In a research note last week, Bank of America-Merrill Lynch noted that both assets were being bolstered by a 'flight to safety' stemming from risks in Europe, including the U.K.'s Brexit.
Given this unusual occurrence, Gartman reasoned that investors may want to consider betting on gains for gold while selling Treasuries in weeks to come, particularly as skittishness over Federal Reserve interest rate policy continues to dominate.
At Jackson Hole, Wyoming, on Friday, Fed Chair Janet Yellen's tone was interpreted as slightly hawkish. She noted that the "Fed has the tools to fight the next recession" and that she "anticipates that gradual rate hikes may be appropriate." However, not much clarity was given to when such hikes would occur. Shortly after, UBS updated its outlook for the likelihood of a rate hike to 25 percent in September and to 53 percent in December.
Immediately following Yellen's speech, the 10-year note spiked and broke out its August range to 1.60. Additionally, the U.S. 2-year note hit a high of .817 percent, its highest level since early June. But, from there, bonds fell sharply as gold gained modestly. The price action confirmed Gartman's instincts to remain cautious.
"You don't want to risk much on this trade," Gartman told CNBC.
"I can see gold breaking up to the upside and I can see the bond market breaking down to the downside. You don't need to risk more than one or two percent," he said. However, "if it starts to work [and] this anomaly of moving in tandem starts to break apart...you could see the gold market move $40 or $50 higher, and you could see the Treasuries note move three or four [basis] points lower."