Rio Tinto Exploration and Calibre Mining Initiate 2021 Exploration Program Including 5,500 Metre Drilling Campaign Prioritizing Prospective Near-Surface Copper and Copper-Gold Mineralization

VANCOUVER, British Columbia, April 08, 2021 (GLOBE NEWSWIRE) -- Calibre Mining Corp. (TSX: CXB; OTCQX: CXBMF) (the “Company” or “Calibre”) is pleased to provide an update on the Borosi exploration project held under an earn-in option agreement between Rio Tinto Exploration (LSE:RIO) (“RTX”) (“Rio Tinto”) and Calibre. Calibre controls a 100% interest in the Borosi concessions located in the prolific Mining Triangle region of northeastern Nicaragua. RTX has the right to earn a 75% interest by spending US$45 million over eleven years in the project (see Calibre news release dated February 24, 2020). The Borosi exploration program is being directed by RTX through a partnership agreement with Calibre as project operator.

Highlights

• 667km² land package strategically positioned over the historic Siuna and Rosita gold/copper mining camps
• Host to prospective copper and copper-gold porphyry and related skarn style mineralization
• Over $20 million in exploration work completed by Calibre over the past ten years
• Project includes Primavera copper-gold porphyry deposit discovered by Calibre in 2011
• Borosi is relatively under-explored for bulk tonnage porphyry style base and precious metals systems
• An initial 5,500 metres of diamond drilling planned for 2021

Darren Hall, President and Chief Executive Officer, commented: “We are excited to launch the 2021 exploration program with our partner Rio Tinto. Partnering with Rio Tinto, a global mining industry leader, provides a significant opportunity to leverage the discovery potential of our large portfolio of base metals properties while we continue to focus on growing gold resources within our 100% owned exploration and operating properties in support of our ‘Hub-and-Spoke’ operating model.”

2021 Exploration Program

Since entering the Borosi option agreement in February 2020, the RTX team has conducted extensive evaluation of exploration data stemming from Calibre’s work over the past 10 years as well as Rio’s own information sources and data archives that go back several decades. More than 50 prospective target areas have been identified within the Borosi concessions. Four of these areas have been prioritized for a first pass drilling campaign totaling 5,500 metres commencing in early Q2 2021. Additionally, an orientation survey has been initiated to characterize the broader geochemical expression surrounding the Primavera copper-gold porphyry deposit discovered by Calibre in 2011. The results of this work will provide an important benchmark to guide future regional reconnaissance work to be carried out under the RTX-Calibre Exploration Alliance agreement the companies also entered in early 2020.