Show waldemar lindgren Lind bren on the vie geology of this district in a report published in economic geology by waldemar lindgren of 0 the united states geological survey on processes ot of and enrichment in the tintic gintic mining district he declares that the camp was once a huge volcanic pile some 2 feet higher than it Is today the report has been reprinted from economic geology and a number of the untie operators are receiving them with the compliments of the author the report la Is short and Is part of the observations made by mr lindgren in making a resurvey of the district for the geological survey this work was begun by him in 19 1911 11 assisted by dr G F loughlin Loughl ln and the district was again revisited in 1914 this report will shortly be issued by the survey which Is now tar far behind in its publications mrs lindgren a deductions as to the geology of the camp are decidedly interesting he lie says that the vey has established a more detailed subdivision ot of formations and mem here hers and the presence of the cam brian and ordovician have been definitely proven previous to the volcanic activity ol 01 the middle tertiary the sediment tary formations were folded into a large syncline with steep westerly and flat easterly limb this syncline was subsequently broken and faulted by numerous fractures extending in various directions during the early or middle part of the tertiary the paleozoic forma eions were broken by a series of violent volcanic eruptions the ig leous rocks comprise a thick series of rhyolite flows succeeded by an ex series of and andes ites at one time a huge volcanic pile must have been standing on the present site of tintic gintic into the lime stone and into the volcanic flows was then introduced introduce ras as the last phase of volcanic activity a great mass of which now occupies the southern part of the district and which cuts oft off the sedimentary rocks along an east west line this erea of is about one mile wide from east to west and about two miles long from the occur ance of high up on the flanks of the range the conclusion Is drawn that this granular rock consolidated at no considerable depth below the surface in places probably less than 1 feet the volcanic pile was soon attacked by erosion and large masses of the covering lava were eroded so that these are no longer present in the central part of the dis brict on oil the northern side how ever a great rhyolite flow still covers the ground north of the town of eureka while the ande sites and lat ites remain in the ridges south of the district and on the long slopes toward goshen valley fhe rhe vertical thickness of the rocks removed by erosion probably did not exceed 2 00 feet in general he says that the ore de posits in tintic gintic are contained in the in the lime stones and dolomites north of the are ea the he veins in the are declared to be r rarely rely rich while the deposits in the sediments have yield ed the great bulk of the ore and are due to replacement the width of the ore zones vary from a few feet toyoto to 60 to feet the zones of deposition are da de dared to show in marked degree a variation of maeral association a ap p patently parent ly dependent upon distance from the intrusive As the erosion is believed to have been between 1 and 2 feet aboe abone the present surface and mm min ing developments now reach a great est depth of 2 feet so that the lowest parts of the deposits must hav been formed from 3 to 4 feet below the surface according to the elevation of tl e shaft and broad ly speaking is found feet above the level of utah lake or at an ele of 4 feet some detail work has also been done on the various minerals found in the district which victor C heikes of the survey declares has produced in gold silver lead copper and zinc from 1869 to the end of 1913 |