mill bay ventures inc. suite 900 - 570 granville street … · 2014-04-09 · mill bay ventures...

MILL BAY VENTURES INC. Suite 900 - 570 Granville Street

Vancouver, BC, Canada V6C 3P1 Bus: 604-682-3701

Email: millbayventures.com

AC CLAIMS PROPERTY CSAMT SURVEY

GIS COMPILATION

Argillite Surface

James L. Wright M.Sc. June 2, 2011

TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 2 SURVEY PROCEDURE . . . . . . . . . . . . . . . . . . . . . . 3 DATA PROCESSING . . . . . . . . . . . . . . . . . . . . . . . 4 INTERPRETATION . . . . . . . . . . . . . . . . . . . . . . . 6 CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . 12 REFERENCES APPENDIX- CSAMT LOGISTICS DVD HOLDER- DATABASE DVD MAP POCKETS (1:6000 & 1:12000 Sets) -

CSAMT SURVEY, LINES GRAVITY SURVEY, COMPLETE BOUGUER ANOMALY, RESIDUAL

GRAVITY SURVEY, COMPLETE BOUGUER ANOMALY, RESIDUAL/ STRUCTURES CSAMT SURVEY, LINE 4461130N, INVERTED RESISTIVITY SECTION CSAMT SURVEY, LINE 4461430N, INVERTED RESISTIVITY SECTION CSAMT SURVEY, LINE 4461730N, INVERTED RESISTIVITY SECTION

J L WRIGHT GEOPHYSICS 1

INTRODUCTION A controlled source audio magneto-telluric (CSAMT) survey was completed over a portion of the AC CLAIMS property with the objective of defining structures and lithologies associated with gold mineralization. Gravity work, reported upon by Wright (2007), indicates a pediment sloping basin ward (west) from the range front with numerous structural offsets indicated. The CSAMT survey is specifically intended to define the pediment geometry and refine locations for the structures. Initial gravity surveys with CSAMT follow-up is a standard technique applied with success in Nevada. Figure 1 shows the property outline relative to roads, county boundaries and topography.

FIGURE 1: Property Location Results of the survey are provided in digital and map formats. Digital products included all raw data and processed files, as well as MAPINFO and ARCGIS GIS files for the three (3) inverted resistivity sections. Also included are data and GIS files for a number of related data sets such as regional gravity, topography, geology, etc. The combined files constitute a complete GIS data base for the property. Maps include inversion plots with interpretive overlay for the three lines at both 1:6000 and 1:12000 scales. Also included are topographic and residual gravity plots with interpreted structures at the two scales. All plot files are also included in digital form as SURFER V9 SRF files. Files, both digital and map, are contained on a DVD located in a sleeve at the rear of the report. A README file on the DVD explains the folder / file organization. Survey procedures and data processing are first reviewed followed by an interpretation of the CSAMT survey with incorporation of multiple data sets. Finally, recommendations and conclusions are presented.


SURVEY PROCEDURE Figure 2 shows a CSAMT line plot overlying topography. The lines are oriented east-west, spaced 300m and arranged to cut the major range front north-south bounding structure. Line numbers correspond to the NAD 27 / UTM 11N northing. Zonge Geosciences, Inc. based in Reno, Nevada conducted the data acquisition under Zonge job number 11073. The survey was conducted during the period of May 16 – 20, 2011 and covered a total of 7.0 line - km. The survey control was established by Zonge personnel using a Trimble PRO-XRS GPS receiver with real time differential corrections provided by OMNISTAR. CSAMT data were acquired using a 50 meter electric-field receiver dipole. Measurements were made in spreads consisting of four electric-field dipoles (4 Ex/1 Hy) with a magnetic-field antenna located in the center of the spread. The data were acquired in the broadside mode of operation with the electric-field dipoles oriented along the survey line and parallel to the transmitter dipole (x component). The magnetic antenna was oriented perpendicular to the survey line. Measurements were made at frequencies ranging from 1 Hz to 8192 Hz in binary steps. One CSAMT transmitter, of a grounded dipole configuration, was used for this survey.

FIGURE 2: CSAMT Lines over Topography

Data were acquired with a Zonge model GDP-32 receiver and Zonge GGT-30 transmitter. The GGT-30 is a constant-current 30 KVA transmitter. Power for the transmitter was provided by a Zonge ZMG-30 motor-generator with a VR-1 voltage regulator. The transmitter was controlled by an XMT-32 transmitter controller. Transmitter-receiver synchronization was maintained with identical crystal oscillators, synchronized each morning before data acquisition.


Data quality was monitored in the field by the operator. Real-time standard-error values are displayed during acquisition. In addition, multiple measurements at a range of frequencies are displayed graphically as resistivity versus frequency curves with error bars showing the data scatter. This allows a visual evaluation of the data quality and remedial action to be taken if necessary. Data quality is also evaluated during post-acquisition processing by reviewing data component plots. Data are edited to remove spurious data if necessary. As a whole, the data are of good quality typified by repeated measurements generally within 10 percent. The smooth nature of the curves and lack of noticeable error bars also demonstrates good data quality. Noisy data are noted along the Battle Mountain – Austin highway (#305) and a power line, which traverses the western ends of the two southern lines. Neither area of interference seriously impacted the survey. Additional logistical details are available in Appendix A, where a more complete discussion of the power line interference is provided. DATA PROCESSING Zonge Geosciences provided averaged and edit files, along with station survey information, for each line in standard Zonge AVG and STN files. These data were processed with Zonge’s SCS2D two dimensional, smooth model, CSAMT inversion software version 3.20z. A variable cell size ranging from 25x20m to 25X40m was selected to better refine data fits. Prior to additional processing all inverted resistivities were converted to logarithms base ten. Gridding with a kriging algorithm using a five meter spacing was implemented. The grids were then mask to the topography, line limits and a depth extent of approximately 500m. Finally, the inverted sections were colored and contoured for map preparation. Contour interval on all plots is 0.05 log ohm-m. The color bar for all products, including GIS files, follows.

Complete Bouguer Anomaly (CBA) gravity data are included as a back-drop to the CSAMT results. Wright (2007) reports on the survey and the color scale used for the plots and figures follows.


FIGURE 3: Plot Example

As noted previously, paper plots are provided at two scales along with SRF plot files. Figure 3 shows an example of the CSAMT interpreted section over the residual gravity and topography plot, which are located in the map pockets. The inverted data for all lines were merged and imported into the VOXLER 3D visualization program, an example image from the program follows.

FIGURE 4: VOXLER Sectional / Iso-Surface Example


INTERPRETATION Rational for CSAMT line placements is reviewed by Figure 5, which shows USGS regional gravity along with the CSAMT lines. Clearly evident on the figures is a major north-south structure at least 30 kilometers in length. The structure intersects the north side of the Caetano Trough in the vicinity of the lines. However, the lines are placed and oriented to test the north-south structure. Immediately east of the lines is a localized gravity high, beneath which lower plate Paleozoic rocks have been drilled.

FIGURE 5: USGS Regional Residual Gravity and CSAMT Lines Figures 6 to 8 shows the inverted resistivity sections rotated to plan about the line. Underlying the sections is the property scale residual gravity, which is considerably more detailed than the regional data of Figure 5. Overlying the section is an interpretation with structures depicted with dashed lines and contacts with dotted lines. Various interpreted rock units are labeled. Underlying both the CSAMT and gravity is the 7.5’ quadrangle topography. Note a vertical exaggeration of 1.3 is applied to better present the results.


FIGURE 6: L4461130N Inverted Section over Residual Gravity & Topography


The three sections are quite similar with the western two thirds exhibiting a layered geometry and the eastern third dominated by a series of nearly vertical structures off setting a complex resistivity pattern. The aforementioned power line, which cuts the western portion of the two southern lines, produces an apparent vertical conductive zone labeled with a (PL) on the figures. These features are spurious and do not reflect conditions in the earth. Layered basin fill dominates the west end of all lines. A thin surface layer of Qal extends across all three sections, reaching a maximum thickness of approximately 80m. Resistivities are variable, but generally elevated, indicating well drained sediments. The Qal layer tends to be thickest on the east end near the major structures and thin to the west. Such a geometry is consistent with recent normal movement on the structures, which rotates the east ends down to allow increased Qal accumulation. This is well demonstrated in two instances on the northern most line. Beneath the Qal on all three lines is a thick layer of moderately resistive material interpreted to be Tertiary Caetano Tuff (Tct). Such an interpretation is supported by airborne magnetic data which shows elevated readings in the area, as is typical of the Tct response. Thicknesses for the Tct fall in the 300-400m span with offsets noted along various structures. Beneath the Tct is a conductive rock unit interpreted as argillites, most likely part of the upper plate sequence. A major structural corridor underlies the eastern portion of the lines, the demarcation with the layering running approximately along Highway 305. The layering is abruptly terminated to be replaced by high angle blocks of rock caught-up in the structural zone. Clearly, this zone is the one predicted by the gravity on the both the regional and property scales. The zone, made-up of approximately four major structures, ranges in width from 300 to 600m and widens to the south. The underlying argillites reappear on the extreme east end of all lines, but as much as 300m shallower. However, the gravity suggests this argillite to be a sliver, which is terminated further east. This termination may be detected on the northern most line. Centered within the zone is a block of high resistivities (purple color) bounded by structures. This block is interpreted to be a rock unit caught-up within the zone. Examination of the underlying gravity in Figures 6 to 8 reveals a portion of the overall gravity high correlates with the resistive block. In fact, it appears the structural zone sheared the western side off the denser material forming the local gravity high and moved portions to the south within the zone, thus producing the elongated “southern arm” to the gravity high. The material within the block is therefore resistive and dense. Two rock types which occur in the area and have such characteristics are massive chert and carbonates possibly related to the lower plate rocks (Pz). Silicification of other rocks could account for the elevated resistivity, but not the anomalously high density. Figure 9 shows the interpreted CSAMT structures transferred to a plan and connected to form surface traces over the residual gravity and horizontal gradient. The “southern arm” to the gravity anomaly mentioned previously is labeled as well. The main gravity break (i.e. gravity zone) falls along the western side of the structural zone, where low density Qal and Tct are rapidly thickening. Examination of the gravity indicates the structural


zone is likely down dropped south of the CSAMT lines and under goes two apparent right lateral shifts. This dropping and shifting is a result of intersection with the north side of the Caetano Trough. While not definitive, offsetting of the structural zone suggests the zone pre-dates formation of the Caetano Trough.

FIGURE 9: Residual Gravity (Upper) and Horizontal Gradient (Lower) over Topography


CONCLUSIONS AND RECOMMNEDATIONS Figures 6 to 8 demonstrate good agreement between the gravity and CSAMT, as well as the increased resolving power of CSAMT over gravity. A major north-south structural zone, first defined by gravity, is well resolved by the CSAMT and revealed to be composed of approximately four major structures. Total offset across the 300-600m wide zone is approximately 300m down to the west. A large blocks of resistive / dense material, interpreted to be either chert or possibly lower plate carbonates, is caught-up in the zone. If fact, this north-south elongated block appears to have been sheared off a larger block to the east. South of the CSAMT lines the zone is down dropped and right laterally offset by structures associated with the Caetano Trough. Such a major structural corridor is a likely channel for hydrothermal fluid movement. Examples in the area include the Wayne Zone at Lonetree and Virgin Fault at Phoenix, both of which are north-south oriented major structures. Drill testing of the zone is warranted. Given the width of the zone, at least two holes forming a fence will be required to cross the entire zone. Further complicating hole placement is Highway 305 and the associated fences / power line. However, if at all possible, the holes should be placed on the CSAMT sections.

REFERENCES

Wright, J. L., 2007, Caetano property, Gravity survey, GIS database: Mill Bay Ventures company report.


APPENDIX

CSAMT SURVEY

ON THE

AC CLAIMS

LANDER COUNTY, NEVADA

FOR

MILL BAY VENTURES INC.

DATA ACQUISITION REPORT

ZONGE JOB# 11073

ISSUE DATE: 26 MAY 2011

ZONGE GEOSCIENCES INC.

924 Greg Street

Sparks, Nevada 89431

INTRODUCTION Zonge Geosciences, Inc. performed a controlled-source, audio-frequency, magnetotelluric (CSAMT) survey on the AC Claims, located in Lander County, Nevada for Mill Bay Ventures, Inc. This survey was conducted during the period of 16 May 2011 to 20 May 2011. The survey area is located in Township 28 North and Range 43-44 east, and lies within the Redrock Spring, Nevada 7.5-minute series topographic sheet. CSAMT data were acquired on three lines for a total of 7 line-kilometers of data coverage. This survey was supervised in the field by Mark Ziminsky, geophysicist, and Steve Zimmer, geophysical crew chief, for Zonge Geosciences, Inc. under Zonge job number 11073. Data files were provided to client representative, James L. Wright of Wright Geophysics, for quality control, modeling and interpretation. DATA ACQUISITION CSAMT data were acquired along three lines oriented east/west. Zonge personnel established survey control for this project using a Trimble PRO-XRS GPS receiver. The GPS data were differentially corrected in real-time using WAAS corrections. This system provides sub-meter accuracy under standard operating conditions. Line control in the field utilized UTM Zone 11N NAD27 (CONUS) datum. CSAMT data were acquired using a 50-meter electric-field receiver dipole. Measurements were made in spreads consisting of four electric-field dipoles (4 Ex/1 Hy) with a magnetic-field antenna located in the center of the spread. The data were acquired in the broadside mode of operation with the electric-field dipoles oriented along the survey line and parallel to the transmitter dipole (x component). The magnetic antenna was oriented perpendicular to the survey line (y component). Measurements were made at frequencies ranging from 0.125 Hz to 8192 Hz in binary steps. One CSAMT transmitter, of a grounded dipole configuration, was used for this survey. The transmitter location is shown on Table 1 with coordinates in UTM Zone 11N NAD27 (CONUS), meters. Each current electrode site consisted of two pits lined with aluminum foil and soaked with salt water. The electrodes were connected to the transmitter with two lengths of insulated 14-gauge wire, separated by approximately two meters.

Transmitter # PID

NAD27 UTM East

NAD27 UTMNorth

Length

Bearing Lines

1 west 494200 4468730

1 center 494900 4468730

1 east 495600 4468730 1400 N90°E All

Table 1: CSAMT transmitter and associated survey lines

CSAMT MEASUREMENTS The CSAMT data are collected by measuring the magnitude and phase of the electric and magnetic fields. Measurements are made at discrete frequencies in binary steps. The receiver measures the magnitude of the received signal and the absolute phase difference between the received signal and the transmitted signal, which is known via synchronization of the transmitter and receiver. The Cagniard resistivity is calculated from the magnitude of the fields and impedance phase is the difference of the absolute phases of the E and H fields. Figure 2 is an example of the log-log component plots for a single spread consisting of 4 E-field dipoles (Ex) and a central magnetic field (Hy). The upper left plot shows Cagniard resistivity versus frequency, the lower left plot shows the impedance phase versus frequency. The upper right plot shows the electric field (Ex) magnitude versus frequency and the lower right plot shows the magnetic field (Hy) magnitude versus frequency. These plots are included on the data CD and present a visual representation of the basic measured data that is useful for interpretation and analysis of data quality.

Figure 2: Example of log-log plots of CSAMT Cagniard Resistivity, impedance phase, electric and magnetic field magnitudes for frequencies of 0.125 Hz to 8192Hz.

INSTRUMENTATION Data were acquired with Zonge model GDP-32II receivers, serial numbers 3238 and 3220. These instruments are backpack-portable, 16 bit, microprocessor-controlled receivers that can gather data on as many as eight channels. The electric-field signal was measured at the receiver site using non-polarizing ceramic Cu-CuSO4 porous-pot electrodes connected to the receiver with insulated 14-gauge wire. CSAMT magnetic-field measurements were made with Zonge ANT/6 antenna coils, serial numbers 246 and 276. The signal source for the CSAMT measurements was a Zonge GGT-30 transmitter, serial number 2094. The GGT-30 is a constant-current 30 KVA transmitter. Power for the transmitter was provided by a Zonge ZMG-30DL motor-generator equipped with a built-in voltage regulator. An XMT-32 transmitter controller, serial number 4148, controlled the transmitter. Transmitter-receiver synchronization was maintained with identical crystal oscillators, synchronized each morning before data acquisition. DATA PROCESSING Routine data processing consists of the following steps: 1) Initial log-log plots are reviewed to evaluate the data. 2) Data identified as spurious by the operator or individual measurements that are obvious outliers with respect to multiple repeat measurements are flagged and removed from further processing. 3) Raw data files (.raw) are processed via the CSAVGW program to produce an intermediate (.zdb) file. Corrections for polarity or calibration errors are made at this step. The output (.zdb) file has a single record containing all data for each individual stack or data block taken for each data channel. 4) The individual measurements (stacks) are averaged for each channel in the CSAVGW program and output in a column-based ASCII file (.avg) with a single averaged value for each parameter for each channel (station). 5) The average data are processed with the ASTATIC algorithm. Individual sounding curves are viewed and final removal of individual measurements that are considered to be affected by coherent noise is made. Log-log plots and the parametric pseudosections are generated at this step. DATA QUALITY Data quality is monitored in the field by the operator. Real-time standard-error values are displayed during acquisition. In addition, multiple measurements at a range of frequencies are displayed graphically as resistivity versus frequency curves with error bars showing the data scatter. This allows a visual evaluation of the data quality and remedial action to be taken if necessary.

Data quality is also evaluated during post-acquisition processing by reviewing data component plots as shown in Figure 2. Data are edited to remove spurious data if necessary. Moderate noise levels were encountered for this survey. The main source of the noise was the western power line crossing lines 4461430N and 4461130N at stations 92180 and 92070, respectively. Data for stations within 100 meters of the western power line were affected at the mid to high frequencies, in particular 512Hz - 8192Hz. The contaminated frequencies were removed from the data. Cultural features encountered on this survey are limited to two power lines, fences along the highway and State Route 305. SAFETY AND ENVIRONMENTAL ISSUES No health, safety incidents or accidents occurred during the course of this survey. No environmental damage was sustained as a direct result of the survey progress. Vehicle travel was kept to existing roads.

PRODUCTION LOG:

Date Notes

5/16/2011 Mobilized from Sparks, Nevada to project. Setup transmitter bipole.

GDP 3238: Line 4461730: 94200 - 93450

5/17/2011 GDP 3220: Line 4461130: 91625 - 92575

GDP 3238: Line 4461730: 93450 - 92450. Line 4461430: 91650 - 92200

5/18/2011 GDP 3220: Line 4461130: 92625 - 93975.

5/19/2011 Mobilized to project. Heavy precipitation all morning. No data were acquired

GDP 3238: Line 4461430: 92250 - 94200

5/20/2011 GDP 3220: Line 4461130: 94025 - 94175. End of project

mill bay ventures inc. suite 900 - 570 granville street … · 2014-04-09 · mill bay ventures...

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