estimation of gold resources and reserves in overburden and bedrock, with a section on An initial economic model for gold ...... dimensional models of the geologic units and gold- mineralized zones .... Average densities (in g/cm3 of samples of various rock ...... data, so that (1) different people could enter data on a variety of ...
An Interagency Report prepared by the U.S. Geological Survey, Saudi Arabian Mission for the Ministry of Petroleum and Mineral Resources Kingdom of Saudi Arabia The work on which this report was based was performed in accordance with a cooperative agreement between the U.S. Geological Survey and the Ministry of Petroleum and Mineral Resources. This report is a product ofDGMR work programs during the years 1410 to 1412 and is listed as Subproject 4.2.4.2.01. The information contained in this report is a product of . Ministry work; if the information herein is used in any form, either quoted or paraphrased, this report should be properly cited using the full serial number, the authors' names, and the year of publication. The correct citation for this report is: Christian, R.P., Bookstrom, A.A., Aruscavage, P.J., and Marasigan, M.S., 1992, Hamd.ah gold prospect, Kingdom of Saudi Arabia: Models for estimation of gold resources and reserves: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-92-8, 27 p., 5 appendices [bound separately).
Tiris report was technically reviewed by P.R. Johnson and K.A. Sargent. The report has been edited and reviewed for conformity with U.S. Geological Survey publication standards. Product names used in this report are for descriptive purposes and in no way imply endorsement by the Geological Survey. The area of study covered by this report is shown on the index map below.
.....
,,. ~...-_ _•..~.-_ _....J•OK"'
-------..
1:20-000
---- -.x;...._.,ot,.,.
....._.,
I '
-N~.
Index map of the Arabian Peninsula showing area of study for this report REPORT DISTRIBUTION: Distribution of this report is limited. Ten copies have been transmitted to the Office of the Deputy Minister, Directorate General of Mineral Resources
Computer-generated model of the Hamdah gold prospect area--by Ralph
P. Christian
HAMDAHGOLD PROSPECT This report is part of a series of five reports on the exploration, metallurgical testing, and preliminary economic analysis of the Harndah gold prospect. These reports cover the period beginning January 1, 1990 and ending May 31, 1992. The reports in this series are: (1) Albert, T.E., and Carten, R.B., 1992, Hamdah Gold Prospect, Kingdom of Saudi Arabia: Results of laboratory test work on the metailurgical response of ore to heap-leach processing: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-92-5, 26 p., 2 appendices. . (2) Cassiday, M.W., and Carten, R.B., 1992, Hamdah gold prospect, Kingdom of Saudi Arabia: Results of the pilot heap-leach test: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR92-7, 26 p., 7 appendices. (3) Bookstrom, A.A., Jannadi, E.H., Bosch, P S., Walker, B.M., Christian, R.P., Carten, R.B., Komi, M.B., and Ben Talib, Majid, 1992, Hamdah gold prospect, Kingdom of Saudi Arabia: Results of geological and geochemical exploration for gold in bedrock and overburden: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-92-6, 72 p., 7 plts., 3 appendices [Appendix C bound separately]. (4) Christian, R.P., Bookstrom, A.A., Aruscavage, P:J., and Marasigan, M.S., 1992, Hamdah gold prospect, Kingdom of Saudi Arabia: Models for estimation of gold resources and reserves: Saudi Arabian Directorate General ofMineral Resources Technical Report USGS-TR-92-8, 27 p., 5 appendices [bound separately]. (5) Christian, R.P. and Bookstrom, A.A., 1992, Hamdah gold prospect, Kingdom of Saudi Arabia: Summary of estimation of gold resources and reserves in overburden and bedrock, with a section on An initial economic model for gold recovery from overburden and bedrock, by J.J. Cape, and K.A. Saib: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-92-4, 13 p.
iii
TABLE OF CONTENTS ABSTRACT ........................................................................................................................... 1 INTRODUCTION .................................................................................................................. Geographic Location ....................................................................................................... Geologic Setting .............................................................................................................. Surface Topography ........................................................................................................ Location Coordinates .................................................. :................................................... Grid Samples ................................................................................................................... Drill holes ... .. .. .. .. .. .. .... .. . .. .. . .. ... .. . ...... .. .. ...... .. ... .............. .. . ... ... ......... ...... .... . ... ......... .. .. .. .. Trench Samples ............................................................................................................... Overburden ............................................................................................................... Bedrock .................................................................................................................... Pit Samples ..................................................................................................................... Overburden and bedrock ...........................................................................................
3 3 3 3 3 3 6 6 6 6 6 6
ANALYTICAL 11ETHODS ................................................................................................... 6 Density Determination Methods ...................................................................................... 6 Assay Methods ................................................................................................................ 8 SUMMARY STATISTICS ..................................................................................................... . All Samples .............................................................................................................. :·...... Grid Samples ................................................................................................................... Trench Samples ............ :.................................................................................................. Drill Holes ...................................................................................................................... Pit Samples .....................................................................................................................
9 9 9 9 9 9
DATABASE REQUIRE11ENTS ............................................................................................ 13 Digital Data Files ............................................................................................................. 13 Steps to Model Ore Reserves ... 1........................................................................................ 14 Discussion ....................................................................................................................... 16 Results ............................................................................................................................ 19 Gold resources and reserves ...................................................................................... 19 Hamdah gold resources and reserves ........................................................................ 19 . Overburden-hosted gold resources and reserves ........................................................ 19 Bedrock-hosted gold resources and reserves ............................................................. 20 CONCLUSION ...................................................................................................................... 21 RECOMMENDATIONS ........................................................................................................ 25 ACKNOWLEDGEMENTS ..................................................................................................... 25 DATA STORAGE ................................................................................................................. 25 Data File ......................................................................................................................... 25 Mineral Occurrence Documentation System .................................. .' ................................. 25 REFERENCES ...................................................................................................................... 26
v
FIGURES 1. Location map of the Hamdah gold prospect ................. , ................................................... 4 2. Base map showing grid, topography, trenches, drill boles, pits, and cross sections at Hamdah gold prospect ................................................................................................. 5 3. Plan view and cross section through drill boles on line A-AA .......................................... 7 4. Plan view and cross section through drill boles on line B-BB ...... :.................................... 8 5. Plan showing overburden blocks having >0.03 ppm gold and zero isopach contour of overburden thickness ................................................................................................... 17 6. Semi-variogram for overburden gold analyses ............................ ." ..................................... 18 7, Semi-variogram for bedrock gold analyses ....................................................................... 18 8. Distribution of tonnage and grade in overburden ore .. ;..................................................... 21 9. Distribution of tonnage and grade in bedrock ore ......................... ,............................ :...... 22
TABLES 1. Summary statistics for data in chemically analyzed samples ............................................ 9 2. Summary statistics for HGO & HGB samples ................................................. :................ 10 3. Summary statistics for HTO & HTB samples ................................................................... 11 4. Summary statistics for HR.O & HR.B samples ........................................ .'.......................... 12
5. Summary statistics for HPO samples ................................................................................ 13 6 . Overburden estimate for gold: inverse-distance vs kriging ............................................... 16 7. Summary of estimates of presently known gold resources and reserves of Hamdah .......... 20 8. Overall total overburden gold-resource estimates ............................................................. 22 9. Overburden gold-resource estimates by quadrant... ........................................................... 23 10. Correlation of overburden at grams of gold per kriged block vs grams of gold per inverse block .................................................................................................. :.......... 24
APPENDICES (BOUND SEPARATELY) APPENDIX A --1ECHBASE FILES ....................................................................... A 1-A 295 (1) Listing of Table of collars ............................................................................. A 1-A 96 (2) Listing of Table of assays ............... :.............................................................. A 97-A 270 (3) Listing of Table of lithology .......................................................................... A 271-A 288 (4) Listing of Table of deviated ...................... :................................................... A 289-A 290 (5) Listing of Table of ore ................................................................................... A 291-A 295 APPENDIX B --LOTUS FILES .............................................................................. B (1) Listing ofHGOCOLL.PRN ........................................................................... B (2) Listing ofHGOASSAY.PRN ......................................................................... B (3) Listing ofHGBCOLL.PRN ...................................... : .................................... B (4) Listing of HGBASSAY .PRN ......................................................................... B (5) Listing of HTOCOLL.PRN ........................................................................... B (6) Listing ofHTOASSAY.PRN ......................................................................... B (7) Listing of HR.BCOLL.PRN ..................... ._._ ......................... :....................... B
vi
1-B 279 1-B 31 32-B 62 63-B 68 69-B 7 4 7 5-B 89 90-B 116 117-B 118
APPENDICES (continued) APPENDIX B --LOTUS FILES (continued) (8) Listing ofHRBASSAY.PRN ........................................................................... B 119-B 192 (9) Listing ofHRBLITH.PRN............................................................................... B 193-B 209 (10) Listing ofHRBDEVI.PRN ............................................................................ B 210 (11) Listing ofHROCOLL.PRN ........................................................................... B 211 (12) Listing ofHROASSAY.PRN ......................................................................... B 212-B 215 (13) Listing ofHROLITH.PRN ............................................................................ B 216-B 217 (14) Listing ofHPOCOLL.PRN ............................................................................ B 218-B 219 (15) Listing ofHPOASSAY.PRN ......................................................................... B 220-B 222 (16) Listing ofHTBCOLL.PRN............................................................................ B 223-B 224 (17) Listing ofHTBASSAY.PRN ......................................................................... B 245-B 267 (18) Listing ofDUMCOLL.PRN .......................................................................... B 268-B 279 APPENDIX C -- TECHBASE FILES ......................................................................... C 1-C 8 (1) TECHBASE database structure ....................................................................... C 1-C 2 (2) TECHBASE description of database variables ................................................ C 3-C 6 (3) TECHBASE calculated fields with equations ................................................. C 7 -C 8 APPENDIXD -- TECHBASERUNLOGFILES ........................................................ D 1-D 81 (1) TECHBASE runlog for program POSTER ...................................................... D 1-D 10 (2) TECHBASE runlog for program SECTION .................................................... D 11-D 35 (3) TECHBASE runlog for program HISTO ......................................................... D 3 6-D 3 8 (4) TECHBASE mnlog for prograni VARIO ........................................................ D 39-D 44 (5) TECHBASE runlog for program RANDCONT ............................................... D 45 (6) TECHBASE runlog for program GRlDCONT ................................................. D 46-D 48 (7) TECHBASE runlog for program MINQ .......................................................... D 49-D 50 (8) TECHBASE runlog for program :LOCATE , .................................................... D 51-D 53 (9) TECHBASE runlog for program INVERSE .................................................... D 54-D 56 (10) TECHBASE runlog for program KRIGE ................... .'................................... D 57-D 58 (11) TECHBASE runlog for program REPORT ................................................... D 59-D 81 APPENDIXE -- TECHBASE MISCELLANEOUS FILES ........................................ E (1) TECHBASE fomi.at files ................................................................................. E (2) TECHBASE calculate files ............................................................................. E (3) TECHBASE polygon files ............................................................................... E
vii
1-E 15 1-E 10 11-E 14 15
-------,.~------,-----------------
'u
HAMDAH GOLD PROSPECT, KINGDOM OF SAUDI ARABIA
BY .
'
RALPH P. CHRISTIAN, ARTHUR A. BOOKSTROM, PHILIP J. ARUS'CAVAGE, AND MARCO S. MARASIGAN
ABSTRACT Computer models were developed to . estimate the overburden and bedrock-hosted gold deposits of the Hamdah gold prospect. The prospect is located in the southern part of the Arabian Shield and includes the largest group of ancient mine working in southern Saudi Arabia. The database contains 9,509 gold assays on samples, including 1,975 samples from a 1.5 km2 surface geochemical grid, 4,672 samples from 104 drill holes (aggregate total depth 3,840 m), 2,740 samples from 6 km of trenches, and 128 samples from 54 pits. Krige and inverse-distance estimators were used to calculate block models for overburden-hosted ore bodies of the Hamdah prospect. Experimental semivariograms for overburden-hosted ore indicate a strong nugget effect (large random variability). A nugget semi-variogram with a sill of gamma=20 was fitted ~o the experimental semi-variogram and used as the ba~rs for kriging. The inverse-distance estimator,_ wrth weighting power of 1.5, gave grade-to~~age estimates that closely match those obtained by kng:mg. Overburden-hosted gold resources of the Hamdah prospect are estimated as 2.86 tonnes of gold in 1 360 000 tonnes of overburden averaging 2.25 g/t (at a' 0.3' g/t cutoff). These are classified as m_e~sured resources. At a 0.75 g/t cutoff grade (a mmrmum_ probably required for economic p~oduction) the overburden-hosted ore reserves are estrmated as 2.63
tonnes of gold in 911,500 tonnes of ore, averaging 2.89 g/t. These are classified as proven resources. Ore grades of bedrock-hosted gold deposits of the Hamdah prospect are e;.._iremely variable over short distances, and current drill hole spacing (::::: 17.5 m) is too wide to permit calculation of interpretable semivariograms. Closer spaced grid drilling will be required to allow geostatistical ore-reserve estimation. Preliminary estimation was done by the inversedistance method, using a weighting power of 1.5. Results are similar to those of a previous estimation, done by contouring averages of ore-grade intercepts (Bosch and others, 1989). Bedrock-hosted gold resources of the Hamdah prospect are estimated as 1.72 tonnes of gold in 303,000 tonnes of ore, averaging 5.68 g/t at a 1 g/t cutoff. These are classified as indicated resources. At an 8 g/t cutoff (a minimum probably required for economic production) the bedrock-hosted reserves are estimated as 1.12 tonnes of gold in 59,700 tonnes of ore, averaging 18.8 g/t. These are classified as probable reserves. The total of measured (overburden-hosted) and indicated (bedrock-hosted) gold resources of the Hamdah prospect is 4.58 tonnes_ The total of proven (overburden-hosted) and probable (bedrock-hosted) gold reserves of the Hamdah prospect is 3. 75 tonnes.
N
·--...._
• .INTRODUCTION GEOGRAPHIC LOCATION
GRID SAMPLES
The Harndah gold prospect is iocated in the southwestern part of the Kingdom of Saudi Arabia, approximately 75 km south-southeast of the town of Tathlith (Fig. 1). The prospect includes an area of about 1.5 km2 centered on the coordinates latitude 18°54'45" and longitude 43°40'45". The Hamdah group of ancient mines is located on the southeast margin of a group of rocky hills, name~Jibal al Hajar (Bookstrom and others, 1992).
Rock-chip samples were collected at 25 m intervals along the grid. The label for each grid location is a unique 6 digit RASS (Rock Analysis Storage System) sample number. A total of 1,975 samples were collected. For the 1,657 overburden samples (HGO, Hamdah Grid Overburden) approximately 10 em of surficial material was removed, and three shovels full of sample (1 each at a 120° angle and approximately 50 em from the surveyed marker flag) were collected at a depths between 10 em and 40 em. Each sample weighed approximately 2 kg.
GEOLOGIC SETTING Geologically, the Hamdah gold prospect lies in the southeastern Neoproterozoic Arabian Shield where it is hosted by greenstone and serpe11tinite of the _Tathlith terrane. The prospect consists of three types of gold deposits (1) bedrock-hosted deposits, associated with dioritic and aplitic intrusions, emplaced along a thrust fault at the base of a serpentinite nappe; (2) ancient mine dumps, containing fine gold not recovered by ancient panning methods; and (3) · alluvial placers, containing fine-grained gold eroded from bedrock deposits and ancient mine dumps (Bookstrom and others, 1992).
Three-hundred-seventeen (317) of the grid points were located on bedrock outcrop. For the 317 grid bedrock samples (HGB, Harndah Grid Bedrock) chip samples were taken at the same angle and distance from the marker flag. Each sample weighed approximately 2 kg. Only one mixed overburden and bedrock sample was taken. This mixed sample was not tagged either HGO or HGB. The data for this sample was used for statistics for all samples, but was not included in either overburden or bedrock orereserve estimations.
DRILLHOLES
SURFACE TOPOGRAPHY
A total of 104 core holes were drilled at the Harndah prospect. Seventy-six (76) holes were collared into bedrock and 28 holes were drilled in overburden. Drilling depths for the 76 bedrock holes ranged from 14.90 meters to 163.35 meters, with an average depth of 47.60 meters. Drilling depths for the 28 overburden holes ranged from 6.10 meters to 18.00 meters, with an average depth of 10.33 meters. Locational coordinates (eastings, northings, and collar elevations) were obtained using standard surveying techniques and are reported using the local coordinate system.
Surface topography at the Hamdah prospect varies from a low of 1340.17 meters above sea level in the southwest corner of the area of study to 1380.50 meters at the top of Jabal Harndah, the highest hill, in the northeast section of the study area.
LOCATION COORDINATES When the field activities began at the Hamdah prospect in 1989, a local coordinate system given the reference point 0,0, located southwest of the current study area, was established. A 1000 m2 grid was established and was oriented 26°NE. Previous geologic maps indicated geologic structure subparallel and perpendicular to this orientation. After preliminary results were obtained, the area of study was expanded to the south to include the south alluvial fan. All coordinate data are expressed in meters easting and northing of the 0,0 reference point (Fig. 2).
Earlier drill holes (by Helaby and Worl, 1980) were labeled FIR-1, FIR-2, etc., after Hajrah, as the area was then termed. In trying to keep as close to the original labeling system as possible, the system was modified by the addition of the year to drill-hole labels in 1989 (FIR-89-1, FIR-89-2, etc.). All drill holes, with the exception of HR-89-4, which was drilled 60° off horizontal, were drilled vertically. (Bosch and others, 1989, section B-BB).
3
I
FIGURE 1.--Location map of the Hamdah gold prospect.
4
""
""~···~····~
~~~~;:lE-~-;=1-~;;~--·~·;~ Kurtosis
f
40.98
Summary statistics for HTB (~amdah Trench Bedrock) samples .1'
Gold
Silver
Arsenic
Copper
;
11
TABLE 4--Summary statistics for HRO and HRB samples
Summary statistics for HRO (Hamdah Drill hole Overburden) samples
Gold
Silver
Arsenic
Copper
Number of 303 ......... samnles ...................................... o-:54......... 'Me·a~
0
0
0
.
1 .........................................................................................._. ................. .
~~:~.:~~~~hl~~-1~~~~-~::~~~~:~:~l·:~:~~~~~:~.:::~::I§§..::~::::::[::::~:~:::::.::~:::::~:::::::.:.:~.l:~:~~::~:~:::~::::::::::~::::::~~: .:::::~::::::.:~::.:::::~~:::~~:.:.:::: Mode
0.03
Kurtosis
207.01
·
Summary statistics for HRB (Hamdah Drill hole Bedrock) samples
Gold Number of
Silver
4368
Copper
Arsenic
4363
. 3390
·
3390
..........~.~-T..P..I.~~...................................:........................................................................................................................... Mean
I
0.50
0.24
I
117.28
47.68
:::::::::::.~:t.:~ :~: : : : : : : 1T: : : : ~: : : : : :~JF: ~: :J: :~: :_:_: : : : : ~ :~l: : :~: :_r: : : : : : : : :~ :~:~ : : : : : : J: : : : : : : :~ :~ :~: : : : : :
. . . . .~~~fa~ne;~----- ......................4.~~-~~........+. . . . . . . . .~._.~-~. . . . . . . . .s.49~-~:.Q~........+. . . . .42i~. -~J..........
::::::::::0~~!!:6~:62::.::::::: ::::::::::::::~JI~~:::::::I:::::::::::::::~~Ag:::::::~ :::::::::::~~§g::::::~::::::I:::::::JI~Q:~:::::::::::::: Minimum
0.00
0.00
0.00
0.00
::::::::::~~~~:~~i::::::::::r:::::::::j:~1.;J:r::::::: :::::::::::::;~r~~:::::::::l.::::::::::~:~~~::;:;:_::::::: : : : : : :~:~:~:~;:;.;:_: : : . . . . . . ~t~0~~~rs. . _. . .lL. . . . . . . . . . .:&·H. . . . . :&·~i--. . . . . ll. . . . . . . . . . . . . . . . .~~~-i-. . . . . +~~ J....................
J._.............................
....
....................................... .................................... 1" ........................................................................ 1" ....................................
Kurtosis
147 4.62
1
1689.67
12
38.42
133.24
TABLE 5--Summary statistics for HPO samples
Summary statistics for HPO (Hamdah Pit) samples
Gold Number of samples
128
Silver
128
Arsenic
'I
Copper
128
128
~=-~~~~~~~:~~~:=·=~==~~~~~~~~~=~~--~~~~I~~-~~~~~~~~- -.-~~~~-~~~:.·.-~~~--~If·~:-~~~~--~--~--~~:·::=-~~~~---.-~~]~-~~~::::. -.-~::::~:·::::::·~~-]!.~~~~~~~~
..........r\1c:;cr8.................. ...................:r9·a ......... .................. o:o6......................... 4.6................................30.............. .
::::::::::~H;}~~~;::::.:=::: ::::::::::::::=:::~:1~.::::::=: :~:.::::::::::::::I:~9:::::::J::.:::::::::::=::§~::§E::::::: ::::::.::::::=::~:Q;:Q~::::.::::~ 33.47 905 .........Variance M'axfmu·n;..........................45:·o0' ...........................0.65 9.:6·6····· .. ·· .............7499 ei6o .............................246 ................ ......... M'in·rn;·u·n;.............................o:o9............................ 6·_·6·s········· ...................0................................_,.5............... . :::::::::~~-~:~:~~:=:::.:.:.:.:~:::.: .:::::::::::::::.:~I~.I::::::: ::.:.:::::::::::::::.I§I:::::::: .:::::::::::::~9.:9.:::::::.:.~~:::: ~.:::::::::=~:?I~:::::.::=::::
........._g_~_E?.f:..Y.~!.: ......... ............. J.9.§:.~.?. ......................?~-~-:?~......... ................ §g._??..........................?.:'!:~~.........
error 7.65 2.66 ..........Std. s.i 4.57 t of gold
> 3.75 t of gold
21
Overburden Ore
3000
r--------------------------------------measured resource
3000
"'0
0
0)
2500
2500
"'0 Q)
c
. .. .. . . . .. .. . . ... ... .................... .................... .................... .................... . . . . ........ .. . . . . . . ... ........ . ........ . ..... ··-· ...........
"(0
•••••••••
-+-'
•
c 0
(.)
0
2000
0
0
•••••••••
0
••••••••••
•
•
••
•
•
•
•
•
•
•
0
••••••
0
•••••••
••••••••••••
0
0
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•
•
•
0
••• • ••••
•••••
••••••••••••••
C/)
0
••••
•••••• 0
••••••••••••••••
•••••
0
0
2000
••
E
ctl ,.....
0)
0
:52 ctl
-+-'
1500
1500
0
I-
1000 0
. 250
500
750
1 000
1250
1000 1500
Thousands of tonnes of ore FIGURE B.-Distribution of tonnage and grade in overburden ore based on different cutoff grades. Assigned cutoff grade is shown below each point. The average grade at each cutoff is shown above the point. (Average grade is rounded to nearest first decimal place.)
bodies of the Hamdah prospect. Experimental semivariograms for overburden-hosted ore indicate a strong nugget effect (large random variability). A nugget serrii-variogram with a sill (and nugget effect) of gamma=20 was fitted to the experimental semivariogram and used as the basis for kriging. The inverse-distance estimator, with weighting power of 1.5,_ gave grade-tonnage estimates that closely match those obtained by kriging (correlation coefficient ~ 0.97 significant at > 99 percent) See Table 10 for correlation coefficients, pair counts, and significance.
Separate models have to be used for each type of ore body. The bedrock-hosted ore at Hamdah is too variable to apply ·meaningful semi-variograms to predict the input for kriging estimators. Based on the results of the inverse-distance and kriging overburden models for the Hamdah gold prospect, a value of 1.5 power was used to predict the· reserve for the bedrockhosted ore. Krige and inverse-distance estimators were used to calculate block models for overburden-hosted ore-
22
•
TABLE 8.--0verall total overburden gold resource estimates Cutoff (g/t)
Grade (g/t) ·
Tons ore
Grams gold
..........9.}............~:.9.~..........J!~.?.Q. .QQ.9. ................ ~. .?.~.9.t9.9.Q ........ ..........9-::L... ........?.~~L.....__J,.?~.Q.!.Q.Q.9____. . ................?&!.Q&Q9.. . . . . . .........9.:.?. ..... ........?.:~.?............ .!!.1?.9.t9..9.9...... ............?.l?.Q!.QQ.9........ ......... .9.:~...... .......~:.?.~..... ......J.!.9.~.9. .QQ.9................. ?.. ?. 1.9.!.9.9.9......... .........9.:.!.............?.:~.!... .............~~.?.t.9.9.9. .................?.!~.?.9.. .9.9. 9........ 2.97 877,000 2,600,000 ........-o0.8. .9. . . _·-·. -·3:1"3 . . . . . . . .-.. . .s.17.:oo""o .......l.......... -..2:' 55a·:aoo....... :-:-:-:-:-:-.:·J·:t-:-:-·-:
-: :-:-:-:-:~;-~-~:-:-·-:-: ·:· ·:·.:.·:·:·:·J1}: ~-~:~-:-:-:-:J:-·-:-:-:·:~-:-.-:·I~·~t~ ~-:-:-:-.·-: ~
...........1:?_............~.:?Z.................?.Z~99 g_au_pr_k_b_obb g_au_pr_i_b_obb >99 na
Southwest Block Pearson Correlation Coefficients
Southeast Block Pearson Correlation Coefficients
g_au_pr_k_b_obb g_au_pr_i_b_obb g_au_pr_k_b_obb 1. 0.9865 g_au_pr_i_b_obb 0.9865 1.
g_au_pr_k_b_obb g_au_pr_i_b_obb 1. 0.9847 g_au_pr_k_b_obb g_au_pr_i_b_obb 0.9847 1.
Pearson Pair Counts
Pearson Pair Counts
g_au_pr_k_b_obb g_au_pr_i_b_obb g_au_pr_k_b_obb 38201 38201 g_au_pr_i_b_obb 38201 38201
g_au_pr_k_b_obb g_au_pr_i_b_obb g_au_pr_k_b_obb 30411 30411 g_au_pr_i_b_obb 30411 30411
Significant at percent
Significant atpercent
g_au_pr_k_b_obb g_au_pr_i_t:i_obb g_au_pr_k_b_obb na >99 g_au_pr_i_b_obb >99 na
g_au_pr_k_b_obb g_au_pr_i_b_obb g_au_pr_k_b_obb na >99 g_au_pr_i_b_obb >99 na
South Center Block Pearson Correlation Coefficients g_au_pr_k_b_obb g_au_pr_i_b_obb g_au_pr_k_b_obb 1. 0.9693 g_au_pr_i_b_obb 0.9693 1. Pearson Pair Counts g_au_pr_k_b_obb g_au_pr_i_b_obb . g_au_pr_k_b_obb 18099 18099 g_au_pr_i_b_obb 18099 18099 Significant at percent g_au_pr_k_b_obb g_au_pr_i_b_obb na >99 g_au_pr_k_b_obb g_au_pr_i_b_obb >99 na
25
indicate that the HBr method gave significantly lower gold assays than the· FA and CN methods in 50 percent of the samples tested. The overall average of FA assays was 142 percent of the overall average of HBr assays, and the overall average of CN assays was 136 percent of overall average of HBr assays. This suggests that the resource and reserve estimates given here, which are based on assays the HBr methods, are conservative, and may represent only about 70 percent of the true amount.
Drill-hole spacing on the geostatistical cross (now l7 .5 m) should be tightened until interpretable semivariogranis are achieved. This will indicate how close the northeast ore zone should be grid-drilled in order to upgrade the probable reserve to a proven reserve. Future assaying should be done by fire assay (FA) and/or cyanide leach (CN) methods. The FA method gives the most reliable results for total contained gold, which is important to know for recovery monitoring. The CN method most closely approximates the recommended recovery method and is therefore the most relevant for determining the amount of recoverable gold. Results of check assaying of 24 samples by BBr, CN, and FA methods (Appendix A) .
When estimating using the krige. algorithm the optional field for estimation variance should be used. The estimation variance is a measure of how well each estimated point is known, based on the variogram.
gratefully acknowledged for the thousands of chemical analyses made at the mobile laboratory site and in Jeddah. The critical assistance of technical specialists is acknowledged, particularly Mir Amjad Hussain, Saeed M. Liban, and Bienvenido R. Gabriel. The encouragement of H.E. Dr. Ibrahim A. Khaberi, Deputy Minister for Mineral Resources and Dr. Mohammed Asa'ad Tawfiq, Assistant Deputy Ministry for Mineral Exploration, was greatly appreciated.
This work could not have been accomplished without the help of a great many people. We would specifically like to acknowledge Richard B. Carten, who lept us focused on our task; geologists Bruce M. Walker, Paul S. Bosch, Eyad H. Jannadi, Majid Ben Talib, and Peter R. Johnson, who helped plan, map, sample, log core and perform numerous other geologic tasks at the Hamdah site and in the office. Adel Hakim and the staff of the DGMRJUSGS Analytical Laboratory are
DATA STORAGE DATA FILE
MINERAL OCCURRENCE DOCUMENTATION SYSTEM
Miscellaneous data for this report, including planning, scheduling, and purchasing logs, are stored as part of Data File USGS~DF-10-7 in the Jeddah office of the U.S. Geological Survey Saudi Arabian Mission.
The Mineral Occurrence Documentation System (MODS) was updated to reflect this report. The Hamdah prospect is MODS Number 0619.
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REFEREN®ES.,· Bookstrom, A.A., Jannadi, E.H., Bosch, P S., Walker, B.M., Christian, R.P., Carten, R.B., Komi, M.B., and Ben Talib, Majid, 1992, Hamdah gold prospect, Kingdom of Saudi Arabia: Results of geological and geochemical exploration for gold in bedrock and overburden: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-92-6, 72 p., 7 plts., 3 appendices [Appendix C bound separately]. Bosch, P.S., Jannadi, Eyad, Helaby, A.M., Johnson, P.R., and Bookstrom, A.A., 1989, Hamdah ancient gold mines, Kingdom of Saudi Arabia, with a section on Ground electromagnetic geophysical surveys by M.A. Bazzari: Saudi Arabian Directorate General of Mineral Resources OpenFile Report USGS-OF-10-7, 112 p., 8 plates, scale 1:2000.
Christian, R.P. and Bookstrom, A.A., 1992, Hamdah gold prospect, Kingdom of Saudi Arabia: Summary of estimation of gold resources and reserves in overburden and bedrock, with a section on An initial economic model for gold recovery from overburden and bedrock, by J.J. Cape, and· K.A. Saib: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-924, l3 p. Helaby, A.M. and Worl R.G., 1980, Exploration and evaluation of the Hajrah-Hamdah group of ancient gold mines, Kingdom of Saudi Arabia: Saudi Arabian Directorate General of Mineral Resources Technical Record 3. Society for Mining, Metallurgy, and Exploration (SME), Inc., 1991, A Guide for Reporting Exploration Information, Resources and Reserves: Mining Engineering, v. 43, no. A, pp. 379-84.
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HAMDAH GOLD PROSPECT, KINGDOM OF SAUDI ARABIA MODELS FOR ESTIMATION OF GOLD RESOURCES AND RESERVES By RALPH P. CHRISTIAN, ARTHUR A. BOOKSTROM, PHILIP J. ARUSCAVAGE, AND MARCOS. MARASIGAN
TECHNICAL REPORT
USGS-TR-92-8(IR 861)
MINISTRY OF PETROLEUM AND MINERAL RESOURCES DIRECTORATE GENERAL OF MINERAL RESOURCES JIDDAH, KINGDOM OF SAUDI ARABIA 1413 AH 1992 AD
