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impactites?

 
 
Reply Sat 23 Feb, 2013 12:52 am
The first time I saw these rocks with holes, one year ago, my first thought was that a meteorite rain could have impacted on them, at that time I didn't have any bit of knowledge about meteorites neither rocks. I thought too that maybe the holes could have been the result of gun shots, maybe lead shots as result of an old battle. Then I found many metallic fragments, I thought that they could be part of a fragmented metallic meteorite because they had that glossy appearance(dessert varnish), they were highly magnetic, heavy. But I was told they were iron oxides, possibly hematites. After that I comprehended that metallic meteorites have regmaglypts and don't streak when rubbed against a surface. With that new information in hand I returned to the promontory of the rocks with holes hoping to find iron encrusted in the rocks, or whatever the rocks would have in the holes. But I couldn't pluck a thing and returned home, at that time I was fascinated with the idea of finding a meteorite but I forget the issue when I read that metallic meteorites don't fragment and that the possibilities of finding one is almost 0%. When I knew the rocks around the place were breccias and when I read about impact breccias, I thought maybe they could be impact breccias, but I disregard myself, that is certainly impossible, I thought. So I considered they were igneous breccias. I went to fotograph the breccias an accidentally I found a fossil nearby and was fascinated with finding others fossils so I collected some rocks. Then I found a rock that had that lava-like melted petrified covering, I thought it could be a fossil. I was told it could be lava, indeed it looked like that, but I doubted it about it because in the surroundings there is no lava like features, I would have it related. I have a couple of stones with black crystallized covering, when I found them I thought the covering was mud and could be detached it easily by washing it, but I was wrong, it was encrusted in the rocks. I remembered that the rock with lava like features was found on the rock with holes promontory. Then the term impactite came to my mind, because I had found the term when reading about meteorites and again when reading about impact breccias. I read a page about an impact crater, Vesala, in Finland. I saw the rocks impacted, they have similar holes that the rocks in the promontory. Then I saw a rock with a melted cover, caused by high temperatures of the impact, it looked like lava, like the rock I had found. I read that pumice can be created by the impact too. When I saw the rock I made the connection: impact breccias, limestone and breccias impacted by impactites, melted covering caused by high temperatures, possibly impact spallation; ingredients of an impact crater, but there are others missing, shatter cones, shocked quartz and the crater itself. Some time ago I had thinking in building a rustic stone oven, I collected fragments from the promontory because they were squared like bricks. Well, I didn't build the oven and I have the fragments in the backyard. I took one of these pieces and I observed that it has iron incrusted, I put a magnet and it sticked. I observed that it is peppered with many tiny iron particles. I went out to collect more photos and some rocks, I observed that the holes in the rocks have some kind of crystal, I found a stone that seemed a breccia, I didn't know that breccias could be as great as the ones found and as small as the stone I had just found. Walking around I found more mega breccias, the distance along I have found breccias is about 7 km. Limestone is uncommon and does not fit with more granite surrounding landscape, however it does not look odd, except for the holes, because it looks like granite at the common sight. I have explored 7 km in an angle of 30 grades. Supposing the impact crater theory is a fact, what could be the dimensions of this crater considering the fact that 7 km of breccias are vissible and the impactites are 100m from one end of the breccias? how old could it be considering the fact that it is not profound and possibly tectonic forces had made the breccias to emerge?
http://www.flickr.com/photos/51986587@N04/sets/72157632811530192/
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rosborne979
 
  1  
Reply Sat 23 Feb, 2013 05:20 am
@tlatoanitzin,
So the magnet you show in your image only sticks to the dark blotches on the rock, and not to the surrounding "lighter" colored areas? Is that right?

The boulders do look like some form of softer rock (at the time) was impacted by debris (smaller rocks). But I'm no expert on this stuff by any means.

The large rocks don't look like magma (cooled) to me, they look more like sandstone or hardened clay. Maybe this is the remains of a massive mudslide that hardened over time. I'm just guessing.

Where is all this located geographically?
0 Replies
 
farmerman
 
  1  
Reply Sat 23 Feb, 2013 05:28 am
@tlatoanitzin,
the only way to satisfy yourrself what the causes are, you need to sample the material around the holes in an oriented fashion and look for shocked quartz under a microcope (you cant tell it just from a hand specimen)

I kinda doubt the regmolypt conclusion, instead it looks like erosion of metallic AND feldspathic inclusions. Was this area a mine site at one time?
Are we in Mexico ?

Usually when we see a imoact or tektite srewn field, you can see where the stuff came from, the trajectories are marked like shotgun pellets coming from one quadrant of the sky. Your rocks seem to have been moved all over the place (probably by humans)
tlatoanitzin
 
  1  
Reply Mon 25 Feb, 2013 12:40 pm
@farmerman,
The magnet sticks to the blotches only. The place is in Tijuana, Mexico. No evidence of mining all around. It seems it was a farm long time ago, but it was abandoned. Many of the fragments of the boulders were used to channel a stream that runs nearby and for walling around. I think the promontory was a kind of quarry. Most of the boulders look like feldspar or quartzite, I have sampled some material from the holes, I observed that it is the same matrix material, but it has a halo of reddish rusty color, and it has in the center green crystals, those are crystals are darker and some are rusty in the center most area. The rock I found previously with the lava like covering, it has the same features that the samples I collected, so I infer it was attached to one of these holes. I honestly hadn't think of an impact crater if I hadn't find the rock with that lava like material. I would be satisfied with inclusions of geological dynamics. But then I found those different kind of breccias. I am myself confused by the geology of the area.
tlatoanitzin
 
  1  
Reply Tue 26 Feb, 2013 08:12 pm
@tlatoanitzin,
I found this pebble, it looks like a shocked pebble from a Spain crater I saw on the net. http://www.flickr.com/photos/51986587@N04/8510393731/sizes/l/in/photostream/

In the promontory I found this rock with small vesicles, I don't know if is volcanic but certainly looks so, it underwent extreme heat. It looks like it was attached to other rock, as a xenolith maybe.
http://www.flickr.com/photos/51986587@N04/8511511794/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8510399263/sizes/l/in/photostream/

There is a peculiar layer of sedimentary black sandstone discovered by the stream.
http://imageshack.us/a/img819/6292/2102201312147.jpg
http://imageshack.us/a/img850/8605/2102201312146.jpg
http://www.flickr.com/photos/51986587@N04/8511503612/sizes/l/in/photostream/

Just there, besides the sandstone rocks I found this rock with planar deformation like features, which I have only seen in microscopical images. I don't know what caused it.
http://imageshack.us/a/img716/2761/2102201312144.jpg
http://imageshack.us/a/img580/6093/2102201312143.jpg
http://imageshack.us/a/img694/8382/2102201312142.jpg

In the stream I found these minerals:
This one that feels and is like a piece of granola bar. Formed of various crystals pieces. I am not sure if the green color of some of the crystals is bio pigmentation of some kind.
http://www.flickr.com/photos/51986587@N04/8510394663/sizes/l/in/photostream/

This other that looks like a pizza slice and is formed of fragments of crystals of similar kind I think. But it has this odd black mineral, it feels like obsidian but resembles charcoal, at one niche very tiny and fine grooves can be seen on this mineral.
http://www.flickr.com/photos/51986587@N04/8510401417/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8511513578/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8510403657/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8510404181/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8511516734/sizes/l/in/photostream/

I sampled the inclusions of some of the holes of the boulders of the promontory and I observed they have a kind of reddish halo, they have green crystals, some of them are darker. They have rusty material, like iron oxide.
http://www.flickr.com/photos/51986587@N04/8510397161/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8511509060/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8511506796/sizes/l/in/photostream/

I was walking around and I found these beautiful breccias:
http://imageshack.us/a/img441/5964/2102201312154.jpg

Then turn my head at right and I saw this wall of brecciated soil, I sighed!, I could watch kink bands of these breccias that stop at an angle of 45 more or less.
http://imageshack.us/a/img713/1968/2102201312153.jpg

I departed farther to photograph some breccias I have sighted previously, not very far. I observed some of the rocks have this concentric damage that make them look like lettuce.
http://imageshack.us/a/img802/2424/2102201312262.jpg
http://imageshack.us/a/img541/5163/2102201312260.jpg
http://imageshack.us/a/img836/7776/2102201312263.jpg
http://imageshack.us/a/img21/2538/2102201312211.jpg

close up image of one of the breccias
http://img547.imageshack.us/img547/145/2102201312225.jpg

I photographed one exposed side of a small mountain, it looks like melting rock flow or unless a flow of some kind.
http://imageshack.us/a/img708/366/2102201312195.jpg

Impact spallation damage?
http://imageshack.us/a/img703/5773/2102201312185.jpg
http://img705.imageshack.us/img705/8459/0402201311840.jpg

Planar fragmentation I think.
http://imageshack.us/a/img22/1171/2102201312247.jpg

The next day I went to the place of the remotest breccias to take some shots. When returning I suddenly noted that a huge halved boulder I have always seen, have patterns similar to shatter cones.
http://www.flickr.com/photos/51986587@N04/8511519840/sizes/l/in/photostream/
http://www.flickr.com/photos/51986587@N04/8510409441/sizes/l/in/photostream/

I was kind of doubtful but when I saw it on the pc I noted the striking resemblance. Then I searched through the photos and found these ones that also resembled shatter cones, but no so strikingly as the boulder.
http://www.flickr.com/photos/51986587@N04/8510413433/sizes/l/in/photostream/

The xenolith of the left of this image looks like shatter cone.
http://www.flickr.com/photos/51986587@N04/8511522876/sizes/l/in/photostream/

But then I had a doubt, it could be that those patterns can be the result of dynamite explosions?

I know shocked quartz presence or absence can determine the impact existence. Unfortunately I haven't access to a microscope to take some shots. What of these signs could be summed up to the impact hypothesis and what other should I discard.







rosborne979
 
  1  
Reply Tue 26 Feb, 2013 08:32 pm
@tlatoanitzin,
It must be nice to get so much pleasure from something as abundant and simple as a rock. You are making me envy geologists.
farmerman
 
  1  
Reply Tue 26 Feb, 2013 10:35 pm
@tlatoanitzin,
Ill look at em more closely over the next day. I only looked at the one "breccia'. It looks like Nepheline Syenite structure with some of the country rock within the "mix" I agree, it is neat, you need to get some closer up and PLEASE!!, put something in the photos fro scale at the outcrop. I always have a small 6" ruler that ive painted each inch bright red and then white, so Ive got 1" stripes adding up to 6". In a pinch I use coins big enough. You were using pesos and thats the only way we can establish scale.

Interesting stuff nonetheless.
Remember Im required to be skeptical until I can satisfy myself . Impact breccias usually have jumbly mixes of xenoliths and matrix, yours seems more ordered.
farmerman
 
  1  
Reply Tue 26 Feb, 2013 10:41 pm
@farmerman,
See how this breccia seems layered and the xenoliths are lmost in line?. If itwere an impactite the breccia wouldnt be bounded by another similar formation and the xenoliths would be all over the place and not lined up. I think this is a layered ignimbritic and pluton mix. (maybe multi layered from several events). its hard to see from the photos. IS the contact point between the breccia and the darker layer abrupt?

    http://imageshack.us/a/img441/5964/2102201312154.jpg
tlatoanitzin
 
  1  
Reply Wed 27 Feb, 2013 12:17 am
@rosborne979,
Indeed, knowledge acquired through rocks is very rewarding. You don't need more than that.
0 Replies
 
tlatoanitzin
 
  1  
Reply Wed 27 Feb, 2013 12:32 am
@farmerman,
You are right, I can see the xenoliths are like flowing, like leaves over a stream. I believed to see a rocky layer too but watching other photos I noted some boulders, including the breccias themselves, were graffitied, and the people painted over the graffiti a gray layer.
http://www.flickr.com/photos/51986587@N04/8509140774/sizes/l/in/set-72157632689139379/
http://www.flickr.com/photos/51986587@N04/8508033151/sizes/l/in/set-72157632689139379/
http://www.flickr.com/photos/51986587@N04/8508030205/sizes/l/in/set-72157632689139379/
It looks like these breccias were part of an outcrop, were cut off by humans and they were thus artificially exfoliated, that is why they look neat.
tlatoanitzin
 
  1  
Reply Wed 27 Feb, 2013 08:54 pm
@tlatoanitzin,
Close up images of the breccias:
http://imageshack.us/a/img51/9780/2702201312454.jpg
http://imageshack.us/a/img27/4813/2702201312453.jpg
http://imageshack.us/a/img542/8517/2702201312452.jpg
http://imageshack.us/a/img443/2801/2702201312455.jpg
http://imageshack.us/a/img33/7571/2702201312449.jpg
http://imageshack.us/a/img716/4125/2702201312448.jpg
http://imageshack.us/a/img694/4002/2702201312447.jpg
http://imageshack.us/a/img12/9081/2702201312446.jpg
http://imageshack.us/a/img843/3636/2702201312445.jpg
http://imageshack.us/a/img255/2541/2702201312450.jpg
They were layered before were broken, it seems.
These boulders are besides the breccias:
http://imageshack.us/a/img716/3740/nuevo3.png
I don't know if they are breccias or just the country rock.

is this exposed side of the mountain is brecciated, how could it be?
http://imageshack.us/a/img441/3987/nuevo4.png
http://imageshack.us/a/img845/626/nuevo5.png
farmerman
 
  1  
Reply Thu 28 Feb, 2013 12:23 pm
@tlatoanitzin,
Ill view em as I get moree time to just stare at the textures some more.
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