Identification_Information: Citation: Citation_Information: Originator: Bawiec, Walter J. Publication_Date: 2000 Title: COVERAGE PERMSKARN -- Permissive Terranes on the Island of Puerto Rico for Podiform Chromite, Copper/Iron Skarn, Volcanogenic Mn, Kuroko Massive Sulfide, Epithermal Qtz-Alunite Au, and Bauxitic Clay Belt Geospatial_Data_Presentation_Form: Map Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: USGS OFR 98-38 Publication_Information: Publication_Place: Reston, Virginia Publisher: U.S. Geological Survey Online_Linkage: () Originator: Ramon Alonzo Harris Originator: Dennis P. Cox Originator: Andrew Griscom Originator: Bruce R. Lipin Originator: Sherman P. Marsh Originator: Greg E. McKelvey Originator: Norman J Page Originator: Johannes H. Schellekens Description: Abstract: The delineation of tracts that are permissive for undiscovered mineral deposits of a specific type requires the input and assimilation of geologic information from multiple earth-science disciplines. The preliminary tracts are usually based upon the distribution of permissive host rocks, which may contain known occurrences. Host rocks are assembled into favorable geologic terranes based upon rock type, age, and (or) depositional environment. Geochemical and geophysical data (magnetism, gravity) can be used to either extend or delete parts of these terranes, especially with respect to surficial cover. Geochemical data show the presence of anomalous metallic elements, or indicative pathfinder elements, which provide circumstantial evidence for the presence of metallic minerals. Gravity and magnetism are important in understanding the geometry and extent of subsurface geology. The degree of known exploration is then examined to determine which areas could be considered as having been explored and (or) exhausted on the basis of previous investigations for each deposit type. The resultant permissive tract is the area that remains after elimination of all areas in which the deposit type could not possibly occur. Purpose: Mineral resource assessment methodology is a continually evolving process, and the tools for mineral resource assessment are constantly being improved. Unlike the oil and gas industry, which has relatively well-documented exploration and production statistics and a much longer history of petroleum-related resource assessment, the minerals industry is less well documented, subject to more variables, and has more complexities. The products from mineral resource assessments are also more diversified (Singer and Mosier, 1981). Initially, mineral assessments attempted only to highlight areas of potential exploration having suitable geologic characteristics. Qualitative assessments, delineating areas and characterizing them as to high, medium, or low potential on the basis of the favorability of geologic characteristics, were provided as mineral resource assessments, but were not found to be very useful when integrating information from other disciplines. With the development of new assessment tools, such as descriptive models and grade and tonnage models (Cox and Singer, 1986; Bliss, 1992), the quantitative mineral resource assessment method of estimating probabilistically the number of undiscovered deposits became possible. Mineral resource assessment has evolved to a point where government officials, policymakers, and managers of private enterprise can now integrate mineral resource potential with information from other disciplines. Supplemental_Information: PODIFORM CHROMITE The model The podiform chromite deposit type consists of irregular masses of chromite in ultramafic parts of ophiolite complexes. The deposits are restricted to dunite bodies within tectonized harzburgite and (or) the lower portions of ultramafic cumulates, both of which are commonly serpentinized (Albers, 1986). While geologically similar, podiform chromite deposits have been subdivided into two grade and tonnage models on the basis of significant differences in tonnages. Median tonnage of minor podiform chromite deposits is 130 mt in California and Oregon (Singer and Page, 1986) having a median Cr2O3 grade of 44 percent; median tonnage of major podiform chromite deposits is 20,000 mt in Turkey and the Philippines (Singer and others, 1986), having a median Cr2O3 grade of 46 percent. Examples in Puerto Rico There are no known examples of podiform chromite occurrences in Puerto Rico. Permissive tracts Tract delineation for podiform chromite deposits is based primarily upon the outcrop pattern of the exposed serpentinite, which occurs only within the southwestern part of Puerto Rico. Areas considered permissive for the occurrence of podiform chromite are restricted to surficial exposures of serpentinite. This map unit is included within the ultramafic rocks and amphibolite terrane. Stream-sediment geochemical patterns, which for southwestern Puerto Rico include anomalies of nickel (150-10,000 PPM), cobalt (50-2,000 PPM), and chromium (2000-10,000 PPM)(figure 24). Geophysical patterns displayed on the "Gravity Boundary Map of Puerto Rico", "Filtered Bouguer Gravity Map of Puerto Rico", and the "Complete Bouguer Gravity Map of Puerto Rico" show lows that are mainly associated with serpentinite (KJs), which is interpreted to be generally antiformal in shape and to have outward-dipping contacts. Tracts that are permissive for podiform chromite deposits are restricted to areas of gravity lows. Locally, the serpentinite is overlain with a thin layer of a two-pyroxene olivine basalt unit, Kpob, which is not included in the delineated tract. Detailed contoured aeromagnetic surveys are not available for much of southwestern Puerto Rico. For this reason, magnetism has been of little help in describing this terrane. However, the serpentinites have been investigated for their magnetic susceptibilities and are described elsewhere (see "Magnetic Map of Puerto Rico"). Undiscovered deposits Due to the limited areal extent of permissive map units and the likelihood that a deposit having tonnage equal to the median for the minor podiform chromite deposit model would have been found, the assessment team determined that the probability of occurrence of one or more undiscovered deposits consistent with the grade and tonnage model is very low. No probabilistic estimate of undiscovered deposits was made. COPPER SKARN The model Copper skarn deposits are irregularly shaped or tabular ore bodies formed in carbonate or calcareous rocks near igneous contacts or in xenoliths in igneous stocks (Cox and Theodore, 1986). These deposits can be extremely irregular in shape, tongues of ore projecting along any available planar structure. The intrusive igneous rocks usually range from tonalite to monzogranite in composition, and the carbonate country rock is commonly altered to marble and calc-silicate hornfels. Primary ore minerals consist of chalcopyrite and minor bornite, along with hematite, magnetite, pyrite, and pyrrhotite. The median tonnage of copper skarn deposits is 560,000 Mt, and 10 percent of the deposits contain 9.2 million Mt or more. The median copper grade is 0.7 percent, and 10 percent of the deposits also contain more than 2.8 g/Mt Au (Jones and Menzie, 1986). Examples in Puerto Rico There are twelve known occurrences of copper skarn in Puerto Rico. Two of these occurrences, Island Queen Mine (site 92) and La Mina (site 164) are classified as mineral deposits and has been the subject of active exploration and production. The Island Queen Mine consists of two 20-to 30-ft -wide bands of carbonate-bearing rocks, altered to skarn, and separated by andesite flows. Ore materials include magnetite, hematite, and chalcopyrite, with secondary malachite, azurite, and chalcocite. One 2-m interval contains 2.83 percent copper and more than 60 percent iron oxide. Production from the Island Queen Mine, during 1951-53, unfortunately was included with production from the Keystone Mine (site 85) and from an iron skarn deposit (Vazquez, 1960). La Mina (site 164), also known as Río Blanco and Spanish Adit, is a copper deposit formed in a limestone bed that has been metamorphosed to a calc-silicate rock along its contact with a tonalite intrusion. Considerable chalcopyrite is present in the limestone near the border of the intrusive mass, and pyrrhotite is the principle sulfide in other areas. At La Mina (site 164), economically important amounts of gold and silver occur in the copper-rich zones (Pease, 1966). Chalcopyrite, pyrrhotite, and pyrite occur with skarn minerals wollastonite, garnet, diopside, and epidote. Permissive tracts Terrane delineation for copper skarn deposits is based primarily on the juxtaposition of tonalite to monzogranite intrusions with carbonate-bearing rocks and the distribution of known copper skarn occurrences. On the basis of surface evidence and subsurface geophysics, three areas were identified as having potential for undiscovered copper skarn deposits: peripheral to (1) the San Lorenzo Batholith, (2) the Río Blanco stock, and (3) the Barranquitas and Piñas stocks ("Intrusive and Structural Map"). The San Lorenzo batholith (unit Ksl) and adjoining quartz diorite (unit Kpgq) complex have known associated copper skarn occurrences, altered metavolcanic rocks (unit TKmv), and calcareous rocks including the Pitahaya Formation (unit Kpi), Torrecilla breccia (unit Kt), and the Robles Formation (unit Kr). The "Magnetic Boundary Map of Puerto Rico" shows intense local magnetic highs around the perimeter of the San Lorenzo batholith and indicates favorable locations for magnetite bearing skarn deposits at the contacts of the San Lorenzo batholith. This map also shows a northeastern limiting boundary of nonmagnetic altered rocks that was used to constrain this permissive tract. The "Filtered Bouguer Gravity Map" and the "Gravity Boundary Map of Puerto Rico" shows the San Lorenzo batholith as a gravity low surrounded by more dense rocks, possibly the result of contact metamorphism. An exception to this halo of gravity-high rocks is near the southeast shoreline where plutonic rocks of Punta Guayanes (unit Kpgg) appear as low-density rocks. The tract that is permissive for copper skarn deposits around the San Lorenzo batholith shows an interior boundary following the surficial outcrop pattern of the plutonic rocks. The exterior boundary of the permissive tract was restrained in the northeast by the Northern fault zone (La Muda?) ("Intrusive and Structural Map") and the inflection point of low magnetic rocks. On the north and west sides, the fault contact between the carbonate-bearing Torrecilla breccia (unit Kt) and the Los Negros Formation (unit Kln). Through Formation A of Berryhill and Glover (1960) (unit Kabcj) approximately a 2-km distance was maintained from the outside edge of the batholith. Tract delineation for copper skarn deposits in the Rio Blanco stock area was based upon mapped altered rock and pyrite occurrences from the 1:20,000-scale mapping, known occurrences, and geologically favorable map units. The "Magnetic Boundary Map of Puerto Rico" shows the Rio Blanco stock as a highly magnetic pluton that may have magnetite-bearing skarn deposits at contacts with carbonate rocks. The "Gravity Boundary Map of Puerto Rico" shows the Rio Blanco stock as a relative low. The permissive tract drawn around the Rio Blanco stock shows an interior limit based upon the outcrop pattern of plutonic rock and an exterior limit based upon a distance of approximately 2 km from the edge of the pluton. Just north of the Barranquitas stock and the Piñas stock ("Intrusive and Structural Map") are seven copper skarn occurrences concentrated within a fault-bounded area. The Torrecilla Breccia (unit Kt) hosts these occurrences, which consists of lava flows, volcanic sandstone, and limestone. The gravity and magnetic patterns in this area are inconclusive due to the small size of the tract and the resolution of the geophysical data. The copper skarn tract is delineated in the area of the Barranquitas stock and the Pinas stock on the basis of known occurrences and the surface exposure of the Torrecilla Breccia (unit Kt). Undiscovered deposits There are 12 known occurrences of copper skarn in Puerto Rico. Due to the low level of prospecting for this deposit type, the assessment team has estimated that there is a 90 percent chance of one or more deposits, a 50 percent chance of four or more deposits, and a 10 percent chance of 8 or more deposits. These deposits are expected to have grades and tonnages consistent with the grade-tonnage model of Jones and Menzie (1986). IRON SKARN The model Iron skarn deposits are irregularly shaped or tabular masses of iron oxides formed in carbonate or calcareous rocks near igneous contacts. As with all skarn deposits, iron skarn deposits are extremely irregular in shape, their morphology being determined by the extent to which fluids can be introduced to the surrounding carbonate-bearing lithologies. Carbonate rocks, calcareous rocks, igneous contacts, and fracture zones near contacts all affect the shape of these ore bodies. Iron skarns consist of magnetite or hematite, and minor chalcopyrite, pyrite and pyrrhotite in calc-silicate contact metasomatic rocks. Intrusive rock types include gabbro, diorite, diabase, syenite, tonalite, granodiorite, and granite. Weathering usually results in magnetite occurring as float. The median grade and tonnage for iron skarn deposits is a size of 7.2 million tonnes and 50 percent iron grade (Mosier and Menzie, 1986). Examples in Puerto Rico There is 1 major mine and 16 known occurrences of this mineral deposit type in Puerto Rico. Iron and copper skarn deposits occur in the same environments of formation. The Keystone Mine (site 85) was developed as an open pit, which, in combination with the Island Queen Mine (site 92), produced approximately 220,000 tons of ore having an iron content greater than 60 percent in the years 1951-53 (Vazquez, 1960). The Keystone mine consisted of magnetite and hematite, and minor chalcopyrite, malachite and other ore minerals concentrated in two lenticular layers approximately 15 m wide. This is believed to be the largest iron ore deposit in Puerto Rico (Broedel, 1961). Permissive tracts Copper skarn deposits and iron skarn deposits of Puerto Rico appear in similar settings and, more likely than not, are co-mingled. Much of what has been stated with respect to defining tracts for the copper skarn mineral deposit type may also be applied to the iron skarn mineral deposit type. The reader is referred to the copper skarn tract delineation section for more discussion on how permissive tracts were delineated. The area around the intrusion at Los Panes ("Intrusive and Structural Map") is considered permissive for the occurrence of iron skarn deposits, in addition to those already mentioned. The intrusion of diorite (unit Kdi) into the Robles Formation (unit Kr), a chiefly calcareous volcaniclastic sandstone and siltstone, resulted in the development of magnetite. However, the richest iron concentrations have not yet been found to be above 10 percent. Undiscovered deposits There are seventeen known occurrences and deposits of iron skarn in Puerto Rico. Because of the moderate to high level of exploration, the assessment team determined that there is only a 10 percent chance of one or more undiscovered iron skarn deposits, a 5 percent chance of two or more, and a 1 percent chance of three or more undiscovered deposits. VOLCANOGENIC MANGANESE The model The descriptive model for the volcanogenic manganese deposit type includes lenses and stratiform bodies of manganese oxide, carbonate, and silicate in volcanic-sedimentary sequences (Koski, 1986). Median tonnage of ore in volcanogenic manganese deposits is 47,000 mt and median grade 42 percent manganese (Mosier, 1986). Manganese deposits in Puerto Rico are in the form of pockets of the minerals pyrolusite and psilomelane that fill irregular chambers within Tertiary limestone units (Meyerhoff, 1933). The limestone units, which are fractured due to faulting, dissolved as ground water and surface water percolated through the fractures. These percolating waters not only dissolved the calcium carbonate of the limestone, but also precipitated highly concentrated bodies of manganese oxide. Examples in Puerto Rico In 1915, in the barrios of Tijeras and Guayabal of Juana Diaz, the Atlantic Ore Company initiated the production of manganese oxide to be used in the manufacture of dry batteries (Pico, 1974). Besides gold and a small amount of iron from the Keystone Mine, manganese is the only metal ever to be exploited commercially in Puerto Rico. There are 14 known occurrences of volcanogenic manganese in Puerto Rico, and three of these occurrences have been upgraded to known deposits. The Juana Diaz Mine (site 2), was an active mine from 1915 to 1939, producing an estimated 80,000 tons of manganese ore at an average grade of 60 percent manganese (Mitchell, 1954). The Gatti Prospect (site 128) was developed in 1932 with the digging of a 35-ft shaft and a 109-ft drift. A vein, varying in thickness from 2 to 6 ft and containing rhodonite and psilomelane, produced about 120 tons of manganese ore that assayed as 52 percent Mn, 0.25 percent Fe, and 6.75 percent silica. The mine work was stopped due to flooding and transportation problems. Aguada (site 115) has manganese ore present as a vein and as float, covering five-acres in area. The ore assayed at 54 percent Mn and occurs in conjunction with deeply weathered bentonite clay. Permissive tracts Tract delineation of permissive areas for volcanogenic manganese deposit types is based primarily upon known occurrences, Cretaceous and Tertiary marine volcaniclastic map units, Tertiary marine volcaniclastic map units, Tertiary basalts and cherts, and the geochemical signature associated with these deposits of Mn, Zn, Pb, Cu, and Ba. Undiscovered deposits Given the presence of 14 known volcanogenic manganese occurrences, including 3 mineral deposits, the large size of the permissive area, the small size of the deposits, and the moderate level of exploration, the mineral resource assessment team estimated that there is a 90 percent chance of one or more undiscovered deposits, a 50 percent chance of three or more undiscovered deposits, and a 10 percent chance of eight or more undiscovered deposits. KUROKO-TYPE MASSIVE SULFIDE The model The Kuroko-type massive sulfide deposit contains copper- and zinc bearing massive sulfide deposits in marine volcanic rocks of intermediate to felsic composition (Singer, 1986). Rock types permissive for Kuroko-type massive sulfide deposits include marine rhyolite, dacite, and subordinate basalt and associated sediments, principally organic-rich mudstone and shale. The tectonic environment is an island arc characterized by extensional faulting and fractures. Median tonnage for Kuroko-type massive sulfide deposits is 1.5 million Mt; 90 percent of the deposits are larger than 120,000 mt; and 10 percent of the deposits are larger than 18 million Mt (Singer and Mosier, 1986). Examples in Puerto Rico There are no examples of the Kuroko-type massive sulfide deposits known to occur in Puerto Rico. Permissive tracts While there are no known occurrences of Kuroko-type massive sulfide deposits in Puerto Rico, the area delineated as permissive for volcanogenic manganese deposits is also a suitable environment for Kuroko-type massive sulfide deposits. The permissive features include marine volcanic rocks of intermediate to felsic composition; marine rhyolite, dacite, subordinate basalt and associated sediments; hot springs related to marine volcanism; island arc tectonic setting; and evidence of associated deposits (volcanogenic manganese). Undiscovered deposits While no Kuroko-type massive sulfide deposits are known to be present in Puerto Rico, the mineral resource assessment team felt that their occurrence was possible on the basis of the above mentioned evidence. It is estimated that there is a 10 percent chance of one or more undiscovered deposits being present. EPITHERMAL QUARTZ-ALUNITE GOLD The model These deposits occur in island arcs and back-arc spreading centers and within vuggy veins and breccias in zones of high-alumina altered rock. Gold, pyrite, and enargite mineralized rock is related to felsic volcanism (Berger, 1986). Associated hydrothermally altered rock is predominantly argillic, the advanced argillic zones surrounding the former feeder conduits for the hydrothermal solutions. The orebodies are always located in or adjacent to the advanced argillic zones (Ashley, 1982). Median tonnage for epithermal quartz-alunite-gold vein deposits is 1.6 million Mt (Mosier and Menzie, 1986). Examples in Puerto Rico There are five mineral occurrences in Puerto Rico that are classified as being of the epithermal quartz-alunite-gold deposit type, and two of these occurrences are mineral deposits. Cerro La Tiza (site 160), consists of alternating bands of quartz and alunite covering a 556-acre area. The ore material of interest is alunite, kaolinite, halloysite, and pyrophyllite, which is the result of hydrothermal (acidic) alteration. Some small-scale sporadic mining of kaolin clays may have been tried locally with the development of pits approximately 200 ft long, but there is no documented production. General analytical data shows zinc (5,000 ppm) and gold (160 ppb) to be present. The city of Cidra is located in a valley underlain by a zone of hydrothermally altered volcanic rock (site 35). The major alteration zone has been poorly prospected, but there is little indication of near-surface economic mineralized rock for either precious metals or copper. The alteration zone is poorly exposed and covered by farms and houses. However, analytical data for soils were 1,400 PPM Zn, 600 PPM Cu, and 3000 PPM Pb. Permissive tracts Tract delineation for the epithermal quartz-alunite gold deposit type is based primarily on permissive rock types identified from known mineral deposits and occurrences, advanced argillic altered rocks associated with plutons, recognized hydrothermally altered rocks, and meta-volcanic rocks. Undiscovered deposits The mineral resource assessment team estimated a 90 percent chance of one or more undiscovered deposits, 50 percent chance of two or more deposits and 10 percent chance of four or more undiscovered epithermal quartz-alunite gold type deposits. KARST-TYPE BAUXITE The model Karst-type bauxite deposits develop through the surficial weathering in wet tropical climates of aluminous sediments (Patterson, 1986). These sediments may be residual or transported material, such as felsic volcanic ash on carbonate rocks. Deposits tend to be concentrated in depressions on karst surfaces. Within Puerto Rico, three kinds of karst topography have developed, related to the limestone-bearing units involved (St. Claire, 1962): tower karst is prominent in areas of the Lares Limestone; gently rolling hills are typical in areas of the Cibao Formation; and mature sinkhole karst is typical in areas of the Aguada Limestone. Examples in Puerto Rico There are no documented occurrences of karst-type bauxite deposits shown, "Metallic Mineral Occurrences in Puerto Rico." However, bauxite as much as 80-ft thick is known to occur in sinkholes within the bauxitic clay belt (Hildebrand, 1960). The mineral assemblage found in these sinkholes includes boehmite, quartz, goethite, hematite, kaolinite, halloysite, anatase, oligoclase, sanidine, and organic matter. In 1961 a Kennedy Bauxite Concession was granted to investigate the development of these sinkhole deposits. No aluminum has yet been reported to have been commercially produced in Puerto Rico. Permissive tract The source of the clays found in sinkholes of the karst topography is postulated to be weathered Cretaceous andesitic volcanics that lie to the south. This is also the case in Jamaica, which has karst and blanket deposits. The bauxitic clay belt runs east-west along the unconformable contact between Tertiary sedimentary rocks and the underlying Cretaceous complex on the north side of the island. Preliminary sampling across the karst belt south of Florida, Puerto Rico, shows that the bauxitic clays are confined largely to the Lares Limestone along a 3-mi wide strip at the south edge of the karst belt (Hildebrand, 1960). The terrane considered permissive for bauxitic clay is delineated by the surface exposure of the Lares Limestone. Undiscovered deposits The bauxite sampled in sinkholes and analyzed for contaminant material showed the presence of silica, largely attributable to the presence of free quartz. The quartz can be removed through a process of pulping, spiraling, thickening, and dewatering. However, because bauxite is a low-priced commodity, the economic feasibility of the above process would require extensive laboratory testing (Hildebrand, 1960). The mineral resource assessment team felt there is a potential for karst-type bauxite deposits in Puerto Rico. However, because of the large size of deposits in the grade and tonnage model (the smallest deposit is approximately one million tonnes), the assessment team did not estimate the probability of numbers of undiscovered deposits. Any undiscovered deposits present in Puerto Rico would be smaller than those in the grade and tonnage model of Mosier (1986), a conclusion based on the geologic and geomorphic style of occurrence, and the improbability that a large surface deposit of this type would be missed. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 1999 Status: Progress: Complete Maintenance_and_Update_Frequency: None Planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -67.27222325 East_Bounding_Coordinate: -65.58745336 North_Bounding_Coordinate: 18.51798423 South_Bounding_Coordinate: 17.7005999 Keywords: Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: Permissive Terranes Podiform Chromite Copper Skarn Iron Skarn Volcanogenic Mn Kuroko Massive Sulfide Epithermal Qtz-Alunite Au Bauxitic Clay Belt Place: Place_Keyword_Thesaurus: None Place_Keyword: Puerto Rico Access_Constraints: None Use_Constraints: Anyone who uses these data must cite U.S. Geological Survey. These data are not to be used at scales showing more detail than 1:200,000. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Bawiec, Walter J. Contact_Organization: U.S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 954 National Center 12201 Sunrise Valley Drive City: Reston State_or_Province: Virginia Postal_Code: 20192 Country: United States Contact_Voice_Telephone: (703)648-4148 Contact_Facsimile_Telephone: (703)648-6383 Contact_Electronic_Mail_Address: wbawiec@usgs.gov Data_Set_Credit: The permissive terranes for the mineral deposit models of Puerto Rico were drawn by a team of earth scientists and economic geologists familiar with Puerto Rico. They included W.J. Bawiec, R. Alonzo, D.P. Cox, A. Griscom, B.R. Lipin, S.P. Marsh, G.E. McKelvey, N.J Page, J.H. Schellekens. Native_Data_Set_Environment: Windows_NT, 4.0, Intel ARC/INFO version 7.1.1 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: The purpose of this map coverage is to show the spatial distribution of permissive terranes for the following mineral deposit types: Podiform Chromite, Copper/Iron Skarn, Volcanogenic Mn, Kuroko Massive Sulfide, Epithermal Qtz-Alunite Au, and Bauxitic Clay belt. The permissive terranes were drawn based upon the geology, geologic terranes, geochemical anomalies, subsurface geophysical patterns, distance from intrusions, known deposits, and mineral occurrences. The boundaries of these permissive terranes were based upon the agreement of a team of earth scientists, inclusing geologists, geochemists, geophysists, and economic geologists. These boundaries are thought to be accurate based upon the information used in the study. However, as more detailed information becomes available in the future, the shape of the spatial distributions of these mineral deposit types are subject to change. Logical_Consistency_Report: Polygon and chain-node topology present. All polygons have a label and all polygons are closed. Completeness_Report: The delineation of tracts that are permissive for undiscovered mineral deposits of a specific type requires the input and assimilation of geologic information from multiple earth-science disciplines. The preliminary tracts are usually based upon the distribution of permissive host rocks, which may contain known occurrences. Host rocks are assembled into favorable geologic terranes based upon rock type, age, and (or) depositional environment. Geochemical and geophysical data (magnetism, gravity) can be used to either extend or delete parts of these terranes, especially with respect to surficial cover. Geochemical data show the presence of anomalous metallic elements, or indicative pathfinder elements, which provide circumstantial evidence for the presence of metallic minerals. Gravity and magnetism are important in understanding the geometry and extent of subsurface geology. The degree of known exploration is then examined to determine which areas could be considered as having been explored and (or) exhausted on the basis of previous investigations for each deposit type. The resultant permissive tract is the area that remains after elimination of all areas in which the deposit type could not possibly occur. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: The boundaries used to delineate the outlines of the permissive terranes consist of geologic contacts, geologic terranes, distances from intrusions, and geophysical magnetic and gravity boundaries. In some instances, when they follow a geologic contact, they are precisely located from the 1:100,000 scale geologic map; but in other instances, such as following a gradient in a magnetic map or picking a distance from an intrusion, the boundaries are much less precise and only indicate a general location. Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Vector Point_and_Vector_Object_Information: SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Point Point_and_Vector_Object_Count: 83 SDTS_Point_and_Vector_Object_Type: String Point_and_Vector_Object_Count: 6339 SDTS_Point_and_Vector_Object_Type: GT-polygon composed of chains Point_and_Vector_Object_Count: 84 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Polyconic Polyconic: Latitude_of_True_Scale: 18 Longitude_of_Central_Meridian: -67 False_Easting: 0.00000 False_Northing: 0.00000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 0.0354962907731 Ordinate_Resolution: 0.0354962907731 Planar_Distance_Units: Meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 294.98 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: The following ITEMS are found in PERMSKARN.PAT and describe the attributes associated with the coverage PERMSKARN. The ITEMS AREA, PERIMETER, PERMSKARN#, and PERMSKARN-ID are Arc/Info generated and never to be altered. The ITEMS FMATN, COLR, COLR2, and SHADE were created to aid in the development and editing of the coverage. All values found in these items are outdated and no longer useful to the user except for COLR2. COLR2 contains the attribute by which each terrane is colored (see PERMSKARN.AML in AML folder) and can also be used to select by terrane type. The values of COLR2 are: 151 - background; 131 - Volconogenic Mn, Kuroko Massive Sulfide; 2 - Bauxitic Clay Belt; 17 - Podiform Chromite. The values of SHADE, which creates horizontal or diagonal lines, are: 9 - Epithermal Qtz-Alunite AU; 30 - Copper/Iron Skarn. The ITEMS found in PERMSKARN.AAT to attribute arcs are all Arc/info generated. The ITEM NOPLOT attributes arcs that are not to be plotted. The purpose in adding arcs and attributing them so they could not be plotted was to prevent buffer overflow when plotting polygons. In the earlier versions of Arc/Info, polygons were not allowed to have more than 10,000 arcs. > > >PERMSKARN.PAT: > >COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME > 1 AREA 4 12 F 3 > 5 PERIMETER 4 12 F 3 > 9 PERMSKARN# 4 5 B - > 13 PERMSKARN-ID 4 5 B - > 17 FMATN 5 5 C - > 22 COLR 4 4 F 0 > 26 COLR2 4 4 F 0 > 30 SHADE 4 4 F 0 > > >PERMSKARN.AAT: > >COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME > 1 FNODE# 4 5 B - > 5 TNODE# 4 5 B - > 9 LPOLY# 4 5 B - > 13 RPOLY# 4 5 B - > 17 LENGTH 4 12 F 3 > 21 PERMSKARN# 4 5 B - > 25 PERMSKARN-ID 4 5 B - > 29 NOPLOT 4 4 F 0 > > Entity_and_Attribute_Detail_Citation: none Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Information Services Contact_Address: Address_Type: mailing address Address: Box 25286, Denver Federal Center City: Denver State_or_Province: Colorado Postal_Code: 80225-0286 Country: United States Contact_Voice_Telephone: 1-800-USA-MAPS Contact_Electronic_Mail_Address: http://mapping.usgs.gov/esic/esic.html Distribution_Liability: This Compact Disc-Read Only Memory (CD-ROM) publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Although all data and software published on this CD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the U.S. Geological Survey as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials. Graphical map depictions on this disc are intended to be used within the map scale limits applicable to the source data. Although software enables the user to show images on the disc at various scales, the user is cautioned to refer to the source documentation for the appropriate map scale limitations. Metadata_Reference_Information: Metadata_Date: 19991101 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Bawiec, Walter J. Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 954 National Center City: Reston State_or_Province: Virginia Postal_Code: 20192 Country: United States Contact_Voice_Telephone: (703)648-6148 Contact_Facsimile_Telephone: (703)648-6383 Contact_Electronic_Mail_Address: wbawiec@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: Version of June 8, 1994 Metadata_Access_Constraints: none Metadata_Use_Constraints: none