Among the highlights, of the 14 holes drilled so far from the 1070 level at the Cuye area, was 99m at 1.48% copper, 12g/t silver, 0.05% zinc, 0.01% lead and 0.7g/t gold.
Mineralised areas noted in core continued to identify large dioritic intrusive inclusions which previously were never studied and were the widest intercepts of copper mineralisation in Sierra Metals history, the company said.
It suggested a new geological interpretation concept in the intrusive rocks, with potentially larger dimensions.
Yauricocha notched up another strong performance for Sierra in the fourth quarter as the company implements an "operation turnaround" programme at its two Mexican mines to improve production.
Sierra produced 14.9 million ounces silver equivalent, 90.4 million pounds copper equivalent and 193.2Mlb zinc equivalent in 2017 across its three operations.
It expects to produce 13.9-16.2Moz AgEq, 89.2-104Mlb CuEq and 183.8-214.5Mlb ZnEq this year.
Shares in the company have traded between C$2.75-$3.75 over the past year and closed down 1c yesterday to $3.12.