Posts Tagged porphyry

Airborne EM in Colombian Porphyry Gold Copper Project

Posted by on Saturday, 8 December, 2012

Bellhaven Copper & Gold Inc. reports the commencement of the previously announced ZTEM (airborne electro-magnetics) survey over the entire La Mina property (1,800 Ha). The survey is also being extended to include an adjacent concession, which the Company is currently in discussions to acquire. The work is contracted to Geotech Ltd., a Canadian geophysical survey company specializing in leading edge airborne technology. The survey is designed to help refine the targets at La Mina, with a particular emphasis on the Garrucha and Cristalina target areas.

The helicopter-borne geophysical survey will result in approximately 132 line kilometres of data along east-west lines, spaced at 200 metres. The Z-TEM Electromagnetic (EM) system is an innovative technique making use of naturally occurring or passive EM fields from worldwide thunderstorm activity as the source of transmitted energy. The passive source combined with a proprietary receiver design, advanced digital electronics, and signal processing results in low noise levels, exceptional resolution, and unparalleled depth penetration. It has been used successfully to identify and map porphyry style mineral systems from Alaska to Chile.

Patrick Highsmith, Bellhaven’s CEO, commented on the program: “We are pleased to bring the ZTEM technology to the Middle Cauca Belt for the first time. It is a proven technique for porphyries in the Americas. This will enable us to prioritize existing geochemical and magnetics anomalies, including on concessions that we are in negotiations to acquire. This is a very cost effective tool that adds immediate value in an emerging mineral district such as La Mina. By sharing the mobilization and some of the administrative costs with neighboring explorers, we have made it even more cost effective.”

Discussion of ZTEM Survey

The survey is expected to identify conductive and resistive features that are associated with large mineral systems such as gold-copper porphyries from surface to considerable depth. The electromagnetic data is sensitive to sulfide minerals, as well as silicification and clay alteration; all of which are associated with the porphyry and epithermal deposits in the Middle Cauca Belt. This will be an important addition to the magnetics data that drove the initial discoveries. The EM data will advance the geologists’ knowledge of the known resource areas, particularly at depth, but it will also upgrade the targeting arsenal elsewhere on the property. This work will also enhance understanding of large structures in the district. Many of these structures have previously been mapped from both surface exposures and drill intercepts; and the Bellhaven team is focused on their importance in controlling mineralization.

The survey crew arrived on site November 17, and began conducting reconnaissance flights a few days later. They are currently flying the survey as cloud cover permits. It is expected that a total of 6 to 8 days of favorable conditions is needed to complete data collection, so the survey should be completed before the end of December.

La Mina Porphyry Gold Copper Project

La Mina is a resource stage porphyry gold-copper project located in the Middle Cauca volcano-plutonic belt in the Department of Antioquia about 45 km southwest of Medellin. The Middle Cauca belt is known to host large porphyry gold deposits such as AngloGold’s La Colosa Deposit (24 Moz Au) and Sunward Resources’ Titiribi Project (11 Moz Au).

Exploration Targets

The La Mina concession includes almost 2,000 hectares. A number of anomalous features are evident from the initial airborne magnetic survey, completed by AngloGold. As surface sampling and drilling progressed, a number of multi-faceted targets emerged. Through the first half of 2012, a total of four known mineralized porphyry systems have been identified; two of these deposits are host to NI 43-101 compliant inferred mineral resources. The two remaining known porphyries will be the focus of future drilling, meant to advance these prospects to the resource stage as well. The exploration pipeline at La Mina includes a number of other targets that, based on geology, geochemistry and geophysics, have characteristics similar to porphyry or porphyry related deposits. There are at least 7 of these discrete targets undergoing additional work, but they have not yet been drilled. The figure below shows total magnetic intensity (reduced to pole) from an airborne magnetics survey. Many of the targets are identified on this map; and more detailed information is available below.

Airborne EM for Porphyry Copper-Gold in Papua New Guinea

Posted by on Thursday, 28 June, 2012
Goldminex Resources Limited updates on recent exploration activities at the Liamu Project in PNG.
Goldminex is focused on the discovery of greater than 2Moz gold or gold equivalent deposits in Papua New Guinea and has extensive prospective tenement holdings consisting of Exploration Licences and Exploration Licence Applications covering 10,754km2.
LIAMU PROJECT (EL 1606) (Goldminex/Vale JV)
The Liamu Project is located 120km east of Port Moresby within the Owen Stanley Region of PNG. Goldminex’s initial exploration work defined the Liamu intrusive complex and several prospects within it. Vale identified Liamu as a high priority target and moved quickly to commence drilling following the signing of the Farm-in Agreement.
 The Liamu Project has 11 prospects exhibiting surface indications of porphyry copper-gold mineralisation within a 35 km2 area.
 3,292m of a planned 4,000m program have been completed in six holes.
 Prospects drilled include Movei, Nesei, Unebu, Iyiowai and Maoba.
 Low-grade copper mineralisation in Maoba hole MABDH002 developed over a 151m interval from 153m depth including the following intersections;
o 59m @ 0.16% Cu from 186m to 245m
o 24m @ 0.21% Cu from 189m to 213m
 Drill results support the potential for Liamu to host a significant copper-gold porphyry system.
 Drill rig remains on site in anticipation of additional drilling in the near term pending results from ongoing investigations.
Ten prospects have been identified by surface geochemsitry at Liamu to date. These are Nesei, Movei, Tikay, Dada, Unebu and Berefana, all within the 5.5km x 1.5km alteration zone known as the Berefana Region, and Imorobi, Biafa, Bubuafu and Iyiowai to the north and east. An eleventh prospect, known as Maoba, is a ZTEM geophysical survey target.

A 4,000 metre diamond drilling program commenced in November 2011 has produced encouraging results at the Movei, Nesei, and Unebu Prospects and, in early 2012, a ZTEM geophysical survey was completed over the Liamu and Jog Project areas.
Maoba Drill Hole – MABDH002

Hole MABDH002 at the Maoba Prospect targeted coincident strong conductor and magnetic anomalies identified by a ZTEM survey completed in January 2012.
ZTEM conductor beneath surface topography showing the trace for MABDH002.
Assay results have been received for the majority of the hole and include the following:
 59 metres @ 0.16% Cu from 186 metres
 24 metres @ 0.21% Cu from 189 metres
The lithology of the above zone was a medium grained pale grey – green, intermediate volcaniclastic unit. Within this volcanic unit were moderately dark grey un-mineralised shoshonitic dykes. The volcaniclastic contains polymict crackle and fluidised, milled breccia zones throughout, Plate 2. Clasts within the breccia were uniformally barren with very fine grained sulphides present in the matrix. Alteration was mainly chlorite – silica – magnetite with areas of intense clay alteration.

Geophysical characteristics of Porphyry Copper Discovery at Tulameen

Posted by on Thursday, 20 October, 2011

Leonard W. Saleken, Chairman of Goldcliff Resource Corporation reports that Goldcliff has made the first significant porphyry copper ore grade discovery in the Copper Mountain mining district in decades. With surface samples highlighted by 0.655% copper – almost double the current reserve grades at the Copper Mountain Mine – and 1.3 grams per tonne silver, the Trojan showing is part of the Bolas anomaly, which is located in the Whipsaw target on the Tulameen property in the Copper Mountain mining district near Princeton, BC, Canada. The Tulameen property is 100 per cent owned by Goldcliff.

The three-pronged Bolas anomaly also contains the Eagle showing, which is highlighted by 0.175% copper and 1.0 grams per tonne silver. The copper mineralization on both the Trojan and the Eagle showings is chalcopyrite with malachite, and the iron sulphides are pyrite and pyrrhotite along with magnetite. These showings are situated on surface, above the substantial Bolas deposit-style chargeability anomaly. The Bolas anomaly is 2,000 long by 1,200 metres wide, and merges to form an area of 1.5 square kilometres at about 300 metres.

The Whipsaw alkalic porphyry copper-silver target area is located along the Copper Mountain south-west copper trend, approximately seven kilometres south-west of the Copper Mountain ore bodies. The Copper Mountain mineral reserves are 232,776,000 tons grading 0.36% Cu, 0.09 Au and 1.25 g/t Ag. The Trojan and Eagle showings are associated with the Bolas anomaly, which contains disseminated sulphide mineralization in the 3 to 5% range.

Bolas 3-D IP Anomaly

The deposit-style Bolas chargeability anomaly is a disseminated iron sulphide body that is located near surface and extends to an estimated depth of 500 metres in Upper Triassic Nicola Group rocks. The Bolas anomaly measures approximately 2,000 meters in a northwest direction by about 1,200 meters southwest. At a depth of around 300 meters, the anomaly merges to form a chargeable body of the order of 1,800,000 square meters or 1.8 square kilometres in size. The iron sulphide content of the rocks within the Bolas anomaly is estimated to be 3 to 5%.


The Bolas chargeability anomaly is a three-pronged star feature with a vertex centre and three end nodes that are referred to as the Whip, Elk and Eagle node areas of chargeability. Close to the surface, the chargeability response millisecond (ms) levels are weak to moderate. With increasing depth, the chargeability response millisecond levels become stronger and begin to merge at about 150 meters in depth. As depth continues to increase, the chargeability star features ultimately merge to form the continuous chargeability anomalous area. The chargeability values in the Bolas anomaly reach their maximum (25 to 30 ms) at about 300 meters below surface and then begin to fade to around 20 to 25 ms at 500 meters.

Whipsaw Target Area

Magnetic Environment

The most visible magnetic feature of the Whipsaw Target is a strong, broad, crescent-shaped magnetic high that fills more than half of the area. Inversion of the ground magnetic indicates that the deep-seated, crescent-shaped magnetic high is consistent with a deep-seated magnetic intrusive rock. A similarly intense, broad crescent-shaped magnetic high in the Copper Mountain area corresponds with mapped diorite intrusive rock and suggests that the magnetic high in the Whipsaw area may well be caused by the same rock type at depth.

The Whipsaw crescent-shaped, magnetic high partially surrounds a subcircular magnetic feature that is low, compared to the crescent-shaped high, but higher relative to magnetic background seen to the north. Once again, a similar pattern can be observed in the Copper Mountain area. There the subcircular magnetic feature corresponds with rocks mapped as monzonite and syenite, suggesting that the deep subcircular magnetic feature at Whipsaw may also be caused by a similar, less magnetic rock type. Strong chargeability anomalies occur within the subcircular magnetic feature.

Resistivity Data

Analysis of inverted resistivity data, with help from chargeability and magnetic inversions as well as magnetic intensity, indicates that the Princeton/Nicola contact may be vertical to sub-vertical and that the Princeton Group rocks could vary from about 150 to over 500 meters in depth, possibly over Nicola Group rocks. This may mean that the area of Princeton rocks could be down-dropped relative to the Nicola rocks across a fault-forming graben. If this is case, the deep moderate to weak chargeability anomalies seen in the area of Princeton rocks may then reflect the tops of chargeable material buried within Nicola rocks.

Airborne Geophysics for Alicia in Peru

Posted by on Saturday, 23 April, 2011

Strait Gold Corporation announces that it has signed contracts for airborne geophysical surveys to be conducted over its Alicia copper-gold project in southern Peru.

Helicopter-borne ZTEM (a deep-penetrating, natural-field electromagnetic system), magnetic and radiometric surveys over the entire 26-sq.-km property are expected to begin within a month. Final results are expected before the end of June.

“Geophysics have been instrumental in identifying primary drill targets on many porphyry-type deposits around the world,” said Strait Gold President Jim Borland. “Combined with results from our reconnaissance drilling program completed earlier this year, these surveys will allow us to zero in on the best targets for our 2011 drilling campaign.”

The airborne surveys are being coordinated with a major mining company that is undertaking similar geophysical surveys in the same general area as the Company’s Alicia Project, resulting in an extremely cost-effective program for Strait Gold.

The Company has also retained Thomas V. Weis and Associates of Centennial, Colorado, to provide geophysical consulting services. Mr. Weis is the former Chief Geophysicist for Newmont Mining.

These airborne geophysical surveys are part of an aggressive exploration campaign planned for Alicia that includes stream sediment geochemistry over the entire property, detailed soil geochemistry over the central portion of the property and additional core drilling.

Strait Gold has an option to earn a 100% interest in the Alicia property situated in the Andahuaylas-Yauri copper belt approximately 500 km southeast of Lima. This belt hosts a number of important copper and copper-gold deposits including Las Bambas (about 40 km west of Alicia) and Antapaccay (about 80 km southeast of Alicia) in which Xstrata is investing an aggregate of US$5.7 billion to develop. The belt also includes the Haquira copper project (about 40 km west of Alicia), which was recently acquired by First Quantum Minerals, and the Constancia copper project (about 60 km east of Alicia), which was recently acquired by HudBay Mining.

The Alicia Project presents a prospective copper-gold-silver project in a favourable porphyry-skarn jurisdiction with potential for significant drill intercepts of moderate to high-grade copper along with significant precious-metal credits.

Past exploration has defined existing skarn zones at surface reasonably well with trench sampling at 60-70 m intervals within the main zone to the south, and at 100 m intervals within the main zone to the north. Highlights of this sampling returned up to 56 m at 1.9% Cu, 0.18 g/t Au and 12.7 g/t Ag from trench Iris 5, and 32 m at 2.8% Cu, 0.32 g/t Au and 14.7 g/t Ag from trench Iris 7. These results are historic in nature and shall not be relied upon. Infill trench sampling between mineralized skarn zones still needs to be performed.

The general geology of the main skarn prospects have been fairly well mapped at 1:5000 scale, however no property wide mapping appears to have been executed, nor any systematic sampling/mapping of the historic workings of high-grade Ag-Pb-Zn+/-Au-Cu veins located 2 km south of the skarn zones.

A ground magnetic and TEM geophysical survey was performed over the main skarn area. The results of the magnetic survey are very useful in mapping the intrusive body and indicate magnetic anomalies where no intrusive outcrop has been mapped but has been observed in the field by Strait geologists. The TEM survey produced a few wide, poorly defined anomalies at depth, some of which were drill tested with no significant results (AL-03, not assayed).

Comprehensive geophysics for Utah’s copper district

Posted by on Thursday, 23 December, 2010

Andover Ventures Inc. announces today that Quantec Geoscience of Toronto, Ontario, Canada are currently conducting an IP (induced polarization) survey on the Big Hill prospect located on Chief Consolidated Mining Company’s (Chief) property (a subsidiary of Andover), East Tintic Mining District, Utah. Data is being collected from IP lines being conducted by Quantec utilizing the Titan IP/ DC system which is an alternate system to conventional IP survey systems. The Titan IP/ DC system provides a better IP and resistivity resolution than conventional IP. Weather permitting, the field work will be completed by the end of 2010.

Western Geco has completed a MT (magnetotelluric) survey on the Big Hill prospect. This data has allowed Western Geco to develop a final MT inversion model for the Big Hill prospect and this model has been sent to Kennecott for their review.

MPX Geophysics based in Markham, Ontario, Canada has completed an airborne magnetic survey. An aeromagnetic survey is a geophysical method used for imaging rock units with variable magnetic characteristics. This passive measurement method measures the intensity of the ambient magnetic field by towing a magnetometer on a pre-determined grid behind a helicopter. The resulting magnetic map will show the distribution of rock units based on their magnetic mineral content. The final report has been forwarded to Kennecott and upon data interpretation will be used to visualize geological units and to interpret subsurface geological structure.

The initial 2010 work program commenced in August of 2010 and included an airborne magnetic survey, IP (induced polarization) survey, a ground MT (magnetotelluric) survey, surface mapping, grab sample analysis with PIMA and assay, review and re-assay of Anglo American core from the Big Hill prospect and a compilation and review of old mine data from Chief’s property.

Under the terms of the agreement, Kennecott may earn a 51% interest in the Big Hill Project by completing a Pre-feasibility Study or incurring $20,000,000 in expenditures, whichever occurs first, and an additional 4% interest by funding all Project costs until delivery of a Feasibility Study accepted by Rio Tinto.

The Big Hill porphyry target is located in the East Tintic Mining District approximately 43 miles south east of Rio Tinto’s Bingham Canyon Mine, which is recognized as one of the worlds largest open pit copper porphyry deposits. A stock work of quartz vienlets occupies the core zone of the Big Hill target area with a lithocap super imposed on the stockwork, a process known as telescoping. Lithocaps usually define the shallow parts of porphyry copper systems typically above the main Cu-Au-Mo zone.

The new porphyry target at 0.5 km depth

Posted by on Thursday, 4 November, 2010

Romios Gold Resources Inc. announces the results of the Titan 24 geophysical survey carried out by Quantec Geoscience (Quantec) during August 2010 on its Trek Property in the Galore Creek area in north-western British Columbia. The objective of the survey was to map and detect porphyry mineralization at depth targeting the North and Tangle Zones. Titan 24 surveys have been a part of the successful identification of porphyry ore bodies and extensions of known ore bodies at other locations in British Columbia. The surveys measured the resistivity (DC), induced polarization (IP), and magnetotelluric (MT) properties of the underlying rock.
Highlights of the Survey:

  • The survey identified a large deep conductor 500 metres long, 300 metres wide and 200 metres high across all three lines in the North Zone. This conductor remains open to the North and the South. This new feature, which lies east and below the previous drilling and occurs from 500 to 675 metres below surface, represents the main target for future drilling. The conductor provides an opportunity for significant added tonnage to the North Zone.
  • The analysis and interpretation of the DC, IP and MT results also identified several chargeable anomalies above the deep conductive zone. These anomalies coincide reasonably well with the results of the existing 23 drill holes on the North Zone. The Company intends to continue drill testing these anomalies in its next drill program.
  • On the Tangle Zone, three pronounced IP anomalies were identified along the profile. These are located above a deep conductive zone which is the main drill target in the Tangle Zone. The IP anomalies and the deep conductor correlate well with grab sample assays and a significant soil copper-gold geochemical anomaly. Romios intends to drill this zone in its next drill program.

Tom Drivas, the President of Romios Gold, states, “We are very pleased with the results from the Titan 24 survey. The upper level results correlate well with the drilling at the North Zone, but what is even more exciting is the new large deep anomaly below our drilling to date which may represent the main porphyry body thought to be the source of the upper level mineralization. The survey results at the Tangle Zone are particularly encouraging as they correlate strongly with high copper-gold soil geochemistry. Romios intends to drill-test the new targets which have the potential to host significant incremental copper-gold porphyry mineralization on Trek.”

North Zone – Line 1
This 1.2 kilometre line extended from east of the known mineralization to the collar of TRK08-05. The results of the survey clearly indicate a two conductive layer structure separated by a resistive sub-surface layer. The deep conductive zone, which also extends through lines 2 and 3, is the main target as it may represent the main porphyry system. The results also indicate a large high chargeability anomaly near hole TRK08-05 that correlates with high content of pyrite, and four small IP anomalies that may represent alteration zones. One large high chargeability anomaly at approximately 250 metres depth may correlate to a possible fracture zone and is located near drill holes TRK08-01, 02, 03 and TRK 09-06 which contain mineralized porphyry occurrences with significant copper-gold mineralization. This anomaly is located at the edge of the profile and cannot be completely resolved by the inversion of the data.

North Zone – Line 2
The second and northern-most line transects the North Zone 500 meters north of Line 1. Line 2 extends from east of the known mineralization westward to terminate 150 meters northwest of TRK10-04. This line displays a zone of high conductivity north of TRK10-04, untested by drilling. Other areas of moderate-high conductivity at the North Zone are associated with copper mineralization. The upper resistive layer is sectioned by two main conductive zones. The main deep conductive zone appears on Line 2 at a depth of 600 metres. A weak IP chargeability anomaly appears near the main conductive anomaly at 250 metres depth and may represent potential alteration or mineralization. Drill holes TRK10-03, 10-05 and 10-06 encountered mineralized porphyry dykes above this zone and confirm the zone’s exploration potential.

North Zone – Line 3
The third Titan 24 survey line was placed between Lines 1 and 2, and transects the center of the North Zone from east to west. Generally, the IP and DC patterns reflect those in Line 1. Three high chargeability anomalies can be identified on this profile. A large IP anomaly on the west side of Line 3 correlates with zones of copper-gold-silver mineralized breccias. The first high chargeability may correspond to a near surface anomaly. The second high chargeability is approximately at a depth of 300 metres and remains to be drill tested. The third high is at 300 metres depth on the west side of Line 3 and correlates with zones of copper-gold-silver mineralized breccias. This IP anomaly dips to the east, mirrors a zone of moderate conductivity, and joins with a significant MT anomaly at 500-650 meters depth, interpreted as being the main deep conductive zone displayed on Line 1 and 2. Drill holes TRK10-07 and 10-08 also encountered mineralized porphyry dykes above this zone and further confirm the zone’s exploration potential.

Tangle Zone – Line 4
Three high chargeability anomalies located at approximately 100 metres depth are above a deep conductive zone which appears to extend from 400 metres to 600 metres depth. Results from each of the DC, IP, and MT surveys transecting the Tangle Zone indicate interconnected conductive anomalies that extend from surface to 600 meters depth. At surface, the conductive anomalies correlate with a 700 x 200 metre-wide area highly anomalous in copper and gold derived from gridded soil sampling. Outcrops in the vicinity of the conductive anomalies and soil anomalies contain bornite and chalcopyrite mineralization in porphyry intrusive. Grab samples assayed up to 9.6 g/t Au, and 16.45% Cu with 7.56 g/t Au. Soil sampling in the area assayed up to 5.31 g/t Au and 12.2% Cu.

Titan 24 Survey Parameters
The Quantec Titan 24 DC, IP and MT system is a state of the art geophysical tool used to explore for copper-gold mineralization. Four 1.2 kilometre-long lines, three transecting the North Zone at 250 meter spacings and one transecting the Tangle Zone, were completed at Trek. Each line was surveyed using a dipole-dipole configuration with a dipole size of 50 metres and measured the resistivity (DC), induced polarization (IP), and magnetotelluric (MT) properties of the underlying rocks. The Titan 24 system is capable of measuring properties simultaneously and comparing them to ensure accuracy. The system’s high-resolution digital signal processing and data multiplicity within the array and over time detects and resolves smaller signals from deeper targets while filtering noise. At these line lengths, the Titan surveys permit reliable, high-resolution analysis from surface to 400 meters depth for DC and IP, and down to 1,000 metres for MT. Inversion of the DC and IP data was completed using the UBC3D inversion code.

You can view the geophysical cross sections showing the Titan 24 survey results at the North and Tangle Zones by visiting the following location on the web:

Exploration Advancement by Airborne Geophysics and Drill Preparation for the Wildcat Property

Posted by on Wednesday, 13 October, 2010

Cayden Resources Inc. announces receipt of ZTEM (Z axis Tipper electromagnetic system) and magnetic airborne geophysical survey results for the Wildcat property in north-central British Columbia.

These results are being used to develop step-out drill targets on previously intersected copper-gold porphyry style mineralization, and to target new porphyry signatures on the property.

The 310 line km survey was completed by the same system operated by Geotech Ltd. that was used to complete a 200 km line orientation survey over the Mt Milligan MBX and Southern Star deposits in October 2008. This relatively new survey technique is capable of being used to map prospective resistivity and conductivity anomalies related to porphyry deposit system host rocks, alteration overprints, and control structures to depths of greater than two kilometres.

Resistivity plans and 2-D inversion sections provided by Geotech delineate a potential north-east trending 2 km wide by 4 km long by 2 km deep monzonite and diorite intrusive complex that hosts previously drill intersected copper-gold bearing porphyry style alteration. Two widely spaced holes previously drilled in this area intersected anomalous copper and gold values from surface to the bottom of one of the holes at 298 m.

Several other completely glacial till covered areas on the property are host to significant resistivity and magnetically anomalous areas with features analogous to the ZTEM orientation survey results received from the Mt Milligan and Pebble deposits flown in recent years by Geotech.

Chief Geologist and Director Dan McCoy, PhD, commented, “The wildcat property has been a sleeper out on the margin of the Mt Milligan porphyry deposit system. Porphyry deposits usually occur in multiples and to-date no other significant copper-gold mineralization that we know of other than at Wildcat has been located at this intermediate range of 12 km to the primary Milligan deposits. With the Wildcat mineralization and several of the new ZTEM drill targets virtually under the newly completed Milligan mine access and concentrate haul road, Cayden is set for an exciting spring drill program.”

Cayden has contracted Seven Drums Management Group to initiate consultation with First Nations Tribal Groups in preparation for permitting a proposed Q2 2011 twelve hole, 2200 m diamond drill program.

Cayden is also actively reviewing numerous property submittals on projects located in the Americas.