Bailey Willis submits fieldnotes on Mt. Province and Abra

Title

Creator

Willis, Bailey

Language

English

Source

The American Chamber of Commerce Journal Volume XVII (Issue No.4) April 1937

Year

1937

Rights

In Copyright - Educational Use Permitted

Fulltext

April, 1937 THE AMERICAN CHAMBER OF COMMERCE JOURNAL 19 Bailey Willis Submits Fieldnotes on Mt. Province and Abra Read discerningly, these notes give many a clue to men asked to take a stake in northern mining ventures “In view of the public interest in mining it appears desirable to state clearly that the object of our studies is not primarily to search for possible mineral districts. It is on the contrary to learn from the rocks and the features of the landscape the successive changes in form, extent, and character of the islands during geologic periods that cover the last twenty million years of their history, Under the action of forces which very slowly, but very surely lift mountain ranges, the founda tions of the archipelago are dislocated and displaced. Vol canoes and earthquakes are incidental results. Air and water cause exposed rock masses to decay, forming soil, and rivers, carve deep canyons in the rising ranges. He who knows rocks and who under stands how they bend and fracture under enormous pressures may deduce from their present structure the nature of the forces that have acted on them. And this knowledge is important to the mining engineer whose ores occur in fissures opened during the movements of the mountains. “As scientists geologists seek to dis cover the structure of the mountain ranges and to explain why they are mountain ranges. As mining engineers they may apply their knowledge of the structure to the systematic develop ment of a mine. “The Willis party is engaged in studying the structure and the later geologic history of the Philippine Ar chipelago. A better understanding of the force's that have created the islands may result from that study. And that knowledge may find application in the national development of mineral resources. We are not pioneers. A number of eminent Filipino, American, and European geologists have* preceded us. We build on their work and hope to make some advance for the bent fit of science and the Philippine Com monwealth. “Our first problem has been to investigate the structure of the central mountain range that extends from Baguio to the northern coast and lies between the Cagayan and Abra valleys. Geologists recognize that it has been rising higher and higher above sea level during several million years and presumably is still being pushed up. During the uplifting the rivers have sunk their channels deeply, but they have not been able to keep pace with the elevation and consequently have steep gradients. “Has the mountain range which is roughly 80 kms. across from East to West and 300 kms. long from South to North, been raistd as a whole or has it broken into blocks. If the latter be true rocks in the larger zones of fracture should be exjtremcly ciushcd, they would be easily washed away and a river would have grown along each zone of displacement or faulting. “I thought it probable that the Agno Valley was eroded on such a fault zone and if so that the faulting might have some relation to the mineral deposits of the Benguct District. But examination of the valley shows that there is no major fault zone on which it could have been sunk and the inference has been abandoned. “A similar inference regarding a possible major fault ex tending north from Trinidad, between Tublay and Kapangan and along the eastern side of the range that is marked by Mts. Binmaca and Guirayan has proved unfounded. “Further north examination of the country between Mts. Data, Bontoc, and Banaue has also failed to discover any evidence of great faults, such as might have developed in the central range. “On the other hand there is evidence that the range has been arched up. Looking north from some high point that commands a distant sky line one may see smooth in a flat the curve, have been we imagine :-e an older surface, which was a continuous flat. It now appears arched, like the top of a loaf of bread. The curved surface is that which would be produced by squeez ing the deep foundations of the range shortening the east-west width at the bottom while the uplift of the surface would result from the rise of the solid rock thus squeezed up. When com pressed in this manner rocks shear into small blocks that slipped past one another in adjusting themselves to the general change of form. It is readily observed all along the mountain road that the rocks are thus broken up and have been squeezed past one another. “We thus have good reason to con clude that the rise of the actual central mountain range is due to pressure from east and west in the foundations of the mountains: that an arched effect has resulted from the change of form, and that this occurred through intense in ternal shearing, instead of by faulting on a large scale. “This conclusion has a bearing upon the probable continuity of mineralized veins. They are not likely to be wide or conti nuously aligned across the direction of pressure. They may be wider or more continuous if they lie across a direction of elongation. But whatever their orientation they are liable to end abruptly in the intricate maze of fractures in the crushed rock. “From this examination of the central range of northern Luzon we turnccT to study the western flank, west of the Abra Valley. That valley has been described by Warren Smith in his pioneer work, as a fault valley. His observation was correct. It is defined by a fault, by a fault of the type known as an overthrust. The effect is easily observed. Coming from Bontoc to Cervantes, looking west, one is faced by the great height of Mt. Malaya (2352 meters) and other high peaks of the range west of the Abra River. Ravines in the face of the mountain are very shallow, they are very young, much younger than the valley of the Abra. Their youth {Please turn to page 23) April, 1937 THE AMERICAN CHAMBER OF COMMERCE JOURNAL 23 main vein of the Macawiwili MiningCompany, whose properties adjoin those of the Benguet-Itogon Goldfields group extends into 'he property. The General Management, Company also advised of this possibility. There are no so-called e scrow shares set aside for claim owners. The com pany owns in its own right nine of the claims, and will be put to no expense in connection with the acquisition of the other 43 claims. There art' 550 shares subscribed at no par value, while the sales value of the issue has been placed at 1*1,000 per share. The pres ent subscribers will relinquish part of their shares to the claim owners foi the 43 claims, and will also relinquish part of their shares to wipe out th*' 1*65,000 that has been spent in develop ment thus far. Th*' claims will be turned over to the company without charge, the idea behind all of this being to start the new company out as a going concern. The Benguet-Itogon property has just been inspected by Robert Dure, geo logist and mining engineer, a member of the staff of R. Y. Hanlon & Co. Mr. Duce is a University of Colorado man with ten years’ field experience since graduation. He took samples during his inspection from Tunnel No. 3, one from the Valentin vein. The average value of th*' samples was 1*115 new valuation. He recommends driving on the Valentin vein at least to 200 feet in all, and stripping the ore to ascertain consistent assay values over this dis tance; and to raise on the vein in No. 3 tunnel with the same objective in mind. Bailey Willis Submits. . . (Continued from page 19} is due to the recent development of the moun tain face, which has been pushed up several thou sand feet. At the same time the whole mountain block has been tilted toward the west. The move ment which can thus raise and tilt a mountain block is much like that of one hand over the other; the left hand, for instance, palm up and fingers slightly bent, the right hand laid on it palm down and pushed forward. The right hand is the mountain block, and the surface of contact of the two palms is the surface of the thrust or overthrust. But the Abra overthrust originates beneath the China Sea and the displacement of the upper block is an eastward movement of several kilometers at least. “The Abra overthrust is a more superficial effect of the pressure that are squeezing the foundations of the central range. “A series of three parallel overthrusts was observed in driving down the west coast between Tagudin and Bauang. They trend No. 20 to 30 degrees W. Each one defines a valley and lies along the northeastern base of a low range of hills. One runs from Balaoan to Santol and beyond. Another of much greater extent passes near Bacnotan on the coast, past Disdis on the Naguilian road, imderlies Mount Santo Tomas, and is identified below the Zigzag on the Kennon Road in Bued canyon. It is a thrust of very considerable magnitude and is the cause of the dominant height of Mt. Santo Tomas, over looking Baguio. A third, very minor thrust forms the valley between San Juan and Naguilian. This series is pushed up from the direction of west by south and appears to be independ ent of the east-west pressures farther north. “It is desirable to note that the forces which thus appear to have affected the mountain region of northern Luzon are deduced from effects in the existing topography. The forces are now active and have been so during very recent AN INVITATION TO ALL MINING EXECUTIVES • You are cordially invited to investigate the highquality and competitive prices of the products of HUMB0LT-DEUTZM0T0REN A. G. BALL MILLS GYRATORY CRUSHERS JAW CRUSHERS ORE SAMPLERS VACUUM PUMPS BELT CONVEYERS CRUSHING ROLLS FILTERS CLASSIFIERS PLACER MACHINES Complete Cyanide & Flotation Plants Sole Representatives Philippine Engineering Corporation Plaza Sta. Cruz MANILA, P. I. Phone 2-23-05 geologic periods. It is generally true that such forces have acted from time to time, with greater or less intensity and have produced similar results. Fissures appropriate for vein forma tions may thus have originated at any time in the past, may have been mineralized at any later time, and may have dislocated in any subsequent movement, 'l'his makes the task of the mining geologist, in trying to unravel the intricacies of vein structure, a very difficult one and taxes the skill of the most experienced. “This progress report is written in the field, while the studies are in progress and is to be regarded as a preliminary account only.” IN RESPONDING TO ADVERTISEMENTS PLEASE MENTION THE AMERICAN CHAMBER OF COMMERCE JOURNAL

pages

19, 23

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