Economic geology of the Alamos Mining District, Sonora, Mexico
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Authors Vazquez Perez, Adalberto, 1944-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/566636 ECONOMIC GEOLOGY OF THE ALAMOS MINING DISTRICT,
SONORA, MEXICO
by
Adalberto Vazquez Perez
A Thesis Submitted to the Faculty of the
DEPARTMENT OF MINING AND GEOLOGICAL ENGINEERING
In Partial Fulfillment of the Requirements For the Degree of
MASTER OF SCIENCE WITH A MAJOR IN GEOLOGICAL ENGINEERING
In the Graduate College
THE UNIVERSITY OF ARIZONA
19 7 5 STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of require ments for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the a u th o r.
SIGNED:
APPROVAL BY THESIS DIRECTOR
This thesis has been approved on the date shown below:
/ 77r WILLIAM C. PETERS Date Professor of Mining and Geological Engineering Con todo carino a
Pupis
B e tito
O sca rito por sus sacrificios ACKNOWLEDGMENTS
I am deeply indebted to individuals both on and off the campus of The University of Arizona for their support.
On campus, I wish to express my deep appreciation to Dr. William
C. Peters, my major professor and advisor, to Dr. De Verle P. Harris and to Mr. Edward Jucevic for their guidance and encouragement.
Off campus, special gratitude is due to Ing. Guillermo P. Salas,
General Director, and to Ing. Ruben Pesquera, Exploration Manager, of the Nonrenewable Natural Resources Council, as well as the National
Council of Science and Technology, of Mexico for their financial support during my stay in Tucson.
i v TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS...... v i i
LIST OF TABLES...... %
ABSTRACT ...... x i
1. INTRODUCTION ...... 1 H 2. REGIONAL GEOLOGY...... 9 Geomorphology ...... 9 S ie r r a Madre O ccid en ta l P rovince ...... 9 Sonoran D esert P rovin ce ...... 13 C o a sta l P la in o f S in a lo a P rovince ...... 13 S t r a t i g r a p h y ...... 14 P r e c a m b r ia n ...... 15 P a l e o z o i c ...... 17 M e s o z o ic ...... 20 C e n o z o ic ...... 24 S tru ctu re and S tru ctu ra l H i s t o r y ...... 26 Sonoran Desert Province ...... 27 S ie r r a Madre O ccid en ta l P rovince ...... 28 3. ALAMOS D IS T R IC T ...... 31 G eneral G eology ...... 31 • Geomorphology ...... 31 S tra tig ra p h y ...... 33 S t r u c t u r e ...... 41 V v i TABLE OF CONTENTS—Continued Page Economic G eology ...... 46 Ore C ontrol ...... 46 Ore Mineralogy 49 Mineral Paragenesis and Zoning ...... 50 Ore G e n e s i s ...... 53 Description of Mines ...... 57 Economic A s p e c t s ...... 88 Grade o f O r e ...... 88 Ore R e s e r v e s ...... 89 E xp loration P r o g r a m ...... 91 Economic C on sid era tio n s ...... 93 4 . STATISTICAL A SP E C T S...... 99 In tro d u ctio n ...... 99 Model and Methodology Employed ...... 100 M u ltip le R egression A n a ly sis ...... 104 C onceptual Framework ...... 104 R e su lts o f A n a ly sis ...... 109 Trend Surface A n a ly sis ...... 113 C onceptual Framework ...... 113 Results of A nalysis ...... 116 5 . CONCLUSIONS AND RECOMMENDATIONS ...... 123 APPENDIX A — ECONOMIC CONSIDERATIONS FOR THE PROSPECTS IN THE ALAMOS MINING DISTRICT EXPLORATION PROGRAM, 1973-75 ...... 128 APPENDIX B — STATISTICAL CALCULATIONS FOR THE ALAMOS MINING DISTRICT EXPLORATION PROGRAM, 1973-75 ...... 141 LIST OF REFERENCES...... 165 LIST OF ILLUSTRATIONS F ig u re Page 1. Location Map of the Alamos Mining D istrict, Sonora, Mexico ...... 4 2. Central Part of the Alamos Mining District ...... 5 3. Geomorphic Provinces in the State of Sonora, Mexico . . . 10 4. Panoramic View of the Tertiary Volcanic Rocks Within the Barranca Section of the Sierra Madre Occidental P rovin ce ...... 12 5. Geologic Map of the State of Sonora, Mexico ...... In p ock et 6. Geologic Map of the Alamos D istrict, Sonora, Mexico . . . In p o ck et 7. Panoramic View o f th e S ie r r a de Alamos ...... 32 8. Exposure of the Barranca Formation (Upper Triassic-Lower J u r a s sic ) in th e P ied ras Verdes Area ...... 36 9. Ridge of Tertiary Rhyolitic Flows Dipping 25° to the E a s t ...... 42 10. Location of Precious-Metal Districts along the "Main Welt" S tru ctu re in th e S ie r r a Madre O ccid en ta l P rovin ce ...... 45 11. Abundance of Base-Metal Sulfides Plotted Against Their H eigh t above Basement ...... 48 12. Paragenetic Sequence for the Alamos Mining District . . . 52 13. Section N 30° E Showing Changes in Mineralogy among Mines in the Sierra de Alamos, Alamos D istrict ...... 54 14. Location and Grouping of Mines Within the Alamos D is t r ic t , Sonora, M exico ...... In p ock et 15. Copper Mineralization, Brecciation, and A rgillic A lte r a tio n in th e P ied ras Verdes A r e a ...... 58 v i i v i i i LIST OF ILLUSTRATIONS— C ontinued Figure Page 16. Capping and O xid ation o f th e P ied ras Verdes P ro sp ect ...... 58 17. Split to the N 10° W of the "Mother Lode" Structure in the Zapopan Tunnel, Quintera Mine ...... 61 18. Outcrop of the "Mother Lode" Structure at the Surface 785 M eters above Sea L evel ...... 61 19. Geologic and Sampling Map of the Promontorio M in e ...... 63 20. Composite Level Plant Map of the Quintera Mine ...... 65 21. • Geologic and Sampling Map of the Zapopan Level, 750 Meters above Sea L ev el, Q uintera M i n e ...... 66 22. Geologic and Sampling Map of the Covacha Level, 730 Meters above Sea L e v e l, Q uintera M i n e ...... 67 23. Geologic and Sampling Map of the Libertad Level, 730 Meters above Sea Level, Quintera M in e ...... 68 24. Old Dump of the Quintera Mine, Alamos D istrict ...... 69 25. Gambusinos Who Are Working the Portal Covacha Level, 730 Meters above Sea Level, Quintera M ine ...... 71 26. Minas Nuevas Mine (or Zambona)...... 73 27. Tertiary Rhyolitic Flows of Cerro Cacharamba ...... 75 28. Exposure at the Surface of the San Manuel V ein ...... 76 29. Picture Showing Brecciation and Oxidation Within the San Manuel V e i n ...... 76 30. Geologic and Sampling Map of the San Manuel M ine ...... 77 31. Geologic Cross-Section and Geologic and Sampling Map of the Plom osas M in e ...... 80 32. Sam pling Map o f th e O tates M i n e ...... 82 33. Geologic and Sampling Map of the Ana Maria Mine, First and Second L evels ...... 84 ix LIST OF ILLUSTRATIONS— C ontinued ig u r e Page 34. Gambusinos Who Are Working the Ana Maria Mine, Portal of Second Level, 1,307 Meters above Sea Level ...... 85 35. Dirt Roads Which Communicate to the Ana Maria Mine in the Alamos D istrict ...... 85 36. Composite Plan View and Cross-Section of the Japon en Mexico M i n e ...... ' . 87 37. Schematic Cross-Section of the Mines Within the "Mother Lode" Vein Showing Areas fo r Ore E xp loration ...... 92 38. Grid o f C e lls fo r th e Alamos D i s t r i c t ...... 102 39. Schematic Representation of the Variables in a Simple R egression A n a ly sis ...... 106 40. Locations of Highest Priority Prospecting Zones Estimated by Multiple Regression Analysis ...... 114 41. Plot of First Degree Equation, Trend Surface Analysis .... 118 42. Plot of Second Degree Equation, Trend Surface Analysis .... 119 43. Plot of Third Degree Equation, Trend Surface Analysis .... 120 44. Location of Highest Priority Prospecting Areas According to Trend S u rface A n a l y s i s ...... 121 LIST OF TABLES T a b le Page 1. Lithologic Correlation of Southern Arizona and Northern Sonora 16 2. Geological Variables Coded for the Alamos Mining District . . . 103 3. Significance of Variables in the Multiple Regression Equation fo r th e Alamos Mining D is t r ic t ...... 110 4. Spatial Distribution by Cell of Known and Predicted Mines for the Alamos Mining D istrict ...... 112 x ABSTRACT The Alamos Mining D istrict lies in the Epithermal Precious Metal Province of northwest Mexico. It has been practically inactive since 1915, not from lack of mineralization, but from political problems in the country. Based upon geologic favorability, the C.R.N.N.R.,* in 1972, decided to carry out a preliminary exploration program to determine the feasibility of installing a mill and a concentration plant in the d i s t r i c t . After three years of geological reconnaissance in 108 mine workings, the nine most favorable prospects were selected as the most important for further exploration. An exploration and preliminary development program is recommended; it is based upon indications that at least 500,000 metric tons, with a grade of 400 grams/ton silver, 0.67 grams/ton gold, 2.88% lead and 3.38% zinc may be found. In addition, favorable geological conditions indicate potential ore reserves of 1 million metric tons with a similar grade. Profitability analyses show that the district is an attractive project for investment. The amount of the capital investment for developing the nine prospects is estimated at 2 million dollars, including exploration and development. *Consejo de Recursos Naturales no Renovables, a governmental institution. x i x i i Finally, geostatistical analysis, multiple regression and trend surface techniques indicate that the Alamos Mining D istrict shows favorable areas of exploration potential in addition to the known ore b o d ie s . CHAPTER 1 INTRODUCTION Purpose and Scope of Study This study is the preliminary result of a survey of the geology and ore deposits of the Alamos Mining D istrict, Sonora, Mexico. The original purpose was to determine the feasibility of installing a concen tration plant. Since the main goal of the survey was a quick, but effective, evaluation of mines and prospects, the investigation was planned as a reconnaissance survey. This left no time for basic and detailed geologic studies involving section measuring and geochronologic determinations. Wisser (1966) provided an excellent study of economic geology in north western Mexico and King (1939) carried out a regional geologic study in southern Sonora; these are used as a basis for classifying the ore deposits and establishing the stratigraphic column in the Alamos Mining D is t r ic t . It is hoped that this preliminary study of the Alamos Mining District might be of some help to the field geologists of the C.R.N.N.R. in their study of this district and similar districts. Also, the infor mation presented here might call the attention of the General Director's Office of the C.R.N.N.R. to the need for investigating the area in more d e t a il . 1 2 Methods of Study The study was carried out in three phases: 1) preliminary reconnaissance of prospects, 2) photogeologic interpretation and field check of geological units and structures, and 3) underground mapping and sampling of prospects. Preliminary Reconnaissance of Prospects This phase of the program was conducted in person from July 1972 to March 1973. During this period, 108 prospects, ranging from small trenches to mines with several levels, were visited. It was impossible to reach the lowest levels of the majority of the mines because of their condition. Therefore, representative chip and channel samples from the veins were taken only at 60% of the prospects. At the remaining 40% of the prospects, samples from the dumps were taken because no veins were exposed. Admittedly, this type of sampling is not representative, but it gives an idea of the ore that was mined. Five hundred samples were collected during this phase. They were analyzed to determine their content of silver (Ag), lead (Pb), zinc (Zn), copper (Cu), and gold (Au). This was done by utilizing the atomic absorption unit at the Nogales, Sonora, office of the C.R.N.N.R. The location of mines was plotted on a topographic map at a scale of 1:250,000 because no larger scale maps were available. Photogeologic Interpretation and Field Check of Geologic Units and Structures The second phase of the program was conducted by the author from March to May, 1973, and from May to July, 1974. This was done with black 3 and white aerial photographs at an approximate scale of 1:55,000. The surface mapping was plotted according to the accuracy permitted by the photo scale. A geologic map was constructed on the basis of an uncon trolled photomosaic at the same scale as the aerial photographs. The photomosaic covers a surface of 1,200 square kilometers. Although this is only about 50% of the area in which the prospects and mines are located, the most important prospects lie in the area mapped. Underground Mapping and Sampling of Prospects This phase of the program was done by Raul Munoz, Jose Perez and Alfredo Cervantes of the C.R.N.N.R. from October of 1973 to date, and by the author during mid-July of 1974. During this period, two mines, Quintera and Promontorio, were partially dewatered and cleaned for detailed sampling and mapping. Also, some small prospects were cleaned and mapped. Mapping control was by brunton compass and tape, and the scale of mapping was 1:1,000. Eleven mines and prospects have been mapped and sampled to the present time. They were selected in order of priority, based upon geologic favorability. In this paper, only nine of the most important prospects are described. Location and Access The Alamos Mining D istrict is located in the southern part of the state of Sonora, Mexico, approximately 40 kilometers east of Navojoa (Figure 1). Roughly, the district covers about 2,000 square kilometers; the most mineralized part, which is located in the center of the district, covers about 100 square kilometers (Figure 2). 2S ~ \ C o b o rco e s ° oMogdoleno •, SONORA ( | ©Hermositlo \ ALAMOS DISTRICT 50 0 k ilo m e te rs Figure 1. Location Map of the Alamos Mining D istrict, Sonora, Mexico. 5 Cocim Europ 18 may Cobn f t Mine or prospect A East vain,'mother lode B' Wast vain Infer rad vein Figure 2. Central Part of the Alamos Mining D istrict. 6 The major town is Alamos, population 5,000. The access.to Alamos is by a 52-kilometer branch road from the main Pacific coast road at Navojoa. Access to other towns and small villages in the district is by dirt roads, which are difficult to travel upon during the rainy season (July to September). History and Past Production As with many Mexican mining districts, the mining history of the Alamos Mining D istrict is not well known. Therefore, the following description can be considered as a historical sketch based upon the sparse available information. Among the geologists who described the district's history are: Rickard (1904), Pearce (1910), Pearce (1911a,b). Bloomer (1909), Brinegar (1910), and Sheldom (1910). All visited the district when the mines were operating. Quiroga (1953), Labounsky (1957) , and Wisser (1966) visited the district when no mines were operating. Sheldom (1910) stated that veins containing silver and gold minerals were discovered by the Spanish Jesuits in the eighteenth century. They worked the mines, principally the Promontorio, and extracted metal from high grade, hand picked ore in crude smelters without prior m illing. The Spaniards worked the mines until about 1800 when political problems prevented them from continuing. Sheldom relates that, in the year 1857, a Frenchman owned the Quintera mine. He went to to Paris and mortgaged the mine to the Egyptian Paris Bank for $250,000.00. After that, with Tom Clark as the mine's manager, the mine 7 paid from $50,000.00 to $100,000.00 in annual dividends for many years, even though milling was expensive. Sheldom (1910, p. 920) further states: "Under the management of J. H. Hendra . . . the Santo Domingo Mine has been developed and a mill has been erected. This ran last year until the political disturbances shut things down." According to Brinegar (1910), the silver production became so great in the 1890's that the Mexican government established a mint in Alamos for coining the metals produced at this point. He also mentions that, in 1808, Von Humbolt noted in his records "that he passed a train of one thousand mules loaded with bars of silver from this district on their way to the City of Mexico" (p. 553). Other important and interesting information is given by Rickard (1904) and Pearce (1910), who emphasized not only the silver production but also the possible copper production in the district, principally from the Piedras Verdes area. Labounsky (1957) insists that the uncertainty created by political problems, namely the Mexican Revolution of 1910-1920, were serious deterrents to obtaining foreign investments to develop Mexican mines. However, he mentions, in respect to the Alamos Mining D istrict (Labounsky, 1957, p. 4): "The entire mining camp was shut down in 1911 when the silver price went down to 48 cent per ounce." According to a paper by Vazquez (1973), an American company milled ore at a rate of 300 tons per day from the dumps during the period 1948 to 1957. The Mexican government, in 1959-1960, installed a pilot 8 plant for m illing ore from dumps. Apparently, there were administrative and technical problems, and the pilot plant was removed in 1962. At the present time, only a few mines are active. These include the Otates, Plomosas, Quintera, San Manuel, Quiriego, La Reina, and La Violeta. Because there is practically no mining equipment installed in the mines, production is small, ranging from 1 to 5 tons per day per mine; In the Quintera and Quiriego mines, the mining operations are restricted to the dumps because of poor underground conditions and lack of mining equipment. The mined ore is sent to Chihuahua City, 600 kilometers away, or to La Reforma, Sinaloa, 300 kilometers away, for concentration and processing because these are the nearest plants for processing silver-lead minerals. In respect to past production, Sheldom (1910) states that the "Mother Lode" Quintera-Promontorio has been worked practically con tinuously for 200 years. He points out (Sheldom, 1910, p. 524): "These dumps are immense and contain easily one-half million tons. They are sufficiently valuable to warrant re-treatment. It is claimed that the mines have produced 100 m illion dollars but this is probably exaggerated." Wisser (1966) estimates a district's past production at 150 million dollars. Therefore, it seems likely that the district's produc tion was somewhere between $100,000.00 and $150,000.00 CHAPTER 2 REGIONAL GEOLOGY Geomorphology Alvarez (1966) made an excellent compilation and re-interpretation of Mexico’s geomorphology, based largely on King (1939) and De Csema (1960). He concluded that the state of Sonora comprises three geomorphic provinces: Sierra Madre Occidental, Sonoran Desert, and Coastal Plain of Sinaloa (Figure 3). S ie r r a Madre O ccid en ta l P rovin ce The Sierra Madre Occidental is a mountainous belt 1,200 kilometers long, with an average width of 250 kilometers. The sierra trends north ward to northwest 10°, and extends from latitudes 20° to 31°N, where it reaches the United States border. The Sierra Madre Occidental Province is divided into three subprovinces or sections: Plateau, Barranca, and Basin and Range (Alvarez, 1966). Plateau Section. This section lies in the most eastern part of the state of Sonora and partially in the state of Chihuahua. It shows a gently rolling surface carved from volcanic rocks. Elevations range from 2,000 to 2,900 meters. There are irregular mountains separated by broad and flat valleys. The valleys are drained by tributaries of the Yaqui, Mayo, and Fuerte rivers, which flow through the deep gorges or barrancas or the Barranca section toward the Gulf of California. Outcropping 9 10 rCSon Luis Rio Colorado / / T 8!...... au-SSia-v- < Coborco ' / / : o ; ! / ' X a& lior~ Cononeo A \ X -' y-s:rro,-° ( / X \ NocozorideGorcio *. * r X ? 4 ' - . ,l ! \ : ( ! y j < y ' *—-(fMozocohui ) r-u ^ r / /./>* / (\ ? ^ / OpHERMOSl'ab' Tecoript E X PL AN AT ION f Sonoran Desert Province E Sierra Madre Occidental Province A ) Basin and Range Section B) Barranca Section C ) Plateau Section ALAMOS EL Coastal Plain of Sinaloa Province DISTRICT 5 0 70 i50 250 kilometers Figure 3. Geomorphic Provinces in the State of Sonora, Mexico. 11 rocks consist principally of Tertiary rhyolitic flows. In a few places they are known to overlie folded Mesozoic rocks. Barranca Section. This section is a longitudianl belt of 40 to 90 kilometers wide and 600 kilometers long. The characteristic geomor- phic features of this section are youthful. Rivers have carved deep gorges or barrancas parallel to the regional, N10°W, trend of the Sierra Madre. Some of the gorges reach 2,000 meters in depth. Exposed rocks within this subprovince consist principally of Tertiary rhyolites and associated volcanic rocks, and scarce sedimentary and intrusive rocks which have been raised by faults to the zone of erosion (Figure 4). Basin and Range Section. This subprovince is a belt 80 to 110 kilometers wide in east-central Sonora, but considerably narrower in northeastern Sonora. It is 500 kilometers long and extends toward the north in the United States where it forms the Great Basin Section of the Basin and Range Province. The main physiographic feature is a series of parallel mountain ranges and intermontane valleys that form horsts and grabens. Some of the ranges from north to south are the San Antonio, • Cananea, Purica, Copper Queen, Nacozari, Aeonchi, Sahuaripa, Moctezuma, Soyopa, and Alamos. They range from 1,500 to 2,000 meters in height. The valleys are drained by the Babispe, Moctezuma, Sonora, Yaqui, and Mayo rivers, which flow toward the Gulf of California. Rocks outcropping in this section consist of sedimentary, volcanic and intrusive rocks ranging in age from Paleozoic to Recent. Figure 4. Panoramic View of the Tertiary Volcanic Rocks Within the Barranca Section of the Sierra Madre Occidental Province. — A youthful topography is evident. N) 13 Sonoran Desert Province This physiographic province covers about 50% of the state of Sonora and extends toward the north in the United States where it forms the Mohave and Gila Desert (Thombury, 1965). The province contains extensive plains that descend from 700 meters to sea level at the Gulf of California. The landscape is composed of isolated ridges, mostly without a definite orientation, which show a mature physiography. Alluvial fans, pediments and cuestas are common features at the base of the mountains. Some of the ranges from north to south are Pinacate, Cubabi, Guijas, Cuevas, Colorada, Bacatete, Buenavista, and Baroyeca, which range from 600 to 1,000 meters in height. Rivers in the Sonoran Desert Province are the Sonoita, Altar, Bacabache, and Sonora, which drain toward the Gulf of California. Exposed rocks consist mainly of PreCambrian and Paleozoic rocks. Coastal Plain of Sinaloa Province This province is located in the southern part of the state of Sonora and extends to the south in the state of Sinaloa. The Coastal Plain is an elongated belt from 25 to 100 kilometers wide and 300 kilometers long. The province is composed of alluvial plains which have been formed by the coalescing of the deltas of the Yaqui and Mayo rivers in the north and the Fuerte, Sinaloa and Rosario rivers farther south. King (1939) suggests that the shoreline is emergent with characteristic offshore bars separated from the mainland by tidal flats and lagoons. 14 . Stratigraphy In 1974, the geology of the state of Sonora was known only in a general manner because there had been detailed geological surveys in only a few localities. The state covers 182,000 square kilometers of which only 10,000 square kilometers have been mapped in detail (Salas, 1971). It is estimated that 90,000 square kilometers are covered in semi-detail and that the remaining 80,000 square kilometers have been mapped in reconnaissance. Moreover, it is considered that 80% of such detailed and semi-detailed mapping has been done in the. central-northern part of the state, from 29° latitude north. Undoubtedly, this is because detailed studies have been made in southern Arizona, in the United States, and much of that geologic knowledge is applicable to northern Sonora. Among the geologists who have studied and published on the regional geology of northern Sonora are Durable (1900), Angermann (1904), Flores (1929), Imlay (1939), Cooper and Arellano (1946), Arellano (1956), Mulchay and Velasco (1954), Fries (1962), De Csema (1960), De Csema and Alencester (1961), Salas (1970), and the C.R.N.N.R.-United Nations (1 9 6 9 ). I s o to p ic age d eterm in a tio n s have been made by Damon, L iv in g sto n , and G iletti (1962), Damon and Mauger (1966), Damon and Bikerman (1964), Damon et al. (1965), Damon (1968), and Livingston (1973). On the other hand, the regional geology of southern Sonora, from 29° latitude south, has been studied only by Flores (1929) and King (1 9 3 9 ). Based upon the work of the authors previously cited, and on the state geologic map, a general description of the geology of the state of 15 Sonora is shown in Figure 5 (in pocket; Comite de la Carta Geologica de Mexico, 1968). Table 1 shows the composite stratigraphic column. Precambrian Precambrian rocks that'outcrop in the state of Sonora are both Older and Younger Precambrian. This division is based on Wilson's terminology (Fries, 1962) and corresponds to the Mazatzal Revolution. This metamorphic event has been estimated at 1,700 my old. However, Damon (1968) considers, by applying new age determinations, that the Mazatzal Revolution occurred between 1,370 and 1,450 my ago, and that a metamorphic event in Arizona and Sonora occurred between 1,630 and 1,760 my ago. This last event is called, by Damon, the Arizonan Revolu tion. In this paper, the Arizonan Revolution is taken as a basis for dividing the Precambrian. The Older Precambrian rocks outcrop in the vicinity of Altar, Bamori, and Magdalena in northwestern Sonora, and Sierra San Antonio and Cabullona in northeastern Sonora. At Altar, they are represented by a sedimentary sequence of shale, limestone, dolomite, and quartzite, with a thickness of 1,700 meters (Cooper and Arellano, 1946). In the vicinity of Bamori, 20 kilometers south of Caborca, they are composed of schists, quartzites, and metavolcanics (Damon et al., 1962; Damon, 1968). At Magdalena, the rocks consist of low-grade calc-schist marble and granite gneiss metasediments (Salas, 1970). In the Cabullona area, the Older Precambrian is represented by a micaceous schist (Taliaferro, 1933), which is correlated with Pinal Schist of southern Arizona. At Sierra de San Antonio, a similar schist is assigned to this age (Ramirez, 1965). Table 1. Lithologic Correlation of Southern Arizona and Northern Sonora. — After Luque (1974). Era P eriod Epoch . Southern Arizona Northern Sonora C enozoic Q uaternary Recent Alluvium, gravel, silt Alluvium, gravel Pleistocene Basalt, elastics Basalt, elastics T e r tia r y P lio c e n e Gila conglomerate Baucarit Formation Miocene ? Unconformity O lig o cen e- Rhyolites, andesites, Undifferentiated Eocene tuffs, granitic volcanic rocks, in tr u s iv e s andesites, rhyo lites, granitic in t r u s iv e s Paleocene Unconformity Unconformity M esozoic Cretaceous Volcanic and intrusive Potrero and Palmar rock s; B isb ee Group Form ations Unconformity Jurassic Undifferentiated volcanic Represo, Lista rocks Blanca Formation Unconformity T r ia s s ic Unconformity Barranca Formation unconformity P a le o z o ic Permian Naco Group (?) Puertecitos Formation Carboniferous Escabrosa Formation Represo Formation Devonian Martin Formation Murcielago Formation S ilu r ia n Abrigo Formation Limestone, shale O rdovician Bolsa quartzite Esperanza Formation Cambrian Unconformity . Unconformity PreCambrian S u p erio r Apache Group, lim estones. Cocotillo Group, s h a le s shales, limestones Unconformity Unconformity M iddle . Pinal schist and Pinal schist and g r a n ite ...... g r a n ite 17 The Younger PreCambrian rocks outcrop in Caborca, Aibo, Sonoita, and Madgalena in northwestern Sonora. At Caborca, they consist of an interbedded sequence of quartzite, shale, limestone, and dolomite, with a thickness of 2,000 meters (Cooper and Arellano, 1946). These Pre- cambrian sedimentary rocks have been compared to the Apache Group and Grand Canyon S e r ie s o f A rizona and th e Pahrump S e r ie s o f C a lifo r n ia by Arellano (1956) and by Fries (1962). In the vicinity of Aibo (Cerro del Arpa) they are represented by an altered red graphic granite on which the later sedimentary rocks rest unconformably (Damon, 1968). In the Sonoita D istrict, the Pinacate gneiss is considered to belong to this age (Damon, 1968). Near Magdalena, the Younger Precambrian is repre sented by low-grade phyllite, quartzite, metaconglomerate, and marble, with a thickness of more than 2,000 meters (Salas, 1970). Fries (1962) estimates that the thickness of the Younger Precambrian rocks decreases toward the east, where the Precambrian is only a few meters in thickness or has been removed completely by erosion. P a le o z o ic Rocks of this age have been recognized throughout the state of Sonora, even though the complete stratigraphic column of this period is doubtful. The most detailed studies of Paleozoic rocks have been carried out by Cooper and Arellano (1946) and by Arellano (1956) in the Altar and Caborca areas, where exposures of Paleozoic rocks are found. 18 Cambrian. Strata of Cambrian age crop out extensively within the Altar and Caborca districts (Cooper and Arellano, 1946). In these dis tricts, the rocks consist of a stratified sequence of limestones, shales, and quartzites, with a thickness of more than 1,200 meters, resting uncon- formably on Precambrian rocks. Cooper et al. (1952) divide the Cambrian sedimentary rocks at Cerro La Provedora into six formations ranging from Lower to Middle Precambrian. All the formations were separated according to characteristic fossils. In the Cananea D istrict, the Cambrian is represented by limestone and quartzite, with a thickness of 100 meters (Mulchay and Velasco, 1954). Ordovician. King (1939) identifies rock at La Casita and at Sierra de Cobachi, 70 kilometers southeast of Hermosillo, as being Ordo vician. At both localities, a massive limestone about 50 meters thick contains Richmond Coral Fauna. He describes (King, 1939, p. 1641): "It is associated with a black limestone with chery layers and concretions, quartzite and siliceous shale. Fossils are not found in these beds but they may be of Lower Ordovician age." Fries (1962), however, thinks that this stratigraphic units corresponds to Upper Precambrian. Silurian. No rocks or fossils of this age have been reported in Sonora, even though Fries (1962) assumes that, near La Casita and Cobachi, there are probably sedimentary rocks of this period. Devonian. Sedimentary rocks of Devonian age are identified as Lower and Upper Devonian. Lower Devonian rocks are exposed in the Altar and Cananea D istricts (Cooper and Arellano, 1946; Maldonado, 1954). They 19 are composed of a sedimentary sequence of limestone and dolomite with a thickness of 285 meters. Upper Devonian rocks are exposed in the Cabullona area (Alvarez, 1966), where they consist of a compact, grey-black limestone associated with interstratified beds of clear limestone. At the base of this formation, there is a pink, carbonaceous shale 100 meters in thickness. No fossils have been found in this last unit. Mississippian. Rocks that have been classified as Mississippian in age are exposed in the Altar, Cabullona, and El Tigre areas. At Altar, they consist of a crinoidal, grey limestone with abundant concre tions of quartz. This formation is named Risani by Torres, Isabal, and Gomez (Alvarez, 1966), and they correlate this unit with the Escabrosa formation in southern Arizona. In the Cabullona area, M ississippian rocks similar to the Risani formation were studied by Taliaferro (1933). At El Tigre, in the Canon Santa Rosa, Imlay (1939) recognizes a sequence of crinoidal limestones and shales with a thickness of 380 meters as belonging to the Lower M ississippian. Pennsylvanian. Strata of Pennsylvanian age are exposed within the Cananea, Cabullona, and El Tigre districts. In the vicinity of Cananea, a fine, stratified limestone outcrops with a thickness of 300 meters. It is correlated with the Naco formation in southern Arizona by Taliaferro (1933). At Cabullona, it is a grey limestone 750 meters thick resting on a sedimentary sequence of Lower Paleozoic rocks (Fries, 1962). In the Tigre area, a sequence of compact limestone and clay with chert, reported by Imlay (1939), belongs to this system. 20 Permian. In the Altar, Hermosillo, and El Tigre districts, rocks of Permian age outcrop. In the vicinity of Altar and Antimonio, they consist of intrusive rocks at the base, with sandstone and shale and a fossiliferous, blue-grey limestone at the top, with a thickness of 160 meters (Cooper and Arellano, 1946). Within the Hermosillo district, at the Cerro de Cobachi, a sedimentary sequence of great reefs of white and blue massive crinoidal limestones, with a thickness of 550 meters is considered by King (1939) to belong to this period. In the Tigre area, Imlay (1939) recognizes a section of grey-white limestone with inclusions of chert and 1,800 meters in thickness as Permian. M esozoic Mesozoic rocks are exposed extensively through the state of Sonora, but are more abundant in the central part, within the Parallel Ranges and Valley Subprovince. They are also exposed in the eastern Sonoran Desert Province, but there they are less abundant. In the Parallel Ranges and Valleys Subprovince, rocks of this age are repre sented chiefly by continental deposits, while in the Sonoran Desert Province they are chiefly marine deposits. The thickness increases from 1,100 meters on the west to 2,300 meters (King, 1939), or perhaps to 3,000 meters (Fries, 1962) in the east. Fossil evidence is the basis for age determination in these systems. Triassic-Jurassic. The characteristic stratigraphic unit of this age is the Barranca Formation — Upper Triassic-Lower Jurassic. It was named, by Dumble (1900), for excellent exposures in the vicinity of the Barranca San Xavier area, 100 kilometers southeast of Hermosillo. Here, 21 the formation is composed of clastic rocks with some beds of coal and graphite. Rocks that have been classified as Upper Triassic-Lower Jurassic are exposed within northern and southern Sonora. In northern Sonora, at the Antimonio Mine, 30 kilometers west of Caborca (King, 1939), and in the vicinity of Benjamin H ill (Flores, 1929), they are represented by a sedimentary sequence of sandstone, shale and limestone 1,200 meters thick. In southern Sonora, King (1939) and Flores (1929) recognize rocks corresponding to this age in the Yaqui River Valley and in the Sierra de Moradillas. In the Yaqui River Valley, they are composed of massive sandstones containing argillaceous horizons and several layers of graphite; the exposed thickness is about 450 meters. Within the Sierra de Moradillas, 50 kilometers southwest of Hermosillo, they consist of graphitic quartzites and indurated sandstones with a thickness of 1,450 m eters. Volcanic rocks of Triassic-Jurassic age have been mapped and dated in southern Arizona between meridians 110° and 111°. They continue into Sonora, where they reach a thickness of 3,000 meters (Hayes, 1966). Cretaceous. Lower and Upper Cretaceous rocks are represented by sedimentary, volcanic, and intrusive rocks. The Lower Cretaceous rocks crop out extensively throughout the state of Sonora, while Upper Creta ceous rocks are restricted to the northeastern part of the state. 1. Sedimentary rocks: According to King (1939), the best exposures of Lower Cretaceous sediments are in the Sahuaripa D istrict between Sahuaripa and Yaqui Rivers. Here, they consist of a 22 sequence of thin-bedded quartzites, massive blue limestone, sandstone, and massive conglomerate with a thickness of 3,500 meters. King correlates this section with the Bisbee group of southern Arizona and with the 900-meter section described by Imlay (1939) near the El Tigre area. Imlay (1939) recognizes the Glance and Morita Formations which extend southward from the Bisbee D istrict into southern Sonora in the Sierra de los Ajos, where they reach a thickness of 2,400 meters. Flores (1929) con siders that a series of limestones and shales near Santa Ana contains characteristic fauna not older than Aptian age. Upper Cretaceous rocks are only exposed at the Cabullona Basin and appear to overlie the Lower Cretaceous unconformably (Taliaferro, 1933). They consist of interstratified volcanic clastic sediments with a thickness of 2,800 meters. 2. Volcanic rocks: King (1939) considers that two periods of Cretaceous volcanism took place in southwestern United States and northwestern Mexico. The first is exposed in the Sahuaripa District and the second in the Cabullona area. At both localities they consist of andesitic flows and tuffs interbedded in the fossiliferrous sedimentary rocks. At Sahuaripa, they are dated as Lower Cretaceous and in the Cabullona area as Upper Cretaceous. Also, King considers that all the older volcanic rocks in the Basin and Range Subprovince are probably of Lower Cretaceous age because, so far, no fossils have been found. King (1939) and Wlsser (1966) state that the Cretaceous volcanic sequence 23 increases toward the west where the section is composed almost wholly of volcanic rocks. 3. Intrusive rocks: The age of the intrusive rocks have been much debated. King (1939) considered the majority of the plutons in central-southern Sonora as Middle Tertiary in age. However, in view of later isotopic age determinations and stratigraphic features, it seems likely that the majority of the plutons are late Cretaceous-Early Tertiary and correspond to the Laramide Revolution. Damon and Mauger (1966) and Livingston (1973), by applying isotopic age determinations, determined that the majority of the intrusives in southern Arizona and northwestern Sonora, in the Basin and Range Subprovince, correspond to the interval of the Laramide Orogeny 52 to 72 my ago. Damon (1968) reports a quartz monzonite intrusive in the Altar District to be 105 my old. Wisser (1966; based on Damon and Bikerman, 1964) states that the Capomaz q u artz m onzonite mass in n orth ern S in a lo a , 10 k ilo m e te r s south of Sonora, and several plutons in northern Sonora, fall within the time range of the Laramide Revolution. Wisser (1966), based on stratigraphic evidence, such as at El Tigre, Guayopita (Hovey, 1906) and Pilares (King, 1939), suggests a late Cretaceous-Early Tertiary age for the intrusive bodies. At El Tigre, granite below Tertiary volcanic rocks intrudes a sequence of limestone and shale of probably Early Cretaceous age. At Guayopita, in western Chihuahua, basal Tertiary rhyolite 24 appears to rest on an eroded surface of limestone invaded by granite. At the Pilares Mine, 10 kilometers east of Nacozari, granite invades limestone and probably is pre-Tertiary in age. Finally, Nisser (1966) emphasizes that, in the western United States, major plutons correspond mainly to Mesozoic age, and that Mid-Tertiary plutons are with few exceptions stocks of small size. It seems likely that this geologic condition may be present in the state of Sonora. C enozoic Cenozoic formations cover a large percentage of the state of Sonora. Tertiary units are composed chiefly of volcanic rocks and clastic-sedimentary rocks. These units are exposed principally within the Sierra Madre Occidental Province. Intrusive rocks of Cretaceous- Tertiary and Mid-Tertiary age have been reported. Quaternary sedimentary rocks are more widespread within the Sonoran Desert Province and within the Coastal Plain of the Gulf of California, as shown in the state geologic map (Figure 5, in pocket). Tertiary. According to King (1939), early Tertiary volcanic rocks are represented by a group of andesites, rhyolite flows, tuffs, and thick clastic deposits. The group rests unconformably upon Cretaceous rocks. The same author states that early Tertiary volcanic rocks show a differ ent composition from both Cretaceous and later Tertiary volcanic rocks. The early Tertiary rocks are chiefly andesitic while late Tertiary rocks are chiefly rhyolitic in composition. The early Tertiary volcanic rocks are best developed in the Barranca section where they reach a thickness 25 of 2,300 meters. Wisser (1966) traversed stratigraphic sections at many localities in the Sierra Madre Occidental Province. His sections show that the volcanic pile in the Plateau, Barranca, and Basin and Range sections consist mainly of intermediate to basic flows of pyro-clastic rocks at the base; whereas the top is composed of rhyolitic tuffs and flows which rest unconformably upon the lower rocks. Imlay (1939), Fries (1962), Alvarez (1966), and the C.R.N.N.R. (1970) report similar lithologic and stratigraphic features to those of King and Wisser. Therefore, this appears to be a correct interpretation of the volcanic p i l e o f th e S ie r r a Madre O c cid en ta l. As stated before, early intrusive rocks of Laramide age are reported by Damon (1968) and Damon and Mauger (1966) and Livingston (1973). Some.of the localities where they outcrop are: La Caridad Deposit, 54 my; San Felipe de Jesus, 49 my (Damon, 1975); Cananea, 58 my and 67 my; Aurora, 54 my; and Capomaz north S in a lo a , 58 my. I n tr u s iv e rocks of Eocene age are reported at La Florida-Barrigoh, 3 kilometers west of Nacozari (Damon, 1975). King (1939) considers that the volcanic pile which forms the Sierra Madre Occidental is of Early Tertiary age. Nevertheless, Wisser (1966), based on absolute age determinations carred out by Damon et al. (1965), concludes that Tertiary volcanism started in Eocene-Oligocene time, reaching its greatest intensity during Oligocene-Miocene time (similar to the Pachuca District in central Mexico). Late Tertiary clastic sedimentary rocks are represented by the Baucarit Formation, named by Durable (1900) for exposures in the vicinity 26 of the Baucarit town, southern Sonora. The formation here is composed of sands, clayey sands, and conglomerates of extremely even bedding. King (1939) describes this formation farther south of Baucarit where the for mation is best exposed. He describes the unit as composed at the base of a basaltic member followed by well-bedded sandstones, conglomerates and some clays which were derived from the older rocks. This formation is chiefly exposed within grabens of the Basin and Range Subprovince. Damon determines the age of the lower basalt member as 21 my in the San Felipe de Jesus area, central Sonora (Damon, 1975). Galbraith (1959) considers that the basaltic flows of the Pinacate area, northwestern Sonora, as late Pliocene. King (1939) estimates that basaltic flows in central Sonora are probably younger than those of the Baucarit Formation. Quaternary. Quaternary sediments cover over one-third of the state of Sonora. They are represented in pediments, alluvial fans, sands, alluvial fills, and gravels which cover the lower parts of rivers and v a lle y s . The alluvial fill may attain a thickness as great as 180 meters, as at Tecoripa (King, 1939), Agua Prieta, and Nacozari valleys (C.R.N.N.R., 1970). Most agricultural activity of the region takes place in the sands and silts of the alluvium and especially in the Coastal Plain of the Gulf of California. Structure and Structural History All the geologists who have studied the geology of the state of Sonora agree, with few exceptions, that the landforms of the state are intimately related to the underlying rocks. Therefore, the structural 27 features of the state are described, based upon the geomorphic provinces and the stratigraphic column described previously. Sonoran Desert Province Within this province, most of the structural features are covered by recent sediments. However, the isolated ridges are interpreted by Thombury (1965) as uplifted blocks bordered by normal faults in advanced stages of erosion. King (1939) points out that the ranges of sedimentary and volcanic rocks appear to be roof pendants in a vast group of granitic batholiths strongly affected by erosion. Within the northern part of the province. Older and Younger Pre- cambrian and Paleozoic rocks are widely exposed. In the central and southern parts of the province, only Paleozoic rocks outcrop; Younger Precambrian and Paleozoic rocks are unconformable (Cooper and Arellano, 1946; Damon, 1968). The Older Precambrian rocks show a predominant northeasterly trend of bedding and faulting, while the Younger Precambrian rocks trend northwesterly (Fries, 1962). This structural change in trend, is inter preted by Damon (1968) to be a result of the Arizonan Revolution. Fries (1962) reports that Paleozoic rocks within the Sonoran Desert Province and the Basin and Range Subprovince show the same northwesterly regional structural trend as the Younger Precambrian rocks. The same author, based on the stratigraphic relationships of Paleozoic and Precambrian rocks, considers that northwestern Sonora was a continental platform or miogeosincline. He names this structure the Sonoran Basin of the Cordilleran Geosincline of North America. The existence of a 28 eugoesinclinal facies in northern Sonora is suggested by De Cserna (1960). However, it now appears that the stratigraphic features do not support his thesis. S ie r r a Madre O ccid en ta l P rovin ce The Basin and Range, Barranca, and Plateau sections which form this province are parallel belts whose structural features trend north 10° west (Alvarez, 1966; King, 1939). Basin and Range Section. Structurally, this section is charac terized by a series of horsts and grabens bordered by normal faults (Fries, 1962; Alvarez, 1966). Although many faults in the northern part of the province are reported as thrusts and overthrusts (King, 1939; Wisser, 1966). Within this subprovince, principally Mesozoic and Cenozoi-c rocks outcrop. The Mesozoic rocks show the same, north-northwestern structural trend of faulting as pre-Mesozoic rocks (Fries, 1962; King, 1939; Wisser, 1966). Fries (1962) considers that during Permian to early-Triassic time a tectonic event, the Sonoran Orogeny, destroyed the structure of the Paleozoic geosincline. He correlates the Sonoran Orogeny with the Appalachian Orogeny of King (1951). Alvarez (1966) emphasizes that during Upper-Triassic to Lower-Jurassic time continental deposits of the Barranca Formation within the Sonoran Basin were deposited. Inlay (1939) points out that, in the vicinity of El Tigre, north western Sonora, the structures trend west-northwesterly. He suggests that this structural feature is related to the Cretaceous geosyncline of northern Sonora and southern Arizona. Taliaferro (1933) also reports a 29 similar north-northwest trend in the Cabullona area. King (1939) recog nizes a Mid-Cretaceous orogeny only in northernmost Sonora. He considers folding and faulting of the pre-Tertiary rocks of northwest Sonora are related to the Laramide Orogeny. During the Laramide Revolution, the majority of the plutons were emplaced, folding and uplifting the pre-Tertiary rocks and forming the horsts and grabens typical of the Basin and Range Section (Wisser, 1966). During upper-Tertiary time, the grabens (valleys) were filled by terrig enous materials and basaltic flows of the Baucarit Formation (King, 1939; Damon, 1975). The main system of faulting trends north to north west 10° (Fries, 1962; Wisser, 1966). Northeast tensional fractures nor mal to the northwest system were formed (Alvarez, 1966). Barranca Section. King (1939) reports that the system of faults in this section trends almost north-south. They have raised sedimentary and intrusive pre-Tertiary rocks to the zone of erosion. However, he con siders that erosion, not structure, is the most important determinant in the deep gorges or barrancas. The faulting is normal and high dipping (Fries, 1962). Upper Tertiary rhyolites are the most abundant rocks which dip from horizontal to 35° to the northeast (Wisser, 1966). Plateau Section. Wisser (1966) considers that the main struc tural feature in this section is a complex elongated uplift that trends northwesterly and coincides closely with the Mesozoic occidental geoanti cline. This uplift is considered to be of tectonic, not erosional, origin. He calls this structure the "main welt" and emphasizes this structure because of the associated precious metal mining districts along 30 the welt. Faults in this section are normal, trending north-south, and are of relatively simple structure (King, 1939). Exposed rocks consist mainly of Tertiary andesitic and rhyolitic flows which lie horizontally, with erosional and angular unconformity, across the andesitic series (Wisser, 1966). CHAPTER 3 ALAMOS DISTRICT General Geology Geomorphology The Alamos Mining D istrict lies in the Basin and Range and Barranca Suprovinces of the Sierra Madre Occidental Province described by Alvarez (1966) and shown in Figure 3. As described previously, the Basin and Range Subprovince consists of an elongated belt, 80 to 110 kilometers wide, of longitudinal moun tains which are separated by intermontane valleys. The average trend of both features is N10°W. In the Alamos Mining District, this belt is only 30 kilometers wide, and 10 kilometers south it ends against the Coastal Plain of Sinaloa Province. The local trend of mountain ranges and valleys is N8°W. The topography in the area is rugged and diverse, ranging from 500 meters in the lower parts. Valley de Alamos, to 1,800 meters in the highest. Sierra de Alamos (Figure 7). The valleys are drained by the Mayo and Cedros rivers and the Cuchujaqui Arroyo and its tributaries which flow toward the Gulf of California. The drainage in the district shows dendritic and radial patterns. The dendritic pattern is common in the lower parts that generally contain granite outcrops; the radial pattern is present around the high mountains that generally contain 31 U l tx) 33 volcanic outcrops. Although both types of drainage are influenced pri marily by structural features, erosion and sedimentation also play an important role in determining the physiographic expression of the intru sive, sedimentary, and volcanic rocks exposed in the district. King (1939, pp. 1636-1637) describes the edges and valleys of the Alamos D istrict as follows: Some of the thick rhyolite flows are cut into high, sheer pinnacles, as in the Sierra de Alamos . . . The plutonic rocks are generally eroded to low pediments . ♦ . The Rio Cedros follows the northern portion of another valley . . ; East of Alamos, the southward continuation of this valley is a broad area of low hills and mesas . . . To the south . . . the alluvial flats of the Coastal Plain extend around and between the mountains. Stratigraphy In the Alamos D istrict, the exposed rocks range in age from Paleozoic (?) to Recent. The stratigraphic column in the area is largely based upon work in southern Sonora by King (1939) and Wisser (1966), and upon the relative stratigraphic position of the exposed rocks. As stated before, no studies of age determinations were done during the field reconnaissance. Within the mapped area, which covers 1^200 square kilom eters, there are exposures of metamorphic, sedimentary, intrusive, and volcanic rocks. A general description of the stratigraphy in the Alamos District is as shown in Figure 6 (in pocket). Paleozoic (?). Even though no exposures of Paleozoic rocks are plotted in the geologic map of the Alamos D istrict, it appears possible that rocks in the vicinity of Presa Mocuzari may be of this age. This 34 assumption is based on work by King (1939), who recognizes that, in the valley of the Mayo River, 7 kilometers north, some exposed rocks may be Paleozoic (King, 1939, p. 1644): "Near the Rio Cedros and to the west of it there are local small outcrops of sedimentary rocks. . . . Their age and structural relations are uncertain, but if the sedimentary rocks near the Mayo and Cedros valleys are Paleozoic these may also be." At Rio Cedros, the sedimentary rocks are described as limestone, red and white quartzite, and slate. The limestone contains crinoid stems, corals, and brachiopods. The assigned age of these rocks is Permian. At the Presa Mocuzari locality, the rocks consist of limestone, quartzite, and slate. It is evident that the rocks are lithologically similar to the Paleozoic rocks of the Cedros and Mayo rivers. However, no fossils were recognized during the geologic reconnaissance due to the intense metamorphism that affected the outcropping rocks. Mesozoic. Mesozoic rocks are exposed in relatively small areas in the Alamos D istrict and are considerably metamorphosed. They cover about five percent of the area. The age of the rocks correspond to the Upper Triassic-Lower Jurassic and Cretaceous systems. 1. Upper Triassic-Lower Jurassic: Within the area studied, the characteristic stratigraphic unit of this age is the Barranca Formation. This unit is exposed in the vicinity of Piedras Verdes town. Here, the formation is almost wholly non-marine and it consists of red quartzite, quartzitic sandstone, slate, and sericitic schist. The whole sequence shows a strong set of 35 joints which makes the original bedding difficult to identify. The approximate thickness of the formation is 150 meters. The metasediments form a characteristic east-west range of h ills 5 kilometers long. They are intruded to the north and the south by quartz diorite and granite, respectively (Figure 8). 2. Cretaceous: The Cretaceous system in the Alamos District is . represented by sedimentary, volcanic, and intrusive rocks. They are widely exposed through the area and are of principal impor tance because they contain much of the known mineralization present in the region. a. Sedimentary rocks: King (1939) considers that the Upper Cretaceous sediments are restricted to the northern part of the state. Therefore, the sedimentary rocks in the more southerly Alamos D istrict are considered of Lower Cretaceous in a g e. Cretaceous strata are represented by massive and by bedded limestones. The massive type is composed of a very compact, dense, grey limestone which commonly shows recrystallization, marblization or silification near the granitic or andesitic intrusives. Some of the localities where these characteris tic limestones are exposed are Mocuzari Village, Rancho Argentina, Rancho Tres Marias, and Piedras Verdes town. The bedded limestone is composed of a fine-grained, light grey limestone. The beds vary from 50 to 80 cm in thickness and contain some interstratified andesitic flows and volcanic 36 Figure 8. Exposure of the Barranca Formation (Upper Triassic-Lower Jurassic) in the Piedras Verdes Area. -- View looking n o rth . 37 detritus of 60 to 90 cm in thickness. The units show an approximate thickness of 250 meters, striking from 10 to 20° northeast and dipping from 50 to 60° southeast. These struc tural features were recognized at Sierra de Alamos, one kilometer south of the Quintera Mine. b. Volcanic rocks: Volcanic rocks of possible Lower Cretaceous age are exposed at some places in the Sierra de Alamos. They consist of green andesitic flows interbedded with volcanic agglomerates which lie unconformably on partially eroded limestone and are intruded by granite at their base. The thickness of the volcanic unit is unknown because of the Tertiary andesitic rocks which overlie this unit. No separa tion between the two andesitic rocks was done in reconnais sance work. For convenience, the volcanic Cretaceous rocks were grouped with the Laramide rocks exposed in the central part of Sierra de Alamos. c. Intrusive rocks: As stated before in Chapter 2, isotopic age determinations (Damon and Mauger, 1966; Livingston, 1973) and stratigraphic evidence (Wisser, 1966) indicate that the majority of the intrusions in the Basin and Range Subprovince are of Laramide age (52 to 72 my). Therefore, the intrusive rocks that are exposed in the district are considered con temporaneous with the Laramide event due to the sim ilar geologic evidence mentioned before. 38 The Laramide intrusive rocks in the Alamos D istrict are represented by a granitic batholith and by a stock of porphyritic andesite. The granitic batholith is widely exposed throughout the district and covers twenty percent of the area. It is part of the basement on which the Tertiary volcanic rocks were laid down (Wisser, 1966). The granitic mass shows magmatic differentiation to granodiorite-quartz diorite in the vicinity of Piedras Verdes town and Presa Mocuzari. Moreover, it shows a different mineralogical composition in the Sierra de Alamos and in the surrounding area. At Sierra de Alamos, the granite is composed largely of quartz and feldspar, and in the valley it shows a substantial amount of mica. Flores (1929) considers the mica-bearing granite to belong to an older group, and the quartz-feldspar granite to be younger. However, field observations appear to indicate that this difference in lithology is due to a regional zoning during the emplacement of the granitic intrusion. The stock of porphyritic andesite (Early Tertiary) is exposed in the central part of Sierra de Alamos and covers roughly five percent of the mapped area. The body intrudes the granitic batholith and includes fragments of volcanic agglomerates which probably were incorporated at the time of the intrusion. Because of the fine porphyritic texture and structure, the andesitic mass is considered to be a hypabyssal 39 intrusion. There are also andesitic dikes of similar texture which cut the granitic mass striking N 20-40° W. It must be pointed out that this andesitic stock is of considerable importance because of silver-lead mineralization which is present as veins within the andesite or in contact with the granite or limestone. Cenozoic. Cenozoic rocks are the most abundant in the district and cover over thirty percent of the area. They rest unconformably on Cretaceous and older rocks and consist of Middle-Tertiary volcanic rocks, Upper Tertiary clastic rocks, and Quaternary rocks. 1. Middle Tertiary: As was explained in Chapter 2, King (1939) and Wisser (1966) agree that within the Sierra Madre Occidental Province the criteria for differentiating between the Tertiary volcanic rocks is based upon the composition of the volcanic flows. The youngest Tertiary volcanic rocks are chiefly ande sitic, whereas the oldest Tertiary volcanic rocks are chiefly rhyolitic in composition. King (1939) considers that Tertiary volcanism corresponds to Paleocene-Eocene time. While Wisser (1966), based on isotopic age determinations, concludes that Tertiary volcanism corresponds to Oligocene-Miocene time. In this paper, the Tertiary volcanic rocks exposed in the Alamos D istrict are considered Middle-Tertiary in age, in agreement with Wisser1s studies. 40 The oldest Tertiary volcanic rocks (Oligocene) in the area studied are represented by andesitic lavas, volcanic agglomerates and tuffs of the same andesitic composition which outcrop irregularly throughout the district. They generally strike, except where there are folded blocks, from N 20° W to N 10° E and dip from 10-20° to the east and from 10-25° to the south, respectively. The .youngest Tertiary volcanic rocks in the area (Miocene) are flows and tuffs of rhyolitic composition. They are exposed generally in the highest parts of the area, such as at Sierra de Alamos and Cerro Cacharamba, forming sheer escarpments. The strike and dip of these rhyolitic flows are similar to that of the andesitic flows. 2. Upper Tertiary: Upper Tertiary rocks in the district are repre sented by the Baucarit Formation which is exposed within the grabens and low parts of the area. In the graben of Arroyo de Alamos, the formation is composed at the base of intermediate thin volcanic flows interbedded with conglomerate. The upper part is composed of a thick-bedded massive conglomerate of acidic and basic igneous rocks. The thickness of the formation varies from 30 to 50 meters (King, 1939) and shows a strike N 15-10° W and a dip from 10 to 20° NE, which are similar to the regional structural system of faulting. The formation lies with angular unconformity upon the older Tertiary volcanic rocks. According to isotopic age determinations (Damon, 1975), and fossil evidence 41 (King, 1939), the Baucarit Formation is of Middle to Upper Miocene in age. 3. Quaternary: Quaternary sediments cover about fifteen percent of the mapped area. They are represented by granitic pediments and residual soils around the Sierra de Alamos and alluvial fans and sands in the Mayo River and secondary streams. Most agricultural activity in the district is in the residual soils of the granitic batholith and in the sands along the strea m s. S tru ctu re The structural features of the Alamos Mining D istrict are closely related to the geomorphic units in which they lie, the Basin and Range and Barranca sections of the Sierra Madre Occidental Province, and the Coastal Plain of Sinaloa Province. As explained earlier, the Basin and Range Subprovince consists of a series of parallel mountains and valleys which show an average trend N 10° W. Within the Alamos D istrict, these ridges are bordered by steep normal faults, which form the regional structural system of faulting, striking N 5-30° W and dipping N 75-85° E (King, 1939). From the Sierra de Alamos to the Coastal Plain of Sinaloa in the west, there are a number of parallel ranges, separated by depressions, some of which are down-faulted areas. But others, perhaps, are the result of down-faulting. The ridges are composed of volcanic flows which dip 20 to 30° to the east (Figure 9). Toward the south of Sierra de I Figure 9. Ridge of Tertiary Rhyolitic Flows Dipping 25° to the East. -- View looking south. 43 Alamos, most of the ranges disappear beneath the alluvium of the Coastal Plain of Sinaloa, possibly due to the southward pitch of the structural features (King, 1939). Locally, the main fracturing in the district is trending from N 20 to 55° E and is normal to the regional system of faulting. The majority of the mineralized veins within the district are localized within these fractures (Vazquez, 1973). Thrusting in the area is represented by faults trending from N 10 to 25° W and dipping N 18 to 27° E. Post mineralization faults which displaced the veins are also present. The displacements along the veins varies from some centimeters to two meters. These structural features were recognized principally during underground mapping. King (1939) considers two important unconformities in the area. First, the Cretaceous unconformity between the Early Tertiary volcanic rocks and the Cretaceous granitic and andesitic intrusions. Second, the Tertiary unconformity between the Middle Tertiary volcanic rocks and the Upper Tertiary clastic rocks (Baucarit Formation). Both unconformities were recognized during the field reconnaissance, but they were not mapped in d e t a il . Wisser (1966) describes the structure of the district as King does, but he includes new ideas which might explain the origin and struc ture of the epithermal precious-metal province of northwestern Mexico: They are: 1. The great pile of the Tertiary volcanic rocks from which erosion has carved the Sierra Madre Occidental. 44 2. The basement upon which the volcanic rocks-were laid down (including all -re-Tertiary rocks). 3. The "main welt" which lies in the Plateau section of the Sierra Madre O c c id e n ta l. Based upon Wisser’s concepts, the basement in the Alamos D istrict is composed of the Triassic-Jurassic Barranca Formation, the Cretaceous limestones, the Laramide granitic batholith and the Laramide andesitic intrusion. Wisser points out that, in most cases, the deposit of pre cious metals lie within the Tertiary volcanic pile, but, where the vol canic pile was thin, the precious metals were deposited close to or entirely within the basement as in the Alamos, La Dura, Lampazos and San Xavier districts. These districts lie in a secondary "welt" that trends parallel to the main welt. The "main welt," a structural unit 900 kilometers long, located 40 kilometers east of the Alamos district in the Plateau Section of the Sierra Madre Occidental Province, is of vital impor tance because of the persistent precious-metal mineralization along it. The veins in the Alamos D istrict trend normal to the axis of the main welt similar to the veins in the Topia and Copala districts in northern Sinaloa (Figure 10). Also, according to Wisser (1960), it is likely that the Alamos Mining D istrict lies in the central part of an elongated dome which was formed by vertical rather than lateral tectonics. Locally, the Sierra da Alamos shows a radial pattern of fractures which suggests a domal s tr u c tu r e . EXPLANATION ZOO Km ALAMOS MINING DISTRICT source Wisser, 1966 Figure 10. Location of Precious-Metal D istricts along the "Main Welt" Structure in the Sierra Madre Occidental Province. 46 Economic Geology Ore Control Within the Alamos Mining D istrict structural and lithological conditions appear to have been the chief factors that controlled the circulation of hydrothermal fluids that produced ore. Structural Conditions. Based upon field mapping evidence, it was determined that structure was the main control in mineral deposition. Ninety percent of the ore deposits in the district correspond to vein fillin g fractures, and 55% of the veins show a preferred orientation of N 20-65° E, normal to the regional system of faulting. Also, 27% of the mineralized veins show an orientation N 15-70° W, which is the regional structural trend of faulting. The remainder of the veins show an orienta tion E-N or N-s. All the veins show a dip between 60 and 85°. Labounsky (1957) mentions that the faulting in the southern part of Sierra de Alamos shows a general fracture pattern that strikes N-W and dips N-E. To the north of Sierra de Alamos, the strike change to north. Labounsky (1957, p. 6) emphasizes: "this important change in the direc tion of fracturing . . . accounts for the tensional openings [the N-E fractures] which served as channels for mineralized solutions to deposit metal values in the vein-filling fractures." The dynamic activity during mineralization is manifested by sheared, brecciated, and recemented wall rock material within the veins. It seems likely that the vein matter could have been deposited while the walls of the vein fractures were being pulled apart during the last stage of the Middle Tertiary volcanic activity. 47 Lithological Conditions. Lithological factors were another impor tant condition that controlled the ore deposition in the Alamos D istrict. Field reconnaissance suggests that there are two types of mineralogical associations related to lithological controls. First, contact metasomatic minerals are represented by scheelite, wollastonite, epidote, and garnet, represented by granite-limestone and andesite-limestone contacts. Second, epithermal minerals, represented by galena, sphalerite, argentite, tetra- hedrite, and pyrite are found mainly in the porphyritic andesite. To a lesser degree they are also found in the granitic batholith and at the granite-andesite contact. The ratio of mineral abundance of the epithermal minerals varies considerably within the veins. The variation in the ratio of these minerals may be the result not only of mineral zoning but also the result of compositional differences in the rocks through which solutions ascended. In northwestern Mexico, Wisser (1966) correlated variations in the mineralogy of veins with the height above the basement at which the minerals were deposited (Figure 11). Wisser (1966, p. 86) explains it as follows: "Although a number of ore bodies low in base sulfides lies fairly close to the basement, all districts with heavy to moderate amounts of base sulfides lie within 500 meters of the basement or wholly within i t . " In the Alamos Mining D istrict, the ore bodies contain heavy to moderate amounts of sulfides and they lie close to or practically within the basement. Therefore, it is believed that Wisser's concept is HEAVY TO MODERATEHEAVY MODERATE TO SPARSE SPARSE TO VERY SPARSE 0 Au'Ag > l i 2CO 1 Vertical range of ora Source: Wisser, 19 6 6 Figure 11. Abundance of Base-Metal Sulfides Plotted Against Their Height above Basement -Px 00 49 in strong agreement with the lithological features (basement) that con trolled the emplacement of the hydrothermal mineralized fluids. Ore M ineralogy The ore veins in the Alamos D istrict contain typical epithermal minerals associated with metals such as silver, lead, zinc, and copper. The primary minerals in the ore bodies are galena, tetrahedrite, argen tine, sphalerite, chalcopyrite, pyrite, and native silver. Supergene mineralization is represented by azurite, malachite, chrysocolla, cerargyrite, goethite, and native silver. Gangue minerals include quartz and, to a lesser extent, calcite and chalcedony. The chalcedony is usually present in geodes and open fractures. Accessory minerals are represented by chlorite, epidote and prehnite. The ore with some varia tions in concentration, is mineralogically very similar among the ore bodies in the district. Hydrothermal alteration in the epithermal ore bodies is repre sented by characteristic propylitic, sericitic, and silicic minerals. Propylitization is present in andesitic wall rocks near the vein- filled fractures. The alteration is extensive but not pervasive, and it extends from some centimeters to a few meters from the veins. The charac teristic minerals are chlorite, epidote, calcite, and pyrite, present as veinlets and disseminations within the porphyritic andesitic rocks. Sericitization is found principally in granitic rocks and some times in andesitic rocks. The sericitic zone is spatially more closely related to the veins than the propylitic zone. Sericitic alteration is 50 recognized near its parent fractures and it extends from 10 to 40 centi meters into the rocks. Silicification is found in both granitic and andesitic rocks and is mostly restricted to its parent fractures. This type of alteration consists of fine-grained quartz and chalcedony present in veinlets and d ru ses. The ore within the district's replacement deposits is composed of metasomatic minerals such as garnet, scheelite, wollastonite, epidote, and diopside. These minerals were formed by the intrusion of the granite or the porphyritic andesite near the contact with the Cretaceous sed im en ts. It should be mentioned that sedimentary deposits of gypsum, magnesite, and limestone are also present within the district. However, . since this paper considers base and precious metals only, the industrial minerals w ill not be discussed. Mineral Paragenesis and Zoning Mineral Paragenesis. Based upon underground and surface mapping in reconnaissance surveys, it appears that the framework of the mineral ization sequence in the Alamos District is as follows: 1. The initial ground preparation of the district consisted of frac turing, shearing, and faulting during the emplacement of the Late Laramide intrusive rocks. The faulting created dilatant areas of low pressure and open space for later Tertiary volcanic activity. 51 2. Following faulting, the open space faults and shear zones were invaded by magma associated with the volcanic rocks which were la id down on th e p r e - e x is t in g ro ck s. 3. The volcanic rocks were faulted and tilted as a result of the up lift of the Sierra Madre Occidental, producing the formation of the "main welt." The faulting followed the same regional system o f f a u lt in g w ith in th e S ie r r a Madre P rovin ce (N 10° W). A lso , normal tensional fractures striking N-E were formed. 4. Propylitic, sericitic, and silicic alteration minerals were formed in the walls of fractures that served as channels for mineralizing solutions. 5. Hydrothermal solutions invaded the major open fractures in which: a. The bulk of quartz was deposited earlier than other minerals. b. Deposits of lenticular and tabular ore bodies carrying the bulk of sulfides were precipitated. c. Irregular deposits in broken zones carrying native silver and copper were formed. d. Oxidation and leaching of sulfides took place. An approximate mineralogical sequence, in the Alamos D istrict, based upon field observations and upon the normal deposition of epithermal deposits (Wisser, 1966; Park and MacDiarmid, 1964) in the Precious Metal Province of Mexico, is shown in Figure 12. Mineral Zoning. By analyzing the different changes in ore and gangue mineralogy among the ore bodies in the area studied, it seems ORE PRIMARY SECONDARY P y r ite ------ Sphalerite - Galena A r g e n tite Tetrahedrite Chalcopyrite S ilv e r G oeth ite M alach ite A zu rite Chrysocolla Cerargyrite GAN CUE Quartz , C a lc ite C h lo r ite Chalcedony P reh n ite Figure 12. Paragenetic Sequence for the Alamos Mining D istrict. S3 likely that three categories of mineral zoning are recognized in the Alamos District: regional zoning, district zoning, and ore body zoning. Very large regional zoning is associated with the precious metal metallogenetic province of central and northwestern Mexico. As stated before, the changes in ore are related to the height above the basement or distance from the source (Wisser, 1966). So, the high concentrations of sulfides lie close to the source, whereas the sparse concentrations of sulfides lie far from the source (Figure 11). D istrict and ore body zoning are shown by the closely grouped mines at Sierra de Alamos and surrounding areas. Some of the mines are La Quintera, Promontorio, Santo Domingo, Zambona, and San Manuel (Figure 2). Within these ore bodies, a conspicuous vertical change in mineralogy is noted. For instance, the Promontorio Mine, which lies in the southern part of the "Mother lode" structure, shows a high content of lead and zinc. On the other hand, the Quintera Mine, located in the central part of the "Mother lode" vein and 200 meters higher, shows a high content of silver and quartz (Figure 13). Without doubt, these arrangements of minerals suggest a mineral zoning from the surface downward. Ore Genesis According to its environment of deposition and metallogenic composition, the ore bodies within the Alamos Mining D istrict are classi fied in order of importance as epithermal, disseminated, and pyrometa- somatic ore bodies. m eters above meters above sea level sea level Quintero Promontories Santo pomingo Zambona sen Manuel depth of mine --200 hor: scale within ore. body kilometers Figure 13. Section N 30° E Showing Changes in Mineralogy among Mines in the Sierra de Alamos, Alamos D istrict. Cn 55 Epithermal Deposits. Wisser (1966) classifies the base-precious metals present in the district within the epithermal precious metals province of northwest Mexico. The common features shared by all these deposits within this province are: 1. Association with volcanic rocks, principally andesite-rhyolite in the erogenic region. 2. Middle to Late Tertiary age. 3. Veins occupy fractures which are often pre-mineral faults. 4. Hydrothermal alteration represented by propylitization, sericiti- zation, and silicification. 5. Tectonic movements which acted parallel to the fracture walls during vein formation. 6. Quartz as the principal gangue mineral which usually has been deposited earlier than the bulk of sulfides. 7. Occurrence of silver in argentite and in less proportion galena and sphalerite. 8. The vein texture shows brecciated fragments cemented by vein m a tter. 9. The ore body is longer on strike than on dip. The ore zone has a very definite bottom. Below the precious metals ore, gangue and base sulfides minerals may persist to the lower lim it of exploration. 10. Association with local domes produced by forces acting vertically not tangentially. 56 Wisser (1966) also stated that m etallic elements may have been transported to their place of deposition by volcanic gas-vapor emmanations. Therefore, comparing the deposits in the Alamos Mining D istrict with the characteristic epithermal features described above, except for the hypabyssal andesitic intrusion, it is concluded that the veins present in the district lie within the epithermal classification of ore deposits. It is estimated that 80% of the prospects in the area lie within this classification. Some of the more important ones, according to structure, size, mine conditions, and accessibility, are: Zambona, Santo Domingo, Promontorio, Quintera, San Manuel, Otates, Plomosa, Ana Maria, La Reina, Violeta, and Japon en Mexico (Figure 14, in pocket). Disseminated Deposits. Pearce (1910) describes the Piedras Verdes Mine as a disseminated ore body. In field reconnaissance mapping, it was recognized that this area shows many of the typical features described by Schwartz (1966) and Bateman (1950) for this type of deposit, such as: 1. Low grade deposit. 2. Association with stock-like intrusions. 3. Disseminated replacement in porphyry or intruded schist. 4. Blanket shape, greater horizontal than vertical dimensions. 5. Similar primary mineralogy. 6. Intense sericitization, in places, silicification. 7. Overlain by leached cappings (Figure 16, p. 58). 8. More or le s s supergene enrichm ent. 57 Consequently, it seems likely that Pearce's statement is true, and that the Piedras Verdes area lies in the category of disseminated prophyry copper type (Figure 15). There are, in addition, some epithermal veins associated with the disseminated mineralization. Pyrometasomatic Deposits. Pyrometasomatic or igneous metamorphic deposits, according to the classification of Park and MacDiarmid (1964), are also present in the Alamos D istrict. They are represented by the classical association of sedimentary and intrusive rocks. The sediments are limestones or shale, and the intrusive rocks are granite or quartz- d io r it e . A brief description of the processes of the pyrometasomatic ore bodies within the district are: 1. The igneous rocks recrystallized the limestone to marble. 2. Hydrothermal fluids coming from the intrusive masses formed lime- silicate minerals such as garnet, wollastonite, and diopside. 3. The introduction of mineralizing solutions rich in tungsten took place, forming fine scheelite crystals within the tactite zone. The pryometasomatic prospects in the district are La Esmeralda, La Mexicana, Victoria, and Guadalupe II. All show a similar mineralogical association. Description of Mines According to geographical distribution and analogous mineralogi cal, structural, and lithological features, the ore bodies in the Alamos Mining District may be grouped in six zones (Figure 14): 58 Figure 15. Copper Mineralization, Brecciation, and Argillic Alteration in the Piedras Verdes Area. — The area suggests a porphyry type deposit. Figure 16. Capping and Oxidation of the Piedras Verdes Prospect. — View looking east. 59 1. Sierra de Alamos (Ag, Pb, Zn). 2. Sierra las Plomosas (Pb, Zn, Ag). 3. Lomas lo s Tanques (Cu, A u). 4. Sierra del Chapote (Au, Cu, Pb). 5. Sierra del Bavispe (Cu, Au, Ag). 6. Sierra San Bernardo (Cu, Ag). As already mentioned, the main purpose of this study is the evaluation of lead-silver-zinc deposits. On the basis of the geologic exploration carried out thus far, and on the old available geologic infor mation, it is concluded that the main lead-silver-zinc deposits lie within the Sierra de Alamos and Sierra las Plomosas groups, and a prospect within the Sierra San Bernardo group. In this paper, only the most promising prospects within these groups are described. Sierra de Alamos Zone. The mines which constitute this group are La Quintera, Promontorio, Santo Domingo, Minas Nuevas, San Manuel, and numerous small mine workings. The mines are located in the Sierra de Alamos, 10 kilometers northwest of Alamos. Their normal access from Minas Nuevas town is by a dirt road. Except for the San Manuel Mine, all the mines lie in an area 2.5 kilometers wide by 7 kilometers long, which commences at Minas Nuevas and finishes at Promontorio Mine (Figure 2). As described previously in Chapter 2, the "basement" in the area is represented by granite, limestone, and porphyritic andesite on which the Tertiary volcanic rocks were laid down. Based on underground mapping and old available information (Brinegar, 1910; Pearce, 1910; Pearce, 60 1911a,b; Bloomer, 1909; Sheldom, 1910) all these types of rocks are exposed within the mine workings. Structurally, this group of mines is located along two well- defined fissure zones, which are about 1.5 kilometers apart and strike in a north-east direction. These two fissure zones are described by Brinegar (1910) and Labounsky (1957) as the east and west veins, which lie within the porphyritic andesite, near the granite-andesite contact or near the andesite-limestone contact. In field reconnaissance, both veins were mapped. 1. East Vein: The Promontorio, Quintera, Santo Domingo, and Minas Nuevas lie within the east vein, the "Mother lode" of the zone (Sheldom, 1910). This vein trends N 20-35° E and dips 60-75° N-W, even though, in the Zapopan tunnel, the vein splits with the. branch striking N 10° W and dipping 72° NE (Figure 17; and Figure 23, p. 68). This structure, which crops out irregularly at the surface, has a length of seven kilometers and an average width of eight meters (Figure 18). A brief description of the mines within the east vein, the "Mother lode," is as follows: a. Promontorio Mine: The Promontorio Mine lies at the southern end of the vein. The mine was operated through a tunnel more than 1,000 meters long at an elevation of 560 meters above sea level. There are three shafts at 250-meter intervals which reach depths of 70, 80, and 90 meters from south to 61 Figure 17. Split to the N 10° W of the "Mother Lode" Structure in the Zapopan Tunnel, Quintera Mine. — View looking N 80° E. 62 north. The mine workings below the tunnel are flooded and no mapping has been done below this level during the present investigation. Labounsky (1957) reports that there are three levels below the tunnel at 40-meter intervals. Bloomer (1909) and Sheldom (1910) state that the deepest mine working is close to 200 meters in depth. Therefore, it seems likely that the miners bottom is presently about 350 meters above s e a le v e l. The ore body exposed in the tunnel is in stope pillars because the majority of the ore above and below this level has been mined out. The vein averages 2.50 meters in width and at some places reaches 5 meters in width. The vein is principally in andesite and in some places in the granite or limestone contact (Figure 19). Based upon the stoped areas, the past production of the mine is estimated at a half million tons, with an average grade of 30 ounces silver per ton (Labounsky, 1957). Pearce (1911a) reports a past produc tion of three-quarters of a million tons of very high grade ore. He states (Pearce, 1911a, p. 209): ". . . and so rich that practically all of it was packed over 60 miles to the coast and from there shipped to England for treatment." At the present time, the mine is inactive, but during the coining months some p illars, which average 700 grams silver per ton, w ill probably be extracted. n r i r l r ' A| W i d t h A s s o y s n o Pb*/. Zn*Z. A g p p m 1 2 . 6 0 0 . 5 5 4 2 0 1 0 3 2 1 8 5 0 . 9 1 3 8 0 2 8 0 3 2 0 5 O 8 1 6 24 3 4 0 4 2 65 0 79 6 60 2 5 2 5 4 80 6 56 14 50 2 6 5 6 3 5 0 4 9 0 9 1 6 6 5 7 2 6 0 1 0 3 2 9 6 2 9 0 6 2 2 0 12 04 12 96 245 9 1 70 4 8 4 15 8 0 1 4 9 0 1 0 1 . 9 0 8 6 4 1 3 9 6 4 6 0 11 5 2 0 4 4 5 7 6 4 3 1 5 12 1 . 5 0 1 71 4 0 5 4 0 13 1 . 7 5 0 9 5 4 .3 2 9 0 14 2 . 2 5 O 7 3 2 .1 0 5 0 2 16 1 . 6 0 0 3 6 0 3 5 7 2 E 3 Tvff f*.• *1 V o lc a n ic o g g l o m e r o t e Porphyritic ondesite Q33 Granite f-v!D Skorn e s r i s v e i n — Mineralized I r o c t u r e Barren Irocture Geologic c o n t a c t F a u l t B R a i s e Shalt ( Hooded ) ESTIMATED ORE RESERVES [2 Winze (Hooded) m e tric t o n s * Q C r o s s c u t Proven 6.000 ik'd Inaccessible workings P r o b a b l e 11000 > = A d . t Possible 60 POO Strike and dip ZC? Slope 20 m eters above S S a m p l e A*—' 8 Cross section Geology by Allredo Cervantes.. 1674. Figure 19. Geologic and Sampling Map of the Promontorio Mine 64 b. Quintera Mine: The Quintera Mine is located in the middle part of the "Mother lode" vein and it practically adjoins the • Promontorio Mine to the south. Topographically, the mine lies at the highest part of the vein, 810 meters above sea level. This mine has been developed by underground explora tion more than the other mines in the district. At the sur face there are three shafts along the vein, with a distance of 750 meters. Pearce (1911a), Sheldom (1910), and Labounsky (1957) agree that there are 16 levels along the vein at 30-meter intervals, and numerous drifts, raises and cross cuts. The deepest level is 420 meters below the surface at an altitude of 360 meters above sea level. In underground reconnaissance, only the first three levels were mapped due to the inaccessibility of the lower levels. According to underground mapping carried out in the first three levels, the ore body lies entirely in the andesitic porphyry intrusion (Figures 20, 21, 22, and 23). Neverthe less, Sheldom (1910) and Pearce (1911a) reported granite in the sixteenth level where the vein is exposed with an average width of 5 meters, at some places attaining a width of 9 to 15 meters (Brinegar, 1910). The past production of the Quintera Mine is estimated at 1.5 million tons by Labounsky (1957) and at 2 million tons by Pearce (1911a). These estimates are reasonable, judging from mine workings and dump size (Figure 24). Libcrtad end Covacha levels,730 meters above Libcrtad sea level Zapopan level,750 meters 4 - ' above sea level TIOIcvcl Inaccessible mine workings Ore shut \ Raise Shaft -r Strike and dip Figure 20 Composite Level Plant Map of the Quintera Mine 66 l-v -1 Porphyritic andesite Mineralized fracture calcite and iron oxides - t----Barren fracture .— Vertical fracture -<• Strike and dip Vein g ] Shaft ■ICxT}' Inaccessible raise y Adit Inaccesiblc mine workings r''.. Slope above level Sample Width Assays no meters Pb°/o Zn*/e Ag ppm 1 0.90 0.41 0.45 270 2 0.95 0.12 0.31 125 3 1.20 0.17 0.69 245 4 0.75 0.25 0.25 120 5 1.90 0.4 3 0.51 237 Figure 21. Geologic and Sampling Map of the Zapopan Level, 750 Meters above Sea Level, Quintera Mine. 67 portal 50 m if v y v v 1 Porphyritic andesite Mineralized fracture, calcite, iron oxides Vertical fracture Vein "T"" Strike and dip Sample Width As says no meters Pb Zn Ag B Raise •/. •/. ppm f~Stopc above or 1 3.20 1.44 2.20 220 below level ?. 1.75 1.57 1.75 255 ^ Ore chute 3 1.20 1.50 3.31 225 Inaccessible mine workings 4 1.15 6.96 1.33 1100 5 3.20 0.43 231 152 A i— i B Cross section 6 2.15 1.10 2.20 4655 A Adit S Sample m eters Figure 22. Geologic and Sampling Map of the Covacha Level, 730 Meters above Sea Level, Quintera Mine. 68 Forphyritic andesite 1 Estcrile fracture Mineralized fracture, calcite and iron oxides Strike and dip Inaccessible mine workings Shaft Adit S Sample Sample Assays ppm no P b Zn Ag 1440 728 49 1680 3680 27 average width of vein 3.20 meters meters s e c t i o n / 5? Figure 23. Geologic and Sampling Map of the Libertad Level, 730 Meters above Sea Level, Quintera Mine. 69 Figure 24. Old Dump of the Quintera Mine, Alamos D istric t. 70 As previously mentioned, the Quintera Mine is active; however, the mining operations are restricted only to the dumps, due principally to the lack of mining equipment (Figure 25). From the dumps, mineral which contains an average grade of one kilogram silver per ton is selected. The production is small and averages only about 5 tons per month. c. Santo Domingo and Minas Nuevas Mines: These mines are located two kilometers north of the Quintera Mine and lie within the northern exposure of the "Mother lode" vein. Both mines are in sheared zones of andesitic volcanic rocks associated with the porphyritic and andesitic intrusion. No detailed studies have been carried out in these mines to date. In reconnaissance work, only some chip samples from pillars were taken. Therefore, the following brief sketch of these mines is based largely upon the old available information. The Santo Domingo Mine lies at an altitude of 550 meters above sea level on the southern slope of the Aduana H ill. The mine workings consist of a glory hole 5 meters wide and 40 meters long. Quiroga (1953) reports that a shaft reaches a depth of 115 meters at the fourth level. In the levels, the vein is exposed with a thickness of 3 meters and an average grade of 500 grams silver per ton. Sheldom (1910) 71 Figure 25. Gambusinos Who Are Working the P ortal Covacha Level, 730 Meters above Sea Level, Quintera Mine. 72 states that the deepest level in the mine reaches 80 meters in depth at an altitude of 470 meters above sea level. No figures of the past production of the Santo Domingo Mine are reported. However, based upon the mine's dumps, it is obvious that this mine has been developed less than the other mines in the "Mother lode" vein. Labounsky (1957) estimates that the past production of the mine was only about 50,000 tons with a grade of 500 grams silver per ton. The Minas Nuevas Mine is located just 200 meters from the Navojoa-Alamos road in the Minas Nuevas village (Figure 26), at an elevation of 490 meters above sea level. The mine workings consist of two shafts 300 meters apart. The first attains only 100 meters in depth, whereas the second reaches 200 meters in depth (Labounsky, 1957). In the second shaft, levels were driven at 10- and 20-meter intervals within the main ore body (Yaeger, 1909). Also, there are numerous raises, stopes, and cross-cuts in the vein. Pearce (1911a) estimates a past production of the Minas Nuevas Mine to have been a quarter of a million tons of 600 grams silver ore. West Vein: Within the west vein, the mines, from north to south, are the Olivedes, Ibarra, Plata Fina, Europa, San Jose, and San Manuel. This structure trends N 20-35° E and dips 55-70° SE in the north and NW in the south. All these mines are located within a distance of four kilometers along the main structure which is exposed irregularly at the surface and averages two 73 Figure 26. Minas Nuevas Mine (or Zambona). 74 meters in width. To the north, the vein is covered by Tertiary volcanic rhyolitic flows at Cerro Cacharamba (Figures 6 and 27). All the prospects within the west vein, excepting the San Manuel Mine, are completely inaccessible. In addition, no information about the mine workings was available. Therefore, the San Manuel Mine is the only prospect which has been mapped in detail, a. San Manuel Mine: The San Manuel Mine is located in a flat area, 3 kilometers west of the Promontorio Mine, at an altitude of 350 meters. On the basis of a structural align ment on the aerial photographs, it seems likely that this mine lies in the southern continuation of the west vein. Furthermore, a sim ilar mineralogy and vein attitude supports this supposition. The San Manuel vein crops out at the surface for a dis tance of 120 meters and is from 1.20 to 2.00 meters wide. It strikes N 20-35° E and dips 80° NW. There is a strong brec- ciation and oxidation within the vein which shows a sharp . contact with its foot wall (Figures 28 and 29). At depth, the ore body shows a tabular shape and similar structural fe a tu r e s . This mine is a relatively new prospect which has been explored only by shallow workings. At the surface, there are three small shafts in a distance of 100 meters. They reach 35, 20, and 25 meters in depth from north to south (Figure 30). Short drifts extend from 15 to 25 meters from the 75 Figure 27. T ertiary R hyolitic Flows of Cerro Cacharamba. 76 Figure 28. Exposure at the Surface of the San Manuel Vein. — View looking N 25° E. ' i • * I Figure 29. Picture Showing Brecciation and Oxidation Within the San Manuel Vein. • # Sample A ssays m Soil no Pb •/« Zn •/. Ag ppm JZZZl Brccciatod granite 1 0.4 8 1.84 163 2 0.11 1.20 78 EH Granite 3 0.25 0.59 164 Vein 4 0 .14 0.40 27 Geologic contact 5 0 .41 0.10 53 Inaccessible mine workings 6 0.09 0.05 17 B Shaft 7 0.32 1.15 700 □ Pit 8 1 .65 1.57 158 (&) Dump 9 2.05 0.75 197 S Sample 10 29.12 15.23 183 average width of vein 2.10 meters o Estimated ore reserves proven 4,000 probable 18000 a r-"' possible 50,000 metric tons - N 30 E -340 330+ -330 320+ -320 meters above sea level m cters Figure 30. Geologic and Sampling Map o f the San Manuel Mine 'vl 78 shaft. Also, there are eight shallow pits along the vein within a distance of 450 meters. At the present time, the mine is being explored and exploited on a small scale. The production is erratic due to the common problem in the district: lack of mining equipment. It varies from 50 to 100 tons per month. Based upon mine workings, the past production is estimated to have been 3,000 tons at a grade of 300 grams silver and 4% lead per ton. Sierra las Plomosas Zone. The most promising prospects within this area are La Plomosas, Otates, and Ana Maria mines. They are located in the Sierra Plomosas some 35 kilometers east of Alamos. The mines can be reached by a dirt road which leads to the San Ignacio sawmill in Chihuahua. Geomorphologically, the Plomosas and Otates mines lie in the transition zone between the Basin and Range and Barranca Sections of the Sierra Madre Occidental Province, where the Ana Maria Mine, 20 kilometers farther east, lies in the Barranca Section (Figure 3). The mines are wholly in Tertiary volcanic rocks, chiefly of ande sitic composition. In the vicinity of the ore bodies, the rocks show a gentle silicification, oxidation, and brecciation, and a strong propyliti- zation. The ore bodies are epithermal veins of lenticular and tabular shape in which galena, argentite, and sphalerite are the main minerals. The Plomosas and Otates mines are new prospects in which only limited underground exploration has been done. Both prospects have been inactive since January 1975 due to economic problems. The Ana Maria Mine 79 has been exploited and explored more than the other mines in the Plomosas Zone. Probably the mine workings date from the early 1900's. 1. Plomosas Mine: The Plomosas Mine is located in the north slope of a small h ill at an elevation of 600 meters above sea level. At the surface, the Plomosas vein is exposed in three outcrops within a distance of 125 meters. The outcrops are small, varying from 5 to 10 meters in length. The vein strikes N 20-38° E and dips 55 to 60° SE, with a thickness of .60 to 1.10 meters. Some 150 meters north of the outcrop, there are indications of propylitization, silicification, and oxidation, which suggest a continuation of the vein. Underground, the vein shows similar structural features as at the surface, but the width increases to 1.70 meters. The mine had been operated through a tunnel 16 meters below the surface. It intersects the Plomosas vein at a distance of 20 meters. From this point, a southeasterly drift in ore reaches a distance of 82 meters. There are two raises in this drift. The first is located 30 meters from the tunnel and connects 19 meters above to the surface. An incline, 40 meters from the tunnel, follows the dip and reaches an inclined depth of 19 meters (Figure 31). Three small drifts have been driven from the incline at different depths. Here, the vein varies from 1.60 to 1.90 meters in width and is exposed along the drifts. At the __ surface, there are two inaccessible shafts 70 meters apart. 0 25 50 Andesite and andesitic aglomerote meters Vein D Shaft (inaccessible) Raise Inaccessible mine workings Adit Level, 625 meters above sea level Dump, surface 645 meters above sea level Projected mine workings 8 Crosscut Sample A $ s a y s no Pb •/• Zn •/. Ag ppm n Portal i 2.2 1.2 25 ------'B Cross section ii 2 5.6 30 115 II s 11-C Proyected tunnel 3 1.2 1.1 40 • 4 2.0 2 6 50 Sample s 13- s 5 4 4 3.1 bO cross s e c t i o n 6 4.5 36 60 Geology by Alfredo Cervantes, 7 6.6 7.1 115 1974 6 17 9 3.2 360 10 20 ___30 9 1.1 1.5 25 m e te r s 10 6.7 3 5 40 11 34 3 6 35 12 3.3 59 27 13 0.0 79 120 e s t i m a t e d ore r e s e r v e s 14 1.2 1.5 metric tons______1 7 15 5 2 6.5 45 P ro v e n 1,200 average width of vein Probable 9,500 1.90 m e te r s Possible 20,000 Figure 31. Geologic Cross-Section and Geologic and Sampling Map of the Plomosas Mine o00 81 Also, there is an inaccessible tunnel 85 meters easterly which probably connects with the main tunnel. The mine production is estimated to have been only 5,000 metric tons with a grade of 4% lead, 3% zinc, and 100 grams silver p er to n . 2. Otates Mine: The Otates Mine is located 2 kilometers southwest from the Plomosas Mine. It lies on a flat surface 40 meters west of a stream bed. At this point, the vein crops out for a length of 10 meters and is from .70 to 1.00 meters in width. It strikes N 80° E and dips 40 to 50° SW. There is evidence at the surface of a possible continuation of the vein along 150 meters north westerly from the outcrop. The mine workings consist only of an inclined shaft within the ore body which reaches a depth of 14 meters and a drift 15 meters long from the shaft bottom (Figure 32). In the mine workings, the vein is exposed with an average thickness of 1.40 meters. According to the limited underground exploration, the mine production has been around 250 tons at a grade of 5% lead, 3% zinc, and 100 grams silver per ton. 3. Ana Maria Mine: The Ana Maria Mine lies 20 kilometers east from the Plomosas and Otates mines, in a range of the Barranca Section of the Sierra Madre Occidental, at an altitude of 1,300 meters above sea level. At the mine, the ore bodies are hydrothermal veins within Tertiary andesitic rocks. The main ore body strikes N 20-35° E 82 4 [> ^ | Porphyritlc volcanic L----- andesite Vein r | Projected mine workings EH Inclined shaft AI----1B Section Dump S Gamplo average width of vein 1.75 meters 'Si Sample A s s a y s no PbV. Zn */o Ag ppm 1 1.7 2.3 380 s 3 ---- 2 4.8 5.5 70 3 3.8 6.4 65 4 3.1 2.4 45 5 3.3 6.0 GO — s6 6 4.1 6.2 100 7 3.6 3.8 130 8 2.1 2.6 95 9 4.1 4.7 1 10 / s9 sl° 10 6.8 4.2 225 1 1 4.1 6.5 75 r 12 3.7 4.2 165 section He ESTIMATED ORE RESERVES metric tons 10 -a Proven 1,200 m eters Probable 6,000 Possible 10,000 Geology by Alfredo Cervantes., 1974. Figure 32. Sampling Map of the Otates Mine. 83 and dips 70 to 75° NW, with an average thickness of 1.90 meters. There are some subsidiary veins within a sheared zone some 3 meters west from the main vein; they strike in all directions and vary from .40 to 1.00 meters wide. The mine workings consist of two levels at 40-meter intervals along the ore body. The first level extends 180 meters, whereas the second is 350 meters long. There are some raises above the levels which vary from 10 to 35 meters in height. Most of the ore, except for a few small pillars, has been removed above the first level. Within the second level, a northeasterly drift in ore, the vein is exposed for a distance of 220 meters with an average thickness of 1.90 meters (Figure 33). At the present time, a small shaft is being sunk at the second level within the ore body, evidently for the purpose of exploring the continuation of the vein (Figures 34 and 35). Based on the stoped areas, it is estimated that the mine has produced about 50,000 tons at an average grade of 5% lead, 3% zinc, and 300 grams silver per ton. Sierra San Bernardo Zone. The Sierra San Bernardo is located some 45 kilometers northeasterly from Alamos town. It is a range in the Barranca Section of the Sierra Madre Occidental. In this Sierra lies the Japon en Mexico Mine, which is the most important prospect in this area so far. Even though this prospect is of difficult access, it is included in this paper due to the high value of the ore body. \ [ 1 ;| Andesitic agglomerate A n d e s i t e V e in F r a c t u r e ____—^ Gradational contact ) ------A d it _____ second level, 1307 meters above s e a l e v e l First level, 1347 m eters above s e a le v e l "2 Slope above or below level rtr::: Inaccessible mine workings R S h a l t Q2 Raise down meters above tea level ,'X, C r o s s c u t \ ; Sloped area A— Section S S a m p le O Sample Assays no Pb ♦/. Zn*/« Ag ppm r..." v . ) i / i 1 2 . 9 4 1 . 8 7 8 7 2 4 1 2 1 2 6 4 0 < 3 1 .1 8 1 8 2 1 6 5 4 2 . 7 9 0 6 3 4 7 1 — ir " ' 5 0 9 6 0 .7 1 2 3 6 6 0 4 8 1 0 0 5 9 7 1 5 7 2 9 8 3 9 0 8 1 4 4 2 3 9 1 2 0 ,r ? , 9 4 1 0 3 61 2 4 0 1320 ; .,"-1 o 1 0 3 6 4 2 3 0 5 8 1 1 2 5 6 4 2 8 6 5 12 3 6 9 2 9 4 2 1 5 v4 & V ‘e ^ 1 2 ____ r :% 1 3 8 48 2 80 166 14 661 2 50 216 1 5 0 1 1 0 4 2 5 3 N 3 « E 16 0 4 3 0 18 1 4 0 1 7 0 3 7 4 2 7 2 3 8 1 8 0 61 0 4 7 1 8 0 1 9 0 4 2 0 4 2 1 9 0 2 0 2 2 7 1 2 5 4 7 5 average width vein I SO m eters Figure 33. Geologic and Sampling Map of the Ana Maria Mine, First and Second Levels 00A Figure 34. Gambusinos Who Are Working the Ana Maria Mine, Portal of Second Level, 1,307 Meters above Sea Level. Figure 35. Dirt Roads Which Communicate to the Ana Maria Mine in the Alamos D istrict. 86 1. Japon en Mexico Mine: The mine is located 20 kilometers east of the San Bernardo village, at an altitude of 1,150 meters. The access to the mine is by a dirt road as far as the Frijol village; from this point, the journey is 12 hours by horse because there are no roads to the mine. The Japon en Mexico prospect lies in the porphyritic volcanic andesite in contact with limestone; however, no indication of metasomatism is present. The ore body is at the andesite- limestone contact, which shows an E-W strike and a dip of 85° N; the average thickness is 1.00 meter. At the surface, there is evidence of a possible continuation of the vein some 80 meters east of the main outcrop. In the vein, the main minerals are sphalerite, argentite, galena, and iron oxides. The gangue mineral is quartz and chalcedony. The mine workings consist of 3 levels at 8-meter intervals. Along the levels, there are 3 drifts in ore which reach 10, 20, and 30 meters in length (Figure 36). Based on the stoped areas, the past production is estimated at 600 tons with an average grade of 1 kilogram silver, 15% zinc, 2% lead, and 8 grams gold per ton. Actually, the mine is active, but the production is not consistent due to the difficulty of shipping the ore and the lack of mining equipment. It is pointed out that the prospects La Reina, within the Sierra de Bavispe zone; La Violeta, within Sierra del Chapote zone; and Piedras 87 meters chovc sea level 11201- 1110 ' -1110 11001 " / / Sample K d Porphyritic vofeanic Assays ---- andesite no Pb •/• Z n •/• Ag ppm Au ppm g g ] Skorn 1 1.51 14.25 584 3.8 2 1.35 15.04 1006 15.3 s = t Vein 3 1.34 23.36 1060 46.3 ^ Geologic contact 4 1.57 15.52 1 1 20 10.2 5 1.97 24.80 4 80 5.5 •’ Projected mine G 1 .51 14.23 976 8.4 Cl'ff workings A Portal B Shaft (inaccessible) Estimated ore reserves metric tons ai— ib Section S Sample Proven 1.500 Probable 5.000 0 5 10 20 Possible 10000 meters F ig u re 36 Composite Plan View and Cross-Section of the Japon en Mexico M ine. 88 Verdes, within Lomas de Los Tanques zone; show also good p ossibilities for finding ore. Consequently, these prospects and some more could give additional ore reserves for the district. Nevertheless, these prospects have not been studied in detail so far. Economic Aspects Grade of Ore On the basis of the preliminary and detailed sampling carried out in the nine prospects previously described and upon the last mineral quotation of the June report of the E.M.J. (1975). The average grade and value of the nine prospects are calculated as follows: S ilv e r 400 grams per ton Gold 0.65 grams per ton Lead 2.88% Zinc 3.38% Copper 0.67% Average value of ore in place equals $116.80 per metric ton (Appendix A shows the calculations in detail). It is emphasized that the calculated ore grade is from sulfides in the oxidized zone some 25 to 50 meters above the water table, because no sampling has been carried out below this level due to inaccessibility of mines or shallow mine workings. Nevertheless, important information about the ore grade below the water table is given by the previous workers who visited the mines when they were operating. Among them, Brinegar (1910, p. 554) states: 89 "The ore from the mines in the west contact . . . assay values range from 15 to 5,000 oz. silver and up to $70.00 in gold." Labounsky (1957, p. 16) em phasizes: "From th e rep o rt o f S u p erin ten d en t C. Mahaut, December, 1908, the Quintera Mine lower workings (13, 14, 15, and 16 levels) showed ore in place at an average of 36 ounces of silver per ton." Also, Sheldom (1910, p. 920) mentions, in respect to the 1,500 feet level of the Quintera Mine: "The vein at depth, for 20 to 30 feet in width, would assay 40 to 50 oz. in silver. Lead gave out and copper came in the amount of 8 to 9%." Concerning the Minas Nuevas mine, there are reports by Pearce (1911b, p. 682): "The vein has been cut by a tunnel at a depth of about 450 feet where a tetrahedrite ore carrying up to 3,000 oz. of silver per ton has been encountered"; and Sheldom (1910, p. 920): "The vein is 20 to 30 feet wide and contains an average of 24 oz. silver with some lead." It appears, according to the cited authors, that the ore sampled from the stopes and pillars was left in its place because at that time such values were uneconomical. Therefore, it seems likely that, if the lower mine workings were sampled, higher ore values could be obtained. Ore R eserves A preliminary estimate of ore reserves, at the nine described ore bodies in the Alamos Mining D istrict, is based upon the limited mine workings, underground mapping and geologic favorability. According to the ore deposits' characteristics, the ore is classified as proven, probable, and possible reserves. 90 Based upon studies of 70 epithermal districts and 40 years of experience within the Precious Metal Province of northwestern Mexico, where the Alamos Mining D istrict lies, Wisser (1966) determined that the average vertical range of ore was 300 meters at the time of ore deposi tion. Therefore, in order to estimate the probable and possible reserves in the mines' district, such reasoning is taken into account. Appendix A shows the estimated reserves of each mine. Proven Reserves. The estimation of proven reserves in this report includes the ore present in the exploration mine workings such as drifts, tunnels, adits, etc. They are calculated according to the dimensions and density where the ore bodies are exposed. They are estimated at 32,000 metric tons. Probable Reserves. This category of reserves is calculated taking into account the measurement of stoped areas in the majority of the mines and assuming the persistent trend of ore bodies in depth. These reserves are estimated only by considering 25 meters below the present mine workings, which appears a reasonable estimation according to Wisser's concept for this type of deposit. They are estimated at 181,000 metric tons. Possible Reserves. These reserves are inferred based upon the favorable structural features which indicate a probable continuity in length and depth of the ore bodies not only in the Sierra de Alamos mines but also in the Sierra Plomosas mines. The reserves are calculated by increasing the depth 25 meters from the level of probable reserves. A very conservative calculation of these reserves is 490,000 metric tons. 91 Moreover, in addition to the ore reserves calculated above, there is an area of "potential ore reserves" among the Promontorio, Quintera, Santo Domingo, and Minas Nuevas mines, which is estimated at a minimum of 1,000,000 metric tons (Figure 37). Exploration Program After analyzing the results of the reconnaissance and detailed surveys in the Alamos Mining D istrict, it is strongly recommended that this work be followed up with an intensive exploration program. The main purpose of the exploration program is two-fold. First, to evaluate and to confirm the possible ore extension in depth below the present workings underground in the mines already described. Second, to explore the area among the old mines in the Sierra de Alamos, with the goal of searching for new ore bodies, principally within the "Mother lode" s tr u c tu r e . The first phase of the program calls for core drilling from the surface and underground as well as underground exploratory workings. It is estimated that, in the old mines, the lower levels will have to be dewatered and the timbering would need some repair. It is calculated that this phase of the program could be carried out by contractors in a period of twelve months at a cost of approximately $350,000.00. An esti mation of the direct cost and time for each mine is explained in Appendix A. i The second phase of the exploration program, which may be carried out simultaneously with the drilling program, would be geochemical and geophysical surveys. Both studies focused to detect new ore bodies meters above meters above sea level sea level 800 -800 600 - • 600 400 .. 400 200 -•200 ABC Explore tion areas for ore Estimated potential ore reserves 1,000,000 metric tons 0 1 2 kilometers her. scale F igu re 37 Schematic Cross-Section of the Mines Within the "Mother Lode" Vein Showing Areas for Ore Exploration. UD ts> 93 within the "Mother lode" structure. The geochemical program would include soil and chip samples perpendicular to the trend of the main structures. The geophysical program would include a Turam survey also perpendicular to the main trend of veins. It must be mentioned that a reconnaissance electromagnetic survey in this area was conducted by Velasco (1962). From this study, he was able to detect some indications of vein in depth. Therefore, it seems likely that such study would give good results. It is estimated that both surveys could be carried out in 4 months by per sonnel of the C.R.N.N.R. at an indirect cost of some $30,000.00. If the possible presence of a new ore body is detected by these methods, some additional drilling would be necessary. Economic Considerations It can be emphasized that the following economic considerations are based on the assumption that at least 70% (500,000 metric tons) of the estimated ore reserves w ill be found. There are, of course, possibilities for profitable operation at other levels of production and with other estimated ore reserves. The preliminary evaluation of the nine mines described in the Alamos D istrict include mining and processing costs, net smelter return, capital requirements, rate of mining and mine life, profitability analysis, and sensitivity analysis. Mining and Processing Costs. 1. Mining: Taking into account the shape, size and attitude of the ore bodies within the different mines in the district, a suitable mining system for extracting the mineral from the deposit appears 94 to be shrinkage sloping combined with cut and fill sloping or sub-level sloping. By utilizing these mining methods, a recovery of 90% from the veins is estimated. The mining costs are calculated by comparing the attitude of the ore bodies in the district with twenty similar mining operations (C. M. M., 1972; Cummings and Given, 1973). The cost of mining is estimated at $15.00 per metric ton, which includes exploration, development, slope preparation, ventilation, hauling, hoisting, and other underground activities. 2. Processing: According to economic considerations, included in this paper, it is determined that the ore from the mines should be treated at the vicinity of the mines and that the concentrates could be sent to the smelters at Chihuahua and Torreon for sm e ltin g . A mill site convenient for tailing disposal could be selected at the vicinity of the Aduana town. In this location, there are old buildings which could be repaired for the operating personnel and u tilities. A m ill operating at a rate of 200 metric tons per day would consist of receiving bin, coarse crushers, ball m ills, flotation cells, and all the equipment for processing. Taking into account that the ore from the veins is coarse grained, it is estimated that an average ratio of concentration would be 1:20 for lead-silver and zinc concentrates for the mineral from all the mines. 95 The operating costs, including labor, supplies, electricity, natural gas, water, and maintenance, are calculated at $10.00 per metric ton of ore. Therefore, the total cost of operation, with a 20% as a security factor, is estimated at a maximum of $30.00 per metric ton of crude ore mined. Appendix A explains the cost in d e t a i l . Net Smelter Return. According to m illing tests and payment sheets for the ore from the Quintera, San Manuel, Otates, and Plomosas mines at the La Reforma plant, the average milling recovery is as fo llo w s : S ilv e r 85% Gold 85% Lead 83% Zinc 80% Therefore, taking into account that the mineralogical features of the Promontorio, Santo Domingo, Ana Maria, and Japon en Mexico mines are analogous to the mines in which milling tests have been done, a similar m illing recovery is assumed for these mines. The average grade of ore from all the mines, including 10% of dilution is calculated as: S ilv e r 366 grams per ton Gold 0 .6 grams p er ton Lead 2.6% Zinc 3.0% Average ratio of concentration is 1:20. 96 According to the last E.M.J. mineral quotation, for June 1975, and based upon the. schedule of La Reforma (1975) plant, which is very similar to the schedules of the Chihuahua and Torreon plants, the net smelter return is calculated as: R atio Concentration Net Net smelter return on Pb-Au-Au concentration $ 1 ,0 0 0 .0 0 1:20 $50.00 Net smelter return on Zn concentration $ 170.00 1:20 $ 8.50 Total return per metric ton mined $58.50 Appendix A explains the calculation in detail. Ratio of Mining and Mine Life. As already mentioned, if during the proposed exploration program 70% of the estimated probable and possible ore reserves could be proven, that is, 500,000 metric tons, the rate of mining is calculated at 200 metric tons/day. Thus, the produc tion per year on a 300 labor days basis could be 60,000 tons. Conse quently, the life of mining operations is estimated as at least 8 years of production. The preproduction period, taking into account the mines' condi tion, is estimated as at least 2 years after commencing the exploration work. Capital Requirements. The estimation of the total capital invest ment, for developing the mines already described, in the Alamos Mining D istrict, is determined based upon similar operating plants (Cummings and Given, 1973; C.M.M., 1972). The total capital investment for this mining venture is estimated at: 97 Capital cost of processing plant $ 850,000.00 Underground equipment and development $ 450,000.00 Mine preproduction cost (exploration) $ 350,000.00 Working capital $ 100, 000.00 S u b -to ta l $1,750,000.00 Overhead (15%) • $ 2 5 0 ,0 0 0 .0 0 Total capital investment (U.S. Dollars) $2,000,000.00 Or $10,000.00 per ton day capacity Profitability Analysis. The estimate of profitability is cal culated according to the mining law of Mexico (Legislacion Minera, 1956) and according to federal laws of taxes of Mexico (Ley Federal de Impuesto, 1966). However, such calculations are only a preliminary figure due to some changes as a result of the nationalization of the mining industry as well as due to the possible agreements with the owners of the mine properties, which are not in the scope of this study. Nevertheless, it is hoped that the economic analyses might give an idea concerning the profitability of a possible investment in the Alamos Mining D istrict. The various economic evaluation techniques included in this paper are net present value, discounted cash flow, payback period, accounting rate of return and present value ratio. They are calculated according to Rudawsky (1970) and are based upon the estimated capital investment, ore reserves, production rate, mine life, gross revenue, and production costs. A summary of the results obtained from the calculations is (Appendix A explains the calculations in d etail): 98 Net present value @ 25% discount ratio $552,400.00 Discounted cash flow return on investment 36.67% Payback period 3 .2 yea rs Present value ratio @ 25% 0 .4 4 5 Accounting rate of return 30.40% Therefore, based upon the results obtained, it is obvious that mining in the district would be a profitable project for investment if the estimated reserves are proven during the exploration program. Sensitivity Analysis. The following analysis is based upon the assumption of a group of favorable conditions acting together in the district. There are many other combinations and conditions that would be favorable but they are not included in this particular analysis. For an idea about the investment's sensitivity because of possible changes in metal price and/or production costs, an unfavorable change of 20% is assumed in the eight years of mine life. From this, the results obtained are (Appendix A includes the calculations in detail): Net present value @ 25% discount ratio $73,722.00 Discounted cash flow return on investment 26.20% Change in the profitability 26.80% Consequently, it is believed that these changes would not have a strong effect on the investment. In addition, the payback period, esti mated on 3.2 years, could also be applicable for measuring the risk. CHAPTER 4 STATISTICAL ASPECTS Introduction . when you can measure what you are speaking about and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of science, whatever the matter may be." Lord Kelvin (Taken from Davis, 1973, p. 1) This chapter considers some geostatistical aspects to provide quantitative estimates of the exploration potential of the Alamos Mining District from the application of statistical techniques to the analysis of systematically mapped geological information. Quantification of geological features and the subsequent use of mathematics, especially statistics, to treat numerical data for classifi cation, correlation, and extrapolation are now widely applied in various branches of geology. Even though the basic foundations for the framework of the application were laid earlier, large-scale processing of data became possible with the advent of the computer. Computer techniques in the various fields of geology have been given by Weiss (1969), Koch and Link (1971), and a recent book by Davis (1973). Among the scientists who have developed the statistical methods are Allais (1957), Harris (1965, 1968, 1973), De Geoffroy and Widnall 99 100 (1970), Krumbein and Graybill (1965) , Sinclair and Woodsworth (1970), Koch and Link (1971) , Agterberg and others (1972) , and Davis (1973) . Allais (1957) was one of the pioneers in developing the statis tical methods to exploration. Nevertheless, he gave no consideration to the geologic features in the area explored. Therefore, his results were based only on mathematical premises. The first significant advances of mathematical reasoning to exploration, taking into account the regional geology of the areas under study, was made by Harris (1965, 1968). Consequently, he was able to predict the metal endowment of various areas according to its size and g eo lo g y . Agterberg and others (1972) and the U. S. Geological Survey (1972), based essentially upon Harris’ model, carried out similar studies to yield tentative estimates of undiscovered resources. Model and Methodology Employed In this paper, the Harris model, with some modifications, is taken as a basis for estimating the exploration mineral potential of the Alamos Mining D istrict. Fundamentally, the methodology and basis of the Harris model are as follows: 1. The region of study is subdivided into an arbitrary number of cells equally spaced (grid), based upon the mapped available geologic information, to quantify a number of geological variables within each cell. 101 2. An area is taken as a ”control area" for estimating the mineral potential of the whole area under study. 3. The "level" of geologic information, such as regional, semi- detailed or detailed, is of vital importance because from these geologic data the level of reliability of the estimated mineral resources in the area are derived. 4. The mathematical technique employed in order to estimate the geologic variables within the area is multivariate geostatistical analysis. ' A brief explanation of the procedure employed with the geological data within the Alamos D istrict is as follows: 1. Based upon the geologic map of the district (Figure 6), the area was subdivided into 140 cells of 2.5 x 2.5 kilometers (Figure 38). 2. No cell was taken as "control area" due to the low level of geologic information (reconnaissance level). 3. The measured geologic features were treated as dummy variables or presence/absence within each cell. The dependent variable chosen was the number of mines per cell, and the independent variables were the geologic features listed in Table 2. 4. The mathematical technique used in order to evaluate the expected number of mines per cell was multiple stepwise regression analysis. The computer program employed was the Statistical Package for the Social Sciences (1975), with a CDC 6400 computer at the Computer Center of The University of Arizona. 109° 10" 109*00" ______i . 1 2 3 4 ■ && 6 7 8 9 10 Mocuzoh 11 12 13 ' 14 15 16 17 18 19 20 .21 22 23 24 25 26 27 4&28 29 30 Piedras Verdes 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 s o 51 52 53 54 55 56 • 57 58 59 60 Minas Nuevas 61 62 63 64 65 • 66 67 * 68 69 70 71 72 73 74 75 76 77 78 79 VS30 Dolisa Alamos 81 82 83 84 05 86 87 88 89 SO - 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 - 110 Oastras 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 . 132 133 134 135 136 . 137 138 139 140 0______5 10 kilometers Figure 38. Grid of Cells for the Alamos D istrict 103 Table 2. Geological Variables Coded for the Alamos Mining D istrict. Measured Variables Dependent variable: number of mines per cell Independent variables: rock type 1. g r a n ite 2. porphyritic andesite (Laramide) 3. volcanic rocks (Tertiary) 4. metamorphic rocks fr a c tu r in g 5. NE fractures 6. NW fractures 7. EW fractures rock age 8. age of rock coordinates 9. X coordinate 10. Y coordinate 11. product XY 2 12. X coordinate squared 2 13. Y coordinate squared 104 5. Based upon the dependent variable within the district, the number of mines per cell, trend surface analysis were computed. The program utilized was Fortran IV of the Kansas Geological Survey > (O’Leary and others, 1965) . Multiple Regression Analysis Conceptual Framework No attempt is made in this chapter to give a detailed, mathemati cal exposition of the theoretical principles involved with this type of analysis. Therefore, in this paper, only the basic concepts are given in a general manner. The definition of multiple regression analysis is given by the Statistical Package for the Social Sciences (SPSS) (1975, p. 321) as follows: "Multiple regression is a general statistical technique through which one can analyse the relationship between a dependent or criterion variable and a set of independent or predictor variables." The general formula of a multiple regression is a linear function of the form: V = b0 . blXl * b2X2 ♦ • • • bnXn where the X’s are the independent variables that are related to Y by the functional form and the coefficients, the b's, of the X’s. In order to clarify this concept, we w ill define a simple regres sion case of two variables, which shows the basic principle of regression analysis, and this undoubtedly can be extended to cases involving three or more variables. 105 In simple regression analysis, values of the dependent variable are predicted from a linear function of the form: y = b 0 + bjX j where the Y' is the predicted value of the dependent variable, Y; b^ is a constant by which all values of the independent variable, X^, are multiplied; and b^ is a constant which is added to each case. The fitted line will cross the Y-axis at point b^ (the intercept) and will have a slo p e b^ (F igu re 3 9 ). The difference between the actual and the estimated variable, Y, for each case is called the residual, i.e ., the error in prediction. It is expressed by the form: Residual = Y - Y * The regression strategy involves the selection of b^ and b^ in such a way that the sum of the squared residuals is smaller than any possible alternative positioning of the line. Therefore, since the sum of the squared residuals is minimized, the regression line is called the "least-squares line" or the line of "best fit." This characteristic is represented by the expression: E(Y-Y')^=SS = minimum res There are three terms which express the variation of the depen dent variable. The first of these is explained or measured by the regres sion line, denoted by the sum of squares due to regression: SS Z Y '2 (ZjV = Z (Y* - Y)2 reg n Y -a x is regression line observations X -axis Figure 39. Schematic Representation of the Variables in a Simple Regression Analysis. 107 The second measure of variation refers to those unexplained by the regression line, denoted by the sum of squares due to residuals (deviations): SSres = 2 CY - Y')2 The third measure of variation is the relationship between the explained and unexplained variations by the regression line, and is measured by the total sum of squares: SST = Z Y2' - — =. Z (Y - Y)2 Therefore, this relationship is expressed by the form: SST * SSr=g + SSr=s or Z (Y - Y )2 = Z (Y* - Y )2 + Z (Y - Y ') 2 The "goodness of fit" of the line to the points can be defined by the ratio of explained variation in the dependent variable, Y, to the total variation in Y: >2 - SSreg Often, the R term is expressed as a percentage. Another useful relation is that the square root of goodness of fit is the "multiple correlation coefficient," R: r = /"i?" = f . In order to test "how good" is the regression, the variance and degrees of freedom are combined for obtaining the mean squares, MS, 108 parameter. The variance between the samples, in particular SS^g, s^reg> and SS^, can be used for this purpose. In this way, the following measures are determined: SS reg v a ria n ce among MS 6 reg m - 1 SS T 6 S variance within MS = »------res N - m where m = number of variables, N = number of samples, and the degrees of freedom = the number of squares minus the number of independent linear restrictions imposed upon the quantities involved. The significance of the variables within the equation can be tested by the F ratio: res Based upon this ratio, the calculated F value can be tested with the theoretical values from statistical tables at the level of signifi cance desired and at the number of degrees of freedom involved. Finally, these values are compared in order to accept or to reject the Null hypothesis of: H : B = 0 : B M 0 1 Consequently, from this concept it is possible to estimate whether or not the regression equation is significant for the proposed model. 109 Results of Analysis According to the criteria of the regression analysis previously described, the basic linear equation of the Alamos Mining D istrict was established as follows: mines = rock type + fracturing + age + coordinates All the variables are listed in Table 2. It must be pointed out that, in this study, a mine includes all kinds, from small prospects to mines of several levels. Therefore, no distinction is made on deposit size. In order to look for the best estimation of number of mines, Y', some arrangements of the independent variables within the regression equation were combined. First, only geologic variables were computed. Second, geologic and geographic (coordinates) variables, including quadratic coordinates, within the equation were included. Finally, in order to analyze the significance of each variable within the equation, stepwise regression was employed. A summary of the computed calculations for the multiple regres sion equation is given. Appendix B includes the calculations in detail. Significance of Variables. Table 3 shows the significance of each variable within the regression equation. From these data, it is indicated that first the intrusive ande site, and secondly, the metasediments, and then NW, HE, and EW fractures are the most important variables in the regression equation. Therefore, it seems likely that these geologic features are intimately related to the emplacement of the ore bodies in the district. 110 Table 3. Significance of Variables in the Multiple Regression Equation for the Alamos Mining D istrict. Code in the Significance Computer V ariab le Program Each Variable All Equation A nd esite* ANT 50.558 50.5 5 8 Metasediments MET 16.655 36.474 MW fr a c tu r e s NWEST 8.042 28.247 NE fractures NEAST 4 .9 5 8 23.041 G ranite GR 2 .9 6 3 19.263 EW fractures EWEST 2.123 16.567 Quadratic X coordinate X2 1.126 14.409 Quadratic Y coordinate Y2 .461 12.614 Y coordinate Y .465 11.218 Volcanic rocks** VOLC .284 10.069 Product X-Y coordinate XY .109 9 .1 0 0 X coordinate X .176 8 .303 Age AGE not in the equation *Includes Laramide porphyritic andesite and Cretaceous volcanic a n d e s ite s . **Includes only volcanic Tertiary rocks. I l l Statistical Results♦ These parameters were estimated on Multiple regression .66305 Coefficient .43964 Standard deviation .62944 Degrees of freedom: regression 12 r e s id u a l 127 Significance of multiple regression, F 8.30333 Theoretical F value at 1% of significance 2.33545 By comparing these values, it is obvious that the calculated F value does not lie within the region of acceptance for the Null hypothesis is rejected. Thus, the alternative hypothesis, H^, is a c c e p te d : H1 : b V h 2 ’ •• •> bn ^ 0 Therefore, this premise indicates that the regression equation is significative, even though it explains only 44% of the variance in number of mines. P re d icted Number o f Mines (Y1) . T able 4 shows th e s p a t ia l d i s t r i bution by cell of both the expected number of mines and the known mines in the district. From these data it is emphasized that: Known mines 43 Expected mines 26 T otal mines 69 Estimation indicates that the Alamos Mining D istrict still has a 60.5% exploration potential in addition to the known ore bodies. 112 Table 4. Spatial Distribution by Cell of Known and Predicted Mines for the Alamos Mining D istrict. Known P re d icted Known P re d icted Mines Mines T o ta l Mines Mines T o ta l C e ll 0 0 (Y'D (Y+Y*) C e ll 0 0 (Y») (Y+Y') 4 1 1 55 2 2 5 1 1 56 1 1 6 1 1 59 1 1 7 1 1 66 2 2 8 1 1 67 1 1 2 9 1 1 68 4 4 10 1 1 69 1 1 11 1 1 76 2 2 17 1 1 77 5 5 18 1 1 78 3 3 19 1 1 79 1 1 20 1 1 80 1 1 21 1 1 81 1 1 27 3 3 86 2 2 28 3 3 87 2 2 29 2 2 88 1 1 2 33 1 1 90 1 1 34 1 1 96 1 1 35 1 1 97 2 2 46 1 1 106 1 1 2 48 1 1 127 1 1 49 1 1 129 1 1 50 1 1 152 1 1 T o ta ls 43 26 69 • Exploration potential in the district is 60.5% in addition to the known o re b o d ie s . 113 Based upon these results, the most important areas for explora tion are Sierra de Alamos, cells 67 and 69, and especially cells 87, 97, and 106; and the area of Piedras Verdes, cells 17, 18, and 19 (Figure 40). It is believed, according to the geologic features previously mentioned in Chapter 3, that these areas are considered also of vital importance by subjective geologic reasoning. Therefore, it is evident that both the quantitative and the geologic methods agree that these areas are the best' targets for future exploration within the Alamos D is t r ic t . Trend Surface Analysis Conceptual Framework Davis (1973, p. 457) defines a trend surface as follows: "A trend may be defined as a linear function of the geographic coordinates of a set of observations so constructed that the squared deviations from the trend are minimized." Also, the same author considers that this concept involves three fundamental parts: 1. A trend surface is based upon the "geographic coordinates" which implies that an observation is a function of its geographic lo c a tio n . 2. A trend surface is a "linear function" of the expression Y = b 1X1 + b 2X2 + . . 109° 10' v 109°00‘ 1...... 1 I ---- * L ' _ . : - r ; I 1 2 3 4 6 7 C 9 10 Mocuzon 11 12 13 14 15 16 20 21 H H 22 23 24 25 26 27 m-A. 28 29 30 Piedros Verdes -27° 10" 31 32 33 34 35 36 3 7 38 39 40 41 42 4 3 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Minos Nucvas 61 62 63 64 65 66 v 60 70 d 71 72 ■ 73 74 75 76 77 76 79 fit- # 3 Ooli so Aiuinoi, 81 62 83 84 85 66 66 89 j 5: -27°00' i 91 92 93 94 95 96 93 99 ICO 101 1 102 103 104 105 107 103 109 110 p i 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 126 12 9 130 131 132 133 134 13b 136 137 138 • 139 140 o _____ 5 10 kilometers F ig u re 40 115 where the b's are coefficients and the X's are some combinations of the geographic coordinates. From this equation the trend components, Y', on an observation are estimated. 3. Linear functions "minimize the squared deviations from the trend." Therefore, the trend line contains the smallest variance about it. Consequently, from these concepts, it can be seen that funda mentally the theoretical aspects of the trend surface techniques are based upon the same theoretical premises of the regression analysis already described. Basically, the purpose of a trend surface analysis is to separate map data into two components, that of "regional nature" and "local fluctuations." The regional component usually is related to the linear function of the form: ♦ V l * b2X2 where Y is a geologic observation, b^ is a constant value related to the mean of the observations, b^ is the coefficient of the east-west coordinate and b^ is the coefficient of the north-south coordinate. In order to search for specific local fluctuations, the basic model of the linear function (first degree equation) is usually expanded to polynomial functions to the second, third, or higher orders. There fore, each geographic variable is simply raised to a higher power, creating new variables. This linear equation is of the expression: Y = b 0 + V l + b2x2 + V l 2 * »4X22 + • • • * V" 116 It is emphasized that the polynomial functions are used for geologic trend analysis merely as a matter of convenience and as a subjective method for a best fit of the distribution. Results of Analysis As previously mentioned, in order to compute the trend surface for the Alamos D istrict, the number of mines per cell was determined (dependent variable). With the goal of estimating the regional and local variations of the trend surface in the area due to mines location, equations of first, second, and third degree were computed. The basic linear function was established of the form: mines = NS coordinates + EW coordinates o r Z = X + Y By utilizing the computer program for trend surface analysis of the Kansas Geological Survey (O'Leary and others, 1965), the following estimations for the Alamos Mining D istrict were obtained. Appendix C shows the calculation in detail. Coefficients of Correlation 1 s t Degree 2nd Degree 3rd Degree r2% .1486 .2261 .3142 R .3855 .4755 .5605 S t . Dev .79 .76 .71 117 By examining these values, it is clear that the level of explained variance (R %) is only 15% in the first degree equation and that this value increases to 31.4% in the third degree equation. There fore, it appears that a high degree equation suggests a better model for the mines distribution within the district. In analyzing the plots of the first, second, and third degree equations, it seems likely that both regional and local structural features are associated with the trend surface analysis. The plot of the first degree equation (Figure 41) appears to be associated with the northwesterly regional trend of fracturing. In addition, it shows an increment toward the northeast which is the local system of fracturing in the area. The plot of the second degree equation (Figure 42) indicates a close association with the local distribution of mines within the Sierra de Alamos and Piedras Verdes areas which, according to the multiple regression analysis and subjective geological reasoning, are the best areas for further exploration. The plot of the third degree equation (Figure 43) shows a better association with the local distribution of mines and structures. It is more restrictive and indicates that the best areas for prospecting are in the central part of Sierra de Alamos and the Piedras Verdes area. It is interesting to note that both the trend surface and the regression analysis coincide in the estimated areas for exploration and specifically cells 17, 18, 19, 67, 69, 87, 97, and 106 (Figure 44). 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A 11.*1 . *a ie»i HIT 64 3 4 *4 4 3 3 2 2 0 AA ll.1 T . A #•• 66 35 4* I 2 1 . #C 11.11 •• AA l i l t 33443210. Al • «•» A 44 333 33 4* 3 2 1 C .A CO C(((C M2I CO 11 72 31 4*4 353 ♦•♦♦*•♦«♦*+#♦ 33 *4 I 2 1 0 . 1C 17.14 .. AA || CCCCCCC III# 30 ll 27 33 * **33 33! ***(♦ 333 44 1 210. A COE 11.21 • AA III 00 11 22 31 44 1333 353) * J 710.A0C I 2.* i . a iai cceccccc:c:c •«• . co 11 22 A3 44 53333333333333 44 I 110. I 0«.f 12.37 • A IB CCCCCCCICCCCCC 111 • 00 111 22 >31 4 4 3)33333 44 13 2 1 3 . A CJ 12.71 • A 18 CCCtCCCCCCCCCCC »•! •* A *. 00 11 12 113 4444* * 4 39 ZIJ.AIC U S 17.15 . A M CCCCC ICCCCC 111 AA •• CO 11 22 331 4 444444444444 ?1 J? 150.A3 tC 13.00 . AA #1 C'CCC CCCCC III AA . .. 60 11 72 2333 44444.*4 331 2 l C . Al CC A CM 13.1* • #123*11704 171*56719 121*36714 12MS6M4 171*36?#* #2343073# 123*34749 123*34744 1II*S»74# 12**3471# 121*3471# kilometers Figure 43. Plot of Third Degree Equation, Trend Surface Analysis 121 &5 Mocuzan - 2 7 ° 10' 66 • 61 106 Rastros kilom eters Figure 44. Location of Highest Priority Prospecting Areas According to Trend Surface Analysis. 122 intimately associated with the geomorphological province in which the Alamos District lies, that is the Basin and Range Subprovince. This feature is indicated by the low values in the valleys and high values in the ridges. Appendix B shows in detail some of the computed operations. It is believed, that the results obtained from these statistical techniques are only the early stage in a comprehensive estimation of the exploration mineral potential within the Alamos D istrict. CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS According to the preliminary results of the geological explora tion carried out in the Alamos Mining D istrict, Sonora, Mexico, it is believed that the following conclusions can be made: 1. The Alamos District has been practically inactive since 1915. Nevertheless, the reason was not for lack of mineralization but a result of political problems in the country. 2. The district's past production is estimated at 150 million dollars. This amount, by itself, gives the district importance. 3. The Alamos D istrict lies in the Epithermal Precious-Metal Province of northwest Mexico, a mineralogical-structural unit 1,000 kilometers long, one of the richest silver provinces in the w orld . 4. Structural and lithological conditions appear to have been the chief factors that controlled the deposition of hydrothermal solutions'within the pre-mineral fractures which controlled the ore emplacement. 5. Until date, 108 prospects, ranging from small trenches to mines with sixteen levels, have been visited. Among these mining workings, nine prospects are considered the most promising ones. They are ranked in order of their location, accessibility, and 123 124 mine conditions: San Manuel, Plomosas, Otates, Ana Maria, Promontorio, Quintera, Santo Domingo, Japon en Mexico, and Minas N uevas. 6. The ore, with some variations in ratio, is mineralogically simi lar among the ore bodies in the district. The primary minerals include galena, tetrahedrite, chalcopyrite, sphalerite, argentite, pyrite, and native silver within quartz as a gangue mineral. 7. To date, the San Manuel, Ana Maria, Promontorio, Quintera, and Japon en Mexico mines are active, but the mining operations are restricted to dumps and some pillars due to the lack of mining equipment. Therefore, the production is small, ranging from 60 to 120 tons per month. 8. The San Manuel, Plomosas, Ana Maria, Otates, and Japon en Mexico are new mining prospects in which only limited underground exploration has been accomplished. Therefore, these prospects are of easy underground access. On the other hand, the Promontorio, Quintera, Santo Domingo, and Minas Nuevas prospects are old mines which reach from 115 to 450 meters in depth. The access to these mines is limited only to the shallow mine workings due to mine conditions. 9. Detailed sampling from the nine prospects shows a combined average grade of silver 400 grams per ton, gold 0.65 grams per ton, lead 2.88%, zinc 3.38%, and copper 0.67%. 10. According to the lim ited underground workings, underground mapping, and geologic favorability, in the nine prospects, a conservative estimate of the ore reserves is: 125 proven reserves 32,000 metric tons probable reserves 181,000 metric tons possible reserves 490,000 metric tons In addition to these ore reserves, there is an area of "potential ore reser v es" among th e o ld mines ("Mother lode" s t r u c t u r e ) , which is estimated at 1,000,000 metric tons. 11. Economic considerations according to the current metal quotations, net smelter return, exploitation, and production costs show: gross value of ore in place $116.80 per metric ton total cost of operation $ 30.00 per metric ton net smelter return $ 58.50 per metric ton 12. Profitability analyses according to various methods of economic evaluation techniques indicate advantageous economic results. They are calculated as: net present value @ 25% discount rate $552,400.00 discounted cash flow return on investment 36.67% payback period 3.2 years present value ratio @ 25% 0.444 accounting rate of return 30.40% 13. Both economic and profitability analyses are based upon the outlined exploration and development program, which estimates that at least 500,000 metric tons could be proven during such a proposed program. The life of mine operations is estimated as at least 8 years of production at a rate of 200 metric tons/day. 126 The total capital investment of this mining venture is estimated at 2 million dollars. 14. Geostatistical analysis, multiple regression analysis and trend surface techniques, indicate that the district has still 60% exploration potential in addition to the known ore bodies. The best estimated areas for exploration are the central part of Sierra de Alamos, just south of the very important old mines of the district; and the Piedras Verdes area, 15 kilometers north of Sierra de Alamos. The outlying districts are not included because no explora- work has been done so far. Based upon the above conclusions, it is strongly recommended that this program be followed with the exploration-development program. The purpose of this program is two-fold. First, to evaluate and to confirm the possible ore extension in depth within the nine prospects already described. Second, to search for new ore bodies, especially in the structure of the Promontorio, Quintera, and Santo Domingo mines, and in the areas estimated to be geostatistically favorable. The next phases recommended are: 1. Drilling from surface and underground as well as underground exploration workings in the nine mines mentioned. The cost of this program phase is estimated to cost $350,000.00 during a period of at least 18 months. 2. A geochemical survey, including chip rocks and soil samples perpendicular to the bearing of the "Mother lode" structure as 127 well as in the areas outlined by the regression and trend surface analysis, cells 67, 69, 87, 97, and 106. The time of this phase is estimated to be 3 months at a cost of $10,000.00. 3. Geophysical investigations (TURAM) perpendicular to the structure among th e Prom ontorio, Q u in tera, and Santo Domingo mines ("Mother lode" structure). The time of this program's phase is calculated at 3 months at a cost of $20,000.00. 4. At the present time, it is not recommended that exploration surveys be conducted in the Piedras Verdes area, because a private company (TRION) is evaluating and exploring the area in d e t a i l . APPENDIX A ECONOMIC CONSIDERATIONS FOR THE PROSPECTS IN THE ALAMOS MINING DISTRICT EXPLORATION PROGRAM, 1973-75 128 Table A.1 Average Grade and Ore Value before Concentration at the Alamos D istrict. No. o f S ilv e r Gold Lead Zinc Copper Gross Value of Raw P rosp ect Samples (gm /ton) (gm /ton) (%) (%) (%) Ore Per Metric Ore* Promontorio 25 325 0 .4 4 .0 8 .0 0 .3 142.80 Q uintera 14 600 0.3 1.5 1.6 2.0 137.60 Santo Domingo 8 500 0 .2 2 .7 0 .9 0 .2 9 8 .5 0 Minas Nuevas 4 250 0 .4 3 .0 1 .0 0 .2 6 5 .3 0 O tates 15 125 0 .6 4 .5 4 .6 0 .8 9 4 .9 5 Plomosas 15 100 0 .5 5 .5 4 .5 1 .0 122.00 Ana Maria 30 200 0 .5 2 .8 3 .0 0 .5 7 8.85 Japon en Mexico 8 900 9 .0 2 .0 18.0 0 .1 345.50 San Manuel 10 250 1 .0 1 .8 2 .9 0 .7 8 5 .6 0 ♦Percentage recovery and grade of concentrate not considered. Prices according to E. M. J., June 1975: Silver @ $4.53/troy oz. Zinc @ $0.389/pound Gold @ $167.25/troy oz. Copper @ $0.63/pound Lead @ $0.233/pound 129 130 Table A.2 Ore Reserves Estimate for the Prospects in the Alamos Mining D istrict. P rosp ect Proven Probable Possible Total Promontorio 5,000 16,000 100,000 121,000 Q uintera 6 ,0 0 0 20,000 50,000 76,000 Quintera dump 10,000 25,000 35,000 Santo Domingo ? 18,000 200,000 218,000 Minas Nuevas ? 18,000 50,0 0 0 6 8 ,000 San Manuel 4 ,0 0 0 17,500 30,000 51,500 O tates 1,200 6,000 10,000 17,200 Plomosas 1,200 9,500 20,000 3 0 ,700 Ana Maria 3 ,0 0 0 16,000 30,000 49,000 Japon en Mexico 1,500 5,000 10,000 16,500 S u b-T otal 31,9 0 0 183,000 490,000 682,900 Total ore reserves e stim a te = + 700,000 metric tons Table A.3 Estimated Grade and Tonnage for the Prospects in the Alamos Mining D istrict. Average Grade Grade x Tonnage = Metal Estimated Tonnage Name of Ag Pb Zn Cu Au 70% of Total Ag Prospect (gm/ton) (*) (%) (*) (gm/ton) Ore Reserves (106gm/ton) (I0 6%) (106%) (103%) (JO^gra/ton) Promontorio 325 4.1 8.0 0.3 0.4 85,000 27.6 34.9 68.0 25.5 34.0 Quintera 600 1.6 1.6 2.0 0.2 75,000 45.0 12.0 12.0 150.0 37.5 Santo Dominto 500 2.6 1.5 0.24 0.35 150,000 75.0 39.0 16.5 36.0 52.5 Minas Nuevas 250 3.0 1.0 0.2 0.4 48,000 12.0 14.4 4.8 9.6 19.2 San Manuel 250 1.8 2.9 1.0 1.0 36,000 . 9.0 6.5 10.5 56.0 36.0 Otates 125 4.5 4.6 0.8 0.6 12,500 1.56 5.7 5.8 10.0 7.5 Plomosas 100 ' 5.5 4.5 1.0 0.5 21,500 2.15 11.8 11.0 21.5 10.7 Ana Maria 200 2.8 2.9 0.5 0.6 35,000 7.0 . 9.8 10.5 17.5 10.5 Japon en Mexico 900 2.0 18.0 0.1 9.0 11,000 9.9 2.2 19.8 11.0 99.0 474,000 189.21 136.3 159.1 517.1 506.90 10% dilution 47,000 Estimated tonnage 521.000 Average metal tonnage quantity of metal Recovery 90% 470.000 quantity of ore EXiWi .Average grade 10% dilution: Average grade before dilution: Silver * 366 grams/ton Silver = 400 grams/ton Lead = 2.62% Lead — 2 • 87*6 Zinc = 3.06% Zinc = 5.38% Copper .= 0.61% Copper = 0.67% Gold = 0.60 grams/ton Gold = 0.65 grams/ton Preliminary average prince = $136.80 per metric ton. 131 Table A. 4 Cost and Time Estimates of the Exploration Program for the Prospects in the Alamos Mining District (in Order of Priorities). D r illin g Meters from C ost Per Underground C ost Per Underground M eter Workings M eter Time T o ta l P rosp ect Workings ($) (m eters) ($) (months) ($) San Manuel 150 70 200 100 6 3 0 ,5 0 0 .0 0 Ana Maria 150 80 200 110 6 34,000.00 Otates 100 70 150 100 4 2 2 ,0 0 0 .0 0 Plomosas 100 60 150 100 4 21,000.00 Japon en Mexico 100 70 150 110 5 2 3 ,5 0 0 .0 0 Promontorio 150 75 200 120 6 3 5 ,2 5 0 .0 0 Q uintera 150 75 200 120 8 3 5 ,2 5 0 .0 0 Santo Domingo 250 75 350 120 12 6 0 ,7 5 0 .0 0 Minas Nuevas 100 75 150 120 8 2 5 ,5 0 0 .0 0 2 8 8 ,7 5 0 .0 0 Overhead (10%) 2 8 ,8 5 0 .0 0 Cost of the geophysical and geochemical studies 30,400.00 Total Cost of Exploration $348,000.00 132 133 Table A.5 Determination of the Operating Cost of Mining and M illing. Mining Costs: In dollars per metric ton (Source: AIME, 1973, for 1969; C.M.M., 1972) Direct Costs, Direct Costs, Shrinkage Stoping Cut and F ill Stoping 100-1,250 T.P.D. 250-1,000 T.P.D. Development 0.52 0 .8 9 S top in g 2 .9 0 3 .5 2 Haulage 0.48 0 .7 7 H o istin g 0 .5 2 0 .4 9 Pumping 0 .0 7 0 .0 6 Ventilation 0 .0 8 0.0 5 O ther 0 .9 0 2 .5 6 General 2.10 3 .5 8 T o ta l 6 .1 0 8 .0 6 C ost fo r 1975 and average = $15. 00 Milling and Concentrating Costs: Processing costs for 400 T.P.D. in dollars per metric ton (Source: AIME, 1973) Labor 2 .3 4 S u p p lies C hem icals 2 .5 4 Maintenance 0 .8 6 Other operations 0.62 Utilities 0.22 T ravel 0 .0 3 O ther 0 .3 3 T o ta l 6 .9 4 Cost for 1975 and average = $10.00 Total Cost of Operation: Cost for 1975 mining $15.00 Cost for 1975 milling and concentration $10.00 Sub-Total $25.00 Overhead (20%) $ 5.00 Total cost of operation $30.00 134 Table A.6 Calculation of the Net Smelter Return on Concentrates: Silver, Lead, and Gold. — Ratio of concentration 1:20 Lead S ilv e r Gold Grade of ore 2.6% 366 gm/ton 0 .6 gm /ton R ecovery 83.0% 85.0% 85.0% Grade of concentrate 43.0% 6222 gm/ton 10.0 gm/ton P r ic e -D ed uction C ontent -D ed uction Payment M etal ($) in Grade M etric Ton P rice (%) Net Lead .2 3 3 /lb 40% 880 lb .0 3 lb 95 169.70 Silver 4.53/oz 6222 gr/ton 200 oz .04 oz 95 853.00 Gold 1 6 7 .0 0 /o z 9 g r /to n 0 .2 9 oz 92 4 4 .3 0 Return smelter before deductions 1067.00 Deductions: Freight (Chihuahua City) 25.00 Moisture probably 10% 2.50 Base charge 25.00 5 2 .5 0 S e c u r ity fa c to r (30%) 15.50 Total deductions 67.00 Net smelter return on lead, gold, and silver concentrates 1000.00 Note: For convenience in calculations, the total recovery of gold and silver are included in lead concentrates. Actually, a small amount of them might appear in the zinc concentrates. 135 Table A.7 Calculation of the Net Smelter Return on Concentrates: Zinc. — Ratio of concentration 1:20. Grade of ore = 3.0%; Recovery = 80.0%; Grade of concentrate = 48.0% P rice -Deduction Content Payment M etal ($) in Grade Metric Ton (%) Net Zinc 0 .3 8 9 /lb 43% 946 lb 85 313.00 Return smelter before deductions 313.00 Deductions: Freight (Saltillo City) 30.00 Moisture probably 8% 2.50 Base charge 53.00 Charge $.90 for 1 cent above 12.5$ 24.00 109.50 S e c u r ity fa c to r (30%) 3 3 .5 0 Total deductions 143.00 Net smelter return on zinc concentrate 170.00 Total return per metric ton mined: Silver, lead, and gold concentrate $1000.00 Zinc concentrate 170.00 Total return on concentrates $1170.00 Total return per ton mined ratio of concentration 1:20 $ 58.50 136 Table A.8 Calculation of the Cash Flow for the Alamos D is t r ic t . Years 2-8 9 Produced tons 60,000 6 0 ,000 Gross revenue 3,510,000 3,510,000 Less operating costs 1,800,000 1 ,8 0 0 ,0 0 0 Gross earnings 1 ,7 1 0 ,0 0 0 1 ,7 1 0 ,0 0 0 Less depreciation 150,000 150,000 B alance 1 ,5 6 0 ,0 0 0 1 ,5 6 0 ,0 0 0 Less tax production and import ta x (30%) 468,000 468,000 Balance 1 ,0 9 2 ,0 0 0 1 ,0 9 2 ,0 0 0 Less state tax (4%) 4 3 ,680 43,6 8 0 B alance 1 ,0 4 8 ,3 2 0 1 ,0 4 8 ,3 2 0 Less income tax (42%) 440,294 440,294 N et income 608,025 608,025 Plus depreciation and amortization 150,000 150,000 Plus depletion (30% of production) 140,400 140,400 Rec working capital 100,000 CASH FLOW 898,425 998,425 137 Table A.9 Estimation of the Net Present Value. Discount Rate Year Cash Flow 10% 25% Present Value 0 - 400,000 1.000 - 400,000 1 -1,600,000 .909* -1,454,000 2 898,425 .640 574,992 3 898,425 .512 459,993 4 898,425 .410 368,354 5 898,425 .328 294,683 6 898,425 .263 235,387 7 898,425 .210 188,670 8 898,425 .168 150,935 9 -98,425 .134 133,790 N et retu rn value @ 25% $ 552,404 Table A.10 Estimation of the Discounted Cash Flow or Internal Rate of R eturn. Discount Discount Year Cash Flow Rate (30%) NPV Rate (40%) NPV 0 - 400,000 1.000 _ 400,000 1.000 400,000 1 .-1,600,000 .826* -1 ,321,600 .826* -1 ,3 2 1 ,6 0 0 2 898,425 .592 531,868 .510 458,198 3 898,425 .455 408,783 .364 327,026 4 898,425 .350 314,449 .260 233,590 5 898,425 .269 241,676 .186 167,107 6 898,425 .207 185,974 .133 119,490 7 898,425 .159 142,850 .095 85,350 8 898,425 .123 110,506 .068 61,093 9 998,425 .094 93,852 .048 47,925 $ 298,958 $ -2 2 6 ,6 2 3 By interpolating. Discounted Cash Flow = 35. 81% *The rate of 10% is considering a financial loan from a bank Table A.11 Calculation of the Present Value Ratio D iscou n t Year Cash Flow Rate (25%) Net Present Value 0 - 400,000 1.000 - 400,000 1 -1,600,000 .800 -1 ,2 8 0 ,0 0 0 2 898,425 .640 574,992 3 898,425 .512 459,994 4 898,425 .410 368,354 5 898,425 .328 294,683 6 898,425 .262 253,387 7 898,425 .210 188,669 8 898,425 .168 150,935 9 998,425 .134 133,789 -2 ,4 2 4 ,2 6 3 1 ,6 8 0 ,0 0 0 744,263 Present Value Ratio = '^ g^ ooo ' 4 .4 3 Table A. 12 Calculation of the Accounting Rate of Return. Average Annual Accounting: Profit after, tax = 4,864,200 _ ggg 025 8 years Accounting rate of return = Y"odo'doo = •304 or 30.40% on the investment 139 Table A.13 Estimation of Pay Back Period and Return of Investment. Pay Back Period: Year 2 898,425 Year 3 1,796,850 Year 4 2,695,275 By interpolating, the pay back period = 3.2 years Return of Investment: Capital investment _ 2,000,000 42% Annual cash flow ** 898,425 Table A.14 Estimation of the Discounted Cash Flow Assuming a 20% Change in the Annual Cash Flows. Discount Rate D iscou n t Year Cash Flow 10% 30% NPV Rate (25%) NPV 1 - 400,000 1.000 - 400,000 - 400,000 2 -1 ,6 0 0 ,0 0 0 .909 -1 ,4 5 4 ,0 0 0 -1 ,4 5 4 ,4 0 0 3 718,740 .392 425,494 .640 459,994 4 . 718,740 .443 319,839 .512 367,995 5 718,740 .350 251,559 .410 294,683 6 718,740 .269 193,341 .328 235,747 7 718,740 .207 148,779 .262 188,310 8 718,740 .159 114,280 .210 150,935 9 818,740 .123 88,405 .168 120,748 .094 76,962 .134 109,711 - 235,740 - 74,123 By interpolating. Discounted Cash Flow = 26.2% Change in the profitability = 26.8% Table A.15 Estimation of the Net Present Value Discount Rate Year Cash Flow 10%* 25% NPV 0 - 400,000 1.000 - 400,000 1 -1 ,6 0 0 ,0 0 0 .909 -1 ,4 5 4 ,4 0 0 2 718,740 .640 459,993 3 718,740 .512 367,995 4 718,740 .410 294,683 5 718,740 .328 235,746 6 718,740 .262 188,310 7 718,740 .210 150,935 8 718,740 .168 120,748 9 818,740 .134 109,711 $ 73,722 Net present value @ 25% = $73,722 *The rate of 10% is considering a financial loan from a bank. APPENDIX B STATISTICAL CALCULATIONS FOR THE ALAMOS MINING DISTRICT EXPLORATION PROGRAM, 1973-75 141 ' 0 7 /1 4 /7 5 PAGE 1 VCGELBACK COMPUTING CENTER NORTHWESTERN UNIVERSITY SPSS ---- STATISTICAL PACKAGE FOR THE SOCIAL SCIENCES VERSION 5.8 — AUGUST 30/ 1974 •i RUN NAME REGRESSION ALAMOS MINING DISTRICT VARIABLE LIST MINES/X/Y/XZ/Y2/XY/GR/ANT,VOLC/MET/NEST/NWEST/EWEST>AGE INPUT FORMAT (8X,F2.0/2F5.0/5X/3F3.0,IX,4F1.0,2X/3F1.0,4X/FI.0) ACCORDING TO YOUR INPUT FORMAT/ VARIABLES ARE TO BE READ AS FOLLOWS VARIABLE format RECORD COLUMNS MINES F 2. 0 1 9- 10 ^ X f 5. 0 1 11- 15 Y F 5. 0 1 16- 20 X2 F 5# 0 1 26- 30 Y2 F 5. 0 1 31- 35 XY ? 5. 0 1 36- 40 GR F 1. o 1 42- 42 ANT F 1. 0 1 43- 43 VOLC F 1. 0 1 44- 4 4 MET F 1. 0 1 45- .45 NEST F 1. 0 1 48- 40 INWEST F 1. 0 1 44- 49 EwEST F 1. 0 1 5C- 50 AGE F 1. 0 1 55- 55 THE INPUT FORMAT PROVIDES FOR 14 VARIABLES. 14 WILL BE READ IT PROVIDES FOR 1 RECORDS (♦CARDS*) PER CASE. A MAXIMUM OF 55 ♦COLUMNS* ARE USED ON A RECORD. # OF CASES 140 REGRESSION VARIA3LES-MINES TO AGE/ REGRESSION-MINES WITH X( 1)Y(1)X2(1)Y2(1>XY(1)GRCl)ANT(1)VOLC(1) METtDNESTCl )NWEST(1)EWESTC1)AGEC D/RESIDUALS OPTION 12 READ INPUT DATA 050700 CM NEEDED FOR REGRESSION 142 RECESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 2 .FILE NONAME (CREATION DATE • 07/14/75 ) + * + + + + + + * » * + + +* + + + + + + + + MULTIP L E R E C» RE S S I 0 N ******** * * ** * * ********* ChPENDENT VARIABLE.. MINES V/.RIABLE(S) ENTERED ON STEP NUMBER 1.. ANT MULTIPLE R .51781 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SCUARE .26813 REGRESSION 1. 24.07616 24-07616 50. 55807 .000 STD DEVIATION .69008 RESIDUAL 138. 65.71670 .47621 i# i r t v »ni re r»i tia c c m 11 T T Hki ______— VARIABLES fJOT IN THE ECUAT ION VARIABLE B STD ERROR B . F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.5412262 .21675601 50.556067 .5178127 X -.21891 ♦99210 6.8953057 .000 .39427 .010 (CONSTANT) .13604651 .6075d002E-01 9.3763994 Y .14894 .97948 3.1061235 • 003 .060 X2 -.22070 .99942 7.0149660 .009 Y2 ♦14728 •99367 3.0375256 .084 XY -.09046 .97302 1.1304162.293 GR .23234 .98101 7.6175227 .006 VCLC -.00246 .99334 .6 3169900E-03 .977 MET .32923 .97532 16.655409 .000 NEST .18162 .95408 4.6733687 • .032 NWEST -.29293 .90734 12.856932 .000 EWEST -.14448 .99654 2.92093G7 .090 AGE .21658 • .98504 6.8741638 143 REGRESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 3 FILE NONAME (CREATION DATE • 07/14/75 ) «.»+* + + ******* + + + + + + * + *+ MULTIPLE REGRESSION * * * * * * * * * * * * * * * * * * * * * * * Cc?EKOENT VARIABLE.. MINES VARIABLE IS) ENTERED ON STEP NUMBER 2.. MET -; .VJL7IPLE R .58945 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SCOARE .34746 REGRESSION 2. 31.19952 15.59976 36.47457 .000 STB DEVIATION .65398 RESIDUAL 137. 58.59334 •42769 VARIABLES IN THE EQUATION —— —— — —— ——— VARIABLES NOT IN THE EQUATION VARIABLE B STD ERROR B F BETA VARIABLE PARTIAL ' TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.4078641 .20800010 45.613594 .4730 >64 X -.09Q77 ' .80878 1.1297148 0 .36015 .290 MET .61641932 .15104206 16.655439 .2351993 r .08745 .93751 1.0481441 .000 .32971 .303 (CONSTANT) •95255996E-01 •61727810E-01 2.3613482 X2 -.11059 .85774 1.6639570 .125 ,0 .197 , Y2 •09390 .96055 1.2097702 .273 XY -.00308 ♦91107 .5868664 5E .925 GR .15491 .90461 3.3438449 .070 VOLC -.05420 .97257 .40075461 . 528 NEST .16065 *94585 3.6030933 .060 NVEST -.23629 .85924 8.0422123 .005 EVEST -.12239 •98860 2.0680526 .153 AGE .13352 .89731 2.4685260 .118 144 REGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 PACE 4 FILE NONAME (CREATION DATE • 07/14/75 ) *********************** MULTIPLE REGRESSION ♦♦*♦♦***♦♦♦*♦*♦♦**♦•**• DEPENDENT VARIABLE.. MINES VARIA3LECS) ENTERED ON STEP NUMBER 3.. NVEST MULTIPLE R .61959 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE .33389 REGRESSION 3. • 34.47092 11.49031 28.24705 .000 STD DEVIATION .63779 RESIDUAL 136. 55.32194 .40678 1 i ! z ————— — —— — VARIABLES IN THE EQUATION VARIABLES NOT IN THE ECU/ 0 variable 8 STD ERROR B F BETA VARIABLE . PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.2426877 .21104326 34.670527 .4175114 X -.11672 .80167 1.8647325 •• .000 .31790 .174 MET •51727797 .15137089 11.691403 .2394631 Y .07681 .93470 .80116456 .001 .27684 .372 NVEST -.32110040 .12380623 8.0422123 -.2059156 X2 -.13281 .85272 2.4236090 .005 -.76752 .122* (CONSTANT) .36021128 •11114468 10.503578 Y2 .03121 .95660 .89617169 .001 .345 XY -.03144 .90293 .13322663 .715 GR .16169 .90453 3.6241671 .059 1 VOLC -.02090 .9*230 .56977144E-01 .603 • NEST .18822 .93804 4.9280633 • .028 * EWEST -.14073 .98508 . 2.7272339 .101 AGE .14201 .89699 2.7733962 • 098 145 REGRESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 5 FILE NONAMe (CREATION DATE ■ 07/14/75 ) ♦ ♦♦♦♦♦ ******** ********* MULTIP L E R 6 G RESSION ** ******* ****** ******** DEPENDENT VARIABLE.. MINES VAR I ABLE(S) ENTERED ON STEP NUMBER 4.. NEST • MULTIPLE R .63646 ANALYSIS OF VARIANCE DF SUMOF SQUARES MEAN SQUARE F SIGNIFICANCE R SCUARE .40572 REGRESSION 4. 36.43072 9.10768 23. 04137 .COO STD DEVIATION .62871 „• RESIDUAL 135. 53.36214 .39528 ■ UAVAKAAOLCJ Q T i m CC liUlMflT* TMii TMP i n c cPOM u u ATIQN VARIABLE a STD ERROR B F BETA variable PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.1402874 .21306484 28.642115 .33:,1075 . X -.12119 •80155 1.9972440 0 .29170 .160 MET .46030677 .15015104 10.232476 .2222233 Y .05209 .91666 .36461155 . 0 0 2 .25691 .547 NwEST . -.37590216 .12255056 9.4084702 -.2204615 X2 -.12793 •85145 2.2293931 .003 -.62174 .133 NEST .25611829 .11502296 4.9580633 .1525367 Y2 .06275 •94588 .52967736 .023 .54202 .463 (CONSTANT) •22455537 .12536107 3.2086531 XY -.04294 .90003 .24756793 .075 .620 GR .14709 .89637 2.9634474 \ • Oo 7 1 VOLC -.04022 .94313 .21709327 . 0 4 2 EVEST -.11303 .96641 1.8930724 .171 . AGE .13005 .89154 2.3053949 . • 131 146 REGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 PAGE 6 FILE NONAME (CREATION DATE * 07/14/75 ) *********************** MULTIPLE REGRESSION *********************** DEPENDENT VARIABLE.. MINES VARIABLECS) ENTERED ON STEP NUMBER 5.. GR MULTIPLE R .64693 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE .41653 REGRESSION 5. 37.53530 7.51706 19.29388 .000 STD DEVIATION .62419 RESIDUAL 134. 52.20755 .38961 • C' VARIABLES IN THE EQUATION------VARIABLES NOT IN THE EQUATION------VARIABLE a STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.1134199 .21210712 27.555448 .3740807 X -.10238 .78528 1.4086984 .000 .23483 .237 MET .41003730 .15455862 7.0361763 .1897122 Y .02204 .87655 .64653452E-G1 .009 .21932 .SCO HUE ST -.37603244 •12166900 9.5519215 -•2205379 X2 -.10502 .82558 1.4832o93 .002 -.82202 .225 NEST •23736042 .11471421 4.2813640 .1413651 * Y2 .03887 .91887 .20120916 • 040 .50232 .654 GR .19472063 .11311322 2.9634474 .1197700 XY -.06457 - .88287 .55661245 .087 •37133 .457 (CONSTANT) .13644059 .13457389 1.0279348 VOLC -.05560 .93401 .41241125 .312 .522 EWEST -.12537 .96436 2.1239200 .147 AGE -.02185 .11065 •63512046E-01 .801 147 REGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 PAGE 7 FILE NONAME (CREATION DATE - 07/14/75 ) ****** ******** ******** ♦ M U L T I PL E R E G RE S S I 0 N ♦ ♦******* * ** * * ********* DEPENDENT VARIABLE.. MINES • VARIA9L £(S) ENTERED ON STEP NUMBER 6.. EVEST MULTIPLE R .65400 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE .42772 REGRESSION 6. 38.40592 6.40099 16. 56707 .000 STD DEVIATION .62159 RESIDUAL 133. 51.38694 .38637 ------—------VARIABLES IN THE EQUATION —————— ————— VARIABLES NOT IN THE EQUATION ------variable B STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.1037399 .21132649 27.281297 .3708452 X -.09033 .77649 1.0858013 0 .28236 .299 MET •38905375 •15459648 6.3339724 .1800037 Y .03159 ^ .87182 .13183582 .013 .20810 .717 NVEST -.38443381 .12129900 10.044503 -.2264672 X2 -.09738 .82166 1.2636676 .002 -.34039 .263 NEST .21367395 .11538653 3.4292003 .1272631 . Y2 .04917 .91330 .31984790 .066 .45219 .573 GR .20129039 .11273197 3.1882367 .1238103 XY -.04858 .86700 .31221440 .076 .38336 .577 EVEST -.17527075 .12026531 2.1239200 -.0973232 VOLC -.04867 .93075 .313362C6 .147 -.15439 .577 (CONSTANT) •20540732 .14212299 2.088S301 AGE -.00982 .10961 •12723C42E-01 .151 .910 148 REGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 PACE 8 FILE NONAME (CREATION DATE - 07/14/75 ) *****♦*♦****♦*♦*♦**♦*♦♦ MULTIPLE REGRESSION A*********.************* DEPENDENT VARIABLE.. MINES VARIA3LECS) ENTERED ON STEP NUMBER 7.. X2 MULTIPLE R .65614 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE .43314 REGRESSION 7. 33.69319 5.55617 14.40902 .000 STD DEVIATION •62G97 r;* RESIDUAL 132. 50.89966 .38560 ------variables in the equation ------VARIABLES NOT IN THE EQUATION ------VARIABLE 3 STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F . SIGNIFICANCE ELASTICITY significance’ ANT ' 1.1247436 .21193860 28.163522 •3776852 X .01950 .04090 •49S2176GE-Q1 • QUO .28773 .£24 MET .32907200 .16339161 A.0562230 .1522519 Y .04392 .85901 .25320594 .04b .17602 .616 NVEST -.39407626 .12148216 10.522903 -.2311204 Y2 .05921 .90463 .46069257 .001 -.36147 • 493 NEST .21207361 .11523107 3.3643696 •1263080 • XY .02235 .47935 .65445164E-01 .068 .44302 .793 GR •17349663 .11443116 2.4331656 .1097903 VOLC -.05650 .92537 .41954220 .121 • 34G39 ' .510 EWEST -.16593930 .12043267 1.3965084 -.0921420 AGE -.01984 .10849 •5156G1C0E-G1 .171 —.14664 . .621 X2 -.10469930E-02 .93136093E-03 1.2636676 -.0312680 o .263 -.24714 (CONSTANT) .30785102 .16571261 3.3295544 .070 149 REGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 ' PAGE 9 FILE NONAME (CREATION DATE • 07/14/75 ) * * + + * * + ♦ * + + + * + + + + + + + + + + MULTIPLE REGRESSION *********************** DEPENDENT VARIABLE.. MINES VARIA3LECS) ENTERED ON STEP NUMBER 8.. Y2 MULTIPLE R .65964 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE .43513 REGRESSION 8. 39.07164 4.88396 12. 61402 .000 STD DEVIATION .62224 C RESIDUAL 131. 50.72121 .33718 _ v A D T A Rf P < UnT rv! rue cnn —————————— vAK1ADLCJ i n tnC CUUAIlUn —————— —— VAKAAoLCJ nU1 * VARIABLE B STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1,1263096 .21238525 26.123335 .3764113 X .02124 •04086 •53657471E-01 0 •26313 • bC9 MET ,31360834 .16530314 3•5992582 .1450974 Y -.05972 .04539 .46526443 • .060 •lo774 .496 NVEST -.38871203 .12193716 10.153779 -.2279743* XY -.05471 .12869 .39025958 .002 -.54974 .533 NEST .20397740 .11013191 3.0350411 .1214831 VOLC -.04585 .88974 .27390434 .031 .43167 . .602 GR .16415923 .11659416 1.9323349 .10:9721 ACE -.01276 •10689 •21177402E-01 .162 .31305 .865 EV6ST -.17180203 ; .12093789 • 2.0163616 -.0913971 • loO -.15133 X2 — • 11069963E-02 •93774691E-03 1.3985655 -.0860607 .239 -.26177 Y2 , 11596793E-02 .17081974E-02 .46069257 .0468703 0 • .496 .14450 (CONSTANT) .28203401 .17328248 2.6490714 .106 • • M cn O REGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 PAGE 10 FILE NONAME (CREATION DATE ■ 07/14/75 ) A********************** MULTIPLE REGRESSION ♦**#♦*♦*♦**♦*****♦*♦*** DEPENDENT VARIABLE.. MINES VARIABLEISI ENTERED ON STEP NUMBER 9.. Y MULTIPLE R •66117 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE •43716 . REGRESSION 9. . 39.25253 4.36139 11.21839 .000 STD DEVIATION .62362 C RESIDUAL 130. 50,54033 .33877 VARIABLES IN THE EQUATION------VARIABLES NOT IN THE EQUATION variable 6 STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.1577860 .21776558 28.266896 .3089865 X .01619 •04056 •33817644E-01 .000 .29613 .854 MET .32567976 •16659428 3.8222009 .1505025 XY -.03501 .11076 .15827111 .053 .17420 .691 N'.'EST -.38673335 .12226958 10.006906 -.2263435 VOLC -.04687 •68953 .28402105 .002 -.84553 • 595 NEST .21561672 .11761409 3.3603271 .1284151 AGE -.01428 •10682 .263167155-01 .069 .45631 .871 GR .18183333 .11966755 2.3093397 .1113739 .131 .34685 EWEST -.17324346 • .12125400 2.0413692 -.0961975 .155 -.15310 o X2 -.10344128E-02 •94600704E-03 1.19563o2 -.0602915 .276 -.24417 Y2 •61023166E-02 .74463123E-02 .67170432 .2465575 .414 .75044 Y -.53738499E-01 .86113829E-01 .46526443 -.2106653 .496 -1.05133 (CONSTANT) .38720101 .23221009 2.7804226 VIM REGRESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 11 FILE NONAME ' (CREATION DATE - 07/14/75 ) + + ++ + + ****** + * + + + +♦ ♦♦** MULTIPLE REGRESSION +*******#***++*+*»**##* DEPENDENT VARIABLE.. MINES VARIABLE(S) ENTERED ON STEf NUMBER 10.. VOLC MULTIPLE R .66210 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE *43333 REGRESSION 10. 39.36356 3.93636 10.06934 .000 STD DEVIATION .62524 ^ RESIDUAL 129. 50.42930 .39092 VARIABLES IN THE EQUATION------:------VARIABLES NOT IN THE EQUATION VARIABLE B STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.1663297 .21895542 28.374700 .3918570 X .02828 •03823 .10246790 0 .29036 .749 MET •33004648 .16864896 4.0177742 .1564042 XY -.02924 .10892 .10953082 .047 .10092 .741 NWEST -.37061595 .12356187 9.3892056 -.2220531 AGE -.00147 .09877 .27651422E-03 .003 -.02767 .987 NEST •22300517 .11076097 3.529055b .1325631 • Ot>3 .47211 CR .13950265 .12086705 2.4581859 .1165605 .119 .36133 EWEST -.16303097. .12197336 1.8991027 -.0933354 .171 -.14054 X2 -.10625892E-02 •95009510E-03 1.2508251 -.0824706 .265 -.25032 • Y2 •59799530E-02 •74704609E-02 .64076709 • 2t-16918 » .425 .74513 Y -•59453909E-01 •86362384E-01 .47392715 -.2132311 .492 -1.06464 VOLC -.79226609E-01 .14066057 .26402105 -.0372839 .595 -.04422 (CONSTANT) .39255898 .23306913 2.8368758 • 095 ... - ' 152 r—•* RE5RESSI0N ALAMOS MINING DISTRICT 07/14/75 PAGE 12 FILE NCNAHE (CREATION DATE - 07/14/75 ) *********************** MULTIPLE REGRESSION *********************** DEPENDENT VARIABLE.. MINES VAR I ABLE(S) ENTERED ON STEP NUMBER 11.. XT MULTIPLE R .66247 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE •43636 REGRESSION 11. 39.40668 3.53243 9.10072 .000 STD DEVIATION .62741 RESIDUAL 128. 50.38618 .39364 • —------—————------— VARIABLES IN THE EQUATION------————------— —————————— VARIABLES NOT IN THE EQUATION VARIABLE 8 STD ERROR 8 F BETA VARIABLE PARTIAL TOLERANCE F SIGNIFICANCE ELASTICITY SIGNIFICANCE ANT 1.1804315 •22380835 27.818200 .3965949 X .03723 .03562 •17629295 .000 .30197 .675 MET .31094384 .18799917 2.7356847 .1438669 AGE .00030 ° .09841 •11600343E-04 .101 .16632 .997 NVEST -.36040767 .12410871 9.3949496 -.2231040 . .003 -.63159 NEST .22076035 .11938785 3.4191797 .1314735 .067 .46719 • GR .19983061 .12527424 2.5457617 .1229438 .113 .38117 EVEST —.16329060 .12325222 1.7552253 -.0906709 • .100 -.14430 X2 -.54221572E-C3 •18357709E-02 • 8 6953834E-01 — .04 20a 7 0 • 7o9 -.12799 Y2 .603 35032E-02 •74981247E-02 .64749106 .2433561 .423 .75100 Y -.47760166E-01 •93587640E-01 .26043103 -.1712915 .611 -.55524 VOLC -.72810059E-01 .15043089 .23426570 -.0342642 .629 -.34064 XY -.16103594E-02 •46671319E-02 .10953662 -.0653975 .741 -.21634 (CONSTANT) .35249195 .26335291 1.7915220 .163 153 REGRESSION ALAMOS MINING DISTRICT __ 0 7 /1 4 /7 5 PAGE 13 FILE . NONAME (CREATION DATE • 07/14/75 ) «♦«********.*********** MULTIPLE REGRESSI ON *•♦***♦**********♦*♦*** DEPENDENT VARIABLE.. MINES VAR IA3L E(S) ENTERED ON STEP NUMBER 12.. X MULTIPLE R .66305 ANALYSIS OF VARIANCE . OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCE R SQUARE .43964 1 REGRESSION 12. 39.47652 3.26971 8.30333 .000 STD DEVIATION .62944 RESIDUAL 127. 50.31634 .39619 . VARIABLES IN THE EQUATION------VARIABLES NOT IN THE EQUATION VARIABLE a STD ERROR B F SETA VARIABLE PARTIAL TOLERANCE F l SIGNIFICANCE. ELASTICITY SIGNIFICANCE ANT 1.1582768 .23064865 25.218709 .3891514 ' " AGE -.00081 .09832 •81968237E-04 • COO .29630 - .993 MET .33054172 .19429391 2.8942373 .1529319 .091 .17680 NW5ST -.37401406 .12543774 8.8903612 -.2193541 .003 -.61761 NEST • .20857116 .12324107 2.8641251 .1242190 .093 .44139 GR .19781684 .12577536 2.4736338 .1216744 .116 .37723 EWEST -.16997156 .12467032 1.8587731 -.0943007 .175 -.15021 X2 -.217546702-02 .430512462-02 .25534865 —.1626606 .614 -.51351 Y2 •57662480E-02 •75492496E-02 .58341698 .2330545 .446 .71050 > Y -.405135852-01 •95463533E-01 .18010524 — .1453017 .672 -.72543 VOLC -.86677075E-01 .15448879 .31478538 -.0407900- .576 -.04538 XY -.216585902-02 •50586683E-02 .18331076 -.0392739 • 6o9 -.29033 X .293585262-01 •69922476E-01 * .17629295 .1477761 .675 . •71669 (CONSTANT) .25153076 .35724419 .49573758 .433 f-LEVEL OR TOLERANCE-LEVEL INSUFFICIENT FOR FURTHER COMPUTATION. 154 DEGRESSION ALAMOS MINING DISTRICT 0 7 /1 4 /7 5 PAGE 14 FILE NONAME (CREATION DATE » 07/14/75 ) *********************** MULTIPLE REGRESSION *********************** . DEPENDENT VARIABLE.. MINES c* SUMMARY TABLE STEP VARIABLE F TO SIGNIFICANCE MULTIPLE R R SQUARE R SQUARE SIMPLE R OVERALL F SIGNIFICANCE ENTERED REMOVED ENTER OR REMOVE CHANGE 1 ANT 50.55307 .000 .51781 .26813 .26613 .51781 50.55807 .000 2 MET 16.65549 .000 .58946 .34746 .07933 .35951 36.47457 .000 3 N WEST f. 8.04221 .005 .61959 .38389 .03643 -.39633 28.24705 .000 4 NEST 4.95606 .02d • 6.16 9 6 .40572 .02183 .26272 23.04137 .000 5 GR 2.96345 ■ .087 ' .64693 .41853 .01236 .26823 19.29338 .000 6 EWEST 2.12392 .147 •65400 .42/72 .00914 -.15356 16.56707 .000 7 X2 1.26367 .263 .65314 .43314 .00543 -•17o2S 14.40902 .000 3 Y 2 .46089 • 493 .65964 .43513 .00199 ♦ 16630 12.61402 .000 9 Y .46526 .496 .66117 .43715 .00201 .20023 •11.21339 .000 10 VCLC .26402 .595 .66210 .43633 .00124 .03854 10.06934 .000 11 XY .10954 .741 .66247 •43886 .00046 .00371 9.10072 .000 12 X .17629 .675 .66305 .43964 .00078 -'.14050 8.30333 .000 155 REGRESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 15 FILE NGNAM5 (CREATION DATE • 07/14/7S ) * * * * * + + + **** +********* M U L T I P L E EGRESSI.ON 4i*4r.************** **♦*♦* iSERVATION Y VALUE Y ESTIMATE RESIDUAL -2SD 0.0 *2S0 1. 0 . 7635772E-01 -.76357726-01 2. 0 • 509 7702E-01 -.50977025-01 3. 0 .37120022-01 -.37120826-01 4. 1.000000 .40dd272 .5911723 5. 0 .3700430 -.3700430 6. 0 • 7535606 -.7505306 7. 1.000000 .86206642-01 .9136934 8. 0 ♦6692338 -.6692333 9. . 1.000000 .7245006 .2754194 10. 0 1.155474 -1.165474 11. 0 , .66264666-01 -.86259636-01 12. 0 c -.1350937 .1390937 13. 0 -.1551073 .1551078 14. 0 -.1595894 .1595394 15. 0 -.1525384 .1525394 16. 0 -.1061097 .1061097 17. 0 .6330905 -.6330906 18. . 0 .6747391 -.6747391 19. 0 .7279200 -.7279200 20. 1.000000 .7926334 . .2073666 21. 1.000000 / .6351702 .3143298 22. 0 .72U7259E-01 -.72872596-01 23. 0 -.1152739 .1152799 24. 0 -.1497716 .1497716 25. 0 .2615015 -.2615015 26. 0 .1912420 -.1912420 27. 3.000000 .9237470 2.076252 23. 3.000000 .4192447 2.500755 70 70 29. 2.000000 1.103922 .8990775 30. 0 .2610974 -.2610974 31. 0 -.55422156-01 .55422156-01 32. 0 .1212707 -.1212707 33. 0 •7663011 -. 7b6o311 34. . 0 .7500670 -.7580670 35. 1.000000 .9693502 .30641706-01 36. 0 .1443761 -.1443761 37. , 0 .20344426-01 -.2034442E-01 38. 0 .2102313 -.2182313 39. 0 .3566303 -.3506303 •tu. 0 .2535691 -.2535691 41. 0 .35435806-01 -.35485002-01 42. 0 •2100123 -.2100128 43. 0 .2741783 » -.2741733 44. 0 .54627956-01 -.54627956-01 45. 0 .55131302-01 -.55101306-01 46. 0 •6498524 -.6498524 47. 0 —.1653231 .153:301 M 48. 0 .9524062 -.9524362 cn 49. 0 .7553049 -.7553049 Ox REGRESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 16 FILE NONAME (CREATION DATE ■ 07/14/75 ) * #+*+*+ + + % + * + + + + * + + + + + ♦* MULTIPLE G R E $ $ I 0 N ft********************* OBSERVATION Y VALUE Y ESTIMATE RESIDUAL 2SD 0.0 +2SD 50. 1.000000 .6157039 .3842961 51. 0 .337A633E-01 -.38748335-01 52. 1.000000 .9156653 .84334725-01 53. 0 -.1054336 .1054336 54. 0 .2554354 -.2554354 55. 2.000000 .6:23656 1.367634 R 56. 1.000000 • .6422856 .3577144 57. 0 .1197525 -.1197525 58. 0 .1527375 -.1527375 59. 1.000000 .7412405 .2537595 60. 0 v .16668458-01 -.16838455-01 61. 0 C .762V953E-01 -.76259535-01 62. 0 .2070552 -.2078552 63. 0 .1104032E-01 -.1 1G4032E-01 64# 0 ' .2523701 -.2523781 65. 0 .50702 87E-01 -.50782675-01 66. 2.000000 •6303679 1.369632 R 6 7. •1.000000 1.721254 -.7212542 63. •4.000000 1.833750 2.161250 R 69. 0 .3442626 -.3442826 70. 0 /; .1941242 -.1941242 71. 0 -.1655963 .1655963 72. 0 .2433192E-02 -.24331925-02 73. 0 -.1965476 .1965476 74. 0 .2404412 -.2404412 75. 0 -. 1332915 .1332915 76. 2.000000 2.102913 -.1029178 77. 5.000000 2.120039 2.379961 R 76. 3.000000 2.143692 .3513082 79. 0 .3260450 -.3260450 SO. 1.000000 .3777633 .6222367 81. 0 .4938758 -.4938758 82. 0 .2011966 -.2611966 83. 0 -.1239525 .1239925 34. 0 .26336435-01 -.26336485-01 6 5. 0 .13226396-01 -.18226395-01 8 6. 2.000000 1. 751756 .2482435 87. 0 1.556376 -1.556376 R 88. • 1.000000 1.249213 -.2492132 89. 0 .1289563 -.1289563 90. 0 .5525228 -.5525228 91. 0 -.1028507 .1028507 92. 0 .603 4707E-01 -.60647075-01 93. 0 .27506145-01 -.27506145-01 94. 0 .56976975-02 -.65976975-02 95. 0 -.45732475-02 .45782475-02 96. ’ 0 1.154955 -1.154955 I 157 97. 0 1.943076 ° -1.943076 R I 98. 0 -.1469370 .1469370 I REGRESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 17 FILE NONANE (CREATION DATE ■ 07/1A/75 ) * + + + + + + + + + + + + + MULTIPLE REGRESSION + ** + * + + ++ + *+ + * + $* + * + + + * OBSERVATION Y VALUE Y ESTIMATE RESIDUAL -2 SO 0.0 + 2SD 99. 0 .2674593 -.2674598 I ICO. 0 -.52942036-01 .52942082-01 I • 101. 0 -.1213423 .1213428 I 102. 0 -.3383536 .3303536 I 103. 0 . 4662279E-02 -.46022795-02 104. 0 -.19292025-01 .19292025-01 I. 105. 0 -.31733025-01 .31733322-01 I. 1Gb. 1.000000 1.412971 -.4129706 I 107. 0 .48756095-01 -.40 75b09£-01 , I 108. 0 .1979526 -.1979526 I 109. 0 . .2316403 -.2316408 I 110. 0 - .2444875 -.2444075 I 111. 0 .2654278 -.2604278 I 112. 0 -.1933910 .1933910 I 113. 0 -.224 92512-01 .22492515-01 I. 114. 0 -. 5316133E-01 .53161335-01 I • 115. 0 • J 4 C 3 (' 2 2 —. 1406022 I 116. •0 .44624272-01 -.44824272-01 » I 117. 0 .12917372-01 -.12917375-01 • I 118. 0 -.2165942 .2105942 I 119. 0 /" .21499272-01 -.21499276-01 • I 120. 0 .32130146-01 -.32100145-01 .1 121. 0 • 32662 b2E-01 -.32662622-01 • I 122. c -.16706305-01 •10700305—01 I. 123. 0 -.2625394 .2625394 I 124. 0 .33110 64E—01 -.83110646-01 . I 125. 0 .2641620 -.2641620 I 126. 0 .9 34 76 042-01 -.93473046-01 I 127. 1.000000 .4737636 .5262164 I 120. 0 .1175935 .-,1175935 I 129. 0 .3123928 -.3123928 I 130. 0 -.2166491 .2165491 I 131. 0 -.2029248 •2029248 I 132. 0 -.47390525-01 .47390522-01 I . 133. 0 -.2934661 .2934661 I 134. 0 -.1203668 ,1203668 I 135. c .53510692-01 -.58510695-01 • I 136. 0 .51103615-01 t . 51103312-01 • I 137. 0 -.1533417 .1533417 I 133. 0 -.99034C3E-01 .99084035-01 I 139. 0 -.1042674 .1042674 I 140. 0 -.4395563 .4395533 I NOTE - <*> INDICATES ESTIMATE CALCULATED WITH MEANS SU3ST1TUT50 R INDICATES POINT OUT OF RANGE Of PLOT 158 NUM5ER OF CASES PLOTTED 140. NUMBER OF 2 S.D. OUTLIERS 8. OR 5.71 PERCENT OF THE TOTA TREND SURFACE ALAMOS MINING DISTRICT COEFFICIENTS OF FIRST-DEGREE EQUATION Z - •39322 + -.04989 X + .09134 Y COEFFICIENTS OF SECOND-DEGREE EQUATION Z * -.81677 +' .12912 X + .41662 Y ♦ -.00927 X2 + -.00726 XY f 02462 Y2 COEFFICIENTS OF THIRO-DEGREE EQUATION Z • ..63807 + -.0 6 325 X + -.70702 Y + .00616 X2 + •02280 XY ♦ 20153 Y2 + -.00020 X3 + -.00199 X2Y ♦ -.00002 XY2 ♦ -.01369 Y3 - ERROR MEASURES SURFACE FIRST-DEGREE SECOND-DEGREE THIRD-DEGREE FOURTH-DEGREE FIFTH-DEGREE SISTH-DEGREE STANDARD DEVIATION .79 .76 .71 0.00 0.00 C.O VARIATION EXPLAINED • BY SURFACE .15299108E+02 .23272696E+02 .32343904E+02 0. 0. 0. VARIATION NOT EXPLAINED BY SURFACE .87636607E+02 .79663018E+02 .70591810E+02 0. 0. 0. TOTAL VARIATION .10293571E+03 .10293571E+03 .10293571E+03 0. 0. 0 . COEFFICIENT OF DETERMINATION .14862779 .22608962 .31421460 0.00000000 0.00000000 0.0000000 COEFFICIENT OF CORRELATION .38552275 .47548882 .56054848 0.00000000 0.00000000 0.0000000 159 TREND SURFACE ALAMOS district X-COORD Y-COORD Z-VALUE IST-SURF: 1ST-RESID 2ND-SURF 2ND-RESI0 3RD-SURF 3RD-RESI0 SURFACE ALAMOS MINING DISTRICT 1.000 1.000 0,000 .435 -.435 -.314 .314 .282 -.282 1.000 2.000 0.000 .526 -.526 .021 -.021 .105 -.105 1.000 3.000 1.000 .617 .383 • 308 • 692 • 166 .834 1.000 4.000 1.000 .709. .291 • 545 .455 • 384 • 616 1.000 5.000 1.000 • 800 .200 .732 k .268 .675 • 325 1.000 6.000 1.000 • 091 .109 .871 .129 .960 • 040 1.000 7.000 1.000 .983 .017 .960 • 040 1.154 -.154 1.000 8.000 1.000 1.074 -.074 1.000 — .000 1.176 -.176 1.000 . 9.000 1.000 1.165 -.165 • 991 .009 .943 .057 1.000 10.000 1.000 1.257 -.257 .933 • 067 .374 .626 2.000 1.000 0.000 .385 -.385 -.220 .220 .253 -.253 2.000 2.000 0.000 ' .476 -.476 .108 -.108 • 092 -.092 2.000 3.000 0.000 .567 -.567 .387 -.387 .170 -.170 2.000 4.000 0.000 .659 -.659 .617 -.617 .404 -.404 2.000 5.000 0.000 .750 -.750 .797 -.797 .713 -.713 2.000 6.000 0.000 . .841 - .841 .929 , -.929 1.014 -1.014 2.000 7.000 1.000 .933 .067 1.011 -.011 ' 1.224 -.224 2.000 8.000 1.000 1.024 -.024 1.043 -.043 1.263 '-.2 6 3 2.000 9.000 1 .000 1.116 -.116 1.027 -.027 1.047 -.047 2.000 10.000 1.000 1.207 -.207 .961 . .039 .494 .506 3.000 1.000 1.000 .335 .665 -.145 1.145 .230 • 770 3.000 2.000 0.000 .426 — .426 .176 -.176 .082 -.082 3.000 3.000 0.000 .518 -.518 .448 -.448 .172 -.172 3.000 4.000 0.000 .609 -.609 .671 -.671 .419 -.419 3.000 5.000 0.000 .700 ' -.700 .844 -.844 .740 -.740 3.000 6,000 0.000 ‘ .792 -.792 .968 — .968 1.054 -1.054 3.000 7.000 3.000 .883 2.117 1.043 1.957 1.277 1.723 3.000 8.000 3.000 .974 2.026 1.068 1.932 1.328 1.672 3.000 . 9.000 2.000 1.066 .934 1.044 .956 1.124 .876 3.000 10.000 0.000 1.157 -1.157 .971 -.971 .584 -.584 4.000 1.000 0.000 . .285 • -.2 35 -.088 • 088 .211 — .211 4.000 2.000 1.000 .376 .624 .226 .774 .072 .928 4.000 3.000 1 .000 .468 .532 .490 .510, . .171 .829 *o\ o 4.000 4.000 1.000 ,559 .441 • 706 • 294 .427 .573 4.000 5.000 1.000 .650 • :l 50 .872 .128 .757 .243 4.000 6.000 1.000 .742 .258 .988 .012 1.079 -.079 4.000 7.000 0 .000 .833 — .833 1.056 —1.056 ' 1.310 -1.310 4.000 8.000 1.000 .924 .076 1.074 -.074 ' 1.370 -.370 4.000 9.000 0.000 1.016 -1.C16 1.043 -1.043 1.175 -1.175 4.000 10.000 0.000 1.107 -1.107 • 963 — .963 .643 -.643 5.000 1.000 0.000 .235 -.235 -.049 .049 .196 -.196 5.000 2.000 0.000 .326 -.326 .257 -.257 • 061 -.061 5.000 3.000 0.000 .418 — .418 .514 -.514 .166 -.166 5.000 4.000 0.000 .509 -.509 • 722 -.722 • 426 — .426 5.000 5.000 0.000 .600 — .600 .881 -.881 .761 -.761 5.000 6.000 1.000 .692 .308 .991 .009 1.087 -.087 5.000 7.000 0.000 .783 -.783 1.051 —1.051 1.324 -1.324 5.000 8.000 1 .000 .875 .125 1.062 -.062 1.388 -.388 5.000 9.000 1.000 .966 .034 1.024 -.024 1.197 -.197 5 .000 10.000 1.000 1.057 — .057 .936 .064 .670 .330 6.000 1.000 0.000 ,185 -.185 -.029 .029 ' • 183 -.103 6.000 2.000 1.000 .277 .723 .270 .730 .050 .950 6.000 3.000 0.000 .363 — .3 68 .520 -.520 • 155 -.155 6.000 4.000 0.000 .459 -.459 .720 -.720 • 416 -.416 6.000 5.000 2.000 .551 1.44 9 • 872 1.128 .751 1.249 6.000 6.000 1.000 .642 .3 58 • 974 .026 1.078 . ' -.078 6.000 7.000 2.000 .733 1.267 1.027 .973 1.315 .685 • 6.000 8.000 1.000 .825 .175 1.031 -.031 1.380 -.380 6.000 9.000 1.000 .916 .084 .985 .015 1.190 -.190 6.000 10.000 0.000 1.007 -1.007 .891 -.891 .663 — .663 7.000 1.000 0.000 • 135 -.135 — • 028 .028 .171 -.171 7.000 2.000 0.000 .227 -.227 .264 -.264 .035 -.035 7.000 3.000 0.000 . .318 . -.318 . .507 ... -.507 • 137 -,137 .. 7.000 4.000 0.000 .409 -.409 .700 -.700 .395 -.395 7.000 5.000 0.000 • 501 -.501 .844 -.844 • 727 -.727 7.000 6.000 2.000 .592 1.408 • 939 1.061 1.051 .949 7.000 7.000 2.000 .683 1.317 .985 1.015 1.284 .716 7.000 8.000 4.0C0 .775 3.225 .981 3.019 1.345 2.655 7.000 9.000 0.000 .666 — .866 .929 -.929 1.152 -1.152 7.000 10.000 1.000 .957 .043 .827 • 173 .622 .378 8.000 1.000 0.000 .085 — .085 -.045 .045 • 160 -.160 8.000 2.000 0.000 .177 -.177 .239 -.239 .016 — .016 161 8.000 ' 3.000 0.000 ' • .268 — •268 .475 -.475 111 -•Ill 8.000 4.000 0.000 .359 -.359 .661 -.661 ' •362 -•362 8.000 5.000 0.000 • 451 -.451 • 798 -.798 •686 — •686 8.000 6.000 2.000 .542 1.458 • 886 1.114 1. 003 • 997 8.000 7.000 5.000 • 633 4.267 .924 4.076 1. 229 3.771 8.000 0.000 0.000 .725 -.725 .913 -.913 1. 283 -1.283 8.000 9.000 1.000 .816 .104 • 853 .147 1. 082 -.082 8.000 10.000 0.000 • 908 -.908 .744 -.744 . 545 -.545 9.000 1.000 „ 0.000 • 036 — .036 -.081 .081 0147 -.147 9.000 . 2.000 0.000 .127 -.127 .196 -.196 -• 008 • 008 * 9.000 3.000 0.000 • 218 -.218 .425 -.425 ♦076 — •076 9.000 4.000 0.000 • 310 -.210 .603 — .603 •315 -.315 9.000 5.000 0.000 - .401 -.401 .733 -.733 e629 -.629 i 9.000 6.000 2.000 .492 1.508 .814 1.186 . 934 1.06b 9.000 7.000 2 .000 .584 1.416 .845 1.155 1. 150 • 850 9.000 8.000 . 2.000 ,675 1.225 .027 1.173 1. 192 • 808 9.000 . 9.000 2.000 .766 1.234 .760 1.240 980 1.020 9.000 10.000 1.000 .850 • 142 .643 .357 •431 .569 10.000 1.000 0.000 -.014 .014 -.135 • 135 •131 -.131 10.000 2.000 0.000 . .077 -.077 .135 -.135 -• 039 .039 10.000 3.000 0.000 • 160 — .168 • 356 -.356 •030 -.030 10.000 4.000 0.000 .260 -.260 .527 -.527 t •255 -.255 10.000 5.000 0.000 .351 -.351 .650 -.650 •553 -.553 10.000 6.000 1.000 • 442 .558 .723 .277 •843 .157 10.000 7.000 2.000 .534 1.466 .747 1.253 1. 043 .957 10.000 8.000 0.000 • 625 -.625 • 722 * -.722 1. 070 -1.070 10.000 9.000 0.000 .716 — .716 .647 — »u47 e843 — .843 10.000 10.000 • 0.000 .808 — .608 .523 -.523 • 278 -.270 11.000 1.000 0.000 -•064 *’ .064 -.208 .208 . 112 -.112 11.000 2.000 0.000 ' .027* -.027 .055 • -.055 — . 077 .077 11.000 3.000 0.000 • 118 -.118 • 268 -.268 -• 027 .027 11.000 4.000 0.000 • 210 • -.210 .433 -.433 •178 -.178 11.000 5.000 ' . 0.000 • 301 — .301 .548 -.540 •458 -.458 11.000 6.000 2.000 .392 1.608 .614 1.306 •729 1.271 162 11.000 7.000 0.000 .484 .484 • 631 — . 631 • 909 . -.909 11.000 8.000 0.000 .575 .575 • 598 598 .917 -.917 11.000 9.000 0.000 .667 .667 .516 516 .670 -.670 11.000 10.000 0.000 .758 .758 .385 ; -. 385 • 087 -.087 12.000 1.000 0.000 -.114 .114 -.300 • 300 .088 -.088 12.000 2.000 0.000 -.023 • 023 -.044 . 044 .124 .124 12.000 .; 3.000 • 0 .000 .069 ••069 .162 162 .097 .097 12.000 4.000 0.000 • 160 .160 .320 320 .085 -.085 12.000 5.000 0.000 . .251 .251 - .427 427 .342 -.342- 12.000 6.000 0.000 .343 .343 .486 ' 406 .590 -.590 12.000 7.000 0.000 •- .434 -.434 .496 — •496 .747 * -.747 12.000 8.000 0.000 .525 • 525 ./ .456 -• 456 .732 -.732 12.000 9.000 0.000 .617 ,617 .367 . -• 367 .461 -.461 12.000 10.000 0 .000 .708 .708 .228 — •220 .146 .146 13.000 1.000 0.000 -.164 .164 -.410 410 .058 -.058 13.000 2.000 0.000 -.073 • 073 -.161 • 161 .181 .181 13.000 3.000 0.000 .019 .019 .038 038 .181 .181 13.000 4.000 0.000 .110 .110 .188 -• 188 .026 .026 13.000 5.000 1.000 .201 .799 • 288 • 712 • 204 .796 13.000 6.000 0.000 .293 .293 .340 340 .424 -.424 13.000 7.000 1.000 . .384 .616 . .342 •658 .555 .445 13.000 8.000 0.000 .475 .475 * .295 — •295 .512 -.512 13.000 9.000 . 1.000 • 567 • 433 . . . .199 •001 • 215 • 705 13.000 10.000 0.000 .658 .658 • 053 -• 053 .420 ' .420 14.000 1.000 0.000 -.214 .214 -.538 . •538 .020 -.020 14.000 2.000 0.000 -.123 • 123 • -.297 297 .249 • 249 14.000 3.000 0.000 . -.031 • 031 — .105 • 105 .280 • 280 14.000 4.000 0.000 ' .060 .060 .038 -• 038 .156 .156 14.000 5.000 0.000 .151 .151 .131 131 .042 -.042 14.000 6.000 ’ 0.000 .243 .243 ♦ 175 — • 175 .232 -.232 14.000 7.000 0.000 .334 .334 • 170 170 .331 -.331 14.000 6.000 0.000 .425 .425 .116 -• 116 .257 -.257 14.000 9.000 0.000 : .517 • 517 • 012 — •012 .071 .071 14.000 10.000 0.000 • 608 •608 -.141, • 141 .737 • 737 163 TREND SURFACE ALAMOS MINING DISTRICT 164 RIOT OF ORIGINAL DATA PLOTTING LIMITS MAXIMUM X • I t.O O O O O O MINIMUM X 1.000000 MAXIMUM T ■ 1 0 .0 0 0 0 0 0 MINIMUM T 1.000000 PLOTTED VALUES HAVE BEEN MULTIPLIED BT A FACTOR OF 10 TO THE T-SCALE IS HORIZONTAL T-VALUE • 1.00 ♦ .0657 X (SCALE VALUEl 109°00' X-SCALE IS VERTICAL 012 5A56TB9 1Z1A567B9 1Z3A56789 1ZSA56789 121*56769 121*56789 121*56789 121*56789 121*56789 121*56(719 121*56789 h^pcuzarx^ 1.1*1.00 *0 1*11.29 1.57 1.71 1.86 <0 22.1* .00 2.2.29 *1 Picdra3%^ 2.57 Verdes 2.71 2.86 *1000 ♦ 2000 27*10 1.1*1.00 1*11.29 1.57 1.71 1.86 «0 *.00 * . l * *.29 * .*1 *.57 *.71 *.86 *0 5.00 5.1* 5.29 5. *V 5.57 5.71 5.66 +0 ♦ 1000 ♦ 1000 6.00 6.1* 6.796. *1 6.57 6.71 6 .86 *0 7.00 7.1* 7.29 . 7.*1 Minas 7.57 7.71 Dolisa Nuevas 7.86 *0 ♦0 ♦5000 ♦1000 8.00 6.1* 6.29 8 *1 8.57 8.71 Ala 8.86 «0 ♦ 1000 9.00 9.1* 9.9.29 *1 9.57 ----27*001 9.71 9.86 *0 1 0 .0 0 10. 1* 10.29 10.*1 10.57 10.71 11.0010.86 *0 ♦ 1000 11.1* 11.29 11.*1 11.57 11.71 11.86 «0 12.0012.1* 12.29 12.*1 12.57 12.71 11.0012.86 *0 15.1* 13.29 11.*1 13.57 11.71 13.86 «0 0123*56789 123*56769 121*36789 121*56789 123*36769 121*36789 121*56769 121*56769 121*36769 121*36769 123*56769 0 5 10 ■+ •+■------K ■■ ------1---- 4- kilom eters LIST OF REFERENCES Agterberg, F. 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Mining in the Alamos and Arteaga districts. The Engineering and Mining Journal, Vol. 89, pp. 699-701. Brinegar, T. P. 1910. The Alamos Promontorio D istrict, Sonora, Mexico. Mining Science Press, Vol. 100, pp. 553-554. C. M. M. 1972. Operating and cost data of underground mines. Canadian Mining Manual, pp. 18-52. Comite de la Carta Geologica de Mexico. 1968. Carta geologica de la Republica Mexicana. Cooper, G. A., and others. 1952. Cambrian stratigraphy and paleontology near Caborca, northwest Sonora, Mexico. Smithsonian M iscell. Coll., Vol. 119, No. 1. Cooper, G. A., and A. R. V. Arellano. 1946. Stratigraphy near Caborca, northwest Sonora. Bull. American Assoc. Petrol. Geols., Vol. 30, pp. 606-611. 165 166 C. R. N. N. R. 1970. Reportes del proyecto cobre en Sonora. Unpublished reports, files of the Consejo de Recursos Naturales no Renovables, Nogales Office, Sonora, Mexico. C. R. N. N. R. and United Nations. 1969. Survey of M etallic Mineral Deposits, Mexico. 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Unconformity Lower Tertiary-Upper Cretaceous intrusive rocks .( La ramide ) Cii PrincipalJy batholits of granitic - granodioritic composition . Cretaceous rocks. Include limestones, shales, sandstones and i ntcr bedded tuffs. Potrero & Palmar formations. Undifferentiated Mesozoic rocks . Mostly rocks of sedimentary origen . T riassic - Jurassic rocks. Include quartzites, coal bearing or graphitic shales, and minor marine limestones .Barranca formation Uncon fo rmit y Paleozoic metamorphic rocks represented by Pmet gneisses,schists, and metavolcanic and sedimentary rocks. Undifferentiated Paleozoic rocks . Include limestones , shale s and sandstones. Ccrro Prieto & Provccdora formations. Undifferentiated Prccambr ian rocks . Older Pre Cambrian is represented by Pinal schist ,metavolcanics,shale and limestones. Younger Precambrian consists of shale, limestone and dolomite. Geologic contact Paul t S c a le GEOLOGIC MAP OF THE STATE OF SONORA, MEXICO Index map F I GURE 5 + S o u rce Plano Geologic© de la Re publico Mexicana., 196% 114' 110' 108' Adalberto Vazquez P.,M. S. Thesis, Dept of Mining &. Geological Engineering., 1975 j 109*15' 109*10' 1 0 9 * 0 5 ' 1 0 9 * 0 0 ' T’ J ...... - OqI M 7 . V ' \ J \ •.<>(«»(, A Orel -5 " :yP^€ 'X . ' EXPLANATION v> WOC U Z * * I ,< : - y 2 C - , xOral / " k-'W ^R E S " GEOLOGIC SYMBOLS * 'J t , "v WAN OS ‘m t A H Oral A \V Z Oral i Alluvium ■ — x 1 ''VB Oral Residual soils \ > - f ' , v ^ ' ?> C a « f e s * / \ Qdt Talus I — 27*10' \ xw V \ Conglomerate,sand. Baucarit Formation. Teg B x X Z / v X z Z ' -x:>. X / unconformity r ' \X y Basalts and basic volcanic agglomerates pyyctiwfS^ —'Ctuo > / t / V . "*vy cgi / 'V- SdX > X ' A A ‘ f ( ....A r y z Tv X Andesites, rhyolites and pyroclasts \ v x ’* X \Cc zo v jjrm / Ool / ( X ^ ZJol - "X x; % \ % / / / T rio Rhyolites and rhyolitic tuffs •A O o l ### unconformity x .f ••, ' v ) / Cand “j ^ X/' Porphyritic andesite ~ \ T - "x\ lA> X A X - V » \^ e . / > • x m t Cgr i-T ? 7 ‘ a c‘ / V Granitic batholith X Cg r. Oral v i j a ^ a : , \ \ N~. T» > ■ V >>r > \ ' \ f Cclza Limestones, sometimes metamorphosed y '■■), r \ \ X V- •' -•••)...... X z X ' Z - / m m ; /.C gr Oral 0 ro I \ v X l ’ x " . ; I met Metasediments: limestones, shales and h r > >> O o t . -A l . x v : >> * sandstones with intense metamorphism. '• \ ■A; - ,V : > : x - r v \ Barranca Formation ( ? ) T,:° - \ v> r Orel cgr X \ x / A r Strike and dip 2 7 * 0 5 '—^ X Geologic contact zCA-XA X -.re>-;. /• X 0 ro I Z—-A -X AC Inferred contact V > > V V K ■vZ \ M ; c' I ‘ y ‘ ‘ X y X r SXJtVA, ^ > & Fault or fracture A - A m X "XT. -A "" 1 c, \ l | X / \ ' yjfjA * x / / - A x Inferred fault Z Z \ / \ xWx :"v " A -----^ . T X ______' X / * ‘L !-..»ev* Tv X V feA / \ t«- . ^^Ool r \ s X S \ ,/A A • X x S x» / X ) > X / IFNrX :W\ Xv X \ 4 TOPOGRAPHIC SYMBOLS B \L, : i A v x x # # y TAX o A L A MCKS t Corvj< SZ A' x y < . " A z '" i X • Og^Nfcr**^* Zw. River / z x \ X i , # ^ v , ; 4 7 7 - z o - . ^ O ml .',v :.d; :)Ac XA X s*SB T E I C 6 U I * X m Stream l / Y - y I 0 °' yz VENAOlTjC) Dam 7 m z i S - - v \ - ■ o« r . z A A 27*00' X X 1 " ^ \ ^ <-b,m: i Paved road \ w & Z Z | z \ T w / - y X X% zWi I __ - Z..X A A X A Z ' Z i r 7 r.,xv - A if.. W 'v|S "/• X °..., ^ . < ■ \ > s X z K -T t • ' X 1 Teg ■'...... i r z ; ' v :• : Z ’r- Z z x / NV) T own : • - | Z 7 cg» _ - ■'.. Gd, ** '* • , L " r x X X z < v A A" — / / ' > ' " X x X Tv Vil lage L f O o !/ A o r 0 / Z x V x-. Center of aerial pothograph X / ~ - V f X T. ^ Oral / x Tv Flight line A x x x b / / / ! ) M y X' / z t ' / ... . A „ > y X V g z X y j , z r ^ ,V Cgr x y_ 7x^xx-y.., ^ 7 T- E A A .Oral y y V Z i z .r / r-> / i / ■' ,. , / Z T'‘ 'j '°; .;< xx) o i i A x Qr ol A'\X z : -A . *0*^ i, ^fVfed. 'VZ " z - / : z Z ^ ^ a z ';' zto-v.-; 7%)\ATALAYA S . A''' ZZ 1 109*15' 109*10' 1 09*05’ Adalberto Vazquez P, M S.Thesis,Dept of Min &Geol.Eng. 1975. 296 — 7 9 2 2940000 m N < \ s \ 7. Wiyi aw 7. \ Geologic MapTCff the Akfmos^)istrict. the ra mapped Area S ^ 2u V»ANvV'SH^f 2«u« L \ r i / ARoncho Son SiUestre ______pifbRAsx pifbRAsx _ ^ ,E I Cupn Zopofe' V erdes Son Antonio i n o t n A n o S o V ^ XICANA M V)T««or M txhic'^' \ “oco,jhui4/OLos Co*Vdolorodo. o d o r o l o d V * o C s o L O / 4 i u h j , o c o “ < E l HI60 * * / t O N A M C A T E V 2 Adalbert©Vazquez P.,M.S.Thesis, Min.of Dept A. 72 Geol.Eng.1975. X ffuncho^t NARANJl i r 'i— W c b ^ i u H o N c n o R f OAIN N GROUPING AND LOCATION F IE WII THE WHITIN MINES OF LMS DISTRICT, ALAMOS IE LdCL GROUPS MINER ALOdlCAL \ 3|oa ls Tongues los 3|Lomas | \ \ OOA MEXICO. SONORA, A I ^ c . ^ rARIA^RcM. kilometers iue 14 Figure S e b e y o h uVE j R D E F MINES OF ira e Alamos de Sierra C E R R O B L A N C O Tra e Chapote del STerra ira e Bavispe del Sierra CHAPOTE r SanBernardo err a r ls Plomosas las rra IHCAE vlOLCTi PICHtCUATE ^ S^LRTE S^LRTE Rcfc*. i c u m n u H h EDIONOA