<p>Laccoliths, lopoliths, dikes and sills are all characteristic modes of occurrence of hypabyssal rocks, generally small in scale compared to most magma chambers. They are magmas which have cooled in a near-surface environment. None of these terms <em>necessarily</em> implies a particular petrologic texture. So, for example a dike or sill may be aphanitic, porphyritic, aplitic, pegmatitic or even glassy obsidian - and other less common textures. Nevertheless, many hypabyssal rocks <em>are</em> porphyritic. All this means is that the magma crystallized in two stages. The first stage was deeper and slower cooling, allowing some crystals to grow, sometimes to much larger size than the rest of the crystalline matrix. The second stage is when the magma is intruded at shallow depth, resulting in much more rapid crystallization of the remaining melt. Hence the porphyritic texture of large crystalls within a fine-grained matrix. </p>

CC BY-SA 3.0
2016-11-04T03:12:02.353Z
2016-11-04T03:12:02.353Z
Gordon Stanger
<p>Laccolith, lobolith and batholith are shapes of igneous rocks which exist below the surface of the earth, dikes and sills too. And the way they formed by makes me think that they have a porphyritic texture, is that right? Or they have a coarse-grained texture? Because they have crystalled below the earth surface anyway?</p>

<geology><structural-geology><igneous><metamorphism>
are laccolith, lobolith, dikes and sills formed of porphyritic texture?
Asmaa
# are laccolith, lobolith, dikes and sills formed of porphyritic texture?

(Asked by: username_0 on 2016-11-03)

Laccolith, lobolith and batholith are shapes of igneous rocks which exist below the surface of the earth, dikes and sills too. And the way they formed by makes me think that they have a porphyritic texture, is that right? Or they have a coarse-grained texture? Because they have crystalled below the earth surface anyway?

**Tags:** geology, structural-geology, igneous, metamorphism


---

## 1 answers

### Answer by username_1 on 2016-11-04. Score: 1 | Accepted answer

Laccoliths, lopoliths, dikes and sills are all characteristic modes of occurrence of hypabyssal rocks, generally small in scale compared to most magma chambers. They are magmas which have cooled in a near-surface environment. None of these terms *necessarily* implies a particular petrologic texture. So, for example a dike or sill may be aphanitic, porphyritic, aplitic, pegmatitic or even glassy obsidian - and other less common textures. Nevertheless, many hypabyssal rocks *are* porphyritic. All this means is that the magma crystallized in two stages. The first stage was deeper and slower cooling, allowing some crystals to grow, sometimes to much larger size than the rest of the crystalline matrix. The second stage is when the magma is intruded at shallow depth, resulting in much more rapid crystallization of the remaining melt. Hence the porphyritic texture of large crystalls within a fine-grained matrix.


---

