Gravity Prospecting for Chromite Deposits in Camaguey Province, Cuba

Abstract

Detailed gravity surveys were made in Camaguey Province, Cuba, as part of a systematic exploration program conducted by the U. S. Geological Survey on behalf of the General Services Administration to locate deposits of refractory‐grade chromite. During the period August 4, 1954, to April 5, 1956, a total of 41,921 gravity stations were established in nine areas embracing about 11.8 square miles in the Camaguey chromite district. The results of the surveys were used in connection with information obtained in geologic investigations to guide exploratory drilling. Gravimeters with low scale constants were used in making measurements sufficiently accurate to delimit anomalies as small as 0.5 gravity unit. The measurements were made over 20×40 and 30×60 meter grids and at stations 20 and 30 meters apart, respectively, along intermediate traverses in anomalous areas. Gravity differences were determined by single observations at individual stations, observing base stations hourly, and re‐observing a few stations to check drift and accuracy of measurement. About 11 percent of the stations established had to be re‐run because of errors in closure, microseisms, and instrument trouble. A large number of anomalies were found and evaluated according to geology, areal extent, and gravity relief. Depths to disturbing hypothetical bodies were computed to guide drilling. Test drilling of 106 positive anomalies revealed that ten features overlie deposits of chromite and 89 occur over bodies of other dense materials. The other seven anomalies were not explained by materials found in drilling. Core drilling on five of the chromite deposits revealed about 236,000 tons of chromite. An additional estimated 12,000 tons are contained in three deposits which were not blocked out. No estimate was made of the tonnage in two small deposits.

2.5D regularized inversion for the interpretation of residual gravity data by a dipping thin sheet: numerical examples and case studies with an insight on sensitivity and non-uniqueness

“…This gravity profile is associated with the largest chromite deposit found in the province (Davis et al 1957). This prominent profile has a trend of S60 o W to N60 o E and overlies a chromite ore body which contains about 115,000 tons, dips steeply to the southwest, and comes within 3 m of the ground surface (Davis et al 1957).…”

“…This prominent profile has a trend of S60 o W to N60 o E and overlies a chromite ore body which contains about 115,000 tons, dips steeply to the southwest, and comes within 3 m of the ground surface (Davis et al 1957).…”

“…These particular data sets were selected in this research paper for a number of reasons. First, these data sets were generated by buried causative ore bodies, which can resemble thin-sheet models (Davis et al 1957;Grant and West 1965;Siegel et al 1957), the subject of this paper. Second, these data sets were measured from sites with known drilling information; hence, we can compare the numerical results yielded from the inversion against those confirmed from drilling.…”

“…Inverse results Davis et al (1957) carried out detailed gravity surveys in the Camaguey Province, Cuba, for chromite exploration. Residual gravity maps were collected over various spatially distributed ore bodies for determining approximately the quantity of chromite in any deposits found.…”

“…This profile is taken normal to the strike of the residual gravity anomaly shown in the middle part of Fig. 6 of Davis et al (1957).…”