－ 相似文献
11.
W. Cullen Sherwood 《Environmental Geology》1989,14(2):99-106
Loading trends and sources of CI– in the South Fork of the Shenandoah River, Virginia were analyzed for the period 1929–1982. CI– has increased from approximately 2 mg/L (2,776 tons/yr) to over 10 mg/L (14,256 tons/yr). Natural CI– is estimated to be 1.01 mg/L (1,388 tons/yr) with precipitation providing 0.99 mg/L and rocks 0.02 mg/L. From 1929 to 1949 CI– concentrations were relatively constant and independent of discharge, conforming to the Type II curve of Davis and Zobrist (1978), indicative of natural or relatively uncontaminated streams. Since 1952 CI– concentrations increased exponentially as river discharge decreases conforming to the Type I curve of Davis and Zobrist for polluted streams. Since 1965 anthropogenic CI– loading at 12,868 tons/yr has remained relatively constant. Four major sources contribute 92.2 percent (11,871 tons/yr) of the anthropogenic CI–: (1) deicing salts—4,149 tons/yr, (2) domestic sewage—3,015 tons/yr, (3) livestock and poultry wastes—2,458 tons/yr, and (4) commercial fertilizers—2,249 tons/yr. 相似文献
12.
Linda A. Johnson John J.W. Rogers Richard M. Nagy 《Geochimica et cosmochimica acta》1976,40(11):1419-1420
The Llano uplift exposes rocks of approximately 1000 m.y. age. The weighted average composition of the exposed crust is: 70.7% SiO2; 0.35% TiO2; 13.6% A12O3; 3.4% total Fe as Fe2O3; 1.1% MgO; 2.6% CaO; 3.3% Na2O; and 4.4% K2O. This composition is similar to, but more potassic, than equivalent estimates for the Canadian shield. 相似文献
13.
14.
The Square Top intrusion, near Nundle, New South Wales, revealsin its mineralogy and chemistry the transition of analcime-olivinetheralite to analcime tinguaite. Chemical, X-ray, and opticaldata are presented on 2 plagioclases, 9 alkali feldspars, 2nephelines and 3 analcimes, from various members of the differentiationsequence. With differentiation, plagio-clase becomes enrichedin Ab and, to a lesser extent, in Or. The coexisting alkalifeldspars initially reveal enrichment in Ab and trend from sanidineto lime anorthoclase; subsequently in the tinguaites, the sanidinesbecome enriched in Or. Nephelines in the lower theralites havehighly sodic compositions and become slightly enriched in Kin the later differentiates. Replacement of Si by NaAl in theanalcimes decreases with progressive differentiation. The rapidcooling of this relatively small intrusion assisted fractionalcrystallization, and resulted in the preservation of disorderedplagioclase and alkali feldspars. The Square Top feldspar crystallizationtrends are compared with trends presented by Tuttle and Bowen(1958). The location of the feldspar boundary curve in the Ab–An–Orsystem and some general relationships in the undersaturatedportion of the Ne–Ks–Qz system, including the heteromorphicfelsic assemblages developed from the lowest temperature liquids,are also discussed. 相似文献
15.
The West Farrington pluton in the North Carolina Piedmont isconcentrically zoned from gabbro-diorite near the chilled marginsto leucogranodiorite in the center. A crystallization modelfor the West Farrington pluton has been derived utilizing chemical,petrographic, field, and experimental data. The model involvessimple in situ fractional crystallization from the margins inward,with minimal contamination, crystal settling and floating, ormetasomatism. Rocks of the pluton can be considered as mixturesof early crystallizing minerals (liquidus or near-liquidus phases)and crystallized interstitial liquids. Relative percentage ofentrapped pore liquid increased with increasing degree of crystallization. The original tonalite magma began crystallizing Fe-Ti spinels,plagioclase, and hornblende within a short temperature interval.Crystallization of these minerals controlled fractionation trends.The initial water content in the magma was probably 2–3per cent; under such conditions water saturation would havebeen reached after about 60 per cent of the magma crystallized,assuming crystallization in the lower epizone at about 2000bars total pressure. 相似文献
16.
17.
18.
J. P. N. Badham 《Mineralium Deposita》1975,10(2):153-175
Polymetallic hydrothermal vein mineralisation of the Ag-Ni, Co Arsenide type, and containing Bi and U, occurs in three mines and five uneconomic veins in the Camsell River area. Each occurrence is described in detail. The veins lie in sulphide-impregnated volcanic rocks of the Aphebian Great Bear Batholith. Large, NE-trending strike-slip faults were initiated during the terminal phases of orogeny (1750 m.y.), and were active intermittently for at least 300 m.y. The veins are located in splays and tension-fractures form the primary faults, and mineralised lenses are found in dilatant zones in these structures. The mineralisation shows a generalised paragenesis of U → Ag+arsenides → Bi, Sulphides, Sulphosalts, but there are variations. A model is presented to explain the temporal and spatial controls of mineralisation and to explain the perturbations in the paragenesis. It is concluded that the mineralisation is of magmatic origin and lateral secretion models are rejected. Discussions of the ultimate origin of the ore elements are not presented here. 相似文献
19.
20.