Geology topics

Herbert Samuel Jacobson

Publications and source records attributed to Herbert Samuel Jacobson.

6 recordsLinked to original sources

USGS1972

Geology of the Karakuz iron mine and vicinity, Hekimhan district, Turkey

The Karakuz mine area located 17 km northwest of the town of Hekimhan in central Turkey was investigated as part of the MTA-USGS Mineral Exploration and Training Project. The fieldwork consisted of geologic mapping supplemented by a magnetometer survey and trenching. The Karakuz mine has been in operation for the past ten years and produced 170,000 tons of iron ore in 1968. The rocks of the area are mafic and ultramafic rocks, limestone, and trachyte intruded by syenite (Cretaceous?), and an Eocene post-intrusive(?) sedimentary sequence. The mafic rocks and the trachyte were altered and mineralized as a result of the syenite(?) intrusion. The mafic rocks were metasomatically altered and the trachyte was partly silicified. Iron oxide minerals are present in the trachyte as irregular replacement bodies and veins and in the metasomatized mafic rocks as veins. A major structure which channeled the intrusion and iron oxide minerals is believed to underlie the area. Steeply dipping fractures trending about N. 80 ° E. and N. 10 ° W. acted as controls on the mineralization. A series of recent post-mineral faults, erosion, and weathering have produced the present landscape. The principal iron deposit is at the Karakuz mine where a central high-grade core is surrounded by low-grade material. The changes in grade reflect changes in the degree of replacement of the trachyte by iron oxides. The minerals are dominantly hematite, but magnetite and limonite are also present. East and west of the mine there are a series of low-grade replacement bodies and veins as well as iron boulder fields. A series of magnetic anomalies are present along the entire 4 km length of the area. The anomalies are interpreted to be caused principally by magnetite-bearing surface boulders and near-surface veins. Only a small part of some of the anomalies may be due to buried deposits of magnetite. The Karakuz mine has a remaining productive life of about 3 years unless low-grade material is mined. This may be feasible if the low-grade is concentrated at the mine. 'Additional exploration of the area is recommended with emphasis on a gravity survey and diamond drilling. Also, an investigation to determine the technical and economic feasibility of utilizing the low-grade material is recommended.

Turkey↗

USGS1972

Aeromagnetic interpretation and mineral investigations in the Ezine, Canakkale-Karabiga, Marmara, and Kapidag areas of northwestern Turkey

Aeromagnetic surveys and mineral investigations are planned or in progress in ten areas of northwestern Turkey (fig. 1). This report reviews results obtained from August 1967 to January 1, 1968, through aeromagnetic interpretation and field investigations in four of the areas (Areas 2, 3,4, and 5). Aeromagnetic interpretation identified 27 prominent anomalies, 17 of which were checked in the field. The majority of these anomalies were found to be caused by minor amounts of magnetite in igneous rocks, including granite stocks, mafic flows, and mafic dikes. Other anomalies are caused by magnetite in metamorphic rocks or by topographic effects. However, massive magnetite boulders were observed in three adjoining localities (Anomalies E2, E3, and E4, fig. 2) in area 2, and magnetite partly replacing a limestone boulder was found in area 3 (Anomaly CK3, fig. 3). Further study of these magnetite exposures is planned. In addition, two iron prospects and one lead prospect were briefly examined. All the prospects were considered small and not worthy of further study at this time.

Open-File Report↗

USGS1972

Aeromagnetic interpretation and mineral investigations in the Bolu, Canakkale-Karabiga, Demirkoy, Ezine, and Orhaneli areas of northwestern Turkey in 1968

This report reviews progress made during 1968 in the continuing Joint Haden Tetkik ve Arama Enstitusu (MSA)-U. S. Geological Survey (USGS) Mineral Exploration and Training Project, Subproject 2. Subproject 2 is concerned with aeromagnetic interpretation of MTA's aeromagnetic surveys, and ground investigations of selected aeromagnetic anomalies. This report includes new aeromagnetic maps for the Bolu, Canakkale-Karabiga, Demirkoy, and Orhaneli areas and reviews ground investigations in five areas. Activities for each area are sunmarized below: 1. Bolu area: The aeromagnetic map shows two belts of anomalies related to regional magnetite-bearing formations and a group of discrete anomalies, some of which may reflect significant concentrations of magnetite. To date three of these anomalies have been checked on the ground and at one a metamorphic rock containing 14 percent magnetite was observed. 2. Canakkale-Karabiga area: Ground checks were made of six aeromagnetic anomalies. At one locality (Cakirly-Koyu) 6 km south of Nazmara Sea a small magnetite deposit was found. The magnetic anomaly over the area is 150 meters long, and about 3 meters deep in the center of the anomaly exposed massive magnetite boulders. 3. Demirkoy area: The aeromagnetic map shows only one significant anomaly which was checked on the ground and found to be caused by minor magnetite at an intrusive contact. 4. Ezine area: A ground survey of 4.5 sq km area was made where magnetite boulders are locally present on the surface. No significant magnetic anomaly or iron mineralization were found. 5. Orhaneli area: The aeromagnetic map o# the area showed regional magnetic anomaly patterns related to magnetite in mafic intrusives, ultramafic rocks, and mafic flow rocks. In addition 16 localized anomalies were identified. Most of these anomalies were checked on the ground but no significant iron deposits were found. The largest deposit found was a one-meter wide magnetite vein. During the 1969 field season further investigation of anomalies in the Bolu and Orhaneli areas is planned.

Open-File Report↗

USGS1972

Geology of the Eymir iron mine, Edremit, Turkey

The Eymir mine near Edremit on Turkey's Aegean coast (long 27?30'E.,1at 39?36'N.) was investigated as part of the Maden Tetkik ve Arama Enstitutsu (MTA)-U. S. Geological Survey (USGS) mineral exploration and training project, for the purpose of increasing the known mineral reserves. Geologic mapping of the mine area indicates that hematite is restricted to argillized, silicified, and pyritized dacite and possibly andesite. Hematite is present as massive replacements, impregnations, disseminations, and fracture fillings. Most of the upper part of the iron deposit consists of a breccia composed mostly of silicifiled dacite fragments in a hematite matrix. The iron deposit was apparently formed in three steps: 1. Argillation, silicification, and pyritization of the andesitic lava and dacite units as a result of a regional intrusion. 2. Intrusion of the Dere Oren dacite stock, with associated faulting, fracturing, and breccia formation at the surface. 3. Deposition of hematite by oxidation of pyrite, and transfer of iron via fractures and faults by hydrothermal or meteoric fluids. The Eymir iron deposit is a blanketlike deposit on the crest of the Sivritepe-Eymir ridge. It is 1300 meters long, 80 to 450 meters wide, and has an average thickness of 18.6 meters. Drill holes in the deposit show the iron content to range from 32.0 to 57.6 percent, and to average 46.5 percent. Most of the gangue is silica, and an arsenic impurity averaging 0.39 percent is present. Most of the deposit cannot be utilized as iron ore because of low iron content, high silica content, and high arsenic content. Ore-dressing tests have shown that it is feasible to concentrate the low-grade material, producing a concentrate having increased iron content and reduced silica content. Tests have shown also that the arsenic content of the ore can be reduced substantially by sintering. Further tests and economic feasibility studies are necessary to determine whether an economic marketable iron ore can be produced. If such studies indicate the technical and economic feasibility of utilizing all the Eymir iron deposit, detailed additional studies are recommended including: 1. A detailed drilling and sampling program to include 60 drill holes averaging 40 meters in depth and detailed sampling of mine dumps. 2. Pilot-plant testing of concentration and sintering procedures. 3. A detailed pre-investment economic feasibility study.

Open-File Report↗

USGS1972

Geology of the Karamadazi iron mine, Kayseri Province, Turkey

A one-week underground geologic mapping program was conducted at the Karamadazi iron mine in order to describe the mine geology and obtain data that might help in the understanding of other similar deposits in Turkey. The Karamadazi mine is in a contact-metasomatic magnetite deposit 65 km. south-southwest of Kayseri, Turkey. The mine currently produces as much as 60,000 tons of iron ore per year containing approximately 60 percent iron. The mine is at a contact between granite and Permian and Carboniferous limestones. The limestones have been metamorphosed to marble and skarn, and the granite has a syenitic contact phase. The skarn has been partly replaced by massive magnetite ore and by minor quartz, calcite, and pyrite gangue. The main magnetite deposits are in a skarn zone 350-meters long by 20 to 70 meters wide that contains an estimated 40 percent magnetite in very irregular, steeply dipping ore bodies. Additional ore may be present under alluvial cover east of the mine; a magnetic survey of this area is recommended.

Kayseri Province↗

USGS1967

Mineral investigations in northeastern Thailand

Fifty-eight mineral prospects of base metals (copper, lead, zinc), iron, manganese, gold, limestone (cement grade), barite, gypsum, and salt were investigated by geological, geophysical, and geochemical surveys, and by pitting, exploratory mining, and diamond drilling from January 1963 to May 1966. Fifty-six of the prospects are in the Loei-Chiengkarn area of northeast Thailand where regional geological, aeromagnetic, and geochemical studies were also performed; the other two prospects are on the Khorat Plateau. The base-metal prospects are in volcanic or carbonate rocks. Four prospects have been tested by diamond drilling; disseminated copper deposits were found at two prospects and local lead-zinc mineralization at the other two.The two copper deposits have estimated proven and probable reserves of 16million tons containing about 1 percent copper, and possible reserves of 62 million tons. The iron prospects are mostly metasomatic, at contacts of granodiorite with sedimentary and volcanic rocks. Four of the iron prospects were tested by diamond drilling; proven, probable, and possible reserves of about 27million tons containing 52 percent iron were developed predominantly in two deposits. Twelve manganese and two gold prospects were investigated, but all are small or low grade. Nonmetallic deposits of barite, gypsum, and limestone (cement grade) were examined in the Loei-Chiengkarn area, and salt was studied at Chaiyaphum. Reserves of approximately 5.5 million tons of barite, half a million tons of gypsum, 12 million tons of limestone (cement grade), and 2,000 million tons of salt were estimated to be present. Economic development of these deposits must await recommended economic feasibility studies and additional geological work, including diamond drilling.

Open-File Report↗