EXHIBIT 99.1

JOINT FILING AGREEMENT

Each of the undersigned hereby agrees that this Amendment No. 17 to the statement on Schedule 13D is being filed with the United States Securities and Exchange Commission on behalf of each of the undersigned pursuant to Rule 13d-1(k) under the United States Securities Exchange Act of 1934, as amended.

Dated: December 18, 2015

Glencore AG

By:	/s/ Thomas Meier
Name:	Thomas Meier
Title:	Officer
By:	/s/ Stephan Huber
Name:	Stephan Huber
Title:	Officer

Glencore International AG

By:	/s/ Aristotelis Mistakidis
Name:	Aristotelis Mistakidis
Title:	Officer
By:	/s/ Martin Haering
Name:	Martin Haering
Title:	Officer

Glencore plc

By:	/s/ John Burton
Name:	John Burton
Title:	Company Secretary