Hellow. I take it you are playing TR 4? You have four Holy Scriptures. Have you done the water scales? If so, you should be in the area at the tunnel where Lara climbs down a blue shaft of light. At the end of the blue light is a huge statue of Horus. There is four pedestals where you put the Holy Scripures on.

The gate part? The gate will automatically shut behind you after you have completed the part where you collected and put in the four Star keys into the walls in a small room. The next area would be, you climb down a shaft of blue light to a small opening in the wall. Go throught this opening to a room where you do the math on the water scales. Complete the water scales and proceed to the room with Horus. If you need more help please ask me. I will do my best you help you through this.