INIS-mf—9688

URANIUM DIVISION

PNOC ENERGY COMPANIES BLDG. PNPC COMPLEX, MERRITT ROAD, FORT BONIFACIO, METRO fl I 1980 • • vlSE»mFIC ILfBftAR) ».»*

URANIUM GEOCHEMICAL EXPLORATION ( IN NORTHWESTERN nCT13198* I 1 GABRIEL SANTOS, JR. AND LOURDES FERNANDEZ I PHILIPPINE ATOMIC ENERGY COMMISSION AND I MANUEL OGENA AND GEORGE TAULI PNOC-EDC . • • . I I ABS1HACT

I A reconnaissani.. geochemical stream water and sediment survey • which was conducted in northwestern Luzon was able to detect '•. (10) uranium anomalous areas. These anomalous areas are located I along a north-south trending zone of Miocene marine elastics and sedimentary rocks with tuffaceous sediment intercalations. In § general, northwest Luzon has low radioactivity except for two anoira- - lous areas which have 3 to 6 times background radioactivity. Radon anomalies occur in sparsely scattered locations.

The anomalous zones appear to be related to major north-s-. . . I faults and secondary northeast-southwest trending structures.

.• - Geochemical corr jlations between uranium and other elements such as copper, lead, zinc, manganese, silver, cobalt, .and nickeJ I are generally very poor. I I I

_ It is suggested that the intermediate intrusives iv the • Cordillera Central are possibly the principal source rodcs of W uranium in the survey area. r r

i i

i i i i i i i - 2 - i I I URANIUM GEOCHEMICAL EXPLORATION IN NORTHWESTERN LUZON •

BY I GABRIEL SANTOS, JR. AND LOURDES FERNANDEZ I PHILIPPINE ATOMIC ENERGY (EMISSION AND I MANUEL OGENA AND GEORGE -TAULI PNOC-EDC I I INTRODUCTION

I The first indication of possible uranium occurrences in • Solsona, , Northwestern Luzon was detected by an airborne gamma spectrometer survey which was carried out by I Huntings Geophysics, Lixl. of London in 1954. Subsequent ground follow-up geologic and radiometric surveys in Solsona area fo< I nearly two decades failed to pinpoint the possible location of m the airborne radiometric anomaly. i

* In 1978, it was decided that the northwestern Luzon region including Ilocos Norte, and be explored systematical- II ly. for uranium using geochemical methods. The exploration was undertaken jointly by PNOC-EDC and PAEC, with the latter providing I I personnel, technical planning and analytical support. The work - which was essentially an orientation survey was covered by a non- I I I I exlusive one year exploration permit from the Bureau of Energy I Development (BED), Ministry of Energy and includes all lands in | Luzon bounded on the South by latitude 16°45' West and on the East by longitude 120o52'30" North and elsewhere by the Luzon T Sea. i The objectives of the orientation survey were to determine the best sampling medium which could be used effectively in a more F intensive reconnaissance survey for pinpointing the presence of i possible uranium mineralization; and to locate the airborne radio- metric anomaly which was detected in 1954. The results of the I orientation survey were submitted as a report to BED in 1979. The results of the survey indicated that the stream water as well as } the -80 mesh size fraction of the stream sediments were the best . sampling media in the geochemical survey. Radon measurements in ' stTeam waters would also be useful in the evaluation of the geoche- I mical results. Heavy mineral concentrates were considered less effective in outlining uranium geochemical anomalies than the | -80 mesh stream sediments fractions.

* The main purpose oe this paper is to describe the results I of the reconnaissance geochemical exploration for uranium in northwestern Luzon. I

I - 2 - I 1 I

LOCATION I The survey area is located in the northwestern part of • Luzon as shown in Fig. 1. The expanded non-exclusive exploration '"» permit area is bounded in the east by longitude 121°00' North and in the south by latitude 16°20' West; and elsewhere by the Luzon I Sea. The area of interest covers.the provinces of Ilocos Norte, most of Abra, Ilocos Sur, Eenguet, and some sections of I Mountain Province. Accessibility to the project area is moderately '-_ easy owing to the presence of well-maintained national and provincial • roads as well as the i iierous barrio roads and trails. The main I road, Route 3 to the area from Manila runs along the western cc. . line passing through San Fernando (269 km.) in La Union> I (408 km.) in Ilocos Sur and City (486 km.) in Ilocos Norte. The eastern part of the area could be reached via Route 2 up to Bontoc (396 km. from Manila).

TOPOGRAPHY

The project area forms a part of the western limb of the Cordillera Central Mountain Range down to the lowlands and the coastal area of northwestern Luzon. The mountain range and the *. " ids are parallel »o each other in the north-south direction. About 30% of the area is characterized by high relief elevations ranging from 1,500 to 2,000 m. and moderate relief with 1,000 m.

- 3 - GEOLOQY OF NORTHERN LUZON

\ VIZCAYA \t

METASEOIMEMf TERRAIN V * ^ «f

fit. I. LOCATION OF NORTHWESTERN LUZON SURVEY AREA, SHOWINS PHYSIOCRAPHIC AND STRUCTURAL PROVINCES OF NORTHEASTERN LUZON, AFTER OURKEE AND PEDERSOS, ltd. I I elevation on the average. Several high peaks can be found, notably, I Mt. Cavitian (2568 m.) and Mt. Clawit (2668 m.) both in Mountain | Province; Mt. Buguias (2841 m.) in Ifugao and Mt. Pulog (2928 m.) in , the highest peak within the project area. I I DRAINAGE The survey area is drained by five major river systems aiii I their numerous tributaries. These drainage systems include Laoag • and Rivers in Ilocos Norte; in Abra; and Amburaya' River in La Union and in Benguet. They all discharge their I loads westward into the Luzon Sea (). Chico River on the east side discharges its load into the larger I which drains the entire Cagayan Valley. About halfway of the down- '. stream reaches of the Laoag and Vintar Rivers, the water gradient* ' are low and the rivers are braided with wide flood plains. These rivers have large discharge specially during the wet 1 months from June to October. The rest of the year is dry. Accord- ing to Fernandez and Pulanco (1964), the Ilocos Coastline is an } emerging shoreline and that most of the stream has probably main- tained its original course.

Geologic structures generally control the trends of the major river systems and their numerous tributaries provide excellent

•p - 4 - opportunities suitable for conducting regional geochemical stream sediment surveys.

GENERAL GEOLOGY

Previous works on the geology of northwestern Luzon include

those of Corby et. al. (1951)f Irving (1952), Durkee and Pederson (1961) and others. The fieological Map of the Philippines compiled in 1963 by the Bureau of Mines is a good source of the geology of northern Luzon. The paper of Fernandez and Pulanco (1964) whid: describes the regional geology of M Luzon as well as the recent geological survey report under the Philippine-Japan Project (1979) are excellent sources of geological information regarding the project area.

The survey area includes more than half of the Cordillera Central and most of the Coastal Folded-Belt, Vigan-Abra High and Laoag Embayment of Durkee and Pederson (1961). Fig. 1 shows the physiographic and structural provinces of northern Luzon and Fig. 2 shows the geological map of northwestern Luzon.

The Cordillera is composed principally of Eocene to Earl) Miocene bedded volcanic rocks and thick post-Middle Miocene sedimen- tary rocks. These rocks have been intruded by Early to Middle Miocene quartzdiorite rocks which resulted in a geanticlinical

- 5 - I

mountain range, trending in the north-south orientation. The major structural lines ulso have a similar direction and in some places, these fault zones are loci of gold and copper mineraliz; V::ns. [Durkee and Pederson (1961); Fernandez and Pulanco (1964); RP- Japan Project Report (1979).3

The Coastal Folded Belt which is located west of Cordillera Central is a region of highly folded and faulted sedimentary rocks trending in the north-south direction. The belt is charac- terized by north-south trendLng anticlines and major faults as well as northeast-southwest secondary fault systems.

The Vigan-Abra high is a topographic high which is composed of thick meta-sedimen'*'1 and bedded volcanics with mafic intrusives. The eastern boundary and probably the western margin are controlled by north trending faults, Durkee and Pederson (1961).

North of the Vigan-Abra high is the Laoag embayment filled with Miocene-Pliocene sediments. Pre-Jurassic crystalline schists and quartzites as well as Cretaceous ultramafic rocks are found in the northern part, in the Suyo area, Ilocos Norte. The older rocks may possibly represent remnants of a continental landmass. A major fault trending in the northwest-southeast direction extei. i.."i, from the Cordillera separates the Miocene limestone of the" northern part of the Laoag embayment.

- 6 - FIELD AND LABORATORY TECHNIQUES

The sampling pattern was designed to collect one set of sample of stream sediment and water from each sampling site, from a stream draining 20-30 sq. km. area. During the orientation phase, sampling was done along easily accessible tributaries. Figure 3 shows the location of the sampling sites.

At each sampling site, 1-2 kg. of stream sediment was collected. (Mineral coi :ntrates were also obtained by panning the sediments using a wooden pan during the orientation survey.) Two stream water samples contained in 150-ml. plastic bottles were initially collected. Radicmetric measurement was also taken around the sampling area. The radon content of the stream water was determined as counts per minute employing a portable radon detector RD 200 and a degassing system model RDU 200 manufactured by EDA Instruments Inc. (See Figs. 4 and 5)

The stream sediment samples were sun-dried and prepared in the field and the minus 80 mesh fraction was separated and sent to the laboratory. During the orientation survey, the following size fractions were separated; -35 m, +80 m, -80 m, +200 m. The mineral concentrates were treated by removing the magnetic minerals and the non-magnetic fraction was separated from the siliceous gangue utilizing heavy media separation.

- 7 - Uranium analyses were done at the PAEC laboratory using the method developed by Smith and Lynch (1969) employing a Jarrell- Ash model 26-000 fluorometer. The sensitivity or limit of detection of the method was about 0.2 ppm and 0.1 ppb uranium for the stream sediment and waters, respectively.

Other trace elements such as copper, lead, zinc, manganese, silver, cobalt and nickel were determined in the uranium leach solution by atomic absorption spectrometry. The limit,of detection for copper, lead, cobalt and nickel was 4 ppm; for zinc and manga- nese, 2 ppm and for si. sr, 0.4 ppm.

- 8 - RESULTS AND DISCUSSION

A total of 522 sampling sets consisting of

stream sediments and water were collected over the 15,000 sq. km.

survey area. Die results of the uranium and trace element analyses

of stream sediments and waters were treated statistically to

determine the background and threshold values using the method

of Lepeltier (1969).

On the basis of geology, the rock units were grouped under sedimentary and volcan. . rocks; and intrusive. Table 2 shows the average background and threshold values of uranium, copper, lea.., zinc, manganese, silver, cobalt and nickel.

From Table 2 it can be seen that the uranium background values is below the detection limit of 0.2 ppm (ND) for the method.

The background and threshold values for uranium in stream waters are ND and 0.55 ppb, respectively.

Uranium in Stream Sediments and Waters

Shown in Figs. 6 and 7 are the uranium distributions in stream sediments and wattvs, respectively. At least one large contiguous stream sediment anomaly zone was outlined in -

Badoc area, Ilocos Norte. Other lesser anomalies were indicated in -, Ilocos Sur; Burgos, I.locos Norte and Malibcong-

Ikmin River area, Abra. - 9 - Table 2 : Average Background and Threshold Values of Uranium and Selected Elements in Geological Units in Northwestern Luzon.

Parts Per Million

U Cu Pb Zn >4i Ag Co Ni Bkgd Th Bkgd Th Bkgd Th Bkgd Th Bkgd Th Bkgd Th Bkgd Th Bkgd Th

Sedimentary and Volcanic Rocks N D 0.4 32 220 17 60 60 200 630 1350 0.4 2 21 47 12 120 No. of Samples 451(3) 452(2) 454 454 454 454 454 454

Intrusive rocks N D 0.4 45 250 15 ]10 57 580 430 2400 0.35 1.55 IS 40 9 41 No. of Samples 68 64 68 68 68 68 68 68 Composite Units N D 0.4 40 330 16 45 60 220 600 1350 0.36 1.65 21 47 9 105 (Sed., Vol- canic § Intrusive) No. of Samples 519(2) 517(4) 521 521 521 521 521 521

Note: Bkgd - Background Th - Threshold ( ) - Excln^ High • •iues Isolated anomalies were also found in , Ilocos Norte and Sabangan-Bontoc, Benguet. Uranium value as high as 1.4 ppm was recorded in Sabangan.

One large stream water anomalous zone was delineated in -, Ilocos Norte. Smaller anomalies were indicated in Burgos, Ilocos Norte. Several isolated anomalies in .- , Ilocos Sur, Bacnotan and Naguilan, La Union were also outlined. A high 7 ppb U found in Sinait, as well as those obtained in San Fernando and Caba maybe due to sea water contamination. However, these anomalies would still warrant a brief closer examination.

In general, there is a very good correlation between the stream sediments and water uranium anomalies in Batac, Burgos and Pagudpud areas in Iloco; Norte and Sinait, Ilocos Sur.

Radon Radioactivity Measurements

Shown in Figures 4 and 5 are the radon and radioactivity maps obtained during the orientation phase of the survey. Four widely separated point anomalies were delineated, three,in Ilocos Norte (Burgos, Sta. Praxedes and Nueva Era) and one in Cabugao, Ilocos Sur. The highest radon measurement (45.3 cpm) was recorded in Burgos.

- 11 - Six anomalous radioactivities corresponding to 3 times background were measured in Dingras-ffercos-Batac, Ilocos Norte and Malibcong, Abra. Exploration Model GRS-101A and Me Phar TV-5 portable scintillometers were used to take the radioactivity- readings.

The uranium anomalies appear to be preferentially situated in areas underlain by Miocene marine elastics overlain with tuff- aceous sediments. In Batac-Badoc area, two major northeast trending faults probably control the extent of the uranium dispersion. Inter- secting north-south an^ northeast trending moderate faults apparently contribute in localizing the uranium anomalies in Cabugao.

In the Malibcong-Ikmin River area, the uranium anomalies are closely related to the Miocene quartzdiorite rocks and northea- southwest structures. The Narvacan-Candon and Bacnotan uranium anomaly in waters are related to strongly folded tuffaceous sand- stone shale.

It may be noted that the uranium anomalies are predominant! distributed in the Coastal Folded Belt and Laoag Embayment. It is believed that the possible principal uranium source rocks are the intrusive intermediate rocks, mainly quartdiorite found in Cordillera Central. The Cordon syenite complex (Baquiran, 1975, Khittel, 1979), located in the southeastern part of the Cordillera is also a possible source rock of uranium in the project area.

- 12 - 1

Si The summary of .significant correlating geochemical and ij geophysical anomalies in Northwestern Luzon are presented in Table 3. The anomalous areas are arranged in their order of \.. .^i- ij tial for finding possible uranium mineralization.

fi It is interesting to note that the regional background and threshold values for copper and zinc obtained in the present work 1 is partly similar to the RP-Japan Project (Phase 1), 1979 as shown m in Table 4.

Table 4. Comparison of Regional Background and Threshold Values Obtained on the RP- ( Japan Project (Phase 1) 1979, and the Present Work. | Cu (ppm) Zn (ppm) BackBa - Thres- • Back- Thres- ground hold ground hold I Present Work 40 33050 I RP-Japan Project 32 125 58 120

It can be seen in Table 4 that even though the geochemical extraction procedures used were different, the results obtained for the regional background are rather closely similar. The thresholds correspond to abscissas at 2.5% probability for Cu anc Zn. The large differences in the threshold values are probably due to the variety of rock units covered in the present womk as compared to the RP-Japan Project. (Please see Fig. 8.)

- 13 - Table 3 : Summary of Correlating Geochemical and Geophysical Anomalies in Northwestern Luzon

Area Uranium in Uranium in Radon Radioactivity Stream Sediments Stream Waters (cpm) (cps) Geology

1. Batac-Badoc Large Large - 3 x background Marine Clastics (N2 to N3)

2. Cabugao- Sinait ^derate Moderate Small Background Marine Clastics CM2 - %) 3. Maiibcong- Up to 8 x Quartz diorite Ikmin River Small clusters Background Background background (Upper Miocene)

4. Narvacan- Candon Background Large Background Background Marine Clastics (N2 " %)

5. Bacnotan- San Gabriel Small Moderate - Background Marine Clastics (N2)

6. Pagudpud Small Small Background Background Marine Clastics 0*2)

7. Burgos Small Small Small Background Marine Clastics, limes tor" (N2) Uranium and thu Trace , -ments

The other trace elements such as copper, lead, zinc, manganese, silver, cobalt and nickel were also determined in the stream sediments to investigate whether any of these could serve as possible indicator or pathfinder element for uranium.

In general there is poor negative (inverse) correlation between uranium and the selected trace.elements except nickel. Shown in Table 4 is thr correlation coefficient between uranium and the other elements.

Table 4. Correl- ion Coefficient between Uranium and l . trace elements.

ELEMENTS CORRELATION COEFFICIENT U vs. Cu - 0.06 U vs. Pb - 0.05 U vs. Zn - 0.08 U vs. Mn - 0.13 U vs. Ag - 0.03 U vs. Co - 0.10 U vs. Ni • 0.05

Shown in Fig. 8" is the recommended areas for follow-up semi- detailed or intermedia/?- density sairjpling surveys. Although the

- IS - predominant uranium anomalies are widely distributed in marine I elastics and sedimentary rocks, it is felt that other possible uranium occurrences, such as vein-type deposits may not be detected I by low density sampling. I I I I I I I I I I I

- 16 - CONCLUSION

The reconnaissance stream sediment and waters geochemical survey which was conducted over a 15,000 sq. km. region in.north- western Luzon has outlined ten (10) uranium geochemical anomalous areas. These anomalous zones are mainly located in marine elastics and sedimentary rocks vith tuffaceous sediments as well as in quartz diorite.

The radioactivity in two anomalous areas is between 3-6 times background. Radon anomalies occur in sparsely scattered points.

The anomalous zones are associated with major north-south faults and secondary northeast-southwest structures.

Geochemical correlations between uranium and the trace elements, copper, lead, zinc, manganese, silver, cobalt and nickel are generally very poor.

It is suggested that the quartz diorite and silicic tuffs in the Cordillera Central as well as the Cordon syenite complex are possibly the principal source rocks of uranium in the survey area.

- 17 - Ml Unit. ENERGY .

r»rrr

ACKNOWLEDGEMENTS

The authors wish to acknowledge the valuable assistance and encouragement of Dr. M. C. Berbano, PNOC-EDC.

The chejnical analyses were performed by the staff of the Nuclear Fuels Research Division, Department of A'uclear Technology and Engineering of PAEC. The staff also assisted in the statistical confutation of the geochemical Oata. REFERENCES

Baquiran, G.B., 1975, "Notes on the Geology and Exploration of of the Karian Copper Deposits, Cordon^ Isabela", Jour. Ceol. Soc. Phil., Vol. 29, pp. 1-12. Corby, G.W., et. al., 1951, "Geology and Oil Possibilities of the Philippines," Rep. of the Philippines Dept. Agric. and Nat. Res., Tech. Bull. 21 363 pp. > Fernandez, J.C. and Pulanco, D., 1964, "Preliminary Report on the Reconnaissance Geology of Northwestern Luzon, Philippines", 1 :reau of Mines. Irving, E.M., 1952, "Geological History and Petroleum Possibili •.., . of the Philippines," Bull. Amer. Assoc. Petrol. Geol., Vol. 36, pp. 437 - 76. Knittel, U., 1979, "Petrography and Origin of the Syenite from Cordon, Isabela, Vol. 33, pp. 34 - 42. Lepeltier, C., 1969, A simplified statistical treatment of geochemical data by graphical representation: Econ. Geol., v. 64, pp. 538-550. Neville, A. and Kennedy, J., "Basic Statistical Methods for Engineers and Scientists", Pennsylvania: International Textbook Co., 1964. Report on Geological Survey of Northwestern Luzon (Phase.1), Sept. 1979, Bureau of Mines - Japan International Cooperation Agency, 124 pp. Smith, A.Y. and Lunch J.J., 1969, Field and Laboratory Methods used by the Geological Survey of Canada in GeochemicaJ Surveys, No. 11. Jranium in Soil, Stream Sediment and Water. Surv. Can. Paper 69-40. P-U <.'8SiJ.it

^ 3 1

URANIUM GEOCHEMICAL EXPLORATION IN NORTHWESTERN LUZON

URANIUM DIVISION

PNOC ENERGY COMPANIES BLDG. PNPC COMPLEX, MERRITT ROAD, FORT BONIFACIO, PHILIPPINES SECTION 1 !

ND1 ND BATONG MT. MINEXtCu)

Mufi ku/un \ LEPA

45'

I2O°I5'

45* 30' ' 2O°I5' SCALE I : 250.0C

KM 5 4 3 2 '0

J20°00 JO l2l°00 30

3270

3269

3168 • 3268

, 2967) -3067 3167 • 3267 34. i i i ; . i -- I20°00* 30 I2I°OO- 3p

INDEX MAP SECTION 10

URANIUM EXPLORATION RECONNAISSANCE GEOCHEM! NORTHWESTERN

ORIENTATION MAP

ARCHIVE NO.. REPO I2I°OO" DATE : SANTO SEPT 1980 a T

I2I°OO' -3275^

250.0C SCALE I : 250,000

KM 5 « 5 2 10

5,0 i2i°oo' so iaa«oo'

- -3475—so 375 3274 3274 -3374 • 3474 ~i • • [ -

3'73 3373 •3473' 3272

3272 • 3372 -3472: 3 3271

3271 3371 • 3471 \ 3270 3270 3370 347O

3269 ^n- 3269 33P.J -3^6 V -Jo' 3ZF8 3168 ' 3268 • 336B^,346a- i«°oo'l I ' 3267 34r 2967J -3067 3167 • 3267 3467 ; I ; .1 • -s IZO°QO' 50 rZI°OO' 30' I22°OO'

INDEX MAP

15"

URANIUM EXPLORATION PROJECT RECONNAISSANCE GEOCHEMICAL SURVEY NORTHWESTERN LUZON

ORIENTATION RADON MAP I SECTION 11

REPO SANTO' DATE : ARCHIVE NO.: REPORT BY: FIGURE NO.: a T 121 °00' SANTOS, OGENA 4 SEPT. 1980 a TAULI

0 I2I°OO' IS '" r" ^- xi i \ \ 11 / \ - -3475 I2O°I5' 30' 45

45 I2O°I5' 30'

Pagudpud

15 Bangui Burgos 15 ; \ / .'

9o30T 10

10 / /

15

15 10 PASUOUIN 20 20 Tomdagai./ 20.. "

20 20 -J BA ARRA 10 15'- 10 20 VINTAR

D LAOAG CITY

20 10 San Nicolas Piddi 10

35

Oingras So sona

30 -

ATAQ_ Marcoi SECTION 1 | N 25 / /

\ Cur nmao

/ , I SEPT. 1980 a TAU

121 "00'

ORIENTATION RADI MAP

Pagudpud LEGEND

•I9°3O' LOCATION OF STREAM

AND WATER SAMPLE

OPERATING MINE

X MINERAL DEPOSITS A

OCCURRENCES

PROVINCIAL CAPITAL

20 SCINTILLOMETER R

COUNTS PER SECOr

BACKGROUND COUNTS -

THRESHOLD COUNTS - 30

NUMBER OF MEASUREMENT \

• ANOMALOUS RAD: (

V tr IECTION 2 / a i AU itn.

I2I°OO' RAD) ORIENTATION RADIOMETRIC P MAP ND- LEGEND

OF STREAM

MINE A OPERATING MINE

EPOSITS A X .__ MINERAL DEPOSITS AND CES OCCURRENCES

L CAPITAL • PROVINCIAL CAPITAL

METER R 20 SCINTILLOMETER READING >ER SECOf-

COUNTS PER SECOND (CPM) UNTS -

BACKGROUND COUNTS - 10 cpm 4TS - 30

THRESHOLD COUNTS -30 cpm UREMEN'i

NUMBER OF MEASUREMENTS- 196 )US RAD1.

• AMOMALOUS RADIOACTIVITY ^

\

45

30

SECTION ( SECTION 2

IS \8L

-V,o/o ,

~~-~. I) . \ Lagangilong ngilang

SECTION 5