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Derivative financial instruments (Tables) | 12 Months Ended
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Dec. 31, 2017
Disclosure of derivative financial instruments [Abstract] |
Disclosure of detailed information about hedge derivatives financial instruments [text block] | The table below presents the composition of open transactions included in the hedge derivative financial instruments as of December 31, 2017:
|  |  |  |  | Quotations |  |  |
Period of settlement |  | MT |  | Fixed |  | Futures |  | Fair value |
|  |  |  |  |  |  |  |  | US$(000) |
January 2018 |  |  | 3,000 |  | 5,972 – 6,050 |  |  | 7,275 |  |  | (3,788) |
February 2018 |  |  | 3,000 |  | 5,972 – 6,050 |  |  | 7,260 |  |  | (3,736) |
March 2018 |  |  | 3,000 |  | 5,972 – 6,050 |  |  | 7,247 |  |  | (3,693) |
April 2018 |  |  | 3,000 |  | 5,805 – 6,050 |  |  | 7,259 |  |  | (3,973) |
May 2018 |  |  | 3,000 |  | 5,900 – 6,300 |  |  | 7,269 |  |  | (3,484) |
June 2018 |  |  | 3,000 |  | 5,900 – 6,325 |  |  | 7,277 |  |  | (3,468) |
July 2018 |  |  | 3,000 |  | 5,960 - 6,350 |  |  | 7,285 |  |  | (3,359) |
August 2018 |  |  | 3,000 |  | 6,520 |  |  | 7,290 |  |  | (2,288) |
September 2018 |  |  | 3,000 |  | 7,100 |  |  | 7,296 |  |  | (580) |
October 2018 |  |  | 3,000 |  | 7,200 |  |  | 7,300 |  |  | (296) |
November 2018 |  |  | 3,000 |  | 7,300 |  |  | 7,305 |  |  | (13) |
December 2018 |  |  | 3,000 |  | 7,300 |  |  | 7,309 |  |  | (27) |
|  |  | 36,000 |  |  |  |  |  |  |  | (28,705) |
The table below presents the composition of open transactions included in the hedge derivative financial instruments as of December 31, 2016:
|  |  |  |  | Quotations |  |  |  |
Period of settlement |  | MT |  | Fixed |  | Futures |  | Fair value |
|  |  |  |  |  |  |  |  |  |  | US$(000) |
January 2017 |  |  | 2,542 |  |  | 4,917 |  |  | 5,526 |  |  | (1,548) |
February 2017 |  |  | 2,270 |  |  | 5,001 |  |  | 5,530 |  |  | (1,199) |
March 2017 |  |  | 1,795 |  |  | 4,860 |  |  | 5,535 |  |  | (1,208) |
April 2017 |  |  | 500 |  |  | 5,720 |  |  | 5,536 |  |  | 92 |
|  |  | 7,107 |  |  |  |  |  |  |  |  | (3,863) |
Disclosure of detailed information about financial instruments [text block] | Embedded derivatives held by the Group as of December 31, 2017 are:
|  |  |  |  |  | Quotations |  |  |  |
Metal |  | Quantity |  | Period of quotations |  | Provisional |  | Future |  | Fair value |
|  |  |  | 2018 |  | US$ |  | US$ |  | US$(000) |
Copper |  | 24,846 DMT |  | January – March |  | 6,645.36 – 6,841.95 |  | 7,112.50 – 7,275.00 |  |  | 2,508 |
Gold |  | 64,898 DMT |  | January – March |  | 1,256.45 – 1,317.67 |  | 1,258.00 – 1,317.10 |  |  | 1,066 |
Silver |  | 326,095 Oz |  | January – April |  | 16.02 – 18.00 |  | 16.07 – 17.21 |  |  | 1,815 |
Lead |  | 22,735 DMT |  | January – April |  | 2,333.23 – 3,110.69 |  | 2,488 – 2,579.75 |  |  | 229 |
Zinc |  | 54,603 DMT |  | January – April |  | 3,103.72 – 3,275.47 |  | 3,226.50 – 3,343.50 |  |  | 1,806 |
Total asset, net |  |  |  |  |  |  |  |  |  |  | 7,424 |
Embedded derivatives held by the Group as of December 31, 2016 are:
|  |  |  |  |  | Quotations |  |  |  |
Metal |  | Quantity |  | Period of quotations |  | Provisional |  | Future |  | Fair value |
|  |  |  | 2017 |  | US$ |  | US$ |  | US$(000) |
Copper |  | 29,121 DMT |  | January - April |  | 2,985.28 – 5,824.00 |  | 5,535.76 – 5,642.25 |  |  | 397 |
Gold |  | 15,370 DMT |  | January – February |  | 1,139.75 – 1,145.90 |  | 1,151.00 – 1,179.40 |  |  | 481 |
Silver |  | 17,124 Oz |  | January - April |  | 16.32 – 19.35 |  | 16.42 – 16.66 |  |  | (1,825) |
Lead |  | 23,636 DMT |  | January - April |  | 1,871.58 – 2,380.60 |  | 2,017.00 – 2,080.00 |  |  | (801) |
Zinc |  | 29,407 DMT |  | January – March |  | 2,291.08 – 2,732.10 |  | 2,578.00 – 2,612.50 |  |  | (172) |
Other |  | 15,082 Oz |  |  |  |  |  |  |  |  | 396 |
Total liability, net |  |  |  |  |  |  |  |  |  |  | (1,524) |

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- Definition The disclosure of detailed information about financial instruments. [Refer: Financial instruments, class [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2017-01-01 -Paragraph 31 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_31&doctype=Standard -URIDate 2017-03-09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2017-01-01 -Paragraph 7 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_7&doctype=Standard -URIDate 2017-03-09 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Note Effective 2018-01-01 -Name IFRS -Number 7 -IssueDate 2017-01-01 -Paragraph 35K -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_35K&doctype=Standard -URIDate 2017-03-09 + Details
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