金瓜石含金角礫岩礦體之構造與成因

Structures and Genesis of Auriferous Breccia Pipes in Chinkuashih

余炳盛(Bing-Sheng Yu)

《鑛冶：中國鑛冶工程學會會刊》 48卷4期 (2004/12) Pp. 57-66

https://doi.org/10.30069/MM.200412_48(4).0005

摘要

金瓜石東邊發育許多重要的角礫岩金礦體，其外形及分布具有下列特性：（1）礦體在砂岩中之分布最普遍，頁岩中次之，安山岩中少有角礫岩礦體。（2）垂直分布一般少於300公尺，但是亦有達700公尺者，而且頂部常有蓋岩。（3）水平長度約十餘公尺至百餘公尺，寬度則約數公尺至數十公尺。（4）礦體規模通雖有由下往上變大者，但亦有擴大後縮小，然後往上再度擴大者。（5）礦體大致垂直，但常有彎曲轉折。（6）礦體常形成南北向長橢圓狀。而在角礫岩礦筒內則呈現各種特殊的構造，例如：『角礫狀』沈積構造、『縞狀』沈積石髓、『磨圓角礫岩』、『解壓片狀裂縫』、『崩落』構造等。從型態及成因的研究可知此等角礫岩礦筒乃高壓熱液爆破而成，非早期認為之斷層角礫。由於角礫岩礦筒可以提供地下深部的訊息，將有助於金瓜石地區可能之潛伏斑岩礦床之調查研究。

關鍵字

金瓜石 ； 角礫岩礦筒 ； 金礦 ； 構造 ； 成因

並列摘要

Numerous auriferous breccia pipes occur as a N10°E trend on the east margin of the Chinkuashih district. They are hosted chiefly in the sandstones and the shales of the Nangkang Formation. These breccia pipes themselves are gene rally several to 20 meters in diameter, and 200~700 meters in vertical dimension. Both the pipes and their mineralized wallrocks contain gold. The minable orebodies are usually elliptical with an N-S length of 30~130 meters and a width of 5~50 meters. Shale is the major component of the fragments in the pipes. Fragments of sandstone, andesite and sedimentary chalcedony with laminated structure are present. The fragments are angular to subangular in shape and generally 1 to 50 cm in diameter. Mill breccia, sheeted fractures, collapse breccia and sedimentary structures are observed. The multi-layers of horizontal graded bedding composed of explosive clasts with in the breccia pipes in the inclined sedimentary rocks, and clast-in-clast structure indicate multiple brecciation in the same pipe. These breccia pipes could provide useful information for prospecting deeper potential porphyry copper in Chinkuashih.

並列關鍵字

Chinkuashih ； Breccia pipes ； Gold mine ； Structure ； Genesis