ShirotnaiaYet another terrific result emanating from Shirotnaia where the strike length for this emerging higher-grade zone is now over a kilometer and where highest grade intervals are being intersected at less than 100 meters below surface; an area, (situated on the extreme northern fringe, with core holes yet to be drilled further north to probe pristine untested terrain is going to generate a great deal of excitement in the period ahead as it is subjected to heightened exploration scrutiny; nonetheless, early as it is, at this precise locality four drill holes have already tapped into a significant gold resource, all apparently related to a very pronounced tectonic zone that is clearly linked to a higher-grade zone of gold mineralization that trends and plunges to the northwest ("NW"). These four diamond drill holes, all clustered together, are as follows:
- DDH2808 10.0 meters @ 1.07 g/t Au; 33.4 meters @ 4.75 g/t Au (including 10.1 meters @ 14.71 g/t Au); 13.0 meters @ 1.46 g/t Au A domain where large very-high-grade 'deep' gold deposits are customary within this particular gold belt.
- C-282 32.8 meters @ 1.44 g/t Au
- DDH2809 135.6 meters @ 1.12 g/t Au; 8.8 meters @ 3.04 g/t Au; 18.2 meters @ 1.56 g/t Au A high-grade pay zone extending 500 feet and open at depth within the same major flexure that hosts two world class gold fields only a few miles away.
- C-281 60.0 meters @ 1.45 g/t Au
Two points call out for further deliberation when pondering the significance of this most recent intercept, which confirms and expands upon prior excellent results from here, -
- This is beginning to look at lot like the world-class Aksu and Quartzite Hills deposits situated a mere 3 kilometers to the NW (northwest); recall that this ‘emerging trend’ also extends to the northwest, directly aligned with these monster deposits.
- The grade (14.71 g/t Au over 10.1 m) being disclosed here is far superior to anything now being discovered anywhere in China, - the world’s largest gold producer.
How about a little perspective:
- Geological Considerations
From at least 3.5 billion years ago the distribution of mineral deposits have been determined by the geological processes that formed them, accordingly, such deposits are commonly clustered in geological provinces; as a consequence, geologists undertaking exploration for gold deposits have long understood their heterogeneous distribution, - to such an extent that experts have made it an art to refine their classification into very specific types based upon their distribution in space and time.
- These mineral deposits exhibit extremely heterogeneous distributions with each major deposit type showing a distinctive (typically unique) temporal pattern; and these individual temporal patterns reflect a complex interplay between fundamental forces of formation and forces of preservation that (in turn) have largely been shaped by changing tectonic processes and environmental conditions.
- In essence: the temporal distribution of gold deposits will reflect the forces that originally produced the deposits (global heat flows in a cooling Earth), the depositional environments in which they formed (changes in tectonic regime), and then the preservation potential of the deposit-hosting environments (where these deposits currently reside).
Worldwide, most metallogenic belts and provinces are dominated by deposits formed in one or more favored epochs and nearly twenty large (many world-class) gold deposits have been disclosed in Kazakhstan, in addition to hundreds of small and medium-sized occurrences, all related to gold-ore mineralization transpiring in the orogenic and postorogenic stages of regional development where gold sourced from the Pre-Cambrian period was trapped during the Caledonian and Hercynian metallogenic epochs, and it is within this very favorable geologic ‘setting’ with its fortunate confluence of necessary factors that Alhambra is finding success.
- Within the metallogenic province of northern Kazakhstan, major gold deposits are located along the trend of deep seated lineaments (orientated within synclinal zones), being composed mainly of Ordovician sediments. Many of Alhambra’s discoveries to date are located along the same structure of this volcano-sediment hosted Orogenic style mineralization (similar to the world-class Aksu/Quartzite Hills gold deposits) and this same distinctive temporal pattern also hosts many other promising targets for Alhambra to explore.
- At all of these sites gold deposits are found in effusive-sedimentary Ordovician masses; with gold deposits genetically and spatially related to granite-like rocks where the larger gold deposits are related to intrusions characterized by multi-stage complex activity; with intrusion formation made up of various structures and ages.
And Alhambra is having a great deal of success in finding many ‘new’ areas to explore.
- Comprehensive ground gravity and high resolution magnetic surveys and a remote sensing survey completed over the Dombraly-Shirotnaia gold trend in conjunction with an ASTER imagery survey have located numerous areas of hydrothermal alteration (associated with the style of gold mineralization known to occur in this region) coupled with many prospective tectonic features (structural controls on the alteration such as faults and fracture zones that serve as trapping mechanisms).
- Globally, most (if not all) metal accumulations of exceptional size are “the end of the spectrum” of decreasing size deposits of the same or similar types; where the 80/20 rule generally prevails, meaning that 20% of the largest deposits contain 80% of the total gold.
The Shirotnaia Project area, located in the south-eastern part of Alhambra’s enormous Northern Kazakhstan license block, resides within a Middle Ordovician volcano-sediment sequence truncated by Late Ordovician to Devonian intrusions where mineralization belongs to the volcano-sediment hosted Orogenic style. Here, mineralization is thought to be related to the anticline-syncline inflexion line and probably to fluid barriers formed by volcanic rocks covering sediments. The source fluids and metals within a mineral system such as this have to be able to migrate in a focused way (‘main fluid pathways’) to a site of deposition where they are contained by the main regional control (‘trap’) for economic quantities of metals to be present. As such, when evaluating geological provinces, the critical question is the one about geodynamics, whereas when evaluating drill targets, the issue of metal transport and deposition are much more relevant.
- This area forms part of the Caledonian-age Kokchetav-North Tienshan basin and fold system with increasingly felsic intrusive magmatism related to 3 orogenic cycles ranging in age from the Pre-Cambrian to the Hercynian with mineralization primarily hosted by Middle to Upper Ordovician volcano-sedimentary rocks of mainly mafic and intermediate composition with interbedded lavas, tuffs and terrigenous clastic rocks.
To better understand what ‘may perhaps’ reside subsurface at Shirotnaia let’s look to the Aksu/Quartzite Hills orogenic gold deposits located a mere 3 kilometers to the south.
- The Shirotnaia zone is located in same area of the ‘Aksu-Balusti Mineral Trend’ as are the massive Aksu gold deposits; moreover, the topography of both the Shirotnaia and Aksu/Quartzite Hills ‘mine sites’ are typical of the ‘‘steppe’’ country found in northern Kazakhstan; residing on the main undulating plain at an average height of 350 meters above sea level.
- With the gold here derived from ancient Pre-Cambrian rocks, the amount of contained gold in any particular deposit will depend directly on the intensity of Caledonian intrusive activity, - - - which is why the very pronounced tectonic zone noted above, clearly linked to the higher-grade zone of gold mineralization now being elucidated at Shirotnaia, is so very interesting and intriguing.
- Since structure is fundamentally the most important factor in gold deposit formation and gold deposits are formed in clusters within the most complex structures, - it makes sense to explore where tectonic activity has formed large and deep breaks/faults in areas of pre-intrusion and ore stages. In addition, gold deposits are chiefly situated close to prominent horst and graben structures among the pre-Cambrian and Palaeozoic basement.
In terms of its structure, the Aksu ore field formed within an asymmetrical syncline that is characterized by tectonic block structures formed by the intersection of several sets of block faults where the ore field structure (and distribution of the main gold bearing ore bodies) is controlled by the emplacement of pronounced trending fault lines.
- Here, mineralization is related to the anticline-syncline inflexion line and fluid barriers formed by volcanic rocks covering sediments. The most recent observations of drill core show that, at local scale, mineralization is controlled by shear zones and contacts between fragmental and porphyritic volcanic rocks.
- Note that the structural style of this deposit and an understanding of the ore forming mineralization is well understood given the longevity of mining in this area, particularly in the underground environment for exploration at Aksu began in 1929 when more than 200 veins were discovered by surface works; and the veins were divided up between six distinct ore zones, each of which was characterized by different geological features, - within the Aksu deposit itself, the quartz-gold veins are directly related to intrusions of Stepnyak type and their contact zones.
- The Aksu ore zone is located on the eastern side of the Aksu-Domralin and Aksu-Zholymbet synclinal zone, which can be traced for several hundred kilometers; and on a regional scale it is evident that all of the large scale gold deposits are located at the intersection between major northeast-southwest and conjugate trending fault zones and north-south trending deep seated lineaments. And yes, - the Aksu and Quartzite Hills deposits are situated at the intersection of such cross faults, namely, Celinograd and Atanasor and the main north-east trending deep lineament. These mineralized centers are often associated with small intrusive bodies of upper Ordovician and Silurian age, which together with the contact rocks play host to the main mineralization. More specifically, the mineralization within Aksu is hosted within Cambrian and Ordovician volcanogenic and sedimentary rocks and associated with intrusive rocks of Upper-Cambrian (gabbro and gabbro-diabase dykes and rod-like bodies), Middle (gabbro-diorites) and Upper-Ordovician (rod-like granodiorites) age.
AT AKSU: The primary deposit lies within the central area of the Aksu ore field and is characterized by late stage (Stepnyak type) intrusions which bisect the axis of the relatively tightly folded Aksu anticline. Intrusions of Stepnyak type of Upper Ordovician age are either small (50 meters by 100 meters) or very large (2.2 kilometers by 5 kilometers); with the largest of them located in the north-eastern part of the ore field where they form three separate massifs (Northern, Central and Southern Aksu).
- Meanwhile, the auriferous quartz veins are found almost exclusively within the intrusive rocks and only rarely within the contact aureoles. Additionally, this mineralization is characterized by a close structural relationship with the first and second stage intrusive dykes, typically with the veins following the contact surface against the dykes. The quartz veins often have a strike length of between 100 meters and 150 meters with a few reaching 300 meters and 600 meters. The thickness varies between 0.05 meters and 0.7 meters, averaging 0.2 meters. Typically, the veins have an overall north-easterly strike and a southeastern dip, with some of them striking northwest and dipping to the southwest. The auriferous veins (with the exception of the Yanvarskaya and Belaya veins) are not laterally extensive, ranging from 120 meters to 150 meters and vary from only a few centimeters up to 0.30 meters in width, with the average being between 0.10 meters and 0.20 meters.
AT QUARTZITE HILLS: The ore bodies of the Quartzite Hills deposit are located within large tectonic fault ‘‘blocks’’ of a strike-slip nature with intersecting oblique faults consisting of breccias and schist units which have undergone late stage silicification, being characterized by intensive schist formation, crush zones and further metasomatic silicification. Moreover, carbon rich clay and carbon-rich-clay-silicious schists are also hosts to mineralization (which will have an impact on the cyanidation recovery process.)
- The ore bodies, ranging from between 50 meters and 200 meters long and between 240 meters and 500 meters deep, are considered to be steeply dipping with a flattened lens and tube-like form (pipe-like).
- Gold mineralization of Quartzite Hills is of a lower grade (780 microns to 790 microns) in comparison to the gold of the Aksu deposit; and it is common for this gold to contain large amounts of silver with a composition of: 79.65% silver, 19.08% gold, 0.11% copper, 0.05% iron. Currently there are six recognized ore bodies at the Quartzite Hills deposit.
Before contemplating what may eventually be disclosed subsequent to further exploration at Shirotnaia (by applying as a paradigm what resides right next door) keep in mind that these gold deposits are pinpointed side by side in the midst of a major flexure of the Aksu-Balusti Mineral Trend ‘within the same area of this prolific flexure.’
- Mining here dates back to 1929 when gold ore was discovered at the Aksu deposit in Northern Kazakhstan; and during the Soviet era, production at Aksu was focused on the extraction of high-grade ore from underground mining rather than oxide and low grade gold ores; with the processing of gold ore based on flotation and gravity technologies.
- Then, after extensive research between 1999 and 2003 on the mineralogy of the gold reserves at its main deposits and the viability of available technologies to process such gold reserves, a modernization program was designed for the transition from flotation and gravity technologies to heap leaching and cyanidation technologies, and, by adopting heap leaching and cyanidation technologies, its owners were able to process low grade ore from open pits and waste dumps and to reprocess on-site tailings, in addition to processing ore extracted from its underground mines, - all at a lower cost per ounce than using flotation and gravity technologies.
Recent data regarding resources and reserves here are hard to come by but we do know as a fact that as of June 13th, 2005, it was estimated that the B and C1 gold reserves and C2 and P1 gold resources under the FSU Classification at the Aksu and nearby Quartzite Hills deposits were approximately 5.4 million ounces and 15.0 million ounces, respectively; constituting a world-class gold deposit.
- At Aksu (including Quartzite Hills), mineable resources average 2.70 g/t gold, - being 8.26 g/t Underground, 2.06 g/t Open Pit, 0.97 g/t Tailings, and 1.00 g/t at the Waste Dumps.
Almost ready to sum up but ahead of that let’s first briefly consider another ‘analogous’ parallel, also a monster, called Zholymbet, - one of the main gold deposits in Northern Kazakhstan located near to Shirotnaia (geologically speaking), residing beyond the Aksu/Quartzite Hills orogenic gold deposit and clearly a ‘potential comparable’. (The Shirotnaia zone is located in a major flexure of the Aksu-Balusti Mineral Trend, and both the massive Aksu/Quartzite Hills gold deposits and Zholymbet are also located within the same area of this flexure).
Exploration began at the Zholymbet deposit in 1932 and during the Soviet era the Zholymbet mine was amongst one of the largest gold mines in Kazakhstan, - with production in the 1980s focused on the extraction of high-grade ore from underground mining rather than oxide and low grade gold ores; with the processing of gold ore based on flotation and gravity technologies.
- The Zholymbet mine still had B and C1 gold reserves and C2 and P1 gold resources under the FSU Classification of approximately 4.3 million ounces (at 2.42 g/t) and 8.2 million ounces (at 3.75 g/t), respectively, as of June 2005. More specifically, as of June, 2005, reserves at Zholymbet were: 1.5 million ounces Underground (at 32.0 g/t), 2.1 million ounces Open Pit (at 1.87 g/t), 0.3 million ounces Tailings (at 0.99 g/t), and 0.4 million ounces Waste Dumps (at 1.20 g/t).
By any chance, - did you notice the large very high grade (32 g/t) Underground gold deposit?
O.K., - so what does this review suggest concerning Alhambra’s Shirotnaia?
- What potential resources will the Shirotnaia Project area (where extensive mineralized zones remain open along both strike and at depth) eventually disclose?
The main takeaway is that (1) the geological setting is ideal for the formation and preservation of massive gold deposits; (2) on a very positive note, a significant proportion of these enormous ore reserves are in the form of oxide ore, which may be mined at extremely favorable economics through open pit methods, - which are significantly cheaper than extracting ore from underground mining; and (3) strong potential exists to discover very large high-grade resources at deeper levels (perhaps just now being revealed by DDH2808) since the probable continuation of high grades to depth is usual for this style of mineralization.
- After finding zones of higher-grade gold mineralization the dynamics shift significantly; from this point going forward, besides further “overview” activity within the very large original project area of 10.0 kilometers by 2.0 kilometers, special focus can now be concentrated on closer-spaced drilling to fully delineate the dimensions and scope of these new zones whose potential is as of yet still unknown but could be just “the tip of the iceberg.” This is good, -
Supplement: Ordovician Considered
The Ordovician is a geologic period (the second of six in the Paleozoic Era); beginning approximately 490 million years ago (with the end of the Cambrian) and ending around 443 million years ago (with the beginning of the Silurian).
During this Ordovician period, volcanism was extensive, and all of the major tectonic plates were in motion; forming subduction zones and back-arc basins (where two plates converge, forcing one plate under another), - such as ‘Kazakhstan’. Many large deposits (of precious and nonferrous metals) were generated during riftogene, subduction and collision stages, with repeated redistribution of chemical elements and combined activity of several ore substance sources.
- Ore formation is a process of multistage localized concentration and accumulation (of previously dispersed trace metals), with typical metallogene commencing within a favorable geological foundation ("geosite" / "play"); commencing with metal source(s), followed by conditions of metal liberation, flux towards the ore site with concurrent or subsequent metal enrichment, and (finally) ore deposition. The terminal stage includes orebody enhancement, modification (through metamorphism) and preservation; with "giants" most likely to form when most, or at least the crucial components of a system, operate at peak efficiency, - so that there is a trend of steady metal increase throughout. Importantly, there must be a role for regional rock mass as a source of metal; with the depletion zones being the mobilization environments.
- However, extensive multi-element geochemical mapping (in ore regions) has shown that ore deposits and zones of enrichment as a whole constitute only a part of the geochemical field. The process may be quite complex, including both enrichment and depletion zones; and, since these appear to be spatially linked to each other, they are a single geochemical system. And, as these geochemical ‘circumstances’ would have it, the size of ore deposit systems vary, ranging from a few hundred square kilometers to thousands of square kilometers (in the case of giant ore deposits).
- Repeated studies have demonstrated that the content of ore metals in the depletion zones is more than 40% below regional background levels; and (where these different zones have been identified) a good correlation exists between the physical dimension of the depletion zone and the abundance of the depleted elements in the corresponding enrichment zone.
The Ordovician system (identified on all the continents except Antarctica) forms part of the structure of the sedimentary mantle of most platforms and is widely found in folded structures; and the thickness of deposits of the Ordovician system reaches 10,000 meters in the interior parts of geosynclinal belts, such as in ‘Kazakhstan’. There were numerous volcanoes in these zones, and thick layers of lavas, tuffs, and siliceous rocks accumulated in addition to detrital sediments. Moreover, both shallow-water and deep-water sediments are found in these places; and as a result of the Taconic orogeny (a major mountain-building episode), folded structures and mountains were formed in the Caledonian geosynclines toward the end of the Ordovician.
Given all of this, deposits of gold (and other metals) are associated with the widespread Ordovician intrusive rocks and geosynclines in Kazakhstan, and many of Kazakhstan’s hydrothermal-sedimentary polymetallic gold deposits are located in the continental riftogene structures, - in fact, all of the multi-million ounce Orogenic deposits (such as Vasilkovskoe, Aksu, Stepnyak, etc.) are genetically related to this.
- By the way, the ‘Ordovician’ was named by the British geologist Charles Lapworth (in 1879) using the name of an ancient Celtic tribe, the Ordovices, renowned for their fierce resistance to Roman domination.