The pair did not provide further details about the cash offer.
Guyana Goldfields had also last week rejected an all-scrip bid from Gran Colombia Gold (TSX: GCM) in favour of Silvercorp's original offer.
In a joint statement released on Sunday, Silvercorp and Guyana said they had entered an amended agreement which would see Silvercorp offer C25c in cash and 0.1849 of a share for each Guyana Goldfields share, for total consideration of $1.30.
This compares with its earlier offer of 60c in cash or 0.1195 of a Silvercorp share.
Guyana Goldfields last week said it rejected the unsolicited bid from Gran Colombia, which had offered an exchange ratio of 0.142 Gran Colombia shares for each Guyana Goldfields share, implying a value of C90c, and was contingent on a concurrent merger with Gold X Mining.
"The board acknowledges that, based on current trading prices, the Gran Colombia proposal represents a premium to the agreed price under the Silvercorp transaction; however, the board is of the view that such premium does not sufficiently compensate the company's shareholders for the increased risk associated with the Gran Colombia proposal," the company had said on Wednesday.
Silvercorp currently holds 9.48% of Guyana Goldfields' shares.
After the transaction, which is subject to approval by two-thirds of Guyana Goldfields shareholders at a meeting scheduled for June 29, they would hold 14.4% of Silvercorp's pro forma basic shares.
The amending agreement values Guyana Goldfields at $227 million and increases the termination fee to $9 million.
Guyana Goldfields' flagship asset is the troubled Aurora gold mine in Guyana, which is headed for a period of care and maintenance, due to COVID-19 travel restrictions prompting the suspension of underground development in March, plus the ore supply gap and funding shortfall for its new life-of-mine plan.
The company has said it would benefit from Silvercorp's underground experience and strong balance sheet.
Silvercorp produces silver, lead and zinc from its mines in China.
Its shares have ranged from $2.12 to $7.70 over the past year and had closed up 10.6% on Friday to $6.38, to capitalise it at $1.1 billion (US$0.78 billion).
Guyana Goldfields shares have ranged from 25c-$1.47 and last traded at 94c, to capitalise it at $164 million (US$116.5 million).