The assistant pastor of a church in Thornton faces charges of sexual assault on a child.

Robert Wyatt, 50, is accused of assaulting a girl whose family attended Agape Bible Church.

Prosecutors claim the abuse started when the girl was 12 and lasted for nearly two years.

He's charged with sexual assault on a child, sexual assault on a child as a pattern of conduct and sexual assault on a child by a person in a position of trust.

Wyatt surrendered to the Adams County Sheriff’s Office on Monday afternoon. His bond is set at $20,000.

9NEWS requested a mugshot for Wyatt but did not receive one by the time of this writing.