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亚利桑那北部科罗拉多高原上的数百个角砾岩筒均形成于古生代沉积岩中,岩筒中的铀、铜矿床产于密西西比系红墙(Redwall)灰岩至三迭系钦纳尔组(Chinle For mation)的岩石中,具穿层特征。这些岩筒并不是典型角砾岩筒,与火山岩不存在时间和空间上的联系,而是红墙灰岩内的溶蚀塌陷与上覆岩层升蚀作用的结果。红墙灰岩中的岩溶作用开始于密西西比纪,并延续到三迭纪或者至少在三迭纪又再次活动。成矿作用产生于中生代,紧接在岩溶作用之后。大峡谷(Grand Canyon)地区角砾岩中的采矿活动开始于19世纪,并一直持续到现在,主要是开采哈克Ⅰ、Ⅱ、Ⅲ号矿床(hack Ⅰ,Ⅱ,Ⅲ),但开采的矿种已从铜变为铀。岩筒规模较小,但其中的矿石品位高,最高可达55％U_3O_8,平均值为0.30—0.60％U_3O_8。地表矿化通常出现在黄铁矿和针铁矿结核中,并沿断裂分布,还原带的原生矿石则主要分布在充填于上覆岩层角砾中的粉砂岩基质中。矿石矿物是沥青铀矿,共生矿物有闪锌矿、方铅矿、黄铜矿、砷黝铜矿、针镍矿、硫镍钴矿和辉铜矿。某些地表结核包上了一层孔雀石外壳,并意外地富集有银。黄铁矿很丰富,某些岩石的有机炭含量也十分高,因此,可以认为有机炭和黄铁矿可能是铀的还原剂。如果铀是以重碳酸盐或碳酸盐化合物形式搬运,那么角砾岩筒就有可能是释放CO_2,使成矿溶液平衡遭受破坏,并造成沥青铀矿沉淀的唯一通道。矿石中许多元素都明显地产生富集。这些元素是:Ag、As、Ba、Cd、Co、Cr、Cs、Cu、Hg、Mo、Ni、Pb、Sb、Se、Sr、U、V、Zn以及稀土元素,其中Cu、Pb、Zn、Ag尤其是As,可能是矿化岩筒最好的地球化学示踪元素。有关成矿溶液的成因现在还不清楚,但角砾岩筒内硅化作用不强烈,根据闪锌矿、白云石、石英和方解石测定的流体包裹体温度为80—173℃,可以认为成矿溶液属低温热液,但高于据科罗拉多高原上地热梯度所推算的温度。除铀矿之外,其它的矿物组合和地球化学特点与密西西比河谷式矿床相类似。
Hundreds of breccia barrels on the Colorado Plateau in northern Arizona are formed in Paleozoic sedimentary rocks with uranium and copper deposits in the Mississippian Redwall limestone to the Chinle Formations mation) rock, with a layer of features. These rock cores are not typical breccia tubes and have no temporal and spatial connection with volcanic rocks. Instead, they are the result of erosion and erosion of overlying strata within red-wall limestone. The karstification in the red-wall limestone began in the Mississippian and continued into the Triassic or at least once again in the Triassic. Mineralization occurred during the Mesozoic, immediately after karstification. Mining activities in the breccia in the Grand Canyon began in the 19th century and have lasted until now, mainly in the mining of hack I, II, III (hack I, II, III) The species has changed from copper to uranium. Rock tube smaller, but the high grade ore, up to 55% U_3O_8, with an average of 0.30-0.60% U_3O_8. Surface mineralization usually occurs in the pyrite and goethite nodules and distributes along the fault. The primary ore in the reduction zone is mainly distributed in the siltstone matrix that is filled in the overburden breccia. Ore minerals are bitumen uranium deposits, and the symbiotic minerals are sphalerite, galena, chalcopyrite, arsenic tetrahedrite, aconite, sulphideite and chalcocite. Some surface nodules are covered with a layer of malachite husks and accidentally enriched with silver. Pyrite is abundant and some rocks have very high organic carbon content. Therefore, organic carbon and pyrite may be considered uranium reductants. If uranium is transported as a bicarbonate or carbonate compound, the breccia cylinder may be the only way to release CO 2, balance the ore-forming solution equilibrium, and cause the precipitation of bitumen uranium deposits. Many elements in ore are clearly enriched. The elements are: Ag, As, Ba, Cd, Co, Cr, Cs, Cu, Hg, Mo, Ni, Pb, Sb, Se, Sr, U, V, Zn and rare earth elements, Ag, especially As, may be the best geochemical tracer element for mineralized rock. The origin of the metallogenic solution is unclear, but the silicidation within the breccia cylinder is not strong. The temperature of the fluid inclusions measured from sphalerite, dolomite, quartz and calcite is 80-173 ° C. It is considered that the ore-forming solution It is a cryogenic hydrothermal fluid, but higher than the temperature estimated from the geothermal gradient over the Colorado Plateau. Other than uranium, other mineral assemblages and geochemical features are similar to the Mississippi Valley deposits.