The Boroo Property is 100% owned by Boroo Gold LLC, a subsidiary of Boroo Pte Ltd.
On April 11, 2024, Steppe Gold Ltd. entered into a share exchange agreement with Centerra and Boroo Pte Ltd. to acquire all shares of Boroo Gold in exchange for shares representing 55.9% of Steppe Gold Ltd’s fully diluted shares.
On August 1, 2024, the acquisition was completed, with Steppe Gold Ltd. issuing 143,796,574 common shares, representing 55.9% of the fully diluted shares, to Boroo Pte Ltd. After the transaction, Boroo Pte Ltd. was determined to control Steppe Gold Ltd., making Boroo Gold a 100% subsidiary of Boroo Pte Ltd.
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Summary:
Boroo Deposit
The Boroo gold deposit is a low silica Au+As sulphide system associated with a zone of quartz-sericite- pyrite (QSP) alteration in the sub horizontal Boroo fault. Boroo is an intrusion-related gold deposit and hosted by a Cambrian-Ordovician sequence of highly deformed shales, siltstones and fine sandstones of the Haraa turbidite sediments, and the Paleozoic granitoids of the Boroo Complex.
Geology
The geology of the Boroo area is dominated by the folded Haraa sediments a fairly monotonous sequence of flysch sediments consisting of siltstone, sandstone and greywacke. These rocks are of regional extent and are interpreted to be of Lower Palaeozoic age. Intrusive rocks of the Boroo Complex, of early Palaeozoic age (~520 to 450 Ma), have intruded the sediments.
Detailed drilling around the Boroo gold deposits shows that the contact between the intrusive and the sedimentary rocks is highly irregular, with sedimentary xenoliths floating in the intrusive rocks in the border zone. A significantly younger igneous event of probably late Palaeozoic age is restricted to narrow vertical and shallow dipping dykes and fissures of granitic to dioritic composition.
Mineralization
The bulk mineable gold mineralisation at Boroo is hosted in a strongly quartz-sericite altered and sulphidised nearly flat lying zone controlled by the Boroo fault. The fault has been traced for a distance of 2.4 km and is thought to be a thrust fault that dips at an angle of 10° to the northwest and trending northeast. It cuts across the intrusive contact between sediments and granitic rocks in the north but is entirely contained within the sediments in the south. In the cross section, the Boroo fault shows a slightly undulated shape with the structure becoming thicker to the northwest, where the alteration and mineralisation decrease. The Boroo fault is variously altered and mineralised, and where these features are strongest, individual deposits are formed. These are termed, from north to south, Zone 2, 3, 4, 5 and 6. All of the deposits are elongated in a north-easterly direction, with a length to width ratio of about two to one. In Zone 2, 4, 5 and 6, mineralisation is controlled by Boroo fault and is in the footwall. But in Zone 3, there is low grade mineralisation in both hanging wall and footwall. Grade thickness contours show the same overall elongation probably caused more by the width than by the gold grade, with the multiple superimposed zones of alteration and mineralisation responsible for the thicker parts. The thickness of the individual deposits thus varies from a few metres at the deposit edges to several tens of metres.
Two main types of mineralisation have been noted:
• Gold-sulphide zones host the largest proportion of gold mineralisation at Boroo. This type of mineralisation is strongly altered quartz-sericite sulphidised zones that occur in thin, irregular veinlets, less often in breccia zones, and disseminated within the pervasive alteration. The intensity of sulphide mineralisation depends on primary host rock and intensity of alteration being stronger in the granites than metasediments. The main sulphide minerals are pyrite, arsenopyrite and rarely chalcopyrite, tetrahedrite and galena occur. It appears that the gold in this mineralisation is relatively fine grained.
• Gold-quartz vein type. The second major gold bearing facies is massive, white quartz veins in which gold is commonly coarse-grained. The thickness of quartz veins varies from a few centimetres up to 3 m and appear as infill veins and veinlets in fractures within mostly metasediments. Veins contain small amount of sulphides and mostly coarse-grained visible gold. This type of mineralisation from a volume perspective is subordinate; however, can carry very high gold values of up to several hundred grams per tonne.
The two main types of mineralisation described above have different gold grade distribution patterns. Gold content is high in quartz. Gold values are also higher where there is quartz stockwork mineralisation associated with pyrite-arsenopyrite ore. Silver values are generally low and are not obviously correlated with gold. Silver values can be higher in the quartz veins in Zone 5 and Zone 6. Silver values, higher than 10 g/t, occur mostly in quartz veins in metasediments and are very variable. The sulphide content in both types of mineralisation is relatively low, typically a few percent. Arsenic is highly anomalous (up to 21,500 g/t) but highly variable in the different zones; 103–112 g/t in Zone 2, 3,158–3,843 g/t in Zone 3 and more than 1% in the metasediments of Zone 5. A positive correlation with gold is restricted to gold values up to about 2 g/t.
Ulaanbulag Deposit
Ulaanbulag deposit depends on the morphology of the mineralized region with shallow dip angle and variable thickness. Mineralization is defined by quartz-cali field cali-sericit-pirite alteration and low silica Au+As sulphide system associated. Ulaanbulag is oregon related gold deposit with its tectonic-macmic environment, its carbon dioxide components, and its geochemical properties.
Geology
In the area of Ulaanbulag deposit, Lower Paleozoic metamorphic-sedimentary rocks of the Shirguu Formation in the Kharaa region, Cenozoic sediments, and Middle-Late Ordovician intrusive rocks of the Boroogol Formation are found in this region.
The Ulaanbulag deposit is complex in terms of geological formation, and the sands of the Shirguu Formation scattered in the central part of the field formed an orebody extending latitudinally in the medium grained, inlaid, feldspar granite of the III phase of the Boroogol Formation in the upper part of the Ulaanbulag fault.
However, in the southern part of the deposit, a large massive of diorite of the Boroogol Formation phase I is found.
In the northern part of the field, several small orebodies of diorite were identified within the granite, occasionally around the boundary between granite and sandstone.
At several locations, the boundary between sandstone and granite is demarcated by the Ulaanbulag inclined fault and its branch faults.
In the geological cross-section, the granite containing orebody in the upper part of the section cuts the diorite found in the lower part, and along their boundary and weakened zone, the Ulaanbulag fault is mapped with a dip of 20-400 degrees southwest.
Mineralization
Two main types of mineralisation have been noted:
• A type of gold-sulfide. Gold-sulphide mineralization, which the majority of the deposit's gold reserves, is identified by beresite metamorphic zones. The gold grade is generally low, it has different distribution in different types of rocks, it is highly variable in small distances, and it has high variability of content. The gold content is directly proportional to the arsenopyrite or arsenic content, regardless of the density of quartz veins and veinlets, as in Boroo deposits. This type of mineralization is mainly contained in the Ulaanbulag fault and metamorphic granite rocks. In metamorphic sandstone and diorite xenoliths, the sulfide content decreases dramatically. This is why these less metamorphic rocks usually have lower gold content. The main sulfides in Ulaanbulag deposit are pyrite and arsenopyrite, and rare minerals such as chalcopyrite, galena, pyrrhotite, sphalerite, and dim ore are found.
• Gold-quartz vein type. Usually, the Ulaanbulag fault and its branches are found along the cracks and fissures, and there are fill veins, veinlets, and breccia-like veins with a thickness of several centimeters to 5 meters. The veins are low sulphide and sometimes contain visible gold inclusions up to 2 mm.