The Cerro Oro Project

Cerro Oro, within the department of Caldas, Colombia

Nature of interest and terms of acquisition

The Cerro Oro project covers approximately 2,750 hectares of which 711 hectares are controlled by a contract and the remainder through applications. The project is in the Caldas department 120 km south of Medellin.

On January 16 2013, the Company entered into a lease agreement on the Cerro Oro property (the "Cerro Oro Option") which required payment of US$10,000 on signing and a payment of US$80,000 upon conversion of the application to a license both of which have been paid. To maintain the lease, annual escalating payments that total $625,000 over five years will be required and thereafter annual payments of US$135,000. The project is also subject to a 1.2% production royalty and a per-ounce bonus for Measured and Indicated NI 43-101 compliant Resource and Reserves.

On April 1, 2014, an exploration contract for the Cerro Oro project was issued by Agencia Nacional de Minera ("ANM"). Currently Miranda is seeking a joint venture funding partner as well as completing a "Consulta Previa" which when approved will allow additional drilling on the property

Location and means of access to the property

Cerro Oro covers approximately 711 hectares and lies within the Caldas department approximately 120 km south of Medellin or approximately midway between the Gran Colombia's historic epithermal Marmato project and Batero Gold's porphyry gold-epithermal Quinchia projects in the prolific Middle Cauca Gold Belt.

History of previous operations and previous operators on the property

Recently, informal miners have developed workings on up to 1.5m veins of quartz-adularia-pyrite that sample up to 12 g Au/t and also excavated local bladed quartz after calcite textures. Adularia and bladed texture is a common feature of the productive parts of low sulfidation gold systems and can be associated with bonanza veins. The gold system at Cerro Oro is probably low sulfidation epithermal in a similar setting as Marmato, but at a higher erosional level.

Outcrop exposure is limited to creek beds but these exposures suggest alteration and mineralization occurs over two square kilometers. Alteration seems to occur within the damage zone of a northwest-trending structural zone up to 600 meters wide. Notably it is common to recover fine free gold by panning crushed outcrop samples and artisanal miners are locally recovering free gold from in situ sap-rock by small-scale hydraulic mining. Informal miners are also recovering a significant portion of gold from veins and fractures using a simple gravity circuit without any chemicals.

Exploration work completed by Miranda and its prior funding partner on the property

Miranda has completed geologic mapping and extensive 2-meter channel sampling. Approximately 416 channel samples have been taken. Twenty percent of those samples assay greater than 0.2 g Au/t. Multiple sub-parallel 0.5 to two meter width veins are identified within an area of alteration greater than 1 sq. km. Locally veins, vein wall rock, and rock unrelated to veins are significantly mineralized. Veins assay as high as 2m @ 12 g Au/t and wall rock and country rock where significantly mineralized assay from 0.5 to 6.0 g Au/t. Samples unrelated to veins have widths up to 6.0 m @ 3.63 g Au/t. These widths and assays come from a database including all rock types, containing assays ranging from non-detectable to 12 g Au/t, with a median value of approximately 0.150 g Au/t.

Outcrop exposure is limited to creek beds. Where accessible in several artisanal mines, veins have been mapped and sampled. Visible fine gold is common in crushed samples of both fresh rock and saprolite - artisanal miners recover gold from in-situ weathered rocks using hydraulic methods within two large drainages on the project.

In 2016 an abbreviated drill program, consisting of 3 drill holes was conducted. This "scout" drilling tested a large low-sulfidation epithermal gold system at Cerro Oro, where mapping and sampling indicate the potential for multiple high-grade gold veins occurring within broader zones of lower grade disseminated and fracture controlled mineralization. The original planned program called for four to five angle holes totaling 1,200 meters.

Due to failure to obtain certain surface easements in a timely manner, the drill program was limited to three angle holes totaling 472 meters. Miranda is working on easement agreements as well as a government requested "Consulta Previa" with nearby indigenous peoples. Miranda has started the "Consulta Previa" process, and intends to pursue it expeditiously.

All three holes completed had significant mineralization and once the Consulta Previa is approved additional drilling with a new funding partner will be pursued.

Cerro Oro drilling highlights (Table below):
  • CO-001: 1m @ 3.67 g Au/t in a locally coliform, sulfide-quartz breccia, interpreted to be a down-dip and strike extension of the "Victoria Vein".
  • CO-003: 1.45m @ 3.53 g Au/t in a heterolithic, matrix supported hydrothermal breccia that forms a contact zone with a dacite porphyry dike. The main breccia is subsequently injected by finer "fluidized" breccia. Several crosscutting sulfide veinlets occur in matrix and clasts. This is a newly recognized mineralization style on the project and indicates complexity and multi-stage mineralization in the system.
Miranda's drilling demonstrated a proof of exploration target concept, and encountered significant multi-stage, telescoped primary epithermal and possible secondary porphyry-style alteration. This alteration and mineralization complexity was not recognized previous to core drilling. The geometry of the "Victoria Vein" and other veins and vein-breccia were defined, which will help design follow up drilling.

These drill results show a strike extent of 130 m along the "Victoria" fault-breccia-vein zone extending from the surface to a depth of 80m. Gold mineralization is strongly correlated with mercury (to 9.6 ppm), antimony (to 139 ppm), arsenic (to 1,900 ppm) and zinc (to 4,740 ppm). No other elements show appreciable elevated values.

In conventional zoning models for epithermal systems, high level to low level elemental occurrences are - Mercury ➜ Antimony ➜ Arsenic ➜ Gold. In the same zoning models, gold is typically minor or absent in the mercury zone and gold begins to occur more strongly at the deepest extent of antimony, while the highest gold grades occur where arsenic begins to diminish as a major element. Zinc is associated with gold in many South American epithermal deposits, and the gold-zinc association at Cerro Oro compares favorably to the same relationship seen at nearby Marmato. Using the same exploration zoning model, Marmato would occur with similar abundant zinc and adularia, but below the zone of mercury-antimony observed at Cerro Oro.

Table of significant drill results defined as 1m or greater, greater than 0.300 g Au/t. True thickness cannot be estimated but all holes are angled to test high-angle vein-faults with an approximate 72° southeast dip:

(g Au/t)
CO-001 30 to 41.7 11.70 0.388
including 30 to 35.7 5.70 0.633
CO-001 56.0 to 60.7 4.70 1.374
including 57.7 to 58.7 1.00 3.670
CO-001 78.5 to 80.5 2.00 0.546
CO-002 65.2 to 66.2 1.00 0.679
CO-002 122.2 to 125 2.80 0.866
including 122.2 to 123.8 1.60 1.170
CO-003 22.3 to 23.4 1.10 1.250
CO-003 34.6 to 36.5 1.90 0.364
CO-003 66.15 to 67.60 1.45 3.530

All five plus-1g Au/t intercepts contained either banded quartz vein or vein-breccia over 1m or greater. The minus-1g Au/t intercepts contained pyritic stockwork or sheeted pyritic veinlets and disseminated pyrite. Fine-grained adularia is associated with all gold occurrences. Some breccias contain matrix supported, mineralized clasts that may be explosively injected from lower depths. Breccias are from 6 m to 20 m wide, although the significant gold intervals within them are narrower. However in CO-001, 4.7 m of mixed banded vein and vein-breccia are significantly mineralized.

Alteration is typified by abundant mixed clays and more local silicification. In core, up to four cross-cutting events are observed. Adularia has two habits of occurrence - both as vein and veinlet selvages or pervasive within other alteration.

This limited drill program tested only 130m of a system that has a mapped 1.5km strike and 600m width. Miranda believes that intercepting multiple mineralized zones justifies continued drill tests of the large epithermal gold system at Cerro Oro. Widely used epithermal zoning models suggest higher gold grades are highly permissible below a near surface zone one of high mercury and antimony.

Miranda intends to do gridded auger soils over the entire alteration zone and where possible determine clay species in soil pits, surface exposures and existing drill core. Gridded soils should indicate the centers of stronger and more continuous areas of gold mineralization. Areas of high-temperature illite may indicate upwelling fluid centers above high-grade mineralization. After modeling structural-dilational controls, future drilling will be designed to test below the mercury-antimony zone.

Geology and mineralization

Adularia in veins and vein-selvages, bladed replacement texture, and abundant stibnite (antimony sulfide) occurrences at Cerro Oro suggest a low-sulfidation epithermal gold system. Adularia and bladed textures are widely reported in geologic literature as being related to fluid boiling that results in high-grade gold deposition in low sulfidation epithermal veins. Stibnite commonly occurs in a zoned distribution above gold in these veins. At Cerro Oro gold-silver mineralization is hosted in sericiticly and argillically altered 2-3MA volcanic tuffs and flows of the Combia Formation associated with extensive multidirectional hematitic fractures zones. This formation overlies porphyry systems epithermal veins systems elsewhere in the Cauca Belt. Gold has a geochemical association with arsenic, mercury and antimony and generally low or background base metal values. Discreet veining is restricted at surface although inferred late-stage quartz-stibnite-gold veins occur locally. Outcrop exposure is limited to creek beds but these exposures suggest alteration and mineralization occurs over two or more square kilometers. Alteration seems controlled predominantly along a northwest-trending structural zone up to 600 meters wide. Notably it is common to recover fine-grained free gold by panning crushed outcrop samples and artisanal miners are locally recovering free gold from in situ rock by small-scale hydraulic mining. Surface exposures are intensely weathered and oxidized but one sub crop exposes mineralization that is typified by close-spaced, pyritic, generally open fractures with minor silica selvages. Miranda infers that alteration and mineralization style at Cerro Oro represents a fracture-controlled to disseminated, low-sulfidation epithermal gold system. Ore fluids have apparently flooded the porous Combia tuffs to create a bulk minable target, as well as high-grade bonanza-type veins typical of those systems. The quartz-adularia gold veins will probably develop be more robust in less porous rocks under the surface tuff. Limited reconnaissance mapping and prospecting suggests alteration is zoned from argillic to siliceous alteration with depth and that the alteration cell at Cerro Oro may have a spatial and structural relationship to porphyry-style mineralization several kilometers away.

High-grade vuggy quartz vein with pyrite and arsenopyrite from artisanal miner's workings