RESEARCH· ·1970·

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LOVERING, COOPER, DREWES, AND CONE B3 >- ..... () I.J.J ...J ...J Corona de Tucson EXPLANATION j !Qun•t' laUte J,.h: (Lre po'Phyry")) ~ ~ ~ ~ Granodiorite to quartz monzonite ~ Granodiorite x2oo 0 H 0:: u } ~ Granodiorite to quartz monzonite ..... :::E
B4 PETROLOGY AND PETROGRAPHY has been dated as about 68 m.y. (million years) (P. E. Damon, written commun., 1964; Drewes, 1968, p. C13). Six small elliptical stocks of Paleocene age, which consist largely of light-gray granodiorite, intrude the structurally complex rocks near Helvetia (Drewes, 1970b). Four of them were sampled for this study (fig. 1). The composition of these stocks is variable, rang- ' ing from granodiorite to quartz monzonite. Their inhomogeneity is exemplified by a stock in which the biotite content ranges from 1 to 10 percent. The rocks of these stocks are distinguishable from the Continental Granodiorite by their fresher appearance, the absence of phenocrysts, and the habit of their biotite, which forms discrete books. J\1odes of these rocks vary widely; that of the s·ample from the northernniost stock shown on figure 1, which is fairly representative of the granodiorite, is, to the nearest percent, quartz, 30; plagioclase, 45; microcline, 13; biotite, 10; and accessory ilmenitic magnetite, apatite, zircon, and sphene, 1. The stocks of Helvetia are not associated with the mineralization of the district. They have been isotopically dated as about .53 m.y. (Drewes and Finnell, 1968, p. 323; R. F. Marvin, written commun., 1968), but geologic field relations indicate that they may be slightly older. Quartz 1atite porphyry, locally referred to as the "ore porphyry," forms six small irregular plugs and many dikes in the Greaterville, Rosemont, and Helvetia mining districts. The four plugs sampled are shown on figure 1. The plugs are surrounded by aureoles of low-grade metamorphosed and mineralized rock. Copper, lead, zinc, and silver are the principal metals produced in these districts, but other metals are also present (Schrader 1915; Creasey and Quick, 1955; Drewes, 1970c). The porphyry is typically a grayishorange-pink, closely fracturedrock with a saccharoidal groundmass. It contains abundant bipyramidal quartz phenocrysts, sparse small biotite phenocrysts, and traces of disseminated sulfides. Modes of the porphyry are very uniform; the ·average of the modes of seven specimens, to the nearest percent, is quartz, 26 ; plagioclase, 45.; potassium feldspar (largely sanidine), 25; biotite, 3; and accessory sphene, apatite, magnetite, zircon, and sulfides, 1. Biotite from three of these plugs has been isotopically dated as about 56 m.y. (R. F. Marvin, written commun., 1967). The quartz latite porphyry appears to have been emplaced at a higher temperature than that at which the barren intrusives were emplaced, as indicated by its bypyramidal quartz and sanidine. The extremely ·irregular shapes of these plugs also suggest that the parent magma of the plugs was highly fluid, a condition that would be favored both by high temperature and by high volatile content. A high metal content of this magma 'is also indicated by the genetically related ore deposits. Biotite concentrates and their copper content Biotite from the Precambrian Continental Granodiorite is olive green and contains less than 5 percent mineral impurities, which .are chiefly chlorite. Biotite from the Cretaceous Madera Canyon Granodiorite is 1nodetate brown and contains about 10 percent ilmenite and sphene as poikilitic inclusions. Approximately 10 percent each of hornblende and chlorite is present in the mineral concentrates as discrete grains. Biotite from the Paleocene granodiorite and quartz monzonite porphyry stocks that have no known copper deposits associated with them is dark yellowish brown and contains about · 5 percent hematite, apatite, and zircon as inclusions. About 5-10 percent chlorite and minor amounts of sphene and plagioclase are present as accessory minerals in the concentrates. Four samples were collected from the quartz latite porphyry plugs, which are closely related to ·copper deposits. These plugs are nearly the same age as the barren monzonite porphyry._ Biotite froin this "ore porphyry" ranges from light brown to moderate brown, and contains about 5 percent apatite, rutile, and ilmenite as inclusions and 5-10 percent chlorite and sphene as accessory minerals in the concentrate. Copper concentrations in the biotites of the four rock types in the Santa Rita Mountains that were sampled are summarized in table 1. This table illustrates the marked increase in copper content of biotite samples from the "ore porphyry" relative to such samples from both the unmineralized older granodiorite and the quartz monzonite stocks of approximately the same age as the mineralized quartz latite porphyry plugs. Copper also increases slightly in whole-rock samples of the ore porphyry, but the copper in biotite separates TABLE 1.-Copper content of biotite samples from selected igneous rocks of the Santa Rita Mountains Rock type [J. L. Finley, analyst) Precambrian granodiorite and quartz monzonite. Cretaceous granodiorite _________ _ Barren Paleocene quartz monzonite. Productive Paleocene quartz latite porphyry. Number of samples 3 2 4 4 Copper content (ppm) Range Mean 30-70 . 50 10Q-200 150 70-150 90 700-7,000 3,400
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Page 3 and 4: CONTENTS GEOLOGIC STUDIES Petrology
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Page 13 and 14: B8 PETROLOGY AND PETROGRAPHY TABLE
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Page 51 and 52: B46 STRUCTURAL GEOLOGY FIGURE 4.-Vi
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B54 GEOPHYSICS (1950), Domzalski (1
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B56 GEOPHYSICS STRATIGRAPHY AND LIT
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B58 GEOPHYSICS STRATIGRAPHY AND LIT
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B60 GEOPHYSICS value. A normal free
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B62 GEOPHYSICS Hammer, Sigmund, 193
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B64 110°45' GEOPHYSICS L I I \ "'\
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GE·OLOGICAL SURVEY RESEA·RCH 1970
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B68 GEOPHYSICS A' San 0 p A c I F I
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B70 GEOPHYSICS lies occur over rela
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B72 GEOPHYSICS 36° 00' A' 40___./
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B74 GEOPHYSICS igneous massif is co
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B76 GEOPHYSICS A 50 Bouguer gravity
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B80 GEOPHYSICS FIGURE 1.-Bouguell'
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B82 GEOPHYSICS J I 37·~~------~~--
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B84 GEOPHYSICS B 600 B' 500 400 (/)
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EXPLANATION Pikes Peak • batholit
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DISTRIBUTION OF URANIUM IN URANIUM-
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B92 GEOCHRONOLOGY Fleischer, R. L.,
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B94 ECONOMIC GEOLOGY 103° 35' w 1/
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'B96 ECONOMIC ·GEOLOGY 0 500 FEET
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B98 ECONOMIC GEOLOGY TABLE !.-Summa
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BlOO ECONOMIC GEOLOGY surface seems
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GE 1 0LOGICAL SURVEY RESEA·RCH 197
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B104 EJrucJh of the four samples wa
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B106 ECONOMIC GEOLOGY R. 56 E. R. 5
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B108 ECONOMIC GEOLOGY outcrop under
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BllO Brady, of the Museum of Northe
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Bll2 PALEONTOLOGY FIGURE 1.-ProtobZ
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B114 PALEONTOLOGY c .,;# I I ' ' lO
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B116 PALEONTOLOGY ments, the larges
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GErOLOGICAL SURVEY RESEA·RCH 1970
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B120 L xMH 'xE soo~~B_R~I __ T_I __
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B122 PALEONTOLOGY Tetrataxis sp. Te
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Bl26 PALEONTOLOGY TABLE 2.-Ranges o
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B128 PALEONTOLOGY l
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BI30 PALEONTOLOGY Ocmt/rrence.-P. m
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Bl32 PALEONTOLOGY proximately 5.7 m
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Bl34 PALEONTOLOGY a b c d e f g - D
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Bl36 PALEONTOLOGY --- 1963. The ori
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B138 PALEONTOLOGY core are m1ssmg,
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B140 PALEONTOLOGY death assemblage:
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Bl42 STRATIGRAPHY EXPLANATION l:.\.
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B144 STRATIGRAPHY ver. We do not in
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B146 STRATIGRAPHY age. A stratigrap
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B148 5 10 15 20 X X Plntygonus Pla.
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B152 STRATIGRAPHY at a depth of 58
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••••• 0 .... ••••
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B156 STRATIGRAPHY REFERENCES Brown,
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B158 STRATIGRAPHY In what follows,
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Bi60 STRATIGRAPHY TABLE !.-Stratigr
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B162 SEDIMENTATION with increasing
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llj ...... ~ TABLE 2.-Specific grav
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B166 TABLE 3.-Settling time for a 1
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Bl68 GEOMORPHOLOGY 74° 44° YERMON
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B170 GEOMORPHOLOGY have also been r
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B172 GEOMORPHOLOGY end of Long Isla
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GEOLOGICAL SURVEY RESEARCH 1970 DET
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~ooo ______________ B176 ANALYTICAL
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B178 terranes where the search for
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B180 Reproducibility Replicate anal
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B182 ANALYTICAL METHODS in the aque
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GEOLOGICAL SURVEY RESEARCH 1970 CHE
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B186 ANALYTICAL METHODS 3.31 percen
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Bl88 ANALYTICAL METHODS 3" 2%" Oute
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B192 GROUND-WATER RECHARGE I T I 14
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B194 GROUND-WATER RECHARGE Therefor
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GEOLOGICAL SURVEY RESEARCH 1970 PRE
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B198 GROUND-WATER RECHARGE the basi
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B200 GROUND-WATER RECHARGE t \ \)
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B202 GROUND-WATER RECHARGE Water is
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B204 GROUND-WATER CONTAMINATION rv
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B206 GROUND-WATER CONTAMINATION TAB
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B208. GROUND-WATER CONTAMINATION fa
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B212 SURFACE WATER plotted, and the
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B216 SURFACE WATER however, if the
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B218 SURFACE WATER TABLE 4.-Variati
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B220 RELATION· BETWEEN GROUND eral
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B222 -0.010 f -0.005 (i) RELATION B
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GEOLOGICAL SURVEY RESEARCH 1970 THE
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'B226 RELATION BETWEEN GROUND WATER
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B228 RELATION, BETWEEN GROUND WATER
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B230 RELATION BETWEEN GROUND WATER
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GEOLOGICAL SURVEY RESEARCH 1970 HYD
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B234 EROSION AND SEDIMENTATION side
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B236 EROSION AND SEDIMENTATION s·o
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B238 EROSION AND SEDIMENTATION Cont
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B240 EROSION AND SEDIMENTATION 2 3
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GEOLOGICAL SURVEY RESEARCH 1970 SPE
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B244 GEOCHEMISTRY OF WATER REFERENC
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B246 HYDROLOGIC TECHNIQUES The upla
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B248 HYDROLOGIC TECHNIQUES type in
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GEOLOGICAL SURVEY RESEARCH 1970 ,,.
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B252 formula may also be useful in
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B256 randomly fluctuating component
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B258 HYDROLOGIC TECHNIQUES 1.0 ~ Qj
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~ B260 HYDROLOGIC TECHNIQUES 1-3, f
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I B262 HYDROLOGIC TECHNIQUES REFERE
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,' B264 Page Gravitational sliding,
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RESEARCH· ·1970·

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