322 
The American Geologist . 
May, 189$ 
We will not close this paper without calling attention to- 
the analogies observed between the region of Huelva in Spain, 
and that which has just been discussed. 
In the region of Huelva, after the deposition of the Culm 7 
an east-west fold was started, bringing up the marine sedi- 
ments of that period w T hile the coal deposits were formed in 
the wrinkles of the central Spanish plateau. Eruptions of 
porphyry or melaphyr occurred, as in the Esterel in France,, 
and these rocks lodged between the disturbed, east-west 
strata. 
Important metalliferous accessions succeeded these erup¬ 
tions, affecting an immense area and producing the very re¬ 
markable deposits of Rio-Tinto, Tharsis etc., in the region of 
Huelva, and those of central Spain: Linares, Almaden, Ciu¬ 
dad real, Castuera, etc. 
The metalliferous accessions appear to have pursued the- 
following order: iron, sulphide of iron, cuprous iron pyrites,, 
sulphide of copper, lead, silver, zinc, antimony, mercury, gold. 
There are regions characterized by ores of copper, others 
by ores of lead, mercury, or antimony. The copper pyrite de¬ 
posits have an east-west strike like the enclosing rocks, and 
are sometimes situated at their contact with basic eruptives.. 
The great deposition of sulphides of iron and copper fol¬ 
lowed immediately after the eruption of these rocks. The 
deposits are formed in wrinkles or zones dislocated and altered 
by the advent of intrusive masses. 
The ver}^ abundant mineral waters which have introduced 
and deposited the sulphides have also been efficient agents in 
the alteration of the enclosing strata. The porphyries them¬ 
selves have been greatly altered and decomposed. 
Thus, in short: east-west folds, east-west intrusions, east- 
west metalliferous deposits, Carboniferous rocks affected by 
the ore-forming agencies, these are the analogies with South 
Africa. 
The ore deposition seems to have been of substantially the 
same age (hercynian) in both countries. That of South Af¬ 
rica, which is perhaps Carboniferous, may have preceded that 
of Spain, which is Permian. But while in Spain the iron py¬ 
rites was accompanied by much copper and little gold, in Af¬ 
rica it was accompanied by much gold and little copper. 
