The intraday seasonality of gold is marked by central bank efforts to keep the gold price from rising or from rising too fast. They want to avoid higher gold prices in order to reduce inflation expectations, reduce money market interest rates and support the U.S. dollar. At times it also has to do with avoiding the impression of panic thus increasing financial market stability. To minimize the effort of these interventions using limited means (gold supplies), the actions often take place close to or directly after the London PM fixing (about 10:00 AM EST). This is expressed in the intraday seasonal chart.
Further information about gold price manipulation can be found in a collection of articles at the website www.gold-eagle.com (external link, opens new window).